A catapult is a ballistic device used to launch a projectile a great distance without the aid of gunpowder or other propellants – particularly various types of ancient and medieval siege engines. A catapult uses the sudden release of stored potential energy to propel its payload. Most convert tension or torsion
energy that was more slowly and manually built up within the device
before release, via springs, bows, twisted rope, elastic, or any of
numerous other materials and mechanisms.
In use since ancient times, the catapult has proven to be one of
the most persistently effective mechanisms in warfare. In modern times
the term can apply to devices ranging from a simple hand-held implement
(also called a "slingshot") to a mechanism for launching aircraft from a ship.
The earliest catapults date to at least the 7th century BC, with King Uzziah, of Judah, recorded as equipping the walls of Jerusalem with machines that shot "great stones". Catapults are mentioned in Yajurveda under the name "Jyah" in chapter 30, verse 7. In the 5th century BC the mangonel appeared in ancient China, a type of traction trebuchet and catapult. Early uses were also attributed to Ajatashatru of Magadha in his, 5th century BC, war against the Licchavis. Greek catapults were invented in the early 4th century BC, being attested by Diodorus Siculus as part of the equipment of a Greek army in 399 BC, and subsequently used at the siege of Motya in 397 BC.
Etymology
The word 'catapult' comes from the Latin 'catapulta', which in turn comes from the GreekAncient Greek: καταπέλτης (katapeltēs), itself from κατά (kata), "downwards" and πάλλω (pallō), "to toss, to hurl". Catapults were invented by the ancient Greeks and in ancient India where they were used by the Magadhan Emperor Ajatashatru around the early to mid 5th century BC.
Ancient mechanical artillery: Catapults (standing), the chain drive of Polybolos (bottom center), Gastraphetes (on wall)Engraving illustrating a Roman catapult design, 1581Roman "catapult-nest" in the Trajan's Dacian Wars
The catapult and crossbow
in Greece are closely intertwined. Primitive catapults were essentially
"the product of relatively straightforward attempts to increase the
range and penetrating power of missiles by strengthening the bow which
propelled them". The historian Diodorus Siculus (fl. 1st century BC), described the invention of a mechanical arrow-firing catapult (katapeltikon) by a Greek task force in 399 BC. The weapon was soon after employed against Motya (397 BC), a key Carthaginian stronghold in Sicily. Diodorus is assumed to have drawn his description from the highly rated history of Philistus,
a contemporary of the events then. The introduction of crossbows
however, can be dated further back: according to the inventor Hero of Alexandria (fl. 1st century AD), who referred to the now lost works of the 3rd-century BC engineer Ctesibius, this weapon was inspired by an earlier foot-held crossbow, called the gastraphetes, which could store more energy than the Greek bows. A detailed description of the gastraphetes, or the "belly-bow", along with a watercolor drawing, is found in Heron's technical treatise Belopoeica.
A third Greek author, Biton (fl. 2nd century BC), whose reliability has been positively reevaluated by recent scholarship, described two advanced forms of the gastraphetes, which he credits to Zopyros, an engineer from southern Italy. Zopyrus has been plausibly equated with a Pythagorean of that name who seems to have flourished in the late 5th century BC. He probably designed his bow-machines on the occasion of the sieges of Cumae and Milet between 421 BC and 401 BC. The bows of these machines already featured a winched pull back system and could apparently throw two missiles at once.
Philo of Byzantium provides probably the most detailed account on the establishment of a theory of belopoietics (belos = "projectile"; poietike
= "(art) of making") circa 200 BC. The central principle to this theory
was that "all parts of a catapult, including the weight or length of
the projectile, were proportional to the size of the torsion springs".
This kind of innovation is indicative of the increasing rate at which
geometry and physics were being assimilated into military enterprises.
From the mid-4th century BC onwards, evidence of the Greek use of
arrow-shooting machines becomes more dense and varied: arrow firing
machines (katapaltai) are briefly mentioned by Aeneas Tacticus in his treatise on siegecraft written around 350 BC. An extant inscription from the Athenian
arsenal, dated between 338 and 326 BC, lists a number of stored
catapults with shooting bolts of varying size and springs of sinews. The later entry is particularly noteworthy as it constitutes the first clear evidence for the switch to torsion catapults, which are more powerful than the more-flexible crossbows and which came to dominate Greek and Roman artillery design thereafter. This move to torsion springs was likely spurred by the engineers of Philip II of Macedonia. Another Athenian inventory from 330 to 329 BC includes catapult bolts with heads and flights.
As the use of catapults became more commonplace, so did the training
required to operate them. Many Greek children were instructed in
catapult usage, as evidenced by "a 3rd Century B.C. inscription from the
island of Ceos in the Cyclades [regulating] catapult shooting
competitions for the young". Arrow firing machines in action are reported from Philip II's siege of Perinth (Thrace) in 340 BC.
At the same time, Greek fortifications began to feature high towers
with shuttered windows in the top, which could have been used to house
anti-personnel arrow shooters, as in Aigosthena. Projectiles included both arrows and (later) stones that were sometimes lit on fire. Onomarchus of Phocis first used catapults on the battlefield against Philip II of Macedon. Philip's son, Alexander the Great, was the next commander in recorded history to make such use of catapults on the battlefield as well as to use them during sieges.
The Romans started to use catapults as arms for their wars against Syracuse, Macedon, Sparta and Aetolia (3rd and 2nd centuries BC). The Roman machine known as an arcuballista was similar to a large crossbow. Later the Romans used ballista catapults on their warships.
Other ancient catapults
In chronological order:
19th century BC, Egypt, walls of the fortress of Buhen appear to contain platforms for siege weapons.
c.750 BC, Judah, King Uzziah is documented as having overseen the construction of machines to "shoot great stones".
between 484 and 468 BC, India, Ajatashatru is recorded in Jaina texts as having used catapults in his campaign against the Licchavis.
between 500 and 300 BC, China, recorded use of mangonels. They were probably used by the Mohists as early as the 4th century BC, descriptions of which can be found in the Mojing (compiled in the 4th century BC). In Chapter 14 of the Mojing, the mangonel is described hurling hollowed out logs filled with burning charcoal at enemy troops. The mangonel was carried westward by the Avars
and appeared next in the eastern Mediterranean by the late 6th century
AD, where it replaced torsion powered siege engines such as the ballista
and onager due to its simpler design and faster rate of fire. The Byzantines adopted the mangonel possibly as early as 587, the
Persians in the early 7th century, and the Arabs in the second half of
the 7th century. The Franks and Saxons adopted the weapon in the 8th century.
Medieval catapults
Replica of a Petraria ArcatinusPetraria Arcatinus catapult in Mercato San Severino, ItalyCatapult 1 Mercato San Severino
Castles and fortified walled cities were common during this period and catapults were used as siege weapons against them. As well as their use in attempts to breach walls, incendiary missiles, or diseased carcasses or garbage could be catapulted over the walls.
Defensive techniques in the Middle Ages progressed to a point that rendered catapults largely ineffective. The Viking siege of Paris
(885–6 A.D.) "saw the employment by both sides of virtually every
instrument of siege craft known to the classical world, including a
variety of catapults", to little effect, resulting in failure.
The most widely used catapults throughout the Middle Ages were as follows:
Ballistae were similar to giant crossbows and were designed to work
through torsion. The projectiles were large arrows or darts made from
wood with an iron tip. These arrows were then shot "along a flat
trajectory" at a target. Ballistae were accurate, but lacked firepower
compared with that of a mangonel or trebuchet. Because of their
immobility, most ballistae were constructed on site following a siege
assessment by the commanding military officer.
The springald's design resembles that of the ballista, being a
crossbow powered by tension. The springald's frame was more compact,
allowing for use inside tighter confines, such as the inside of a castle
or tower, but compromising its power.
This machine was designed to throw heavy projectiles from a
"bowl-shaped bucket at the end of its arm". Mangonels were mostly used
for “firing various missiles at fortresses, castles, and cities,” with a
range of up to 1,300 ft (400 m). These missiles included anything from
stones to excrement to rotting carcasses. Mangonels were relatively
simple to construct, and eventually wheels were added to increase
mobility.
Mangonels are also sometimes referred to as Onagers. Onager
catapults initially launched projectiles from a sling, which was later
changed to a "bowl-shaped bucket". The word Onager is derived from the Greek word onagros for "wild ass", referring to the "kicking motion and force"
that were recreated in the Mangonel's design. Historical records
regarding onagers are scarce. The most detailed account of Mangonel use
is from “Eric Marsden's translation of a text written by Ammianus
Marcellius in the 4th Century AD” describing its construction and combat
usage.
Mongol warriors using trebuchet to besiege a city
Trebuchets were probably the most powerful catapult employed in the
Middle Ages. The most commonly used ammunition were stones, but "darts
and sharp wooden poles" could be substituted if necessary. The most
effective kind of ammunition though involved fire, such as "firebrands,
and deadly Greek Fire".
Trebuchets came in two different designs: Traction, which were powered
by people, or Counterpoise, where the people were replaced with "a
weight on the short end". The most famous historical account of trebuchet use dates back to the siege of Stirling Castle in 1304, when the army of Edward I constructed a giant trebuchet known as Warwolf, which then proceeded to "level a section of [castle] wall, successfully concluding the siege".
A simplified trebuchet, where the trebuchet's single counterweight is split, swinging on either side of a central support post.
Leonardo da Vinci's catapult
Leonardo da Vinci sought to improve the efficiency and range of earlier designs. His design incorporated a large wooden leaf spring as an accumulator to power the catapult. Both ends of the bow are connected by a rope, similar to the design of a bow and arrow.
The leaf spring was not used to pull the catapult armature directly,
rather the rope was wound around a drum. The catapult armature was
attached to this drum which would be turned until enough potential
energy was stored in the deformation of the spring. The drum would then
be disengaged from the winding mechanism, and the catapult arm would
snap around. Though no records exist of this design being built during Leonardo's lifetime, contemporary enthusiasts have reconstructed it.
The last large scale military use of catapults was during the trench warfare of World War I. During the early stages of the war, catapults were used to throw hand grenades across no man's land into enemy trenches. They were eventually replaced by small mortars.
The SPBG (Silent Projector of Bottles and Grenades) was a soviet
proposal anti-tank weapon that launched grenades from a spring loaded
shuttle up to 100 m (330 ft).
In the 1840s, the invention of vulcanizedrubber
allowed the making of small hand-held catapults, either improvised from
Y-shaped sticks or manufactured for sale; both were popular with
children and teenagers. These devices were also known as slingshots in the United States.
Special variants called aircraft catapults
are used to launch planes from land bases and sea carriers when the
takeoff runway is too short for a powered takeoff or simply impractical
to extend. Ships also use them to launch torpedoes and deploy bombs against submarines. Small catapults, referred to as "traps", are still widely used to launch clay targets into the air in the sport of clay pigeon shooting.
Entertainment
In the 1990s and early 2000s, a powerful catapult, a trebuchet, was
used by thrill-seekers first on private property and in 2001–2002 at
Middlemoor Water Park, Somerset, England, to experience being catapulted
through the air for 100 feet (30 m). The practice has been discontinued
due to a fatality at the Water Park. There had been an injury when the
trebuchet was in use on private property. Injury and death occurred when
those two participants failed to land onto the safety net.
The operators of the trebuchet were tried, but found not guilty of
manslaughter, though the jury noted that the fatality might have been
avoided had the operators "imposed stricter safety measures."Human cannonballcircus acts use a catapult launch mechanism, rather than gunpowder, and are risky ventures for the human cannonballs.
Early launched roller coasters used a catapult system powered by a diesel engine or a dropped weight to acquire their momentum, such as Shuttle Loop installations between 1977 and 1978. The catapult system for roller coasters has been replaced by flywheels and later linear motors.
Pumpkin chunking
is another widely popularized use, in which people compete to see who
can launch a pumpkin the farthest by mechanical means (although the
world record is held by a pneumatic air cannon).
Other
In January 2011, a homemade catapult was discovered that was used to smugglecannabis
into the United States from Mexico. The machine was found 20 ft (6.1 m)
from the border fence with 4.4 pounds (2.0 kg) bales of cannabis ready
to launch.
In artificial heart valve is a one-way valveimplanted into a person's heart to replace a heart valve that is not functioning properly (valvular heart disease).
Artificial heart valves can be separated into three broad classes:
mechanical heart valves, bioprosthetic tissue valves and engineered
tissue valves.
The human heart contains four valves: tricuspid valve, pulmonary valve, mitral valve and aortic valve.
Their main purpose is to keep blood flowing in the proper direction
through the heart, and from the heart into the major blood vessels
connected to it (the pulmonary artery and the aorta). Heart valves can malfunction for a variety of reasons, which can impede the flow of blood through the valve (stenosis) and/or let blood flow backwards through the valve (regurgitation). Both processes put strain on the heart and may lead to serious problems, including heart failure. While some dysfunctional valves can be treated with drugs or repaired, others need to be replaced with an artificial valve.
Background
3D Medical Animation still shot of Artificial Heart Valve
A heart contains four valves (tricuspid, pulmonary, mitral and aortic
valves) which open and close as blood passes through the heart. Blood enters the heart in the right atrium and passes through the tricuspid valve to the right ventricle. From there, blood is pumped through the pulmonary valve to enter the lungs. After being oxygenated, blood passes to the left atrium, where is it pumped through the mitral valve to the left ventricle. The left ventricle pumps blood to the aorta through the aortic valve.
There are many potential causes of heart valve damage, such as
birth defects, age related changes, and effects from other disorders,
such as rheumatic fever and infections causing endocarditis. High blood pressure and heart failure which can enlarge the heart and arteries, and scar tissue can form after a heart attack or injury.
The three main types of artificial heart valves are mechanical,
biological (bioprosthetic/tissue), and tissue-engineered valves. In the
US, UK and the European Union, the most common type of artificial heart
valve is the bioprosthetic valve. Mechanical valves are more commonly
used in Asia and Latin America. Companies that manufacture heart valves include Edwards Lifesciences, Medtronic, Abbott (St. Jude Medical), CryoLife, and LifeNet Health.
Mechanical valves
Mechanical
valves come in three main types – caged ball, tilting-disc and
bileaflet – with various modifications on these designs. Caged ball valves are no longer implanted. Bileaflet valves are the most common type of mechanical valve implanted in patients today.
Caged ball valves
Caged ball valve
The first artificial heart valve was the caged ball valve, a type of ball check valve,
in which a ball is housed inside a cage. When the heart contracts and
the blood pressure in the chamber of the heart exceeds the pressure on
the outside of the chamber, the ball is pushed against the cage and
allows blood to flow. When the heart finishes contracting, the pressure
inside the chamber drops and the ball moves back against the base of the
valve forming a seal.
In 1952, Charles A. Hufnagel
implanted caged ball heart valves into ten patients (six of whom
survived the operation), marking the first success in prosthetic heart
valves. A similar valve was invented by Miles 'Lowell' Edwards and Albert Starr in 1960, commonly referred to as the Starr-Edwards silastic ball valve. This consisted of a silicone ball enclosed in a methyl metacrylate
cage welded to a ring. The Starr-Edwards valve was first implanted in a
human on August 25, 1960, and was discontinued by Edwards Lifesciences
in 2007.
Caged ball valves are strongly associated with blood clot formation, so people who have one required a high degree of anticoagulation, usually with a target INR of 3.0–4.5.
Tilting-disc valves
tilting-disc valve
Introduced in 1969, the first clinically available tilting-disc valve was the Bjork-Shiley valve. Tilting‑disc valves, a type of swing check valve, are made of a metal ring covered by an ePTFE
fabric. The metal ring holds, by means of two metal supports, a disc
that opens when the heart beats to let blood flow through, then closes
again to prevent blood flowing backwards. The disc is usually made of an
extremely hard carbon material (pyrolytic carbon), enabling the valve to function for years without wearing out.
Bileaflet valves
Bileaflet valve
Introduced in 1979, bileaflet valves are made of two semicircular
leaflets that revolve around struts attached to the valve housing. With a
larger opening than caged ball or tilting-disc valves, they carry a
lower risk of blood clots. They are, however, vulnerable to blood
backflow.
Advantages of mechanical valves
The major advantage of mechanical valves over bioprosthetic valves is their greater durability. Made from metal and/or pyrolytic carbon, they can last 20–30 years.
Disadvantages of mechanical valves
One of the major drawbacks of mechanical heart valves is that they are associated with an increased risk of blood clots. Clots formed by red blood cell and platelet damage can block blood vessels leading to stroke. People with mechanical valves need to take anticoagulants (blood thinners), such as warfarin, for the rest of their life. Mechanical heart valves can also cause mechanical hemolytic anemia, a condition where the red blood cells are damaged as they pass through the valve. Cavitation,
the rapid formation of microbubbles in a fluid such as blood due to a
localized drop of pressure, can lead to mechanical heart valve failure, so cavitation testing is an essential part of the valve design verification process.
Many of the complications associated with mechanical heart valves can be explained through fluid mechanics.
For example, blood clot formation is a side effect of high shear
stresses created by the design of the valves. From an engineering
perspective, an ideal heart valve would produce minimal pressure drops,
have small regurgitation volumes, minimize turbulence, reduce prevalence
of high stresses, and not create flow separations in the vicinity of
the valve.
Implanted mechanical valves can cause foreign body rejection. The
blood may coagulate and eventually result in a hemostasis. The usage of
anticoagulation drugs will be interminable to prevent thrombosis.
Bioprosthetic tissue valves
Bioprosthetic valves are usually made from animal tissue (heterograft/xenograft) attached to a metal or polymer support. Bovine (cow) tissue is most commonly used, but some are made from porcine (pig) tissue. The tissue is treated to prevent rejection and calcification.
Alternatives to animal tissue valves are sometimes used, where valves are used from human donors, as in aortic homografts and pulmonary autografts.
An aortic homograft is an aortic valve from a human donor, retrieved
either after their death or from a heart that is removed to be replaced
during a heart transplant. A pulmonary autograft, also known as the Ross procedure, is where the aortic valve is removed and replaced with the patient's own pulmonary valve
(the valve between the right ventricle and the pulmonary artery). A
pulmonary homograft (a pulmonary valve taken from a cadaver) is then
used to replace the patient's own pulmonary valve. This procedure was
first performed in 1967 and is used primarily in children, as it allows
the patient's own pulmonary valve (now in the aortic position) to grow
with the child.
Advantages of bioprosthetic heart valves
Bioprosthetic
valves are less likely than mechanical valves to cause blood clots, so
do not require lifelong anticoagulation. As a result, people with
bioprosthetic valves have a lower risk of bleeding than those with
mechanical valves.
Disadvantages of bioprosthetic heart valves
Tissue valves are less durable than mechanical valves, typically lasting 10–20 years.
This means that people with bioprosthetic valves have a higher
incidence of requiring another aortic valve replacement in their
lifetime. Bioprosthetic valves tend to deteriorate more quickly in younger patients.
In recent years, scientists have developed a new tissue
preservation technology, with the aim of improving the durability of
bioprosthetic valves. In sheep and rabbit studies, tissue preserved
using this new technology had less calcification than control tissue. A valve containing this tissue is now marketed, but long-term durability data in patients are not yet available.
Current bioprosthetic valves lack longevity, and will calcify over time. When a valve calcifies, the valve cusps become stiff and thick and cannot close completely.
Moreover, bioprosthetic valves can't grow with or adapt to the patient:
if a child has bioprosthetic valves they will need to get the valves
replaced several times to fit their physical growth.
Tissue-engineered valves
For over 30 years researchers have been trying to grow heart valves in vitro. These tissue‑engineered valves involve seeding human cells on to a scaffold.
The two main types of scaffold are natural scaffolds, such as
decellularized tissue, or scaffolds made from degradable polymers. The scaffold acts as an extracellular matrix, guiding tissue growth into the correct 3D structure of the heart valve. Some tissue-engineered heart valves have been tested in clinical trials, but none are commercially available.
Tissue engineered heart valves can be person-specific and 3D modeled to fit an individual recipient 3D printing is used because of its high accuracy and precision of dealing with different biomaterials. Cells that are used for tissue engineered heart valves are expected to secrete the extracellular matrix (ECM). Extracellular matrix provides support to maintain the shape of the valves and determines the cell activities.
Scientists can follow the structure of heart valves to produce
something that looks similar to them, but since tissue engineered valves
lack the natural cellular basis, they either fail to perform their
functions like natural heart valves, or function when they are implanted
but gradually degrade over time.
An ideal tissue engineered heart valve would be non‐thrombogenic,
biocompatible, durable, resistant to calcification, grow with the
surrounding heart, and exhibit a physiological hemodynamic profile.
To achieve these goals, the scaffold should be carefully chosen—there
are three main candidates: decellularized ECM (xenografts or
homografts), natural polymers, and synthetic polymers.
Differences between mechanical and tissue valves
Mechanical and tissue valves are made of different materials. Mechanical valves are generally made of titanium and carbon.
Tissue valves are made up of human or animal tissue. The valves
composed of human tissue, known as allografts or homografts, are from
donors' human hearts.
Mechanical valves can be a better choice for younger people and
people at risk of valve deterioration due to its durability. It is also
preferable for people who are already taking blood thinners and people
who would be unlikely to tolerate another valve replacement operation.
Tissue valves are better for older age groups as another valve
replacement operation may not be needed in their lifetime. Due to the
risk of forming blood clots for mechanical valves and severe bleeding as
a major side effect of taking blood-thinning medications, people who
have a risk of blood bleeding and are not willing to take warfarin may
also consider tissue valves. Other patients who may be more suitable for
tissue valves are people who have other planned surgeries and unable to
take blood-thinning medications. People who plan to become pregnant may
also consider tissue valves as warfarin causes risks in pregnancy.
Functional requirements of artificial heart valves
An artificial heart valve should ideally function like a natural heart valve. The functioning of natural heart valves is characterized by many advantages:
Minimal regurgitation – This means that the amount of blood
leaking backwards through the valve as it closes is small. Some degree
of valvular regurgitation is inevitable and natural, up to around 5 ml
per beat. However, several heart valve pathologies (e.g. rheumatic endocarditis)
may lead to clinically significant valvular regurgitation. A desirable
characteristic of heart valve prostheses is that regurgitation is
minimal over the full range of physiological heart function.
Minimal transvalvular pressure gradient – Whenever a fluid flows through a restriction, such as a valve, a pressuregradient
arises over the restriction. This pressure gradient is a result of the
increased resistance to flow through the restriction. Natural heart
valves have a low transvalvular pressure gradient as they present little
obstruction to the flow through themselves, normally less than 16 mmHg.
A desirable characteristic of heart valve prostheses is that their
transvalvular pressure gradient is as small as possible.
Non-thrombogenic – Natural heart valves are lined with an endothelium
comparable with the endothelium lining the heart chambers, so they are
not normally thrombogenic (i.e. they don't cause blood clots). Blood
clots can be hazardous because they can lodge in, and block, downstream arteries (e.g. coronary arteries, leading to heart attack [myocardial infarction]; or cerebral arteries, leading to stroke). A desirable characteristic of artificial heart valves is that they are non- or minimally thrombogenic.
Self-repairing – Valve leaflets retain some capacity for repair thanks to regenerative cells (e.g. fibroblasts) in the connective tissue from which the leaflets are composed. As the human heart beats approximately 3.4×109
times during a typical human lifespan, this limited but nevertheless
present repair capacity is critically important. No heart valve
prostheses can currently self-repair, but tissue-engineered valves may
eventually offer such capabilities.
Artificial heart valve repair
Artificial heart valves are expected to last from 10 to 30 years.
The most common problems with artificial heart valves are various
forms of degeneration, including gross billowing of leaflets, ischemic
mitral valve pathology, and minor chordal lengthening.
The repairing process of the artificial heart valve regurgitation and
stenosis usually requires an open-heart surgery, and a repair or partial
replacement of regurgitant valves is usually preferred.
Researchers are investigating catheter-based surgery that allows repair of an artificial heart valve without large incisions.
Researchers are investigating Interchangeable Prosthetic Heart
Valve that allows redo and fast-track repair of an artificial heart
valve.
Additional images
3D Rendering of Mechanical Valve
3D Rendering of Mechanical Valve (St. Francis model)
Surgery on the great vessels (e.g., aortic coarctation repair, Blalock–Thomas–Taussig shunt creation, closure of patent ductus arteriosus) became common after the turn of the century. However, operations on the heart valves were unknown until, in 1925, Henry Souttar operated successfully on a young woman with mitral valve stenosis. He made an opening in the appendage of the left atrium and inserted a finger in order to palpate and explore the damaged mitral valve. The patient survived for several years, but Souttar's colleagues considered the procedure unjustified, and he could not continue.
Cardiac surgery changed significantly after World War II. In 1947, Thomas Sellors of Middlesex Hospital in London operated on a Tetralogy of Fallot patient with pulmonary stenosis and successfully divided the stenosed pulmonary valve. In 1948, Russell Brock, probably unaware of Sellors's work,
used a specially designed dilator in three cases of pulmonary stenosis.
Later that year, he designed a punch to resect a stenosed infundibulum,
which is often associated with Tetralogy of Fallot. Many thousands of
these "blind" operations were performed until the introduction of cardiopulmonary bypass made direct surgery on valves possible.
Also in 1948, four surgeons carried out successful operations for mitral valve stenosis resulting from rheumatic fever. Horace Smithy of Charlotte used a valvulotome to remove a portion of a patient's mitral valve, while three other doctors—Charles Bailey of Hahnemann University Hospital in Philadelphia; Dwight Harken in Boston; and Russell Brock of Guy's Hospital
in London—adopted Souttar's method. All four men began their work
independently of one another within a period of a few months. This time,
Souttar's technique was widely adopted, with some modifications.
Open-heart
surgery is any kind of surgery in which a surgeon makes a large
incision (cut) in the chest to open the rib cage and operate on the
heart. "Open" refers to the chest, not the heart. Depending on the type
of surgery, the surgeon also may open the heart.
Dr. Wilfred G. Bigelow of the University of Toronto
found that procedures involving opening the patient's heart could be
performed better in a bloodless and motionless environment. Therefore,
during such surgery, the heart is temporarily stopped, and the patient
is placed on cardiopulmonary bypass,
meaning a machine pumps their blood and oxygen. Because the machine
cannot function the same way as the heart, surgeons try to minimize the
time a patient spends on it.
Cardiopulmonary bypass was developed after surgeons realized the limitations of hypothermia
in cardiac surgery: Complex intracardiac repairs take time, and the
patient needs blood flow to the body (particularly to the brain), as
well as heart and lung function. In July 1952, Forest Dodrill
was the first to use a mechanical pump in a human to bypass the left
side of the heart whilst allowing the patient's lungs to oxygenate the
blood, in order to operate on the mitral valve. In 1953, Dr. John Heysham Gibbon of Jefferson Medical School in Philadelphia reported the first successful use of extracorporeal circulation by means of an oxygenator, but he abandoned the method after subsequent failures.
In 1954, Dr. Lillehei performed a series of successful operations with
the controlled cross-circulation technique, in which the patient's
mother or father was used as a "heart-lung machine". Dr. John W. Kirklin at the Mayo Clinic was the first to use a Gibbon-type pump-oxygenator.
Nazih Zuhdi performed the first total intentional hemodilution
open-heart surgery on Terry Gene Nix, age 7, on 25 February 1960 at
Mercy Hospital in Oklahoma City. The operation was a success; however,
Nix died three years later. In March 1961, Zuhdi, Carey, and Greer performed open-heart surgery on a child, aged 3+1⁄2, using the total intentional hemodilution machine.
Modern beating-heart surgery
In the early 1990s, surgeons began to perform off-pump coronary artery bypass,
done without cardiopulmonary bypass. In these operations, the heart
continues beating during surgery, but is stabilized to provide an almost
still work area in which to connect a conduit vessel that bypasses a
blockage. The conduit vessel that is often used is the Saphenous vein.
This vein is harvested using a technique known as endoscopic vessel harvesting (EVH).
Heart transplant
In
1945, the Soviet pathologist Nikolai Sinitsyn successfully transplanted
a heart from one frog to another frog and from one dog to another dog.
Coronary artery bypass grafting,
also called revascularization, is a common surgical procedure to create
an alternative path to deliver blood supply to the heart and body, with
the goal of preventing clot formation. This can be done in many ways, and the arteries used can be taken from several areas of the body.
Arteries are typically harvested from the chest, arm, or wrist and then
attached to a portion of the coronary artery, relieving pressure and
limiting clotting factors in that area of the heart.
The procedure is typically performed because of coronary artery disease
(CAD), in which a plaque-like substance builds up in the coronary
artery, the main pathway carrying oxygen-rich blood to the heart. This
can cause a blockage and/or a rupture, which can lead to a heart attack.
Minimally invasive surgery
As an alternative to open-heart surgery, which involves a five- to eight-inch incision in the chest wall, a surgeon may perform an endoscopic procedure by making very small incisions through which a camera and specialized tools are inserted.
In robot-assisted heart surgery,
a machine controlled by a cardiac surgeon is used to perform a
procedure. The main advantage to this is the size of the incision
required: three small port holes instead of an incision big enough for
the surgeon's hands.
The use of robotics in heart surgery continues to be evaluated, but
early research has shown it to be a safe alternative to traditional
techniques.
Post-surgical procedures
As
with any surgical procedure, cardiac surgery requires postoperative
precautions to avoid complications. Incision care is needed to avoid
infection and minimize scarring. Swelling and loss of appetite are common.
Recovery from open-heart surgery begins with about 48 hours in an intensive care unit, where heart rate, blood pressure,
and oxygen levels are closely monitored. Chest tubes are inserted to
drain blood around the heart and lungs. After discharge from the
hospital, compression socks may be recommended in order to regulate blood flow.
Risks
The
advancement of cardiac surgery and cardiopulmonary bypass techniques has
greatly reduced the mortality rates of these procedures. For instance,
repairs of congenital heart defects are currently estimated to have 4–6%
mortality rates.
A major concern with cardiac surgery is neurological damage. Stroke occurs in 2–3% of all people undergoing cardiac surgery, and the rate is higher in patients with other risk factors for stroke. A more subtle complication attributed to cardiopulmonary bypass is postperfusion syndrome, sometimes called "pumphead". The neurocognitive symptoms of postperfusion syndrome were initially thought to be permanent, but turned out to be transient, with no permanent neurological impairment.
In order to assess the performance of surgical units and individual surgeons, a popular risk model has been created called the EuroSCORE. It takes a number of health factors from a patient and, using precalculated logistic regression coefficients, attempts to quantify the probability that they will survive to discharge. Within the United Kingdom, the EuroSCORE was used to give a breakdown of all cardiothoracic surgery
centres and to indicate whether the units and their individuals
surgeons performed within an acceptable range. The results are available
on the Care Quality Commission website.
Pharmacological and non-pharmacological
prevention approaches may reduce the risk of atrial fibrillation after
an operation and reduce the length of hospital stays, however there is
no evidence that this improves mortality.
Non-pharmacologic approaches
Preoperative physical therapy may reduce postoperative pulmonary complications, such as pneumonia and atelectasis,
in patients undergoing elective cardiac surgery and may decrease the
length of hospital stay by more than three days on average. There is evidence that quitting smoking at least four weeks before surgery may reduce the risk of postoperative complications.
Pharmacological approaches
Beta-blocking
medication is sometimes prescribed during cardiac surgery. There is
some low certainty evidence that this perioperative blockade of
beta-adrenergic receptors may reduce the incidence of atrial fibrillation and ventricular arrhythmias in patients undergoing cardiac surgery.
Vascular surgery is a surgical subspecialty in which vascular diseases involving the arteries, veins, or lymphatic vessels,
are managed by medical therapy, minimally-invasive catheter procedures
and surgical reconstruction. The specialty evolved from general and cardiovascular surgery
where it refined the management of just the vessels, no longer treating
the heart or other organs. Modern vascular surgery includes open
surgery techniques, endovascular (minimally invasive) techniques and
medical management of vascular diseases - unlike the parent
specialities. The vascular surgeon is trained in the diagnosis and
management of diseases affecting all parts of the vascular system
excluding the coronaries and intracranial vasculature. Vascular surgeons
also are called to assist other physicians to carry out surgery near
vessels, or to salvage vascular injuries that include hemorrhage
control, dissection, occlusion or simply for safe exposure of vascular
structures.
History
Early leaders of the field included Russian surgeon Nikolai Korotkov, noted for developing early surgical techniques, American interventional radiologistCharles Theodore Dotter
who is credited with inventing minimally invasive angioplasty (1964),
and Australian Robert Paton, who helped the field achieve recognition as
a specialty. Edwin Wylie of San Francisco was one of the early American
pioneers who developed and fostered advanced training in vascular
surgery and pushed for its recognition as a specialty in the United
States in the 1970s. The most notable historic figure in vascular
surgery is the 1912 Nobel Prize winning surgeon, Alexis Carrel for his techniques used to suture vessels.
Evolution
Medical science has advanced significantly since 1507, when Leonardo da Vinci drew this diagram of the internal organs and vascular systems of a woman.
The specialty continues to be based on operative arterial and venous
surgery but since the early 1990s has evolved greatly. There is now
considerable emphasis on minimally invasive alternatives to surgery. The
field was originally pioneered by interventional radiologists like Dr. Charles Dotter, who invented angioplasty using serial dilatation of vessels.
The surgeon Dr. Thomas J. Fogarty invented a balloon catheter,
designed to remove clots from occluded vessels, which was used as the
eventual model to do endovascular angioplasty. Further development of
the field has occurred via joint efforts between interventional radiology, vascular surgery, and interventional cardiology.
This area of vascular surgery is called Endovascular Surgery or
Interventional Vascular Radiology, a term that some in the specialty
append to their primary qualification as Vascular Surgeon. Endovascular
and endovenous procedures (e.g., EVAR) can now form the bulk of a vascular surgeon's practice.
The treatment of the aorta, the body's largest artery, dates back
to Greek surgeon Antyllus, who first performed surgeries for various
aneurysms in the second century AD. Modern treatment of aortic diseases
stems from development and advancements from Michael DeBakey and Denton Cooley.
In 1955, DeBakey and Cooley performed the first replacement of a
thoracic aneurysm with a homograft. In 1958, they began using the Dacron
graft, resulting in a revolution for surgeons in the repair of aortic
aneurysms. He also was first to perform cardiopulmonary bypass to repair
the ascending aorta, using antegrade perfusion of the brachiocephalic
artery.
Dr. Ted Diethrich, one of Dr. DeBakey's associates, went on to pioneer many of the minimally invasive techniques that later became hallmarks of endovascular surgery. Dietrich later founded the Arizona Heart Hospital
in 1998 and served as its medical director from 1998 to 2010. In 2000,
Diethrich performed the first endovascular aneurysm repair (EVAR) for
ruptured abdominal aortic aneurysm. Dietrich trained several future
leaders in the field of endovascular surgery at the Arizona Heart
Hospital including Venkatesh Ramaiah, MD who served as medical director of the institution following Dietrich's death in 2017.
The development of endovascular surgery has been accompanied by a gradual separation of vascular surgery from its origin in general surgery.
Most vascular surgeons would now confine their practice to vascular
surgery and, similarly, general surgeons would not be trained or
practise the larger vascular surgery operations or most endovascular
procedures. More recently, professional vascular surgery societies and
their training program have formally separated vascular surgery into a
separate specialty with its own training program, meetings and
accreditation. Notable societies are Society for Vascular Surgery
(SVS), USA; Australia and New Zealand Society of Vascular Surgeons
(ANZSVS). Local societies also exist (e.g., New South Wales Vascular and
Melbourne Vascular Surgical Association (MVSA)). Larger societies of
surgery actively separate and encourage specialty surgical societies
under their umbrella (e.g., Royal Australasian College of Surgeons (RACS)).
Currently
Arterial and venous disease treatment by angiography, stenting, and non-operative varicose vein treatment sclerotherapy, endovenous laser treatment
have largely replaced major surgery in many first world countries.
These procedures provide reasonable outcomes that are comparable to
surgery with the advantage of short hospital stay (day or overnight for
most cases) with lower morbidity and mortality rates. Historically
performed by interventional radiologists, vascular surgeons have become
increasingly proficient with endovascular methods.
The durability of endovascular arterial procedures is generally good,
especially when viewed in the context of their common clinical usage
i.e. arterial disease occurring in elderly patients and usually
associated with concurrent significant patient comorbidities especially
ischemic heart disease. The cost savings from shorter hospital stays and
less morbidity are considerable but are somewhat balanced by the high
cost of imaging equipment, construction and staffing of dedicated
procedural suites, and of the implant devices themselves.
The benefits for younger patients and in venous disease are less
persuasive but there are strong trends towards nonoperative treatment
options driven by patient preference, health insurance company costs,
trial demonstrating comparable efficacy at least in the medium term.
A recent trend in the United States is the stand-alone day
angiography facility associated with a private vascular surgery clinic,
thus allowing treatment of most arterial endovascular cases conveniently
and possibly with lesser overall community cost.
Similar non-hospital treatment facilities for non-operative vein
treatment have existed for some years and are now widespread in many
countries.
NHS England
conducted a review of all 70 vascular surgery sites across England in
2018 as part of its Getting It Right First Time programme. The review
specified that vascular hubs should perform at least 60 abdominal aortic
aneurysm procedures and 40 carotid endarterectomies a year. 12 trusts
missed both targets and many more missed one of them. A programme of
concentrating vascular surgery in fewer centres is proceeding.
Infrarenal aortic occlusion imaged with magnetic resonance angiography (MRA).
The management of arterial pathology excluding coronary and
intracranial disease is within the scope of vascular surgeons. Disease
states generally arise from narrowing of the arterial system known as stenosis or abnormal dilation referred to as an aneurysm. There are multiple mechanisms by which the arterial lumen can narrow, the most common of which is atherosclerosis. Symptomatic stenosis may also result from a complication of arterial dissection. Other less common causes of stenosis include fibromuscular dysplasia,
radiation induced fibrosis or cystic adventitial disease. Dilation of
an artery which retains histologic layers is called an aneurysm. An
aneurysms can be fusiform (concentric dilation), saccular (outpouching)
or a combination of the two. Arterial dilation which does not contain
three histologic layers is considered a pseudoaneurysm.
Additionally, there are a number of congenital vascular anomalies which
lead to symptomatic disease that are managed by the vascular surgeon, a
few of which include aberrant subclavian artery, popliteal artery entrapment syndrome or persistent sciatic artery.
Vascular surgeons treat arterial diseases with a range of therapies
including lifestyle modification, medications, endovascular therapy and
surgery.
The aorta is the largest artery in the body and the descending aorta has both a thoracic and an abdominal component. A thoracic aortic aneurysm is located in the chest, and an abdominal aortic aneurysm
is located in the abdomen. Not pictured here are aneurysms which span
both cavities and are referred to as thoracoabdominal aortic aneurysms.
Abdominal
An abdominal aortic aneurysm
(AAA) refers to aneurysmal dilation of the aorta confined to the
abdominal cavity. Most commonly, aneurysms are asymptomatic and located
in the infrarenal position. Often, they are discovered incidentally or
on screening exams in patients with risk factors such as a history of
smoking. Patients with aneurysms which have a diameter less than 5 cm
are at <1% rupture risk per year. When the aneurysm meets size
criteria it can be treated with aortic replacement or EVAR.
Thoracic
Thoracic aortic aneurysms are contained in the chest. Aneurysms of the descending aorta can often be treated with thoracic endovascular aortic repair or TEVAR.
Treating aneurysms which involve the ascending aorta are generally
within the scope of cardiac surgeons, but upcoming endovascular
technology may allow for a more minimally invasive approach in some
patients.
Thoracoabdominal
Thoroacoabdominal aneurysms are those which span the chest and abdominal cavities. The Crawford classification was developed and describes five types of thoracoabdominal aneurysms.
Abdominal aortic aneurysms can be classified as infrarenal, juxtarenal, pararenal or suprarenal as depicted in the illustration.
The Crawford Classification (Extent I-IV) and the Safi modification
(Extent V) for thoracoabdominal aortic aneurysms is pictured above.
Other arterial aneurysms
In addition to treating aneurysms which arise from the aorta, vascular surgeons also treat aneurysms elsewhere in the body.
Indications for repair differ slightly between arteries. For
instance, current guidelines recommend repair of renal and splenic
artery aneurysms greater than 3 cm, and those of any size in women of
childbearing age; whereas celiac and hepatic artery aneurysms are
indicated for repair when their size is greater than 2 cm. This is in
contrast to superior mesenteric artery aneurysms which should be
repaired regardless of size when they are discovered.
Popliteal artery
A popliteal artery aneurysm is an arterial aneurysm localized in the popliteal artery which courses behind the knee. Unlike aneurysms located in the abdomen, popliteal artery aneurysm rarely present with rupture but rather with symptoms of acute limb ischemia
due to embolization of thrombus. Thus, when a patient presents with an
asymptomatic popliteal aneurysm that is greater than 2 cm in diameter a
vascular surgeon are able to offer vascular bypass or endovascular
exclusion depending on several factors.
Early
classification schemes of aortic dissection. Stanford type A are those
which originate in the ascending aorta whereas Stanford type B originate
distal to the left subclavian artery (descending aorta). The Debakey classification describes where the original tear is and the extent of the dissection.
Whereas cardiac surgeons
are usually in charge of managing type A dissections, type B
dissections are typically managed by vascular surgeons. The most common
risk factor for type B aortic dissection is hypertension. The first line treatment for type B aortic dissection is aimed at reducing both heart rate and blood pressure and is referred to as anti-impulse therapy.
A thoracic aortic stent graft, seen on chest X-ray which was placed during a TEVAR procedure.
Should initial medical management fail or there is the involvement of
a major branch of the aorta, vascular surgery may be needed for these
type B dissections. Treatment may include thoracic endovascular aortic
repair (TEVAR) with or without extra-anatomic bypass such as carotid-carotid bypass, carotid-subclavian bypass, or subclavian-carotid transposition.
Visceral artery dissection
Visceral artery dissections are arterial dissections involving the superior mesenteric artery, celiac artery, renal arteries, hepatic artery
and others. When they are an extension of an aortic dissection, this
condition is managed simultaneously with aortic treatment. In isolation,
visceral artery dissections are discovered incidentally in up to a
third of patients and in these cases may be managed medically by a
vascular surgeon. In cases where the dissection results in organ damage
it is generally accepted by vascular surgeons that surgery is necessary.
Surgical management strategies depend on the associated complications,
surgical ability and patient preference.
Mesenteric ischemia
Mesenteric ischemia results from the acute or chronic obstruction of the superior mesenteric artery (SMA). The SMA arises from the abdominal aorta and usually supplies blood from the distal duodenum through two-thirds of the transverse colon and the pancreas.
Chronic mesenteric ischemia
The symptoms of chronic mesenteric ischemia can be classified as abdominal angina
which is abdominal pain which occurs a fixed period of time after
eating. Due to this, patient's may avoid eating, resulting in unintended
weight loss. The first surgical treatment is thought to be performed by
R.S. Shaw and described in the New England Journal of Medicine in 1958. The procedure Shaw described is referred to as mesenteric endarterectomy. Since then, many advances in treatment have been made in minimally invasive, endovascular techniques including angioplasty and stenting.
The
renal arteries supply oxygenated blood to the kidneys. The kidneys
serve to filter the flood and control blood pressure through the
renin-angiotensin system. One cause of resistant hypertension is
atherosclerotic disease in the renal arteries and is generally referred
to as renovascular hypertension.
If renovascular hypertension is diagnosed and maximal medical fails to
control high blood pressure, the vascular surgeon may offer surgical
treatment, either endovascular or open surgical reconstruction.
Cerebrovascular disease
Carotid ultrasound.Carotid endarterectomy.
Vascular surgeons are responsible for treating extracranial
cerebrovascular disease as well as the interpretation of non-invasive
vascular imaging relating to extracranial and intracranial circulation
such as carotid ultrasonography and transcranial doppler. The most common of cerebrovascular conditions treated by vascular surgeons is carotid artery stenosis which is a narrowing of the carotid arteries and may be either clinically symptomatic or asymptomatic (silent). Carotid artery stenosis is caused by atherosclerosis whereby the buildup of atheromatous plaque inside the artery causes narrowing.
Symptoms of carotid artery stenosis can include transient ischemic attack or stroke.
Both symptomatic and asymptomatic carotid stenosis can be diagnosed
with the aid of carotid duplex ultrasound which allows for the
estimation of severity of narrowing as well as characterize the plaque.
Treatment can include medical therapy, carotid endarterectomy or carotid stenting.
Peripheral artery disease PAD is the abnormal narrowing of the arteries which supply the limbs. Patients with this condition can present with intermittent claudication which is pain mainly in the calves and thighs while walking. If there is progression, a patient may also present with chronic limb threatening ischemia
which encompasses pain at rest and non-healing wounds. Vascular
surgeons are experts in the diagnosis, medical management, endovascular
and open surgical treatment of PAD.
Illustration of atherosclerosis causing arterial obstruction which clinically presents at peripheral artery disease.
ABI testing is used by vascular surgeons in the diagnosis of PAD. The blood pressure in the arm and leg are compared as a ratio.
Angioplasty (pictured) and stenting are two endovascular treatments employed by the vascular surgeon.
Management of venous diseases
Chronic venous disease
Chronic venous insufficiency
is the abnormal pooling of blood in the lower extremity venous system
which can lead to reticular veins, varicose veins, chronic edema and
inflammation among other things. Population data suggests that chronic
venous insufficiency affects up to 40% of females and 17% of males. When chronic insufficiency leads to pain, swelling and skin changes it is referred to as chronic venous disease. Chronic venous insufficiency (CVI) is distinguished from post-thrombotic syndrome (PTS) in that CVI is primarily an issue of valvular incompetence of the superficial or deep veins whereas PTS may occur as a long-term complication of deep venous thrombosis.
The vascular surgeon has several modalities to treat lower
extremity venous disease which including medical, interventional and
surgical procedures. For instance, venous ulceration may be treated with
Unna's boots, superficial venous reflux with radiofrequency, laser ablation or vein stripping
if indicated. When indicated, insufficiency in the deep veins may be
treated with reconstruction of the venous valves with internal or
external valvuloplasty.
Varicose veins
A medical illustration of lower extremity varicose veins.
Lower extremity varicose veins is the condition in which the superficial veins become tortuous(snakelike) and dilated (enlarged) to greater than 3mm in the upright position. Incompetent or faulty valves are often present in these veins when investigated with duplex ultrasonography. Vascular treatments can include compression stockings, venous ablation or vein stripping, depending on specific patient presentation, severity of disease, among other things.
Nonthrombotic iliac vein lesions
Nonthrombotic iliac vein lesions (NIVL) include May-Thurner Syndrome
(MTS) whereby there is compression of the left iliac venous outflow
usually by the right iliac artery leading to left leg discomfort, pain,
swelling and varicose veins. NIVL encompasses compression of the iliac
veins on either the right or left side.
Vascular surgeons may offer different treatment modalities depending on
the patient presentation. Minimally invasive diagnostic and therapeutic
options might include intravascular ultrasound, venography and iliac vein stenting whereas surgical management may be offered in refractory cases.
Surgical management strategies involve reconstruction or bypass of the
affected segment such as cross-pubic venous bypass, also known as the
Palma procedure.
Deep vein thrombosis
Deep vein thrombosis (DVT) is the formation of thrombus in a deep vein. DVT is more likely to occur in the lower extremity than the upper extremity or jugular vein. When a DVT involves the pelvic and lower extremity veins it can sometimes be classified as an iliofemoral DVT. Some evidence to suggests that performing an intervention in these cases may be beneficial whereas other evidence does not. Overall, the data shows that there may be a reduction in the incidence in post-thrombotic syndrome in patients who undergo certain procedures for iliofemoral DVT but it is not without risks.
A vascular surgeon may offer venogram, endovascular suction or
mechanical thrombectomy and in some cases pharmacomechanical
thrombectomy. Some lower extremity DVT can be severe enough to cause a condition called phlegmasia cerulea dolens or phlegmasia alba dolens
and can be limb-threatening events. When phlegmasia is present,
intervention is often warranted and may include venous thrombectomy.
Post-thrombotic syndrome
Post-thrombotic syndrome (PTS) is a medical condition that sometimes occurs as a long-term complication of DVT and is characterized by long term edema
and skin changes following DVT. Presenting symptoms may include
itchiness, pain, cramps and paresthesia. It is estimated that between
20% and 50% of patients will experience some degree of PTS. A treatment strategy for PTS may involve the use of compression stockings.
Pulmonary embolism
Surgical management of an acute pulmonary embolism (pulmonary thrombectomy)
is uncommon and has largely been abandoned because of poor long-term
outcomes. However, recently, it has gone through a resurgence with the
revision of the surgical technique and is thought to benefit certain
people. Chronic pulmonary embolism leading to pulmonary hypertension (known as chronic thromboembolic hypertension) is treated with a surgical procedure known as a pulmonary thromboendarterectomy.
Patients with chronic kidney disease may have progression of disease which requires renal replacement therapy to filter their blood. One strategy for this therapy is hemodialysis,
which is a procedure that involves filtering a patient's blood to
remove waste products and returning their blood back to them. One method
which avoids repeated arterial trauma is to create an arteriovenous fistula (AVF). The first procedure described for this purpose is named the Cimino fistula,
after one of the surgeons who first had success with it. Vascular
surgeons may create an AVF for a patient as well as undertake minimally
invasive procedures to ensure the fistula remains patent.
Management of vascular trauma
One
way that vascular trauma may be understood is by categorizing vascular
injury by three criteria: mechanism of injury, anatomical site of injury
and contextual circumstances. Mechanism of injury refers to etiology,
e.g. iatrogenic, blunt, penetrating, blast injury,
etc. Anatomical site functionally refers to whether there is
compressible versus non-compressible hemorrhage, while contextual
circumstances refers to injuries sustained in the civilian or military
realm. Each context can be further broken down: military into combatant
vs. noncombatant and civil into urban vs rural trauma.
This categorization scheme is of both epidemiologic and clinical
significance. For instance, arterial injury in military combatants
currently occurs predominantly in males in their twenties who are
exposed to improvised explosive devices or gunshot wounds; whereas in
the civilian realm, one study conducted in the United States showed the
most common mechanisms to include motor vehicle collisions, firearm
injuries, stab wounds and falls from heights.
Blunt thoracic aortic injury
Advances
in vascular surgery, specifically endovascular technologies, have led
to a dramatic change in the operative approach to blunt thoracic aortic injury (BTAI). BTAI results from a high speed insult to the thorax such as a motor vehicle collision
or a fall from a height. One widely-used classification scheme is based
on the extent of injury to the anatomic layers of the aorta as seen
with computed tomography angiography or intravascular ultrasound.
Grade 1 BTAI are those which tear the aortic intima; grade 2 injuries
refer to intramural hematoma; grade 3 injuries are pseudoaneurysm and
are only contained by adventitial tissue; and grade 4 refer to free
rupture of blood into the chest and surrounding tissue. When indicated, first line intervention involves TEVAR.
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