A diagram of a heart with an ECG indicator; diagrams like this are used in Cardiology.
Cardiology is the branch of medicine dealing with disorders of the heart and blood vessels. The field is commonly divided in the branches of congenital heart defects, coronary artery disease, heart failure, valvular heart disease and electrophysiology. Physicians specializing in this field of medicine are called cardiologists.
The term cardiology is derived from the Greek word καρδιά (transliterated as kardia and meaning heart or inner self).
Monday, January 8, 2007
Atrium (anatomy)
From Wikipedia, the free encyclopedia
In anatomy, the atrium (plural: atria) refers to a chamber or space. As such it may for example be the atrium of the lateral ventricle in the brain or, popularly, the blood collection chamber of a heart. It has a thin-walled structure that allows blood to return to the heart. There is at least one atrium in an animal with a closed circulatory system. In fish, the circulatory system is very simple: a two-chambered heart including one atrium and one ventricle. In other vertebrate groups, the circulatory system is much more complicated. Their circulatory systems are divided into two types: a three-chambered heart, with two atria and one ventricle, or a four-chambered heart, with two atria and two ventricles. The atrium's function in the circulatory system includes receiving blood as it returns to the heart to complete a circulating cycle, whereas the ventricle's function is to pump blood out of the heart to start a new cycle.
Human heart
Humans have a four chambered heart.
The right atrium receives de-oxygenated blood from the superior vena cava and inferior vena cava. The left atrium receives oxygenated blood from the left and right pulmonary veins.
The atria do not have valves at their inlets. As a result, a venous pulsation is normal and can be detected in the jugular vein (see: jugular venous pressure).
Internally, there is the rough musculae pectinati, crista terminalis which acts as a boundary inside the atrium and the smooth walled part derived from the sinus venosus. There is also a fossa ovalis in the interatrial septum which was used in the fetal period as a means of bypassing the lung.
There are two atria, one on either side of the heart. On the right side is the atrium that holds blood that needs oxygen. It sends blood to the right ventricle which sends it to the lungs for oxygen. After it comes back, it is sent to the left atrium. The blood is pumped from the left atrium and sent to the ventricle where it is sent out of the heart. It is then sent to all the rest of the body.
In anatomy, the atrium (plural: atria) refers to a chamber or space. As such it may for example be the atrium of the lateral ventricle in the brain or, popularly, the blood collection chamber of a heart. It has a thin-walled structure that allows blood to return to the heart. There is at least one atrium in an animal with a closed circulatory system. In fish, the circulatory system is very simple: a two-chambered heart including one atrium and one ventricle. In other vertebrate groups, the circulatory system is much more complicated. Their circulatory systems are divided into two types: a three-chambered heart, with two atria and one ventricle, or a four-chambered heart, with two atria and two ventricles. The atrium's function in the circulatory system includes receiving blood as it returns to the heart to complete a circulating cycle, whereas the ventricle's function is to pump blood out of the heart to start a new cycle.
Human heart
Humans have a four chambered heart.
The right atrium receives de-oxygenated blood from the superior vena cava and inferior vena cava. The left atrium receives oxygenated blood from the left and right pulmonary veins.
The atria do not have valves at their inlets. As a result, a venous pulsation is normal and can be detected in the jugular vein (see: jugular venous pressure).
Internally, there is the rough musculae pectinati, crista terminalis which acts as a boundary inside the atrium and the smooth walled part derived from the sinus venosus. There is also a fossa ovalis in the interatrial septum which was used in the fetal period as a means of bypassing the lung.
There are two atria, one on either side of the heart. On the right side is the atrium that holds blood that needs oxygen. It sends blood to the right ventricle which sends it to the lungs for oxygen. After it comes back, it is sent to the left atrium. The blood is pumped from the left atrium and sent to the ventricle where it is sent out of the heart. It is then sent to all the rest of the body.
Artificial heart
An AbioCor artificial heart
Artificial heartFrom Wikipedia, the free encyclopedia
An artificial heart is a prosthetic device that is implanted into the body to replace the original biological heart. It is distinct from a cardiac pump, which is an external device used to provide the functions of both the heart and the lungs. Thus, the cardiac pump need not be connected to both blood circuits. Also, a cardiac pump is only suitable for use not longer than a few hours, while for the artificial heart the current record is 17 months.
This synthetic replacement for an organic mammalian heart (usually human), remains one of the long-sought Holy Grails of modern medicine. Although the heart is conceptually a simple organ (basically a muscle that functions as a pump), it embodies complex subtleties that defy straightforward emulation using synthetic materials and power supplies. The obvious benefit of a functional artificial heart would be to lower the need for heart transplants, because the demand for donor hearts (as it is for all organs) always greatly exceeds supply. A heart-lung machine was used in 1953 during the first successful open heart surgery. Dr. John Heysham Gibbon performed the operation and developed the heart-lung substitute himself. Whether this could be counted as an artificial heart is a subject of debate. In either case, the first official artificial heart that was patented was done so by Paul Winchell in 1963. Winchell subsequently assigned the patent to the University of Utah, where Robert Jarvik ultimately used it as the model for his Jarvik-7. One of the innovations of the Jarvik-7 was the inner coating of rough material, the contribution of a man named David Gernes. This coating helped the blood to clot and coat the inside of the device, enabling a more natural blood flow. Early attempts prior to the Jarvik-7 were disappointing; hosts died within hours or days and/or suffered massive foreign-body rejection problems. Jarvik's human designs were more impressive but his patients succumbed as well; his first Jarvik-7 patient, 61-year-old retired dentist Barney Clark, survived for 112 days after it was implanted at the University of Utah on December 2, 1982. Another problem is that an artificial heart requires an external power supply such as a battery pack worn on the patient's waist; no design so far has been able to use the body's own natural biological energy.
After about 90 people received the Jarvik device, the artificial hearts were banned for permanent use in patients with heart failure, because most of the recipients could not live more than half a year. However, it is used temporarily for some heart transplantation candidates who cannot find a natural heart immediately but urgently need an efficiently working heart.
On July 2, 2001, Robert Tools received the first completely self-contained artificial heart transplant in a surgery done by University of Louisville doctors at Jewish Hospital in Louisville, Kentucky. It is called the AbioCor Implantable Replacement Heart. Tom Christerson survived for 17 months after his artificial heart transplant.
The Syncardia CardioWest total artificial heart (CW-TAH) was developed by University of Arizona researchers and approved for bridge-to-transplant use in 2004. It is the first implantable artificial heart to be approved by the U.S. Food and Drug Administration. The longest CW-TAH implantation went 602 days (approximately 20 months.) (1)
The AbioMed company of Danvers, Massachusetts produced the AbioCor device, which on September 6, 2006 became the first fully implantable artificial heart to be approved, albeit under Humanitarian Use Device rules.
Most doctors are confident that with increased understanding of the heart and continuing improvements in prosthetics engineering, computer science, electronics, battery technology, fuel cells, etc. that the practical artificial heart will be a reality sometime in the 21st century.
In fiction
The earliest example of a fictional artificial heart is the French pulp hero the Nyctalope.
In the fictional Star Trek universe, Captain Jean-Luc Picard had an artificial heart implanted in 2328, which was later replaced twice. Joseph Sisko, father of Benjamin Sisko, had several artificial organs, including a new aorta he received in 2372.
The British science fiction series Space: 1999 had a character, Victor Bergman (portrayed by Barry Morse), with an artificial heart. He was able to modify its rate of operation with a wrist-worn device.
The novels of Philip K. Dick feature the use of 'artiforgs' or artificial organs.
The German heavy metal band Accept wrote about artificial hearts in their album "Metal Heart" (1985).
In the 1987 movie Robocop, there is a commercial for an artificial heart clinic called "The Family Heart Center" where surgeons operate on persons and implant artificial hearts from "the complete line of hearts by Jensen and Yamaha," encouraging its customers "You pick the heart!" These hearts come with extended warranties, financing, and qualify for "health tax credit."
References
(1) N. Gray, Jr, C. Selzman. Current status of the total artificial heart. American Heart Journal, 152, (1):4-10. July 2006. link
FDA Approval Press Release September 5, 2006.
Further Reading
George B. Griffenhagen and Calvin H. Hughes. The history of the mechanical heart. Smithsonian Report for 1955, (Pub. 4241): 339-356, 1956.
Retrieved from "http://en.wikipedia.org/wiki/Artificial_heart"
Heart cancer
From Wikipedia, the free encyclopedia
Heart cancer is a extremely rare form of cancer of the heart. Heart cancer is divided into primary tumors of the heart and secondary tumors of the heart. Most heart cancers are benign myxomas, fibromas, rhabdomyomas and hamartomas, although malignant sarcomas (such as angiosarcoma or cardiac sarcoma) have been known to occur. In a study of 12,487 autopsies performed in Hong Kong seven cardiac tumors were found, most of which were benign. However, cancer can also spread to heart from other parts of the body. In addition the heart can be affected by treatment for cancer in other parts of the body.[1] [2]
References
1. ^ Heart cancer: Is there such a thing? from the Mayo Clinic website, retrieved on November 11, 2006.
2. ^ Heart Cancer from the U.S. Department of Energy website, retrieved on November 11, 2006.
Heart cancer is a extremely rare form of cancer of the heart. Heart cancer is divided into primary tumors of the heart and secondary tumors of the heart. Most heart cancers are benign myxomas, fibromas, rhabdomyomas and hamartomas, although malignant sarcomas (such as angiosarcoma or cardiac sarcoma) have been known to occur. In a study of 12,487 autopsies performed in Hong Kong seven cardiac tumors were found, most of which were benign. However, cancer can also spread to heart from other parts of the body. In addition the heart can be affected by treatment for cancer in other parts of the body.[1] [2]
References
1. ^ Heart cancer: Is there such a thing? from the Mayo Clinic website, retrieved on November 11, 2006.
2. ^ Heart Cancer from the U.S. Department of Energy website, retrieved on November 11, 2006.
The heart is a hollow.
The heart and lungs, from an older edition of Gray's Anatomy.
This article is about the organ. For the symbol of love, see Heart (symbol). For other uses, see Heart (disambiguation).
The heart is a hollow, muscular organ in vertebrates, responsible for pumping blood through the blood vessels by repeated, rhythmic contractions, or a similar structure in annelids, mollusks, and arthropods. The term cardiac (as in cardiology) means "related to the heart" and comes from the Greek καρδιά, kardia, for "heart." The heart is composed of cardiac muscle, an involuntary muscle tissue which is found only within this organ.
Contents
[hide]
• 1 Early development
• 2 Structure
• 3 Physiology
o 3.1 Regulation of the cardiac cycle
o 3.2 Other physiological functions
• 4 First aid
• 5 The hearts of other animals
o 5.1 Vertebrates
o 5.2 Invertebrates
o 5.3 Heartbeat
• 6 Food use
• 7 As a symbol
• 8 References
Early development
Main article: Heart development
At 21 days after conception, the human heart rate begins beating at 75-80 beats per minute and accelerates linearly for the first month of beating.
The human embryonic heart begins beating approximately 21 days after conception, or five weeks after the last normal menstrual period (LMP), which is the date normally used to date pregnancy. The human heart begins beating at a rate near the mother’s, about 75-80 beats per minute (bpm). The embryonic heart rate (EHR) then accelerates linearly for the first month of beating, peaking at 165-185 bpm during the early 7th week, (early 9th week after the LMP). This acceleration is approximately 3.3 bpm per day, or about 10 bpm every three days, an increase of 100 bpm in the first month. [1]
After peaking at about 9.2 weeks after the LMP, it decelerates to about 150 bpm (+/-25 bpm) during the 15th week after the LMP. After the 15th week the deceleration slows reaching an average rate of about 145 (+/-25 bpm) bpm at term. The regression formula which describes this acceleration before the embryo reaches 25 mm in crown-rump length or 9.2 LMP weeks is:
Age in days = EHR(0.3)+6
See: Embryonic Heart Rates Compared in Assisted and Non-Assisted Pregnancies
There is no difference in male and female heart rates before birth.[1]] Structure
Anterior (frontal) view of the opened heart. Arrows indicate normal blood flow. Image provided courtesy of www.3dscience.com.
In the human body, the heart is normally situated to the left of the middle of the thorax, underneath the breastbone (see diagrams). The heart is usually felt to be on the left side because the left heart (left ventricle) is stronger (it pumps to all body parts). The left lung is smaller than the right lung because the heart occupies more of the left hemithorax. The heart is enclosed by a sac known as the pericardium and is surrounded by the lungs. The pericardium is a double membrane structure containing a serous fluid to reduce friction during heart contractions. The mediastinum, a subdivision of the thoracic cavity, is the name of the heart cavity.
The apex is the blunt point situated in an inferior (pointing down and left) direction. A stethoscope can be placed directly over the apex so that the beats can be counted. This physical location is between the sixth and seventh rib, just to the left of the sternum [2]. In normal adults, the mass of the heart is 250-350, or about three fourths the size of a clenched fist. g (9-12 oz), but extremely diseased hearts can be up to 1000 g (2 lb) in mass due to hypertrophy. It consists of four chambers, the two upper atria (singular: atrium ) and the two lower ventricles. On the left is a picture of a fresh human heart which was removed from a 64-year-old British male.
The function of the right side of the heart (see right heart) is to collect deoxygenated blood, in the right atrium, from the body and pump it, via the right ventricle, into the lungs (pulmonary circulation) so that carbon dioxide can be dropped off and oxygen picked up (gas exchange). This happens through a passive process called diffusion. The left side (see left heart) collects oxygenated blood from the lungs into the left atrium. From the left atrium the blood moves to the left ventricle which pumps it out to the body. On both sides, the lower ventricles are thicker and stronger than the upper atria. The muscle wall surrounding the left ventricle is thicker than the wall surrounding the right ventricle due to the higher force needed to pump the blood through the systemic circulation.
Physiology
Regulation of the cardiac cycle
Cardiac muscle is myogenic (able to contract and relax on its own). It is a specialized muscle found nowhere else but in the heart because it has its own conducting system. This is in contrast with skeletal muscle, which requires either conscious or reflex nervous stimuli. The heart's rhythmic contractions occur spontaneously, although the waves or nerves can be changed by nervous frequency influences such as exercise or the perception of danger.
The rhythmic sequence of contractions is coordinated by the sinoatrial and atrioventricular nodes. The sinoatrial node, often known as the cardiac pacemaker, is located in the upper wall of the right atrium and is responsible for the wave of electrical stimulation (See action potential) that initiates atria contraction. Once the wave reaches the atrioventricular node, situated in the lower right atrium, it is conducted through the bundles of His and causes contraction of the ventricles. The time taken for the wave to reach this node from the sinoatrial nerve creates a delay between contraction of the two chambers and ensures that each contraction is coordinated simultaneously throughout all of the heart. In the event of severe pathology, the Purkinje fibers can also act as a pacemaker; this is usually not the case because their rate of spontaneous firing is considerably lower than that of the other pacemakers and hence is overridden.
Other physiological functions
The heart also secretes atrial natriuretic factor (ANF), a powerful peptide hormone that affects the blood vessels, the adrenal glands, the kidneys, and the regulatory regions of the brain in order to regulate blood pressure and volume.
First aid
See cardiac arrest for emergencies involving the heart
If a person is encountered in cardiac arrest (no heartbeat), cardiopulmonary resuscitation (CPR) should be started, and help called. If an automated external defibrillator is available, this device may automatically administer defibrillation if this is indicated.
The hearts of other animals
Main article: Circulatory system#Types of circulatory systems
Vertebrates
The hearts of fish have only two chambers: one atrium and one ventricle. In fish, the system has only one circuit. The blood pumps through the gills and on to the bodily tissues before returning to the heart.
Amphibians and most reptiles have a three-chambered heart, in which oxygenated blood from the lungs and de-oxygenated blood from the respiring tissues enter by separate atria, and are directed via a spiral valve to the appropriate vessel—aorta for oxygenated blood and pulmonary artery for deoxygenated blood. The spiral valve is essential to keeping the mixing of the two types of blood to a minimum, enabling the animal to have higher metabolic rates, and be more active than otherwise.
Mammals, birds and crocodiles show complete separation of the heart into two pumps, for a total of four heart chambers; it is thought that the four-chambered heart of birds evolved independently of that of mammals.
Invertebrates
Many invertebrates, such as bivalves and arthropods, exhibit an open circulatory system where blood flows both in vessels and freely in the body cavity. In these animals the blood usually collects in a series of specialised sinuses, or cavities, where it directly comes in contact with tissues. It is then returned to the heart and is again released into the body.
The earthworm has no heart; instead it has five aortic arches that serve the same purpose.
Heartbeat
Smaller animals have faster heartbeats. This is evident within a species as well, as the young beat their hearts faster than the adults. See Early development above for information about the early human heart rates.
The Gray Whale's heart beats 9 times per minute, Harbour Seal 10 when diving, 140 when on land, elephant 25, human 72, sparrow 500, shrew 600, and hummingbird 1,200 when hovering. These heart rates usually vary on the animal's ratio of surface area to body mass; an elephant with relatively less surface area than a mouse loses proportionally less heat and requires comparatively less blood to be pumped throughout its body. An ectothermic animal will usually have a slower, and more variable heartbeat than an endothermic animal of similar size.
Food use
The hearts of cattle, sheep, pigs, chickens and certain fowl are consumed as food in many countries. They are counted among offal, but being a muscle, the taste of heart is much more like regular meat than that of other offal. It resembles venison in structure and taste.
As a symbol
For more details on this topic, see Heart (symbol).
The heart was historically seen by some as the seat of the soul and the organ responsible for human thought. Even though we now know that the heart has nothing to do with thought or love, people still carry on using the term "heart" metaphorically when talking about love. When used in this metaphorical sense, the heart is often illustrated as an icon (♥).
The term "heart" can also refer to the core or center of anything e.g. "The heart of the matter".
References
1. ^ Terry J. DuBose Sex, Heart Rate and Age
See also
• Artificial heart
• Atrium
• Cardiology
• Cardiothoracic Surgery
• Cardiovascular pathology
• Circulatory system
• Echocardiography
• Electrical conduction system of the heart
• Haemodynamics
• Heart cancer
• Heart defects
• Heart rate
• Heart transplant
• Human anatomy
• Pulse
• Ventricle
• Aorta
• Ventricular hypertrophy
• Holiday heart syndrome
• Circle map — simplified mathematical model of the beating heart.
• MUGA scan
• Cardiac stress test
Sunday, January 7, 2007
Papillary muscle
In anatomy, the papillary muscles of the heart serve to limit the movements of the mitral and tricuspid valves and prevent them from being inverted. They do not close or open the valves, which close passively in response to pressure gradients. Instead they brace the valves against the high pressure.
The U wave in an ECG represents papillary muscle repolarization. It usually does not appear unless a patient's electrolytes are imbalanced.
The U wave in an ECG represents papillary muscle repolarization. It usually does not appear unless a patient's electrolytes are imbalanced.
Coronary artery bypass surgery
Coronary artery bypass surgery, also coronary artery bypass graft surgery, and colloquially heart bypass or bypass surgery is a surgical procedure performed to relieve angina and reduce the risk of death from coronary artery disease. Arteries and /or veins from elsewhere in the patient's body are grafted from the aorta to the coronary arteries to bypass atherosclerotic narrowings and improve the blood supply to the coronary circulation supplying the myocardium (heart muscle).
Early in a coronary artery bypass surgery during vein harvesting from the legs (left of image) and the establishment of bypass (placement of the aortic cannula) (bottom of image). The perfusionist and heart-lung machine (HLM) are on the upper right. The patient's head (not seen) is at the bottom.
Coronary artery bypass surgery during mobilization (freeing) of the right coronary artery from its surrounding tissue, adipose tissue (yellow). The tube visible at the bottom is the aortic cannula (returns blood from the HLM). The tube above it (obscured by the surgeon on the right) is the venous cannula (receives blood from the body). The patient's heart is stopped and the aorta is cross-clamped. The patient's head (not seen) is at the bottom.
Contents
1 History
2 Terminology
2.1 Number of bypasses
3 Prognosis
4 Complications
5 Procedure (Simplified)
6 Conduits used for bypass
6.1 Graft patency
7 Minimally Invasive CABG
//
History
The technique was pioneered by Argentinian René Favaloro and others at the Cleveland Clinic in the late 1960s.[1] Currently, about 500,000 CABGs are performed in the United States each year.
Terminology
There are many variations on terminology, in which one or more of 'artery', 'bypass' or 'graft' is left out. The most frequently used acronym for this type of surgery is CABG (pronounced 'cabbage'),[2] pluralized as CABG's (pronounced 'cabbages'). More recently the term aortocoronary bypass (ACB) has come into popular use. CAGS (Coronary Artery Graft Surgery, pronounced phonetically) has been used (primarily outside the United States) and should not be confused with Coronary Angiography (CAG).
Number of bypasses
The terms single bypass, double bypass, triple bypass and quadruple bypass refer to the number of coronary arteries bypassed in the procedure. In other words, a double bypass means two coronary arteries are bypassed (e.g. the left anterior descending (LAD) coronary artery and right coronary artery (RCA)); a triple bypass means three vessels are bypassed (e.g. LAD, RCA, left circumflex artery (LCX)); a quadruple bypass means four vessels are bypassed (e.g. LAD, RCA, LCX, first diagnonal artery of the LAD). Less commonly more than four coronary arteries may be bypassed.
A greater number of bypasses does not imply a person is "sicker," nor does a lesser number imply a person is "healthier." A person with a large amount of coronary artery disease (CAD) may receive less bypass grafts due to the lack of suitable "target" vessels. A coronary artery may be unsuitable for bypass grafting it if it is small (< title="Stenosis" href="http://en.wikipedia.org/wiki/Stenosis">stenosis ("narrowing") of the left main coronary artery requires only two bypasses (to the LAD and the LCX). However, a left main lesion places a person at the highest risk for death from a cardiac cause.[citation needed]
The surgeon reviews the coronary angiogram prior to surgery and identifies the lesions (or "blockages") in the coronary arteries. The surgeon will estimate of the number of bypass grafts prior to surgery, but the final decision is made in the operating room upon examination of the heart.
Prognosis
Prognosis following CABG depends on a variety of factors, but successful grafts typically last around 10-15 years. In general, CABG improves the chances of survival of patients who are at high risk (meaning those presenting with angina pain shown to be due to ischemic heart disease), but statistically after about 5 years the difference in survival rate between those who have had surgery and those treated by drug therapy diminishes. Age at the time of CABG is critical to the prognosis, younger patients with no complicating diseases have a high probability of greater longevity. The older patient can usually be expected to suffer further blockage of the coronary arteries.
Complications
Infection at incision sites
Deep vein thrombosis (DVT)
Nonunion or malunion of the sternum
Anesthetic complications such as malignant hyperthermia)
Myocardial infarction due to hypoperfusion, early graft occlusion, or graft failure
Acute renal failure due to hypoperfusion
Stroke during reperfusion
Stenosis of the graft, particularly of saphenous vein grafts
Keloid scarring
Chronic pain at incision sites
Postoperative stress-related illnesses such as constipation, chronic bracing, memory loss, trench mouth, and teeth grinding
Death due to myocardial infarction, stroke, renal failure, or sepsis
Most commonly, the sternum is cut down the middle with a bone saw and the chest opened (a procedure known as median sternotomy). Depending on a number of factors, the surgeon may decide to place the patient on cardiopulmonary bypass ("on-pump") or use stabilizing devices to hold the heart still while sewing the anastomoses ("off-pump"). Blood vessels are harvested from elsewhere in the body for grafting. Sometimes artery end branches supplying tissues near the heart are rerouted to create the bypass.
Procedure (Simplified)
1) An artery may be detached from the chest wall and the open end attached to the coronary artery below the blocked area.
2) A piece of a long vein in the leg may be taken. One end is sewn onto the large artery leaving the heart -- the aorta. The other end of the vein is attached or "grafted" to the coronary artery below the blocked area.
Either way, blood can use this new path to flow freely to the heart muscle.
Conduits used for bypass
The choice of conduits is highly surgeon and institution dependent. Typically, the left internal thoracic artery (LITA) (previously referred to as left internal mammary artery or LIMA) is grafted to the Left Anterior Descending artery and a combination of other arteries and veins is used for other coronary arteries. The right internal thoracic artery (RITA), the great saphenous vein from the leg and the radial artery from the forearm are frequently used. The right gastroepiploic artery from the stomach is used infrequently used given the difficult mobilization from the abdomen.
Graft patency
Grafts can become diseased and may occlude in the months to years after bypass surgery is performed. Patency is a term used to describe the chance that a graft remain open. A graft is considered patent if there is flow through the graft without any significant (>70% diameter) stenosis in the graft.
Graft patency is dependent on a number of factors, including the type of graft used (internal thoracic artery, radial artery, or great saphenous vein), the size or the coronary artery that the graft is anastomosed with, and, of course, the skill of the surgeon(s) performing the procedure. Arterial grafts (e.g. LITA, radial) are far more sensitive to rough handling than the saphenous veins and may go into spasm if handled improperly.
Generally the best patency rates are achieved with the in-situ (the proximal end is left connected to the subclavian artery) left internal thoracic artery with the distal end being anastomosed with the coronary artery (typically the left anterior descending artery or a diagonal branch artery). Lesser patency rates can be expected with radial artery grafts and "free" internal thoracic artery grafts (where the proximal end of the thoracic artery is excised from its origin from the subclavian artery and re-anastomosed with the ascending aorta). Saphenous vein grafts have worse patency rates, but are more available, as the patients can have multiple segments of the saphenous vein used to bypass different arteries.
Veins that are used either have their valves removed or are turned around so that the valves in them do not occlude blood flow in the graft. LITA grafts are longer-lasting than vein grafts, both because the artery is more robust than a vein and because, being already connected to the arterial tree, the LITA need only be grafted at one end. The LITA is usually grafted to the left anterior descending coronary artery (LAD) because of its superior long-term patency when compared to saphenous vein grafts.[3][4]
Minimally Invasive CABG
Alternate methods of minimally invasive coronary artery bypass surgery have been developed in recent times. Off-pump coronary artery bypass surgery (OPCAB) is a technique of performing bypass surgery without the use of cardiopulmonary bypass (the heart-lung machine). Futher refinements to OPCAB have resulted in Minimally invasive direct coronary artery bypass surgery (MIDCAB) which is a technique of performing bypass surgery through a 5 to 10 cm incision.
Early in a coronary artery bypass surgery during vein harvesting from the legs (left of image) and the establishment of bypass (placement of the aortic cannula) (bottom of image). The perfusionist and heart-lung machine (HLM) are on the upper right. The patient's head (not seen) is at the bottom.
Coronary artery bypass surgery during mobilization (freeing) of the right coronary artery from its surrounding tissue, adipose tissue (yellow). The tube visible at the bottom is the aortic cannula (returns blood from the HLM). The tube above it (obscured by the surgeon on the right) is the venous cannula (receives blood from the body). The patient's heart is stopped and the aorta is cross-clamped. The patient's head (not seen) is at the bottom.
Contents
1 History
2 Terminology
2.1 Number of bypasses
3 Prognosis
4 Complications
5 Procedure (Simplified)
6 Conduits used for bypass
6.1 Graft patency
7 Minimally Invasive CABG
//
History
The technique was pioneered by Argentinian René Favaloro and others at the Cleveland Clinic in the late 1960s.[1] Currently, about 500,000 CABGs are performed in the United States each year.
Terminology
There are many variations on terminology, in which one or more of 'artery', 'bypass' or 'graft' is left out. The most frequently used acronym for this type of surgery is CABG (pronounced 'cabbage'),[2] pluralized as CABG's (pronounced 'cabbages'). More recently the term aortocoronary bypass (ACB) has come into popular use. CAGS (Coronary Artery Graft Surgery, pronounced phonetically) has been used (primarily outside the United States) and should not be confused with Coronary Angiography (CAG).
Number of bypasses
The terms single bypass, double bypass, triple bypass and quadruple bypass refer to the number of coronary arteries bypassed in the procedure. In other words, a double bypass means two coronary arteries are bypassed (e.g. the left anterior descending (LAD) coronary artery and right coronary artery (RCA)); a triple bypass means three vessels are bypassed (e.g. LAD, RCA, left circumflex artery (LCX)); a quadruple bypass means four vessels are bypassed (e.g. LAD, RCA, LCX, first diagnonal artery of the LAD). Less commonly more than four coronary arteries may be bypassed.
A greater number of bypasses does not imply a person is "sicker," nor does a lesser number imply a person is "healthier." A person with a large amount of coronary artery disease (CAD) may receive less bypass grafts due to the lack of suitable "target" vessels. A coronary artery may be unsuitable for bypass grafting it if it is small (< title="Stenosis" href="http://en.wikipedia.org/wiki/Stenosis">stenosis ("narrowing") of the left main coronary artery requires only two bypasses (to the LAD and the LCX). However, a left main lesion places a person at the highest risk for death from a cardiac cause.[citation needed]
The surgeon reviews the coronary angiogram prior to surgery and identifies the lesions (or "blockages") in the coronary arteries. The surgeon will estimate of the number of bypass grafts prior to surgery, but the final decision is made in the operating room upon examination of the heart.
Prognosis
Prognosis following CABG depends on a variety of factors, but successful grafts typically last around 10-15 years. In general, CABG improves the chances of survival of patients who are at high risk (meaning those presenting with angina pain shown to be due to ischemic heart disease), but statistically after about 5 years the difference in survival rate between those who have had surgery and those treated by drug therapy diminishes. Age at the time of CABG is critical to the prognosis, younger patients with no complicating diseases have a high probability of greater longevity. The older patient can usually be expected to suffer further blockage of the coronary arteries.
Complications
Infection at incision sites
Deep vein thrombosis (DVT)
Nonunion or malunion of the sternum
Anesthetic complications such as malignant hyperthermia)
Myocardial infarction due to hypoperfusion, early graft occlusion, or graft failure
Acute renal failure due to hypoperfusion
Stroke during reperfusion
Stenosis of the graft, particularly of saphenous vein grafts
Keloid scarring
Chronic pain at incision sites
Postoperative stress-related illnesses such as constipation, chronic bracing, memory loss, trench mouth, and teeth grinding
Death due to myocardial infarction, stroke, renal failure, or sepsis
Most commonly, the sternum is cut down the middle with a bone saw and the chest opened (a procedure known as median sternotomy). Depending on a number of factors, the surgeon may decide to place the patient on cardiopulmonary bypass ("on-pump") or use stabilizing devices to hold the heart still while sewing the anastomoses ("off-pump"). Blood vessels are harvested from elsewhere in the body for grafting. Sometimes artery end branches supplying tissues near the heart are rerouted to create the bypass.
Procedure (Simplified)
1) An artery may be detached from the chest wall and the open end attached to the coronary artery below the blocked area.
2) A piece of a long vein in the leg may be taken. One end is sewn onto the large artery leaving the heart -- the aorta. The other end of the vein is attached or "grafted" to the coronary artery below the blocked area.
Either way, blood can use this new path to flow freely to the heart muscle.
Conduits used for bypass
The choice of conduits is highly surgeon and institution dependent. Typically, the left internal thoracic artery (LITA) (previously referred to as left internal mammary artery or LIMA) is grafted to the Left Anterior Descending artery and a combination of other arteries and veins is used for other coronary arteries. The right internal thoracic artery (RITA), the great saphenous vein from the leg and the radial artery from the forearm are frequently used. The right gastroepiploic artery from the stomach is used infrequently used given the difficult mobilization from the abdomen.
Graft patency
Grafts can become diseased and may occlude in the months to years after bypass surgery is performed. Patency is a term used to describe the chance that a graft remain open. A graft is considered patent if there is flow through the graft without any significant (>70% diameter) stenosis in the graft.
Graft patency is dependent on a number of factors, including the type of graft used (internal thoracic artery, radial artery, or great saphenous vein), the size or the coronary artery that the graft is anastomosed with, and, of course, the skill of the surgeon(s) performing the procedure. Arterial grafts (e.g. LITA, radial) are far more sensitive to rough handling than the saphenous veins and may go into spasm if handled improperly.
Generally the best patency rates are achieved with the in-situ (the proximal end is left connected to the subclavian artery) left internal thoracic artery with the distal end being anastomosed with the coronary artery (typically the left anterior descending artery or a diagonal branch artery). Lesser patency rates can be expected with radial artery grafts and "free" internal thoracic artery grafts (where the proximal end of the thoracic artery is excised from its origin from the subclavian artery and re-anastomosed with the ascending aorta). Saphenous vein grafts have worse patency rates, but are more available, as the patients can have multiple segments of the saphenous vein used to bypass different arteries.
Veins that are used either have their valves removed or are turned around so that the valves in them do not occlude blood flow in the graft. LITA grafts are longer-lasting than vein grafts, both because the artery is more robust than a vein and because, being already connected to the arterial tree, the LITA need only be grafted at one end. The LITA is usually grafted to the left anterior descending coronary artery (LAD) because of its superior long-term patency when compared to saphenous vein grafts.[3][4]
Minimally Invasive CABG
Alternate methods of minimally invasive coronary artery bypass surgery have been developed in recent times. Off-pump coronary artery bypass surgery (OPCAB) is a technique of performing bypass surgery without the use of cardiopulmonary bypass (the heart-lung machine). Futher refinements to OPCAB have resulted in Minimally invasive direct coronary artery bypass surgery (MIDCAB) which is a technique of performing bypass surgery through a 5 to 10 cm incision.
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