Medical Info

Overview: Coronary Artery Disease and Bypass Surgery

Disclaimer: I am not a doctor or specialist in Cardiology, Heart Surgery or Heart Pharmocology. I have provided links on the HEART LINKS page to real experts. But I went through this and had to learn it the hard way. Information is essential to understand and cope with the consequences of heart disease and especially surgery. The information that follows has been culled from various sources. If there are factual errors, they are mine. I have inserted a compilation of the reports of the doctors and surgeons on my case as a counterpoint to the drier technical discussions.

Coronary Artery Disease

Coronary Artery Disease (or CAD) is the leading cause of death in the United States, accounting for over 900,000 deaths annually. More than two of every five Americans die of cardiovascular disease. Additionally, over 3 million Americans suffer occasional chest pains due to coronary artery blockages. Despite this , the US is still only 17th in cardiovascular disease mortality worldwide. As common as it is, CAD has not yet been eradicated by preventative measures. In fact, it is only within about the last 50 years that the role of cholesterol and dietary fat in the development of CAD has really been understood. A number of other "risk factors" have also been identified, including family history of CAD, hypertension, smoking, diabetes, and lifestyle issues such as lack of exercise or Type A personality, etc.

The heart is a muscle; like other muscles in the body, it is composed of millions of specialized cells which contract, or shorten, under the proper conditions, and develop a force of contraction. In the heart, the muscle fibers are aligned in a circular manner to form a conical shaped chamber. As the heart muscle cells contract in unison, blood is forced out of the chamber and flows to every organ and cell in the body. This requires a tremendous amount of energy, so the heart must have its own source of blood to bring nutrients to its cells. A normal heart in an average sized person will pump 4 to 5 liters of blood per minute. The average heart will beat almost 4 million times per year. The "fuel" for this effort comes exclusively from the nutrition carried to the heart muscle cells by way of the vascular system. This is an image of a normal heart.

The main chamber for pumping oxygen-rich red blood to the body is called the left ventricle. After the blood exits the left ventricle, it enters the main channel of the vascular highway, called the aorta, a tube of specialized tissue capable of carrying the entire 4 or 5 liters per minute to the rest of the body under pressure . The very first branches arising from the aorta are small vessels, called the coronary arteries, which connect to the surface of the heart. There are two main coronary arteries, one to the left ventricle (called the left main coronary artery or LMCA) and another called the right main coronary artery (RMCA) which supplies mostly the right ventricle but also part of the undersurface of the left ventricle. These main coronary artery give rise to branches which thread into the heart muscle, bringing vital nutrients to each muscle cell.

When coronary artery disease occurs, the channel inside these arteries becomes progressively "plugged" with plaque material. This process is known as atherosclerosis. In this disease, the inner channel of the coronary artery becomes obstructed by buildup of cholesterol and other body fats on the lining of the blood vessel wall. Over time, the bodies own inflammatory response to these fatty molecules leads to enlargement and protrusion of the plaque into the flow channel of the artery. If the plaque is large enough, the entire channel can become obstructed to blood flow. This is an image of a severely blocked Left Main Coronary Artery (dissection). You can see the plaque material clogging the flow channel; it is almost completely blocked on the right of the picture (arrow).

This is a cross-section of a severely blocked artery. (1) is the arterial wall; (2) is an area of calcified or hardened plaque, intruding into the cell wall; (3) is the remaining open flow channel; (4) is the fatty material clogging most of the arterial passage.

When this happens, the heart muscle cells no longer receive vital nourishment from the blood stream. When the demand for blood supply is increased, such as during physical exercise and/or emotional stress, the blocked arteries may not be able to deliver enough blood to meet the needs of the heart muscle cells. This situation is called ischemia, and is best described as a shortfall between nutrient demand and supply. As a result, most (but not all) patients will notice chest pain or pressure with futher exercise. This pain is called angina pectoris (or just angina). If the obstucted artery closes suddenly, then permanent damage to the muscle cells in that region of the heart can occur. This process is known as a heart attack, or myocardial infarction (MI). These two images show the damage from a severe MI; the pale tannish tissue (arrows) has died and formed scar tissue. In the second image, a cross-section, the area of infarction extents from the ventrical wall into the septum, or wall between the left and right ventricals.

Some patients will need intervention to prevent further attacks. Surgery is not always necessary, but for many patients surgical revascularization still provides the best long term result.

Diagnosis: Angiography

Coronary Angiography is the diagnostic x-ray procedure designed to visualize the arteries of the heart. These tiny blood vessels are only 1 to 3 millimeters in diameter. Thus it takes special x-ray equipment and techniques to obtain images of sufficient quality for diagnosis and surgical decision making. Coronary angiography has become the cornerstone for both diagnosis and treatment of coronary artery disease (CAD) worldwide.

In this test, the patient is brought to the x-ray (or radiology) procedure room where specialized fluoroscopic equipment is available. The patient must lay motionless on the x-ray table, with their hands to the side or overhead. It is normal for a patient to be apprehensive and nervous during this procedure. The team in the catheterization laboratory (or cath lab) will commonly administer medications designed to relax the patient and relieve both pain and anxiety during the procedure. A sterile area is prepared in the groin by cleansing the skin with topical antiseptic agents and covering the region with sterile drapes. The skin is "numbed" with local anesthesia (similar to the Novocaine injection used by a dentist). The cardiologist places a needle into the main artery in the upper leg, called the femoral artery. Through this needle, a flexible wire is passed and threaded backward into the arterial tree until the wire reaches the main aorta (as confirmed by x-ray fluoroscopy). Over the wire, a long plastic tube (also known as angiogram catheter) is threaded into the aorta. The initial wire serves as a guiding system to ensure that the catheter tracks into the aorta properly.

The angiogram catheter is maneuvered into position just above the outlet valve of the left ventricle, (also known as the aortic valve). With careful maneuvering, the tip of the catheter can be positioned at the mouth of the main coronary arteries. Once positioned, specialized contrast agent, or angiogram dye is selectively injected into the mouth of the coronary artery while continuous x-ray images are exposed onto movie film. During the actual injection, the patient notices a flushing sensation starting in the chest and migrating to the head and sometimes the entire body. This sensation is a side effect of the dye matierial, and occurs to a varying degree in all patients. The flushing sensation is bothersome, but is short-lived. It is not an allergic reaction.

" Thallum images:
A. On planar images, there is borderline increased lung uptake. There are severe perfusion defects involving the anterior, septal, apical and inferior walls. The lateral wall is relatively preserved. The cavity is enlarged. On delayed images, there is some degree of redistribution in the septum and inferior wall.
B. On tomographic images, there is a severe, primarily fixed anteroseptal and apical perfusion defect that partly distributes at 3 hours. The lateral wall is also abnormal at peak exercise, and significantly redistributes on delayed images.
Left ventricular function was severely impaired with evidence of an anterior septal and apical aneurysm. "

As the dye travels down the branches of the coronary artery itself, continouous images are exposed onto movie film. The composite roll of images is known as a cineangiogram. In most modern cath labs, the cardiologist can also see the preliminary results immediately on the overhead video screen. Digitized images are also saved on computer and replayed onto the video screen as needed. In nearly all cases, multiple views from different angles are necessary in order to ascertain the precise location and severity of the coronary artery blockages. In some views, a blockage may not initially appear to be that severe. However, from another angle of view, the artery may appear nearly occluded. Thus it is important for the cardiologist to rotate the fluoroscopy equipment and obtain pictures from multiple views.

After completion of the coronary angiogram procedure, the cardiologist reviews the final images on a specialized projector, making measurements of each blockage seen. Blockages in the channel of an artery are rated by percentage (i.e. the percent of the flow channel that is obstructed). For blockages that involve less than 50% of the vessel diameter, intervention is usually not necessary. In general terms, when plaque buildup is blocking more than 50% of the vessel diameter, the blockage is considered clinicially significant. However, most blockages are not considered serious until they reach at least 75% narrowing of the diameter of the artery. At this point, there will always be significant impairment of blood flow. Such lesions are clinically important and thus candidates for treatment.

This is an example of a 99% blockage in the most important coronary artery, the left anterior descending (LAD). The normal parts of the coronary vessels are clearly seen as smooth unbroken white channels against the black background of the undyed tissues.

Here is a view of the right coronary artery (RCA) demonstrating two high grade (> 90%) blockages.

In my case, I was diagnosed as having "severe three-vessel" CAD; none of the three main arteries were operable, and th e damage had already been done. In addition, as a result of the MI, I had an aneurism at the base of my heart, somewhat like the one shown in these images. In an aneurism, a part of the heart wall bulges out and becomes very thin and non-contractile.

Because most of the damage was old, the stress placed on the remaining functional heart muscle of my left ventrical had caused it to enlarge and become "flabby", resulting in Congestive Heart Failure, a condition in which the heart is not able to pump the blood with sufficient energy to carry fluids out of the tissues of the body, especially the lungs, lower extremeties, and around the heart. This is an image of a severely enlarged heart, showing the left ventrical; compare this to the normal heart above.

Depending on lesion size, shape, length, location and other factors, some blockages can be treated without bypass surgery, by techniques like baloon angioplasty. However, there are many patients in whom the blockages cannot be easily or safely modified by such techniques. Coronary Artery Bypass Grafting (CABG) is the treatment of choice for such patients. For example, in patients with multiple high grade blockages, it is more effective to restore circulation throughout the heart with bypass surgery. If the cardiologist feels that surgery is warranted, the films and clinical situation are reviewed by a consulting surgeon. The surgeon utilizes the cineangiogram images to plan both the location and number of potential bypass grafts needed in order to optimize that patients surgical result.

"Films were sent for review. Dr. Sansonetti felt that the patient was a surgical candidate and agreed to accept the patient for further evaluation. The patient is transferred and coronary bypass graft surgery is anticipated for the next several days.
Transfer Diagnoses:
Coronary artery disease with probable prior, clinically unrecognized anterior septal myocardial infarction with extensive remodelling, aneurysm formation, moderate-to-severely impaired left ventricular function, but with normal diastolic pressure and absence of congestion. Recent unstable angina with severe three vessel coronary artery disease."

Any surgeon intending to reconstruct the circulation to the heart will need a road map of the blood vessels and the location of the blockages. The test most frequently used for this information is called a coronary angiogram. In this test, the small blood vessels feeding the heart are imaged with special x-ray techniques. In summary, the coronary arteries are injected with a special dye solution, usually a slightly radioactive thalium solution, which shows up on x-ray film. As the dye travels down the branches of the coronary artery itself, moving pictures (or cineangiograms) are taken with the x-ray camera. The patient can sometimes watch this on a video screen. The series of angiographic movies are recorded and reviewed by the cardiologist and decisions then are made about the relative benefits of different treatments.

Surgery

Surgical reconstruction of the blocked arteries began in the late 1960's and has proven to be extremely successful. The operation called Coronary Artery Bypass Grafting (CABG or "cabbage") is the foundation of surgical management of heart disease, restoring the blood supply to the heart muscle by creating a new route (aka bypass) for the blood to flow around the blockages. CABG is the most common operation performed on the human heart, and in fact is currently the most common procedure of any kind in the USA. Last year, over 200,000 CABGs were performed nationwide.

Now there are many other treatment options, but surgery remains the mainstay for a large group of patients for which other options are not effective. Coronary Artery Bypass Grafting doesn't remove the obstructing blockages in the arteries. The procedure "reroutes" the flow of blood by using a "detour" pathway. Typically, the blockages occur in the first centimeter or two of the major branches feeding the heart. The smaller branches are usually not involved until very late life. Thus, it is possible to hook a new source of blood into the artery just beyond the last major blockage. Blood flows into the artery through a different path (such as a vein bypass graft) and reaches the heart muscle tissue where it is needed. Once the blood flow is restored, the symptoms of exertional chest discomfort are relieved .

"This 47 year old patient entered St. Vincent Hospital with chest pain and syncope. He has a reduced EF. The circumflex is the only artery open and it has 95% lesion. The anteroapical wall is profoundly dilated and akinetic."

The most common material used to build this new pathway is a vein from the lower extremity called the Greater Saphenous Vein (or GSV) running from just inside the ankle bone up to the groin. This vein is the right size, shape, and length for use as a bypass conduit. The other major vessel used as a bypass graft is the Left Internal Mammary Artery (LIMA),which lies alongside the undersurface of the breastbone (aka sternum). By detaching the lower end of the LIMA, the vessel can be transplanted to the surface of the heart.

"With the patient supine on the operating table, general endotracheal anesthesia was induced and the patient was prepared and draped sterilely from the chin to the ankles. The greater saphenous vein was harvested from the left thigh. It was good caliber and quality. The side branches were ligated with 4-0 silk and when the incision was dry it was closed in the usual fashion."

Regardless of which conduit is used for the bypass, the main advantage offered by this surgical approach is the restoration of blood supply to the heart. The vein or mammary artery provide a new and unobstructed route for blood flow. When the surgeon connects the bypass to the native coronary artery beyound the obstruction, blood has a new path in which to flow into the blood vessel beyound the blockage. Then when the heart demands more blood flow, the situation can be met by the new source of blood flowing through the bypass graft. It is important for the surgeon to provide a bypass for each major branch that is obstructed. In that way, the whole heart will have more blood supply, and the anginal (chest) pains will be relieved.

A typical CABG operation begins with a vertical opening into the front of the chest. The breast bone is divided with a specialized (reciprocating) saw, similar to a "jig" saw used in woodworking designed just for this incision. The split sternum is spread open with a device that functions like a winch. The soft tissues in front of the heart are parted, and the membrane surrounding the heart (the pericardium) is incised. Next, the surgeon removes the Internal Mammary Artery from the chest wall to provide a donor artery for grafting.

Simultaneously, an assistant surgeon proceeds with harvesting additional conduit, usually the Greater Saphenous Vein (GSV) from the inside of the calf or thigh. This vein is long, straight, and the proper caliber for use as a donor graft to the heart and removal of the GSV does not impair the return of blue blood from the extremity.

"Simultaneously, a median sternotomy was perfomed, the sternum was split with an oscillating saw, the sternal retractor was placed. The pericardium was then opened and the patient was sytemically heparinized. The aorta was cannulated in the usual fashion and a single venous cannula, two-stage, was placed through the right atrial appendage. A cardioplegia needle was placed proximal to the aortic cannula and was secured."

After all the donor vessels are harvested, the patients blood is thinned with a large dose of the potent anticoagulant heparin. This renders the blood incapable of clotting when exposed to the plastic tubing and surfaces of the heart-lung machine. The patients circulation is connected to the heart-lung bypass circuit, and the body placed onto the support machinery. Then the body temperature is lowered (by refrigerating the blood as it circulates through the machine). In addition, blood flow to the heart is separated from that going to the rest of the body by a vascular clamp applied to the aorta just below the insertion of the arterial return cannula. The coronary arteries are then perfused with a cold potassium solution. The heart is immediately rendered motionless, cold, and relaxed. The body is preserved by the nutrient flow provided by the heart-lung circuit, while the heart is preserved by the low temperature and other conditions managed by the surgeon.

"Cardiopulmonary bypass was initiated and the patient was kept warme while a retrograde cardiplegia catheter was placed through the right atrium into the coronary sinus. The paient was then cooled to 27degrees C. When the heart arrested from the cold, the aortic crossclamp was placed and 400cc of cold blood cardioplegia were infused into the aortic root and 400cc's were infused retrograde into the coronary sinus. There was good electrical arrest of the heart and the heart was well decompressed. Iced saline was placed in the pericardial sac."

These are images of the procedure, with the heart-lung bypass machine attached to the heart.

Next, each target vessel is identified as it runs across the surface of the heart. For each intended bypass, the surgeon makes a tiny opening into the front wall of the target coronary artery with a very fine knife. The opening is expanded with specialized scissors. A donor vessel, either vein or IMA is stitched to this opening with delicate fine suture material. Currently, the best suture material is made from polypropylene and is finer in diameter than a human hair. After all the grafts are sutured to the heart arteries, the vascular clamp is released, allowing blood to flow into the native heart arteries again.

"The heart was inspected to see if there were graftable arteries that did not show up on the cadiac catheterization. A large area of the apex was a thin scar that inverted when the heart was well decompressed and the entire ridge along the LAD was dense and infarcted. The right coronary was inspected. It appeared non dominant. The OM1 was an intramyocardial branch. It was thin-walled and not easy to work with."

Internal Mammary Artery grafts are already attached at their origin from the main artery to the arm (the subclavian artery). Blood flowing through the IMA directly comes from the subclavian artery. However, GSV grafts are detached at both ends. After connecting one end of the vein to the coronary artery, the other end must then be connected to a source of red blood. This is done by partially occluding a segment of the ascending aorta with a specialized, curved vascular clamp. Holes are created in the front wall of the aorta, and the veins are anchored to these openings with fine suture. After releasing this partially occluding clamp, the veins fill with red blood from the aorta and deliver this blood to the coronary arteries downstream. This image shows a heart with two grafts (arrows); the wire is for a pacemaker device, sometimes needed if arrhythmias are present.

"An end-to-side anastomosis was performed. The flow was 80 cc's/min. Cardioplegia was infused through the graft and through the root. An attempt was made to re-infuse the cardioplegia retrograde, but the coronary sinus catheter, despite being deflated when the heart was being moved, had poked out through the coronary sinus and the retrograde catheter was then pulled back a little bit and the rent in the coronary sinus oversewn with 4-0 prolene. The retrograde catheter was removed and furher cardioplegia was given through the graft and through the root. There was some electrical actiity during the rest of the graft. The true inferior wall of the heart was served by what appeared to be the OM-2 branch. An end-to-side anastomosis was perfomed and the flow was 180 cc's/min."

After the heart has had a chance to recover from the temporary arrest period, the heart-lung circuit can be gradually withdrawn. When the heart is beating strongly again, then the heart-lung machine is stopped, and the equipment removed. The anticoagulant (heparin) is chemically reversed (with a drug called protamine). The surgeon then inspects and controls any remaining bleeding. Finally, the wounds are closed and the patient sent to intensive care for recovery.

"The aortic crossclamp was removed. The patient was slowly rewarmed to 37 degrees C. The heart started beating ventricular tachycardia requiring two cadioversions of 30 joules to achieve normal sinus rhythm. The cardioplegia needle was removed and a Lambert Kay clamp was placed on the aortic root. The cardioplegia site was used for one proximal anastomosis and a 4.5mm punch was used to make one additional aortotomy site for the the saphenous vein grafts. These were performed in an end-to-side fashion using 5-0 prolene running suture. Marker rings were applied and attached loosely to the proximal anastomotic area using the same prolene suture. Hemosatis was adequate at all anastomotic sites. Two right ventricular pacing wires and two atrical appendage wires were placed and secured. Because of the patient's preoperative cardiac index of 1.5, and the known dilated cardiomyopathy, 5 mcg. of Dobutamine was initiated. There was good contractility response to this, and the patient came off bypass well with good BP, normal sins rhythm of about 100, and as the case progressed, the Dobutamine was weaned to 2.5 mcg. When hemodynamics were stable, the venous line was removed through purse string suture and Protamine was given to reverse the Heparin. The arota was decannulated and a horizontal mattress suture of 4-0 prolene was used in addition. Two straight #36 chest tubes were placed in the pericardial space. Mediastinal fat and some of the pericardium was closed anteriorly with a 3-0 prolene. The sternotomy was closed with heavy wire and two layers of Dexon in the usual fashion. Sterile dressings were applied and the patient was transported to the Intesive Recovery Room in stable condition."

Many patients, without any major post-operative problems, can leave the hospital in about 4 to 6 days from surgery. It will take about another several weeks for most patients to feel stronger and regain normal body habits, such as appetite, sleep patterns, bowel patterns, etc. For patients who work in non-physical jobs, many can return to employment within 4 to 6 weeks of surgery. Usually, antianginal medications are no longer needed. However, high blood pressure, diabetic medications , cholesterol-lowering drugs and other medicines (such as ACE inhibitors and Beta Blockers) will often be prescribed to treat the underlying causes of the disease. A program of exercise and diet regulation is also usually prescribed, as well as stress-reducing programs and, often, counselling.

Other Information

Glossary:

Ace Inhibitor

Aneursim

Angina

Angiogram

Angioplasty

Aorta

Atherosclerosis

Beta Blocker

Cardiomyopathy

Cardiovascular Accident

Cholesterol

Cholesterol reducing drugs

Congestive Heart Failure

Coronary Artery Bypass Graft (CABG)

Diuretic

Echocardiogram (see Sonogram)
Edema

EKG

Fibrillation

Heart Attack

Hypercholesteremia

Hypertension

Infarct, Infarction

Lipids

Myocardial Infarction

Pacemaker

Cardiac Rehabilitation

Saphenous Vein

Sonogram

Stress Test

Stroke

Thrombus

Transfat

Vasodilator

Ventrical

Signs of a Heart Attack:

Pain, "heaviness" or crushing sensation in center of chest, sometimes radiating to the back, the neck and jaw and the left arm. Not related to exercise or other exertion nor relieved by resting.
Heartburn-like sensation not relieved by antacids or other remedies
Faintness, dizziness, cold sweat
Shortness of breath on normal activity

These symptoms may or not signal a heart attack, but if they continue or are recurring, you should see your doctor as soon as possible. A large percentage of people do not survive their first heart attack. In my case, I had had two major heart attacks and not known it, so-called "silent" heart attacks. It is important to know your family's medical history and if you are genetically susceptible to heart disease, these symptoms may be a serious danger sign and should be taken seriously. An unneeded trip to the emergency room is better than a trip to the morgue!