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Coronary artery disease

Coronary Artery Disease

Coronary Artery Disease, or CAD, is the single leading cause of death in the United States, accounting for over 900,000 deaths annually. More estimates show that over 3 million Americans suffer from occasional chest pains due to coronary artery blockages. However, the U.S. is still only 17th in cardiovascular disease mortality worldwide. Other countries, such as Russia, Poland, Hungary and Finland, continue to have higher mortality and morbidity from CAD than the U.S., making this a world-wide healthcare issue. As common as CAD has become, it still has not been eradicated by preventative measures. In fact, it is only within the last 40 or 50 years that the role of cholesterol and dietary fat in the development of this disease has really been understood. However, a number of other "risk factors" have also been identified, including family history, hypertension, smoking, diabetes, and lifestyle issues such as lack of exercise or Type A personality.

The heart is a muscle just like the muscles in the arm or leg. Any of these muscles, including the heart, is composed of millions of small cells which contract, or shorten, under the proper conditions. A muscle cell, also known as myocyte, can physically shorten due to the unique manner foreshortening the length of the cell in the process. When millions of such cells act simultaneously, the muscle body shortens and develops a force of contraction. This is the same mechanism that occurs when you raise your arm, walk and lift.

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 into the vascular tree, then from there it flows to every organ and cell in the body. In essence, the vascular tree is the highway to the rest of the body. The task of continuously pumping the blood to the body requires a great deal of energy. The heart must have its own source of blood to bring nutrients to each heart muscle cell. The heart of a normal sized person will pump four to five liters of blood per minute, and the average heart will beat almost 4 million times per year. It is estimated that the energy required to continuously pump blood at these rates is almost 5 watts of power per hour. The substrate fro this astronomical effort comes exclusively from the chemical byproducts of nutrition which are carried to the heart muscle cells by way of the vascular system.

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. The aorta is a tube of specialized tissue capable of carrying the entire four to five liters per minute to the rest of the body under a blood pressure of 140 millimeters of mercury, somewhat like the pressure of a garden hose. The very first branches arising from the aorta are small ‘feeder or nutrient’ vessels, called the coronary arteries which double back onto the surface of the heart. There are two main coronary arteries, one to the left ventricle, called the left main coronary artery, and another called the right main coronary artery which supplies mostly the right ventricle but also part of the undersurface of the left ventricle. These main coronary arteries give rise to several braches which then dive into heart muscle, bringing vital nutrients to each muscle cell.

Once coronary artery disease occurs, the channel inside these small but vital arteries becomes progressively ‘clogged’ with plaque material. This process is known as arteriosclerosis. In this disease, the inner channel of the coronary artery becomes obstructed and other body fats which invade the lining of the blood vessel wall. Over time, the bodies own inflammatory response to these fatty molecules leads to the flow channel of the artery. If the plaque is large enough, the entire channel can become obstructed to blood flow. The heart muscle cells normally fed by this vessel are no longer able to receive vital nourishment from the blood stream. Under situations where the demand for blood supply is increased, such as during physical exercise and/emotional stress; the blood arteries may not be able to deliver enough blood to meet the nutrient demand and supply. When this occurs, most patients will notice chest pain or pressure with further exercise. This pain is called angina pectoris. If the obstructed 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. After evaluation of the extent of coronary heart disease, some patients will need intervention to prevent further attacks. Modern tools at our disposal, there is not always a need to perform surgery. However, for many patients surgical reconstruction still provides the best long term results.

Surgical reconstruction of the blocked arteries began in the late 1960’s and has proven to be remarkably successful. The operation we call Coronary Artery Bypass Grafting (CABG) is the foundation of surgical management. The goad is to restore the blood supply to the heart muscle by creating a new route, or bypass, for the blood to flow around the blockage. Not only is CABG the most common operation performed on the human heart, it is currently the most common procedure of any kind in the U.S. Over 200,000 were performed nationwide last year.

Alexis Carrel, the famous experimental vascular surgeon, was the first to attempt a direct hookup to the coronary artery. Carrel developed most of the suturing techniques for small vessel hookups that are still used today. In 1910, Dr. Carrel reported to the American Surgical Association his first attempt to suture a ceratoid artery graft to the left coronary system in an experimental animal. Unfortunately, the animal did not survive; the principle of directly grafting into the coronary artery branches was demonstrated. However, this particular contribution went largely unnoticed for over 50 years. Eventually Dr. Carrel was honored for his lifetime accomplishments in developing the techniques of vascular surgery with the Nobel Prize in Medicine.

In the 1930’s and 1940’s, there were several attempts to bring new blood supply to the heart, most notably the Beck procedure and the Vineberg procedure. Unfortunately, those procedures did not directly connect a new source of blood to the heart arteries, and the success rates were not very high. During the 1940’s and 1950’s, the innovative Canadian surgeon Gordon Murray made two major advances. First was the introduction of the powerful anti-coagulant (blood thinner) heparin into the field of vascular surgery. The second initial success reported by Murray was direct suturing of a graft to the coronary artery of dogs. However, widespread clinical usage of Murray’s discoveries was delayed due to the primitive and largely unavailable angiographies techniques present at that time. Thal and Demikhov both reported similar success in connecting the internal mammary artery to the coronary artery in experimental animals in 1956. The development of modern surgical techniques awaited major developments in X-ray diagnostic techniques. It was Dr. Mason Sones at the Cleveland Clinic who accidentally injected angiography dye into the mouth of the coronary arteries for the first time in a living patient. Dr. Sones was aware of the significance of this observation, so he went about designing catheters and techniques to routinely X-ray the various coronary arteries in human patients. The utility of the Sones techniques for safely documenting coronary artery blockages in humans was readily apparent and the procedure gained immediate popularity throughout the world. Other researches meanwhile were pursuing a means of supporting the circulation while the heart beat was temporarily stopped. Pumping the blood and restoring the oxygen content of the blood, the artificial heart-lung machine was gradually designed and modified in the 1950’s and early 1960’s. As improvements were made in heart-lung technology, its use spread to other types of heart operations. Although most of the initial cases of coronary artery surgery took place on the beating heart without the benefit of the heart-lung machine, surgeons quickly realized the advantages offered by performing these reconstructions when the heart was motionless.

Dr. David Sabiston is credited with attempting to directly suture a saphenous vein bypass graft into the coronary circulation at Duke University in 1962. His first vein bypass patient dies from a stroke, and Dr. Sabiston did not officially report his technique until 1974. The fist investigator to report the results of a whole series of direct coronary artery vein bypass grafts in an animal model was Dr. Lester Savage in 1963. In 1966, Kolesson in Leningrad, USSR reported the use of the internal mammary artery (from the inside of the chest wall) to create a bypass to the coronary artery in 6 patients, with 5 survivors. Dr. Renee Favalore, in May 1967, an Argentinean working at the Cleveland Clinic, reported initial results in a small series of patients where coronary bypass was performed in human patients with the saphenous vein from the leg. After these milestones, many investigators began to expand on the concept of reconstructing the blood supply to the heart with bypass grafts. The medical community immediately recognized the results of these pioneering efforts. Surgery remains the mainstay for a large group of patients for which other options are not effective. However there are many other treatment options.

Any surgery that is intended to the reconstruction of circulation of the heart will require a road map of the blood vessels and the location of the blockages. Coronary angiogram is a test most frequently used for this information. In this test, the small blood vessels feeding the heart are imaged the special X-ray techniques. The coronary arteries are injected with a special dye solution which shows up on X-ray film. As the dye travels down the branches of the coronary artery itself, moving pictures are taken with the X-ray camera. The entire series of angiographic movies are reviewed by the cardiologist and decisions made about the relative of the different treatments. Usually the operation is scheduled at a time that is best for the patient and surgeon, except in urgent cases. The surgeon must know of any changes in health as the surgery approaches. A cold or flu can lead to infections that could affect surgery. Most patients are admitted to the hospital one to three days before coronary artery bypass surgery. Patients can’t have anything by mouth after midnight on the day of the surgery. Once in the operating room, the patient receives an anesthetic that causes sleep. Once the patient is out, a breathing tube is put into the mouth, and a drainage tube in the bladder. After the surgery, the patient will spend one to two days in the intensive care unit to be monitored closely. There are many different types of equipment used after the surgery. An electrocardiogram (ECG) is used to monitor the patient’s heart, chest tubes to drain fluid from around the heart, a breathing tube to help breathing, a urinary catheter to drain urine from the bladder, and an intravenous (IV) tube in your arm. The breathing tube is usually removed after 24 hours. Usually patients are not able to talk while the breathing tube is in. For the first few days, most patients experience moderate pain and soreness from the surgical incisions. The patients start breathing and coughing exercises and use a breathing instrument once the tube is out. Doing these exercises helps clear the lungs and prevents any infection such as pneumonia. Because of the soreness, this may be uncomfortable at first, but this is a very important part of a quick recovery. Patients may start getting out of bed on the day after surgery. It may be tiring at first, but the patient’s strength will improve. Standing or walking may produce a burning sensation in eh leg where the graft was taken. The patient’s ankle may also swell. Wearing elastic support socks help decrease the swelling. Foot and ankle exercises and walking also help the circulation in your legs and fasten the healing process. Gradually the symptoms disappear. A slight fever is not uncommon after surgery. Today most surgeons use stitches that dissolve by themselves. If the patient has regular stitches or staples, they are removed from the chest about a week after surgery, and a few days later the ones in the chest are removed. One to two weeks after bypass surgery the patients are released from the hospital. Once the patient is home, it will take time to heal. There are good days and bad days that come along with the healing process. Taking the medications and eating properly are important factors that will facilitate one’s recovery. It is also important to get rest and begin to increase the patient’s physical activity. A patient may not have much of an appetite, at first, but eating will increase one’s strength. The food served in the hospital is not always heart-healthy. This is because initially the most importing thing is that the food appeals to the patient so that they will eat. Once the patients regain their appetite, eating a heart healthy diet becomes more important.

It is very normal to be emotional after heart surgery or any health crisis. Fear, anger, and feelings of depression are quite common; family members are likely to experience these feelings as well. This is a very normal part of the healing process and will resolve over time. Patients able to talk about their feelings and discussing their heart surgery and recovery are important. Returning to regular activities that the patient enjoys is important.

There are important incisions guidelines that patients need to go by. Some general guidelines for proper incision care are:

1. If the incisions are dry and healing showers (10 minutes or less) are allowed.

2. Quick baths are fine, however too much moisture can cause premature dissolving of stitches.

3. Extreme water temperatures should be avoided.

4. Water and gentle soap are permitted, but do not scrub with a washcloth or sponge until the skin is healed.

5. Ointments, lotions, and dressing are not recommended.

6. Tightness, numbness, and slight itching of incision area are normal.

The patient should notify their doctor if they experience the following signs of infection:

1. Opening of the incision or increased drainage.

2. Increased warmth or redness around incision.

3. Fever greater than 100 degrees F.

If the patient notices swelling of their feet or ankles, they need to try propping their feet up, however they should avoid crossing their legs. Regularly walking and support pantyhose are also recommended.

For the first six to eight weeks after surgery, the patient may feel tired or weak. Gradually resuming activities and developing an exercise program during this time are recommended. At first, take daily walks and resume household chores such as cleaning and fixing meals as the patient is able. Allow time to rest if one gets tired. Avoid lifting, pulling or pushing and heavy objects. If a patient does too much activity in a day, the body will let them know. This might be right away, or it may take a day or so to catch up. Symptoms of over-exertion include chest discomfort, extreme fatigue, excessive shortness of breath, rapid or irregular heart rate, and light headedness. If the patient experiences these symptoms, they should sit or lie down and rest. If symptoms persist longer than 20 to 30 minutes, the patient should call their doctor.

The patient should limit the fat and cholesterol in the diet after bypass surgery. Walking and swimming may be recommended to get strength back. The doctor may recommend the patient to join a cardiac rehabilitation program. These programs can help you make lifestyle changes like starting a new diet, quitting smoking, and learning to deal with stress. One can usually go back to work in 4 to 6 weeks, but physically demanding jobs require a longer recovery. In some extreme cases, one may need to find a new job that is not physically demanding. Twenty to thirty percent of bypass patients will need a second procedure within ten years.

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