Science and Profession
Vascular medicine, especially peripheral vascular
surgery, has become an important specialty of general surgery. In the past, general surgeons performed surgery on the arteries and veins, but technical advances have led to the creation of vascular surgery as a field of its own.
Western society has produced an older population because of its high level of primary care, but with this older population come the ravages of atherosclerosis. The modern lifestyle is ideally suited to the formation of atherosclerosis in many arteries as a result of cigarette smoking, stress and high blood pressure, a fatty diet, and a sedentary lifestyle. Peripheral vascular surgeons can contribute in a positive way and help many patients with these diseases. This help may come in the form of stroke prevention, the restoration of blood flow to a leg that might otherwise not be saved, or occasionally the saving of a life through repair of a ruptured aortic aneurysm.
One of the most common arteries affected by atherosclerosis is the carotid artery, in the neck. This artery branches high in the neck near the jawline. One branch continues up into the brain, supplying a large part of the area that controls motor and sensory function. Atherosclerosis tends to occur at areas of branching arteries, and the carotid bifurcation is no exception. The buildup of material in this location is especially hazardous, because small pieces of the material, called emboli, can break off the arterial wall, travel up the artery, and lodge in the brain.
When an embolus lodges in the small arteries of the brain, it blocks the flow of blood to the area of brain tissue supplied by those arteries. This results in ischemia, or restricted blood flow, and the body functions controlled by that part of the brain may be altered. If the ophthalmic artery is involved, then blindness can ensue. If the middle cerebral artery is involved, then symptoms of motor and sensory dysfunction, such as abnormal sensation, numbness, weakness, or paralysis of one side of the body, can occur. Fortunately, very small emboli often do not cause permanent loss of neurological function, and a complete recovery is possible. They are, however, warning signs that atherosclerotic debris resides in the carotid artery, and if treatment is not begun and the brain tissue is irreversibly damaged, a permanent stroke might occur. If this happens, the patient will lose some neurologic function and may be unable to see to his or her own daily needs. The patient also may need extensive and expensive rehabilitation. Strokes can be prevented if the warning signs are properly interpreted and acted upon.
Atherosclerosis also results in stenoses, or blockages, in other arteries. Depending on the location of these blockages, various symptoms can result. If the arteries to the intestines are involved, patients can feel abdominal pain that is very difficult to diagnose, given that there are many other causes of abdominal pain, such as ulcer disease, gallbladder problems, and colitis. Intestinal ischemia is somewhat rare and often is not thought of as a cause of abdominal pain. These patients may have to endure this pain for a long period of time and may experience severe eating problems, weight loss, and addictions to painkillers. If the problem is properly diagnosed, many patients can be helped with nonsurgical and surgical techniques, resulting in the cessation of pain, the regained ability to eat, and the maintenance of proper nourishment.
One form of atherosclerotic arterial disease is called
renovascular hypertension. In this syndrome, plaque builds up in the renal (kidney) arteries. Patients with renovascular hypertension exhibit a type of high blood pressure, or hypertension, that is somewhat different from the kind of high blood pressure that affects most patients. The majority of patients with hypertension have what is called essential hypertension, for which there is no known cause. For the minority of patients whose hypertension results from pathology in the renal arteries, the blood flow in these arteries is decreased because of atherosclerotic plaques in the arterial walls that severely limit the space through which blood can flow. When this happens, the kidney “senses” this decreased flow and releases a variety of chemical hormones that serve to increase the blood flow. These hormones indirectly raise the blood pressure by trying to preserve blood flow to the kidney.
Renovascular hypertension is often difficult to diagnose and treat. Many patients need to take up to five kinds of blood-pressure pills to keep their pressure under reasonable control; such patients should be screened for renovascular hypertension. A variety of treatments can be offered to these patients once a diagnosis is made, although the medicines they must take all have significant side effects.
The arteries that supply the muscles and nerves of the extremities also can be affected by atherosclerotic disease. Peculiarly, the upper extremities are usually spared of this disease, whereas the
lower extremities are not. The mildest form of lower-extremity disease manifests itself in the form of claudication, a term that describes the specific symptoms that develop in an ischemic limb. Most of the time, there are no symptoms when a patient is at rest, but when the patient undergoes the physical stress of walking or other exercise, pain develops in the limb in certain areas that correspond to the areas of muscle tissue supplied by the blocked artery. A characteristic pain syndrome develops after a certain amount of exercise and repeats itself regularly. The pain stops after exercise, and this cessation of pain also follows a pattern.
Claudication is the classic example of arterial occlusive disease. If the disease is severe enough, it may cause resting pain. Such patients have profound ischemia of their leg(s), which is limb threatening and requires intervention. People afflicted with ischemia of the leg have difficulty healing small scrapes and cuts on the feet, sometimes causing them to turn into large lesions that do not heal. If these lesions become secondarily infected, they can also become limb threatening and ultimately necessitate amputation. In many patients, however, amputation can be avoided by timely intervention with either surgery or other techniques.
A rather curious phenomenon occurs in some patients whereby there is a focal dilatation of a portion of an artery. The mechanism by which this occurs is largely unknown, but it may be related in some way to the atherosclerotic process. Instead of a buildup of debris in the arterial wall resulting in a blockage in the artery, aneurysms are characterized by a thinned-out wall. They enlarge over time and can cause problems. They may clot off entirely or become a source of emboli, giving rise to problems farther down the arterial tree. The most devastating complication of an aneurysm, however, is acute rupture. Laplace’s law of hemodynamics states that wall tension in a tube of fluid is related to the fourth power of the radius. Accordingly, as an aneurysm enlarges, the wall tension increases in exponential fashion. If rupture does occur, it can lead to rapid blood loss if expert medical and surgical care is not readily available.
Aneurysms can form anywhere in the body, but they most commonly occur in the aorta (the main artery coming out from the heart) directly beneath the umbilicus. Because this location is surgically accessible, repair of these aneurysms is a common operation. In this location, most aneurysms will not cause a problem until they measure approximately five centimeters in diameter, at which size the risk of rupture becomes significant. Smaller aneurysms are usually monitored with serial examinations over time, and if they do enlarge, then the appropriate therapy can be instituted. Other, less common areas of aneurysm formation include the splenic, renal, iliac, femoral, and popliteal arteries. Similar complications can ensue with these aneurysms.
The majority of peripheral vascular surgery practice deals with the diseases of the arteries, but venous disease is a very common problem that many physicians in many specialties must address. Patients with simple
phlebitis of the superficial
veins of the leg usually require no more than supportive care until they feel better, but if the clots are in or extend into the deep veins of the leg, much more aggressive treatment is necessary. A clot in this location has a chance of migrating into the lungs (pulmonary embolus) and can be fatal. Therefore, intensive treatment with intravenous and then oral blood thinners (anticoagulants) is mandatory. There are some patients who then have chronic venous problems because the clots in their legs can damage the valves in the veins. This results in severe pain, swelling, and even ulceration of the legs that can be very difficult to treat.
Diagnostic and Treatment Techniques
Many patients who suffer from vascular diseases are not treated with surgery right away. They may ultimately need an operation, but often long periods of time elapse before surgery is undertaken. Nonoperative therapy, such as quitting smoking, lowering serum cholesterol, or starting an exercise program, is often all that is needed to control certain aspects of the patient’s symptoms. Vascular surgeons provide guidelines for patients who need this sort of therapy.
Atherosclerosis may appear in many forms and affect patients differently. For example, a forty-five-year-old postal carrier complains of pain in his or her thighs in the same location whenever he or she walks more than a few hundred feet. This person may have been a heavy smoker for many years, his or her cholesterol levels may be elevated, and there may be many relatives in his or her family with hardening of the arteries. Such a person has a classic case of claudication resulting from atherosclerotic occlusive disease of the arteries that supply the thigh muscles. The patient has several options. Other causes of leg pain must be ruled out, such as nerve problems or back conditions, but when this is accomplished, the field of vascular surgery can help this patient maintain his or her lifestyle. If the patient would like to investigate options for intervention, an arteriogram is performed next. In this procedure, specially trained radiologists insert a small tube into the arteries and take pictures after dye has been injected. This allows an exact replica of the patient’s arterial anatomy to be projected in two dimensions. The arteriogram allows the surgeons and radiologists to determine the best course of action for this patient.
Some atherosclerotic plaques are in particular locations that may allow their treatment with balloon angioplasty rather than open surgery. In this procedure, again performed by trained radiologists or some vascular surgeons, a catheter with a balloon at its end is inserted into the artery, and the balloon is inflated in the area of the offending plaque in an effort to open the clogged artery. This procedure is often performed on the arteries of the heart, but it can also be performed on other arteries, such as those in the kidneys, intestines, or legs. A vascular surgeon usually oversees the care of the patient, as not all the balloon procedures are completely successful and open surgery is sometimes necessary. Open surgery might include a bypass graft with a woven or knitted prosthetic artery or a graft made with an expendable vein in the patient’s leg, using the same vein as for heart bypass surgery. The postal worker described above could be a candidate for either a balloon procedure or a surgical bypass graft, but in either case, he or she should be restored to almost normal walking capability and be able to return to work.
Another common scenario might involve a more serious situation. A person may have an open sore on his or her foot that has been there for more than six months and is getting bigger, perhaps infected. This person may also be a heavy smoker with cholesterol problems and severe diabetes mellitus. He or she has not walked more than a block in the past few years because this causes his or her feet to hurt. The problem may be related to poor blood flow to the legs and feet, and the diabetes certainly does not help. Before vascular surgery techniques became popular, this patient ultimately would have required an amputation of the leg, either below or above the knee. It is physically and emotionally difficult for patients to cope with such a loss, and the long, expensive period of rehabilitation includes learning to walk with a prosthetic extremity. This patient would be a good candidate for an arteriogram and would undoubtedly need some surgery. This would most likely be in the form of a bypass graft, which could stretch from the groin all the way to the foot, crossing the knee and the ankle. Ultimately, a successful outcome would be healing of the open sore and control of the infection; the patient would then be able to continue walking with his or her own leg.
Another situation that might involve vascular surgery is as follows. A patient has a history of deep vein clots following prior major surgery. Treatment consisted of long-term blood thinners, and the patient may have had no major problems since that time. The patient now needs a hip operation, however, and hip operations carry a high risk of blood-clot formation in the deep veins of the leg. Because deep-vein thrombosis carries risks of a pulmonary embolus as well as chronic problems in the leg, a vascular surgeon is called upon to help design a program that can prevent these complications from occurring. The usual methods of prophylaxis do not necessarily apply to this patient, and as the patient is labeled high risk, it might be most prudent to place a device in the body to catch any pulmonary emboli if they occur. The theory behind this management is that, in this high-risk patient, the formation of blood clots in the legs is almost unavoidable, and the majority of effort should be aimed at preventing the most serious, potentially fatal complication: the pulmonary embolus. In this case, vascular surgeons could place a filter device in the main vein that carries blood to the heart and lungs, which would effectively trap any free-floating emboli that could cause a problem.
Perspective and Prospects
Peripheral vascular surgery has assumed a paramount role in medical practice. By 1900, significant contributions had been made regarding the basic reconstructive techniques needed to sew arteries together. The work of Alexis Carrel in the early twentieth century is considered the most important contribution to the technical art of vascular surgery. His techniques for transplanting organs and sewing arteries together are still routinely performed. By the 1950s, synthetic materials were introduced as arterial replacements, which became acceptable treatment for many patients.
In addition to balloon angioplasty, nonsurgical or minimally invasive surgical techniques for opening blocked arteries and veins to improve blood flow include the use of a stent, or a small mesh tube, which can be expanded inside a blocked blood vessel to increase its diameter and then remain there to hold it open; an atherectomy, in which a thin tube is inserted into the vessel to cut away the plaque; and thrombolysis, which is the use of either traditional pharmaceuticals or biopharmaceuticals to break down blood clots. Although technically performing a bypass graft is feasible, the graft cannot approach the durability and performance of a native artery and typically does not last longer than fifteen years. Research involving the transplantation of human arteries may solve some of these problems and allow more patients to benefit from surgery.
Vascular surgery can benefit large numbers of people simply because of the nature of atherosclerosis. It may be a product of habits, the environment, or genetic makeup, but it is widely accepted that as the population ages, more and more people will suffer from diseases that can be helped by vascular surgery, allowing them to maintain lifestyles that are as productive as possible. Basic scientific research into the mechanisms of atherosclerosis may yield important answers and lead to new therapies for patients with vascular disease.
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