Revascularization: Bypass Surgery and Angioplasty

If angina cannot be controlled adequately with medications, or if patients have severe side effects such as asthma or depression with beta blockers or severe headaches with nitroglycerin, then revascularization may need to be considered. This consists of opening clogged arteries or replacing blocked arteries with a patient’s own veins or arteries to bypass the blockage. Coronary artery bypass grafting (CABG) is open-heart surgery, and it has been available since the early 1970s. In the mid 1980s, nonsurgical revascularization was developed using balloons guided to the coronary arteries through X-ray equipment. This is known as percutaneous transluminal coronary angioplasty (PTCA).

Patients with unstable angina, or those who are felt to be at high risk, are referred for coronary angiography. This is a specialized X ray used to determine exactly where the blockages to the coronary arteries exist. An intravenous catheter is inserted into the femoral artery in the groin or into the brachial artery at the elbow. Through this sheath long catheters are guided using X-ray equipment through the major arteries to the heart. Dye is injected into the coronary arteries and X rays measure the extent of blockages.

Cardiac catheterization does carry a small but real risk, including allergic reactions (one in one thousand patients), MI (one in one thousand), stroke (one in two thousand), or death (one in one thousand). Other complications include renal failure. Risk factors that predispose to heart disease and that increase with age (e.g., diabetes, hypertension) also increase the risk for renal disease.

Patients are required to lie on their back for five to six hours after the catheter has been removed to prevent significant bleeding. Even with precautions, large bruising may occasionally result. This will resolve spontaneously, but may take days or even weeks.

Following angiography, the type or extent of blockage and the number of coronary arteries involved determines the best treatment. Studies comparing surgery to medical therapy have determined what degree of blockage most benefits from surgery. Unfortunately, patients over the age of sixty-seven were excluded from these trials. Because older patients have an increased risk of dying from surgery, as well as other complications such as stroke, renal failure, postoperative infection, and prolonged hospitalization, it is difficult to be certain that this same benefit is present. By benefit we understand a reduction in mortality. The original trials showing the benefit of surgery also tended to exclude women, who make up more than 50 percent of the elderly population. In addition, these trials were conducted in the 1970s, and since then there have been considerable improvements in both medical therapy and surgical therapy.

The rationale for surgical intervention is that risks taken at the time of surgery will pay off with long-term benefits. A review by Yusuf, Zucker, Peduzzi, et al. of the trials comparing bypass surgery and medical therapy show that the peak benefit of surgery over medical therapy occurs at five years after surgery. At this point, mortality rates are 10.2 percent for surgical patients vs. 15.8 percent for those having medical therapy in the under sixty-five age group.

Expected mortality for patients under the age of sixty-five who undergo bypass surgery and have no other major medical problems is less than 1 percent. Over the age of seventy, operative mortality may increase to 2 to 5 percent; and over the age of eighty this increases to 5 to 10 percent. Depending on operative risk factors, which are certainly increased in older patients, mortality may climb to 20 percent, and emergency surgery has a ten-fold increase in risk to 35 percent. The major risk factors include an ejection fraction (fraction of blood pumped out of the heart with each beat) less than 20 percent, repeat surgery, emergency surgery, female sex, diabetes, age greater than seventy, left main disease (two of the three arteries to the heart branch of the short left main artery; if it is blocked fifty percent, this is considered a significant risk), recent MI, and/or three-vessel coronary artery disease. The incidence of coronary artery disease also increases with age, and the greatest growth in the use of bypass surgery has been in the elderly. Older age also predisposes to other risk factors for heart disease, such as underlying lung disease, kidney problems, cerebrovascular disease, diabetes, and problems with infection and healing postoperatively.

Stroke is another possible operative complication. The risk of stroke is less than 2 percent for Figure 2 The Heart: Frontal View SOURCE: Suggested by brochure issued by Pfizer Canada Inc. (1996) and created by Symphony Medical Communications of Oslo, Norway (1996). Figure 3 The Heart: Pacemaker SOURCE: Suggested by brochure issued by Pfizer Canada Inc. (1996) and created by Symphony Medical Communications of Oslo, Norway (1996). those under age seventy and greater than 6 percent for those over age seventy. A less well-documented area of concern is that of cognitive change or decline following bypass surgery. While more difficult to measure, this may have great significance for patients’ independent living and quality of life postoperatively.

Renal failure also increases with increasing age after bypass surgery. It occurs in less than 1 percent of patients under the age of seventy, but is present in almost 2 percent of patients over the age of eighty. Predisposing factors would be renal failure preoperatively, diabetes, and hypertension. Older patients tend to have longer hospital stays postoperatively.

The long-term mortality rates are three to four times greater for older patients at five to ten years after surgery. It is, therefore, somewhat difficult to extrapolate older data on younger patients to older patients, who clearly have greater risks but may not have as much benefit regarding survival. The reasons to undertake any intervention, whether it be medication or surgery, are either to prolong life or to improve symptoms. While the evidence for bypass surgery prolonging life in patients over the age of sixty-five remains unclear, there certainly is improvement in symptoms of angina and quality of life in older patients, provided major complications are avoided.

Bypass surgery is done under general anesthesia, usually lasting three to four hours. The chest or sternum is split, while a specialized pump maintains circulation to the vital organs. The heart is then stopped and arteries or veins are attached to the aorta. The other ends are reattached to the native arteries beyond the blockages. Veins are generally harvested from the leg; arteries from the forearm or chest. Although there are three major arteries supplying the heart, these all have multiple branches, and patients may have up to five or six bypasses done during surgery. During the first twenty-four to forty-eight hours after surgery, the patient is placed in the intensive care unit. Following this, the patient is transferred to a regular hospital ward for mobilization and monitoring of complications. The great majority of patients do very well with this surgery and return to a full and active life.