NEW CHALLENGES IN INTERNAL MEDICINE
0025-7125/92 $0.00 + .20
MYOCARDIAL REV ASCULARIZATION Coronary Angioplasty and Bypass Surgery Indications Jay L. Hollman, MD
Coronary artery disease (CAD) is still the leading cause of overall mortality in the United States despite a decline observed in death rates over the past 25 years. Although considerable advances have been achieved in medical treatment, many patients do not respond well to pharmacologic approaches, and they require more effective and aggressive therapies. Coronary artery bypass grafting (CABG) and percutaneous transluminal coronary angioplasty (PTCA) have been performed increasingly over the last 20 and 10 years, respectively, for the treatment of atherosclerotic coronary disease. The growth in PTCA is both complementary and threatening to CABG. This controversy has ignited many debates between cardiologists and cardiac surgeons over the role of each procedure. This debate will no doubt continue as new devices are developed for coronary interventions. This article reviews this controversy and provides information to internists so that they will be fully prepared to advise patients about their treatment options.
BACKGROUND TO THE CONTROVERSY Part of the problem is understanding certain evolutionary changes that have occurred and that continue to affect the balance between CABG and PTCA. In interpretating older literature, major milestones From the Department of Cardiology, Ochsner Clinic of Baton Rouge, Baton Rouge, Louisiana THE MEDICAL CLINICS OF NORTH AMERICA VOLUME 76' NUMBER 5' SEPTEMBER 1992
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that have changed the direction of these procedures must be taken into account. For bypass surgery, these events are the development of routine cardioplegia in the late 1970s43 and the acceptance of the internal thoracic (mammary) artery as the graft of choice in the mid-1980s. 45 The routine use of cardioplegia allows surgeons to perform more complex revascularization procedures with better myocardial protection. At Cleveland Clinic, the perioperative myocardial infarction rate was 2.3% to 11.6% before 1978 and 0.8% to 1.6% after 1978. 66 The long-term patency rate and improved survival following the internal thoracic artery bypass have made it the conduit of choice for bypass surgery.45 The use of steerable, over-the-wire systems in 1982 was an important development in coronary angioplasty. This increased greatly the number of patients in whom angioplasty could be attempted and also increased the primary success rate from 65% to 70% to greater than 90%.34 Technology has steadily lowered the profile of the balloon catheter with slight improvements in success and lowering of complication rates,73 but the continued limitations of the inability to cross total occlusion and a recurrent stenosis rate of 20%-30% remain. The profound shift in indications is best illustrated by Figure 1. In 1979, only 2000 PICA procedures were performed in the United States, which was small compared with the 144,000 bypass surgeries performed. Almost all patients were candidates for bypass surgery. By the mid-1980s, PTCA had grown to 82,000 in number, whereas CABG numbered about 205,000. Clearly, PTCA was being used now for Revascularization in 1979
Revascularization in 1985
B Revascularization in 1990
Figure 1. A, B, and C represent the evolution of the balance between coronary angioplasty and bypass surgery over time. Circle on the left labeled "Medical Therapy" represents patients with mild coronary artery disease who were not ill enough to require bypass surgery in 1979; the circle on the right represents patients with severe coronary disease who were thought to have an unfavorable risk:benefit ratio for bypass surgery in 1979. This group remains the same for A, B, and C. A portion of coronary angioplasty's growth has been at the expense of bypass surgery; however, bypass surgery's volume has been maintained by performing surgery on patients who were thought to be too ill for surgery in 1979.
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patients whose condition would not have been considered severe enough to require surgery in the 1970s. The indications for CABG had expanded to patients whose disease would have been considered too severe for CABG in the 1970s. By the late 1980s, the number of PTCA procedures in the United States had surpassed those of CABG and began to include angioplasty being performed on patients who had been considered too well or too sick for bypass surgery in the 1970s. This later shift was possible because of better methods of patient stabilization, such as perfusion catheters, intra-aortic balloon pump, and percutaneous bypass. 60, 65 Currently, the patient population undergoing CABG is older, more likely to have had prior myocardial infarction, more likely to have worse left ventricular function, and more often is female,u Moreover, cardiac surgeons are performing more reoperations and more emergency operations. 4 Mortality and length of stay are increasing for cardiac surgery. 15, 55
THE DECISION FOR REVASCULARIZATION THERAPY
A full discussion of when to cross over from medical to revascularization therapy with either PT CA or CABG is beyond the scope of this review. However, in general, patients with unstable angina do better with revascularization therapy than with medical therapy. The spectrum between stable exertion angina and unstable angina is continuous and must be factored into the equation. Angina that is regarded as unstable because of a decrease in exercise tolerance is not as ominous as the angina occurring at rest that is associated with transient ST segment elevation. The more unstable the angina, the more revascularization therapy is to be favored. The amount of myocardium at risk, the severity of symptoms, and the age of the patient may affect the decision to recommend revascularization therapy (Fig. 2). Prolongation of life becomes a factor when the patient has triple vessel CAD or significant left main coronary artery obstruction, even if the patient has stable angina. 24 , 52, 61
Figure 2. This graph is useful for understanding when revascularization therapy is indicated. Point "a" may represent a patient with minimal angina symptoms but severe two- or three-vessel disease with most of the heart muscle at risk. Point "b" might represent a patient with a severe lesion in a branch of a major coronary artery. In this case, most cardiologists would el
0025-7125/92 $0.00 + .20
MYOCARDIAL REV ASCULARIZATION Coronary Angioplasty and Bypass Surgery Indications Jay L. Hollman, MD
Coronary artery disease (CAD) is still the leading cause of overall mortality in the United States despite a decline observed in death rates over the past 25 years. Although considerable advances have been achieved in medical treatment, many patients do not respond well to pharmacologic approaches, and they require more effective and aggressive therapies. Coronary artery bypass grafting (CABG) and percutaneous transluminal coronary angioplasty (PTCA) have been performed increasingly over the last 20 and 10 years, respectively, for the treatment of atherosclerotic coronary disease. The growth in PTCA is both complementary and threatening to CABG. This controversy has ignited many debates between cardiologists and cardiac surgeons over the role of each procedure. This debate will no doubt continue as new devices are developed for coronary interventions. This article reviews this controversy and provides information to internists so that they will be fully prepared to advise patients about their treatment options.
BACKGROUND TO THE CONTROVERSY Part of the problem is understanding certain evolutionary changes that have occurred and that continue to affect the balance between CABG and PTCA. In interpretating older literature, major milestones From the Department of Cardiology, Ochsner Clinic of Baton Rouge, Baton Rouge, Louisiana THE MEDICAL CLINICS OF NORTH AMERICA VOLUME 76' NUMBER 5' SEPTEMBER 1992
1083
1084
HOLLMAN
that have changed the direction of these procedures must be taken into account. For bypass surgery, these events are the development of routine cardioplegia in the late 1970s43 and the acceptance of the internal thoracic (mammary) artery as the graft of choice in the mid-1980s. 45 The routine use of cardioplegia allows surgeons to perform more complex revascularization procedures with better myocardial protection. At Cleveland Clinic, the perioperative myocardial infarction rate was 2.3% to 11.6% before 1978 and 0.8% to 1.6% after 1978. 66 The long-term patency rate and improved survival following the internal thoracic artery bypass have made it the conduit of choice for bypass surgery.45 The use of steerable, over-the-wire systems in 1982 was an important development in coronary angioplasty. This increased greatly the number of patients in whom angioplasty could be attempted and also increased the primary success rate from 65% to 70% to greater than 90%.34 Technology has steadily lowered the profile of the balloon catheter with slight improvements in success and lowering of complication rates,73 but the continued limitations of the inability to cross total occlusion and a recurrent stenosis rate of 20%-30% remain. The profound shift in indications is best illustrated by Figure 1. In 1979, only 2000 PICA procedures were performed in the United States, which was small compared with the 144,000 bypass surgeries performed. Almost all patients were candidates for bypass surgery. By the mid-1980s, PTCA had grown to 82,000 in number, whereas CABG numbered about 205,000. Clearly, PTCA was being used now for Revascularization in 1979
Revascularization in 1985
B Revascularization in 1990
Figure 1. A, B, and C represent the evolution of the balance between coronary angioplasty and bypass surgery over time. Circle on the left labeled "Medical Therapy" represents patients with mild coronary artery disease who were not ill enough to require bypass surgery in 1979; the circle on the right represents patients with severe coronary disease who were thought to have an unfavorable risk:benefit ratio for bypass surgery in 1979. This group remains the same for A, B, and C. A portion of coronary angioplasty's growth has been at the expense of bypass surgery; however, bypass surgery's volume has been maintained by performing surgery on patients who were thought to be too ill for surgery in 1979.
1085
MYOCARDIAL REVASCULARIZATION
patients whose condition would not have been considered severe enough to require surgery in the 1970s. The indications for CABG had expanded to patients whose disease would have been considered too severe for CABG in the 1970s. By the late 1980s, the number of PTCA procedures in the United States had surpassed those of CABG and began to include angioplasty being performed on patients who had been considered too well or too sick for bypass surgery in the 1970s. This later shift was possible because of better methods of patient stabilization, such as perfusion catheters, intra-aortic balloon pump, and percutaneous bypass. 60, 65 Currently, the patient population undergoing CABG is older, more likely to have had prior myocardial infarction, more likely to have worse left ventricular function, and more often is female,u Moreover, cardiac surgeons are performing more reoperations and more emergency operations. 4 Mortality and length of stay are increasing for cardiac surgery. 15, 55
THE DECISION FOR REVASCULARIZATION THERAPY
A full discussion of when to cross over from medical to revascularization therapy with either PT CA or CABG is beyond the scope of this review. However, in general, patients with unstable angina do better with revascularization therapy than with medical therapy. The spectrum between stable exertion angina and unstable angina is continuous and must be factored into the equation. Angina that is regarded as unstable because of a decrease in exercise tolerance is not as ominous as the angina occurring at rest that is associated with transient ST segment elevation. The more unstable the angina, the more revascularization therapy is to be favored. The amount of myocardium at risk, the severity of symptoms, and the age of the patient may affect the decision to recommend revascularization therapy (Fig. 2). Prolongation of life becomes a factor when the patient has triple vessel CAD or significant left main coronary artery obstruction, even if the patient has stable angina. 24 , 52, 61
Figure 2. This graph is useful for understanding when revascularization therapy is indicated. Point "a" may represent a patient with minimal angina symptoms but severe two- or three-vessel disease with most of the heart muscle at risk. Point "b" might represent a patient with a severe lesion in a branch of a major coronary artery. In this case, most cardiologists would el
