The choice of percutaneous coronary revascularization rather than medical or surgical therapy was made by the attending cardiologist. Initially, only balloon angioplasty was performed, according to conventional techniques.11 Later in the study period, other procedures, such as atherectomy, laser angioplasty, and coronary stenting, were also employed, although balloon angioplasty remained the most common procedure. In cases of multivessel disease, the culprit lesion was generally treated first. Identification of the culprit lesion was based on the findings on electrocardiography, regional left ventricular functional studies, thallium scintigraphy, and coronary angiography.
Follow-up angiography was usually performed only if the attending physician was concerned about recurrent symptoms suggestive of myocardial ischemia. The need for additional coronary revascularization of the target lesion or other segments was also determined by the attending physician. Although all additional percutaneous coronary interventions were documented, data on the segment treated were available only for procedures performed at the Mayo Clinic. The left ventricular ejection fraction was determined by ventriculography at the time of diagnostic angiography in most patients, and during follow-up, as indicated clinically, by echocardiography, radionuclide studies, or left ventricular angiography.
The severity of coronary artery disease was assessed visually by at least two observers using orthogonal views. Single-vessel coronary artery disease was defined as stenosis of at least 70 percent of the diameter of only one major epicardial artery. Two- or three-vessel disease was diagnosed if there were one or two additional major epicardial arteries with at least 70 percent stenosis, respectively. Among patients with 50 percent or more stenosis of the left main coronary artery, those with a right dominant artery were considered to have two-vessel disease and those with a left dominant artery were considered to have three-vessel disease.
Q-wave myocardial infarction was defined as the presence of new Q waves on the electrocardiogram,12 with serum creatine kinase concentrations that were at least three times higher than normal or positive tests for MB isoenzymes, an episode of prolonged angina, or new regional wall-motion abnormalities.
Angina was classified according to the classification system of the Canadian Cardiovascular Society.13 Severe angina was defined as class III or IV.
Complete revascularization was defined as successful dilation of all stenoses of 70 percent or more. Incomplete revascularization was defined as successful dilation of one or more stenoses but with one or more remaining arteries with at least 70 percent stenosis.
The angiographic success of revascularization was defined as a reduction of at least 20 percentage points in the stenosis of at least one lesion, resulting in a residual stenosis of less than 50 percent of the luminal diameter. Clinical success was defined as angiographic success without the in-hospital complications of death, Q-wave myocardial infarction, or referral for coronary-artery bypass grafting.
Death from cardiac causes was defined as death due to myocardial infarction, an arrhythmic event, heart failure, or complications of cardiac surgery or transplantation.