To determine the influence of adjunctive treatment with coumadin or aspirin on recurrence rate after percutaneous transluminal coronary angioplasty (PTCA), 248 patients in whom PTCA was assessed to be a primary success were randomized to either 325 mm aspirin daily or to coumadin treatment sufficient to maintain a prothrombin time 2 to 2.5 times the control value. The follow-up protocol included stress testing and coronary angiographic examinations 3 to 6 months after PTCA. All patients were followed for at least 9 months. Of the 122 patients randomized to coumadin 44 AFTER REVASCULARIZATION PROCEDURES such as coronary artery bypass grafting and coronary angioplasty there is often recurrence of stenosis. Several adjunctive therapies have been recommended to prevent thrombus formation with closure of graft or vessel. Early investigators in angioplasty recommended the use of coumadin as long-term adjunctive therapy after femoropopliteal transluminal angioplasty with the Dotter technique.' Thereafter, coumadin therapy was also used for peripheral dilatation with the balloon technique2 and later applied in coronary angioplasty.3 Long-term patency of 75% was achieved in European patients with adjunctive coumadin therapy after percutaneous transluminal coronary angioplasty (PTCA). The use of coumadin therapy was also supported by selected studies of the effectiveness of anticoagulants in patients after myocardial infarction.5 6 Other studies demonstrated benefit from the administration of aspirin after infarction.7-9 Schneider et al.10 reported the results of a randomized study comparing aspirin and

Obstruction to blood flow is accompanied by a pressure gradient across the obstructed site. In certain clinical settings, magnitude of pressure gradient has been used to judge severity of obstruction, and gradient reduction to judge success of an interventional procedure. In percutaneous transluminal coronary angioplasty (PTCA) the relationships between transstenotic pressure gradient, diameter stenosis, and lesion length are imprecisely known. We therefore examined 4263 sets of measurements in patients who underwent PTCA on single, discrete coronary arterial lesions. Multivar-iate regression analysis demonstrated that pressure gradient was artifactually elevated by about 12 mm Hg at low values of diameter stenosis but increased by the 4th power of stenosis as expected from fluid dynamics models. Pressure gradient was dampened and relatively constant at values of diameter stenosis of 60% or higher, probably because of total or near-total occlusion of the artery. Lesion length was not found to influence pressure gradient. Reductions in diameter stenosis (AD) and pressure gradient (AG) were related nonlinearly, with AD proportional to the square root of AG, suggesting that a reduction in gradient is directly proportional to an increase in cross-sectional area of the stenosis. The predictive value of final post-PTCA pressure gradients was found: a final gradient of 15 mm Hg or less predicted a final post-PTCA diameter stenosis of 30% or less, with 75% sensitivity and 29% specificity (p < .01). The results of this study suggest that (1) pressure gradient as currently measured during PTCA is related to diameter stenosis but not to lesion length (2) reductions in pressure gradient and diameter stenosis are nonlinearly related, and (3) reductions in pressure gradient and final post-PTCA pressure gradient are useful indicators of initial angiographic outcome. Circulation 73, No. 6, 1223-1230, 1986 THE FUNDAMENTAL aim of percutaneous transluminal coronary angioplasty (PTCA) is to enlarge a coronary artery lumen at a site of discrete, atheromatous obstruction.' By reducing obstruction, coronary blood flow is increased and, in particular, coronary flow reserve is increased.t7 Assessing enlargement of a coronary artery lumen during the course of a dilatation procedure is often difficult. Fluoroscopy with high-resolution video imaging can outline an arterial lumen but is suboptimal for quantitative analysis. Caliper or other quantitative methods for measuring a stenosis can be applied to cineangiographic film' but are unavailable during the procedure.

SUMMARY Forty-nine patients in whom percutaneous transluminal coronary angioplasty (PTCA) was attempted were evaluated by thallium-201 myocardial scintigraphy after exercise and at rest before the intervention. After successful PTCA of a single stenosis in a native vessel (30 of 44 patients) and of a stenosis in an aortocoronary bypass graft (three of five patients), scintigraphy was repeated within 3 weeks in 30 patients. Long-term follow-up studies by scintigraphy at 5-6-month intervals up to more than 2 years (mean follow-up 18 months) were performed in 16 patients.Before PTCA, clear-cut regions of decreased thallium-201 activity were observed in 43 of 49 patients. Thallium-201 activity within this zone was reduced to 74 ± 1% (SEM) of maximal myocardial thallium-201 activity after exercise, but returned to normal (> 80%) at rest (88 ± 1%, p < 0.001). After PTCA, no distinct defects were recognizable in the region of previously decreased thallium-201 activity, and the respective values were 89 ± 1% after exercise at identical work loads (p < 0.001 compared with the corresponding values before PTCA) and 94 + 1% (p < 0.01) at rest. These results paralleled the angiographic findings, which showed an increase in luminal diameter in the stenotic segment of the treated vessel from an average of 15 ± 2% of the pre-and poststenotic vessel diameter before PTCA to 67 ± 3% (p < 0.001) after PTCA. During long-term follow-up, thallium-201 activity remained normal after exercise in the entire heart in 13 of 16 patients. In three patients, a new defect in the same location as before treatment reappeared 4½/2, 6 and 29½/2 months after PTCA because the stenosis recurred, as documented by angiography.We conclude that thallium-201 exercise scintigraphy permits the best documentation of the ongoing changes in myocardial perfusion after PTCA.THE FEASIBILITY of instrumental exploration of the coronary arterial tree through a transaortic approach and its implications for removal of atheromatous tissue by retrograde curettage was first studied in dogs and human cadavers by May' and Absolon et al.2 Eight years later, Dotter and Judkins3 described a new nonoperative technique to dilate arteriosclerotic obstructions of the femoral arteries by means of tapered catheters of different outer diameters. In 1976, Gruentzig4' 5 reported encouraging results in the treatment of femoropopliteal and iliac artery obstructions using a double-lumen catheter with a nonelastic balloon at its tip. Once placed in the stenotic lesion, high pressure inflation of the balloon compressed the obstructing atheromatous material against the vascular wall, thereby enlarging the lumen. With miniaturization of the dilating catheter and with the development of appropriate guiding catheters adapted from the Judkins-type catheters for selective coronary arteriography, the system became suitable for the treatment of coronary artery stenoses.8

796-802, 1983. IN THE FIRST PATIENTS we treated with percutaneous transluminal coronary angioplasty (PTCA) serial bicycle exercise tests were done in an ongoing prospective study to determine the immediate and long-termn functional outcome of the operation. Comparisons were possible between patients in whom PTCA was successful and those in whom it failed and who underwent subsequent coronary artery bypass grafting (CABG). Previous studies have shown that PTCA is able to restore coronary blood flow, alleviate symptoms, and improve left ventricular perfusion and work capacity. 1' Other reports have addressed the topic of the use of exercise tests to determine outcome ifi patients who undergo CABG5-15; in some of these studies results were compared with those in a group receiv-