Eighteen patients with chronic angina despite surgical and medical therapy were treated with an improved system of enhanced external counterpulsation (EECP) (1 hour daily for a total of 36 hours). Patients underwent a baseline treadmill thallium-201 stress test. After EECP treatment, a thallium stress test was repeated for the same exercise duration. One week after treatment, patients also underwent a maximal stress test. All patients improved in anginal symptoms and generally decreased antianginal medications, with 16 obtaining complete relief from angina. Pre- and post-thallium stress testing performed for the same duration showed complete resolution of ischemic defects in 12 patients (67%), reduction in the area of ischemia in 2 (11%), and no change in 4 (22%). Thus, a decrease in myocardial ischemia was observed in 14 patients (78%; p less than 0.01). The exercise duration of maximal stress testing after EECP significantly improved from 8.14 +/- 0.71 to 9.72 +/- 0.77 minutes (p less than 0.005), although the double product did not change significantly. Analysis of these 2 tests in the subgroup of 14 patients with improvement in thallium studies showed significant increases in both exercise duration (8.58 +/- 0.66 to 10.44 +/- 0.59 minutes; p less than 0.001) and double product (21,827 +/- 2,044 to 24,842 +/- 1,707 mm Hg.beats/min; p less than 0.01). The improvement in reperfusion defects and increase in exercise duration are reflections of improved perfusion to ischemic regions of the myocardium. EECP uses additional thigh balloons and sequenced balloon inflation, effecting a significant increase in diastolic augmentation over previously available methods.(ABSTRACT TRUNCATED AT 250 WORDS)