The efficacy of EECP in treating stable angina pectoris has been evaluated in 2 RCTs and several observational regis- try studies. In MUST-EECP (Multicenter Study of Enhanced External Counterpulsation), 139 patients with angina, docu- mented CAD, and evidence of ischemia on exercise testing were randomized to 35 hours of active counterpulsation or to inac- tive counterpulsation (with insufficient pressure to alter blood Time to 1-mm ST-segment depression on stress testing increased significantly in patients treated with active counterpulsation (from 337 18 s to 379 18 s) compared with placebo (from 326 21 s to 330 20 s; P=0.01). The groups did not differ in terms of exercise duration, change in daily nitro- glycerin use, or mean frequency of angina, although the percent- age reduction in frequency of anginal episodes was somewhat greater among patients who received active counterpulsation. Of patients receiving EECP, 55% reported adverse events, including leg and back pain and skin abrasions, compared with 26% in the control group (relative risk: 2.13; 95% CI: 1.35 to 3.38), with approximately half of these events categorized as device related. An additional trial of EECP was conducted in 42 symptomatic patients with CAD who were randomized (2:1 ratio) to 35 hours of either EECP (n=28) or sham EECP (n=14).51 Over the 7-week study period, average Canadian Cardiovascular Society angina class improved with EECP as compared with control (3.16 0.47 to 1.20 0.40 and 2.93 0.26 to 2.93 0.26 in EECP and sham control, respectively; P<0.001). Data from RCTs on long-term outcomes are lacking. patients, Canadian Cardiovascular Society anginal class was improved by 1 class in 86% of EECP-treated patients (95% CI: 82% to 90%). 