The efficacy of EECP in treating stable angina pectoris has been evaluated in a single RCT and several observational registry studies. In MUST-EECP (Multicenter Study of En- hanced External Counterpulsation), 139 patients with angina, documented CAD, and evidence of ischemia on exercise testing were randomized to 35 hours of active counterpulsa- tion or to inactive counterpulsation.910 Time to $1-mm ST-segment depression increased significantly in patients treated with active counterpulsation (from 337618 s to 379618 s) compared with placebo (from 326621 s to 330620 s; P50.01), although there was no difference be- tween the groups in exercise duration. More active counter- pulsation patients experienced a decrease in anginal episodes. Of patients receiving EECP, 55% reported adverse events, including leg and back pain and skin abrasions, compared with 26% in the control group, with approximately half of these events categorized as device related. In a meta-analysis of 13 observational studies that tracked 949 patients, anginal class as categorized by the CCS classi- fication was improved by $1 class in 86% (95% CI: 82% to 90%).939 The EECP Consortium reported results in 2289 consecutive patients undergoing EECP therapy at 84 partic- ipating centers, including a subgroup of 175 patients from 7 centers who underwent radionuclide perfusion stress tests before and after therapy.940 Treatment was associated with improved perfusion images and increased exercise duration. Similarly, the International EECP Registry reported improve- ment of $1 angina class in 81% of patients immediately after the last treatment.941 In general, existing data, largely from uncontrolled studies, suggest a benefit from EECP in patients with angina refrac- tory to other therapy. Additional data from well-designed RCTs are needed to better define the role of this therapeutic strategy in patients with SIHD.942 4.4.4.2. 