Enhanced External Counterpulsation Versus Standard Medical Therapy for Chronic Refractory Angina: A Systematic Review...

Background: Chronic refractory angina is a disabling syndrome of persistent ischemic symptoms despite guideline-directed medical therapy and, in many patients, prior coronary revascularization. Enhanced external counterpulsation [EECP] is a noninvasive therapy that augments diastolic coronary perfusion, reduces systolic afterload, improves endothelial function, and may promote collateral recruitment. Although developed for obstructive coronary artery disease, its vascular and microvascular effects may also be relevant to contemporary ischemic syndromes, including ischemia with non-obstructive coronary arteries [INOCA] and myocardial infarction with non-obstructive coronary arteries [MINOCA]. A contemporary quantitative synthesis of EECP across angina burden, functional capacity, quality of life, and safety is therefore warranted. Methods: We performed a systematic review and meta-analysis of randomized trials and prospective studies of adults with chronic refractory angina treated with EECP versus standard medical therapy, usual care, or sham EECP. Outcomes were Canadian Cardiovascular Society [CCS] angina class, nitroglycerin use, the 6 min walk test [6MWT], treadmill exercise testing, quality-of-life measures, adverse events, and treatment withdrawal. Because the eligible evidence combined sham-controlled randomized trials with single-arm and registry cohorts, pooled estimates were derived using random-effects models and are interpreted in that context. Results: Twenty-six studies were included. EECP was associated with improvement across every prespecified domain: CCS angina class [standardized mean difference [SMD] -1.56; 95% confidence interval [CI], -2.54 to -0.58; p = 0.002], nitroglycerin use [SMD -2.41; 95% CI, -3.34 to -1.49; p < 0.00001], 6MWT [SMD 1.59; 95% CI, 0.64 to 2.54; p = 0.001], treadmill exercise testing [SMD 1.03; 95% CI, 0.15 to 1.91; p = 0.02], and quality of life [SMD 1.12; 95% CI, 0.71 to 1.53; p < 0.00001]. Heterogeneity was high for all pooled outcomes [I² ≥ 79%], and the largest effect sizes were driven substantially by uncontrolled before-after data. Conclusions: EECP is associated with statistically significant and clinically meaningful reductions in angina burden and nitrate use, with parallel improvements in objective exercise capacity and patient-reported quality of life among patients with chronic refractory angina. These findings support EECP as a reasonable adjunctive option for appropriately selected patients who remain symptomatic despite conventional treatment, while the magnitude of heterogeneity and the contribution of non-randomized data temper the certainty of the pooled estimates and underscore the need for standardized protocols, contemporary sham-controlled trials, and dedicated investigation in INOCA and MINOCA populations.