Combined Effects of Nicorandil and Enhanced External Counterpulsation on Coronary Microcirculation and Exercise Capacity in Patients With Coronary Slow Flow Phenomenon: A Randomized, Controlled, 3-Arm Trial.
PURPOSE: To evaluate the combined efficacy and safety of combined nicorandil and enhanced external counterpulsation (EECP) therapy compared with respective monotherapies in patients with coronary slow flow phenomenon (CSFP). METHODS: In this prospective, randomized, 3-arm clinical trial, 309 patients with angiographically defined CSFP based on corrected TIMI frame count were assigned (1:1:1) to the Nicorandil group (N group, n = 103), the EECP group (E group, n = 103), or the Combined therapy group (N+E group, n = 103). The trial was prospectively registered at ClinicalTrials.gov (NCT07534410). IMR and CFR were measured to characterize coronary microvascular physiological status and treatment response. The primary endpoint was corrected TFC at 6 months. Key secondary endpoints included invasive physiological indices (IMR and CFR), Seattle Angina Questionnaire scores, 6-minute walk test (6MWT) distance, peak oxygen uptake via cardiopulmonary exercise testing, and the 12-month rate of re-hospitalization due to recurrent angina. FINDINGS: At 6 months, the N+E group demonstrated superior improvement in coronary hemodynamics compared to the N and E monotherapy groups, with significantly lower TFC (30.4 ± 3.5 vs 38.2 ± 3.8 and 37.5 ± 4.0, respectively; P < 0.001) and IMR (21.2 ± 2.8 vs 28.4 ± 3.2 and 27.6 ± 3.5, respectively; P < 0.001). Clinical symptoms and functional capacity showed the most substantial gains in the N+E group, with significantly higher Seattle Angina Questionnaire angina frequency scores (87.5 ± 8.8) and 6MWT distances (506.8 ± 41.8 m) compared to monotherapy groups (all P < 0.001). Furthermore, peak oxygen uptake in the N+E group increased to 23.5 ± 2.6 mL/kg/min, significantly outperforming the N and E groups (P < 0.001). During the 12-month follow-up, the observed rate of re-hospitalization due to recurrent angina was lower in the N+E group (5.8%) than in the N group (17.5%, P = 0.017), although this clinical outcome should be interpreted cautiously because the trial was powered primarily for physiological endpoints. No significant differences were observed in the incidence of adverse reactions among the 3 groups (P = 0.954). IMPLICATIONS: For patients with CSFP, the combination of Nicorandil and EECP improved coronary microvascular function, anginal symptoms, and objective exercise tolerance more effectively than either active monotherapy. The lower observed rate of angina-related re-hospitalization suggests a potential clinical benefit, but this finding should be considered exploratory and requires confirmation in trials adequately powered for clinical outcomes.