Metoprolol vs. Diltiazem in Patients with Angina and Non-Obstructive Coronary Artery Disease with or Without Evidence of Coronary Microvascular Spasm on Acetylcholine Testing

<b>Background:</b> Pharmacologic therapy guided by invasive coronary function tests (CFTs) may improve symptomatic outcomes in patients with angina and non-obstructive coronary artery disease (ANOCA). In this study, we specifically aimed to investigate whether the induction of coronary microvascular spasm (CMVS) by the acetylcholine (Ach) test predicts a better therapeutic effect of calcium-channel blocker therapy compared to beta-blocker therapy. <b>Methods:</b> We enrolled 31 ANOCA patients, who were divided into two groups according to the result of Ach testing: 16 patients with CMVS (CMVS group) and 15 patients with a negative test (NEG group). Patients with Ach-induced epicardial spasm were excluded. In an open-label crossover trial, patients were randomly assigned to each receive, for a period of 4 weeks, either metoprolol (50 mg twice daily) or diltiazem (120 mg twice daily). At the end of each 4-week period, patients underwent an ECG-exercise stress test (EST) and were invited to fill out the Seattle Angina Questionnaire (SAQ). <b>Results:</b> No significant differences were found between metoprolol and diltiazem in terms of SAQ scores, and ECG-EST results were also largely comparable with the two drug treatments, both in the CMVS group and the NEG group. In particular, the SAQ summary score was 63.1 ± 24 and 66.0 ± 25 (<i>p</i> = 0.59) for metoprolol and diltiazem, respectively, in the CMVS group, and 70.9 ± 17 and 74.3 ± 16 (<i>p</i> = 0.37) with the two drugs, respectively, in the NEG group. <b>Conclusions:</b> Our small open-label study shows that patients with ANOCA with negative Ach test or Ach-induced CMVS show largely comparable short-term symptomatic outcomes and ECG-EST results when treated with either metoprolol or diltiazem.