Abstract
BACKGROUND: Coronary microvascular dysfunction (CMD) is increasingly implicated in heart failure, but reversal with guideline-directed medical therapy (GDMT) is rarely documented using invasive physiology. CASE SUMMARY: A 53-year-old man presented with paroxysmal nocturnal dyspnea. Electrocardiography showed precordial ST-T changes; brain natriuretic peptide was 419 pg/mL; left ventricular ejection fraction 35% with anteroseptal hypokinesis. Coronary angiography revealed intermediate proximal left anterior descending artery disease with nonischemic fractional flow reserve (0.84). Invasive indices indicated CMD (mean transit time [Tmn] 2.41/0.70 s; coronary flow reserve [CFR] 3.4; index of microvascular resistance [IMR] 59). After GDMT, left ventricular ejection fraction normalized (63%), and brain natriuretic peptide fell to 4.0 pg/mL at 3 months. Repeat physiology showed restored microvascular function (Tmn 0.84/0.20 s; CFR 4.2; IMR 15); fractional flow reserve remained nonischemic (0.82). DISCUSSION: Marked improvement in IMR/CFR supports CMD-rather than epicardial stenosis-as the principal driver of the initial ischemic phenotype. GDMT may enhance microvascular vasodilator tone and myocardial energetics, improving CMD. TAKE-HOME MESSAGE: Contemporary GDMT may favorably modulate the coronary microcirculation; improvement in CMD may parallel clinical recovery.