A pilot study on coronary microvascular dysfunction in obstructive hypertrophic cardiomyopathy: impact of percutaneous transluminal septal myocardial ablation

Coronary microvascular dysfunction (CMD) is well-characterized in the context of coronary artery disease, but its relationship to obstructive hypertrophic cardiomyopathy (oHCM) is poorly understood. In addition, the impact of percutaneous transluminal septal myocardial ablation (PTSMA) on CMD has not been fully evaluated. Between October 2023 and May 2024, PTSMA was performed on 10 patients with oHCM. A pressure guidewire in the left anterior descending artery (LAD) was used to invasively assess CMD before and after the procedure. Measurements were recorded for resting full-cycle ratio (RFR), fractional flow reserve (FFR), coronary flow reserve (CFR), and index of microcirculatory resistance (IMR). The 10 patients had a median age of 66 [57-75] years, with a resting left ventricular pressure gradient of 44 [17-84] mmHg, measured via catheterization. Prior to PTSMA, the RFR measured in the LAD was 0.93 [0.91-0.96], and the FFR was 0.95 [0.92-0.95], which were both within normal limits. However, the CFR was reduced to 1.8 [1.6-2.1], and the IMR was elevated to 31 [25-39], which indicated CMD. Post-procedure, the left ventricular pressure gradient decreased to 5 [2-8] mmHg, CFR improved to 2.5 [2.2-3.6], and IMR decreased to 22 [17-26], indicating improvement in CMD. In patients with oHCM, myocardial hypertrophy contributes to left ventricular outflow tract obstruction and CMD. This study demonstrated that PTSMA as a septal reduction therapy improved the left ventricular pressure gradient and CMD.