Improvement of Microvascular Ischemia by Atrioventricular Sequential Pacing in Non-Obstructive Hypertrophic Cardiomyopathy.

BACKGROUND

Therapeutic options for symptomatic non-obstructive hypertrophic cardiomyopathy (nHCM) remain limited. We investigated whether right ventricular apical (RVA) pacing with optimal atrioventricular delay (AVD) can improve myocardial oxygen supply-demand mismatch, assessed using coronary sinus (CS) lactate as a marker of microvascular ischemia.

METHODS

Patients underwent atrial pacing at 70% of target heart rate followed by AV sequential pacing at individually optimized AVD. CS lactate levels were measured at baseline, during atrial pacing, after washout, and during AV sequential pacing.

RESULTS

Baseline CS lactate was 0.55 ± 0.15 mmol/L and increased to 1.13 ± 0.29 mmol/L during atrial pacing. After washout, levels returned to near baseline (0.59 ± 0.21 mmol/L). During AV sequential pacing at optimal AVD (142.8 ± 20.6 ms), CS lactate decreased to 0.86 ± 0.31 mmol/L, showing a significant reduction compared to atrial pacing (p = 0.026). In 15 of 18 patients, CS lactate decreased during AV pacing compared with atrial pacing.

CONCLUSIONS

AV sequential pacing at optimized AVD reduces CS lactate during exertion in most patients with nHCM, suggesting improved myocardial oxygen balance and reduced microvascular ischemia.