PO-03-024 BENEFICIAL EFFECTS OF HIGH OUTPUT HIS BUNDLE PACING IN PATIENTS WITH HEART FAILURE AND NARROW QRS

Abstract

Cardiac Resynchronization Therapy (CRT) decreases heart failure (HF) hospitalizations and mortality and increases left ventricular Ejection Fraction (EF) in patients with dilated cardiomyopathy, left bundle branch block and QRS>130msec. However, CRT is not beneficial in HF patients with narrow QRS. We performed His Bundle Pacing (HBP) with high output (3.5V/1msec) in HF patients with dilated or ischemic cardiomyopathy and narrow QRS to evaluate hemodynamic benefit independent of the QRS duration or AV delay shortening. 10 male patients with dilated (7 patients) or ischemic (3 patients) cardiomyopathy (EF<35%) and narrow QRS (<110ms) were referred for implantation of a defibrillator. We implanted an ICD- HBP system, and we collected clinical, echocardiographic, and electrocardiographic data. We obtained HBP in all 10 patients successfully. Basal mean EF was 30±4% and increased to 42±6% (P<0.001) after a median follow-up of 100 days. Left ventricular end-diastolic diameter and left ventricular end-diastolic volume decreased from 63±5 to 60±7ml (P=0.004) and from 188±78 to 143±38ml (P=0.029), respectively. Left ventricular end-systolic volume decreased from 136±69 to 84±31 (P=0.009). NYHA class decreased by one class in every patient after only one month. Baseline QRS duration remained stable after pacing from 107±7 to 118±15ms. In one patient an iatrogenic right bundle branch block was created which was corrected partially by His bundle pacing. PQ after implantation was shorter (from 167±23 to 121±14 (P=0.030) so as to pace the ventricle. HBP threshold was 1.24V±0.50/1msec, the impedance was 529±116 Ohms while R-wave was 3.8±1.7mV. In one out of 10 patients, threshold increased from 1 to 2V/1msec in 6months and then remained stable. In the other nine patients, threshold remained stable. HBP in HF patients with dilated or ischemic cardiomyopathy and narrow QRS improves hemodynamic function and decreases NYHA class. This benefit appears to be produced by a higher stimulation output. We exclude that a very short AV delay could be favorable, by measuring acute EF changes only after pacing output increase and without AV delay modifications. To our knowledge these are the first cases of beneficial HBP in HF patients with narrow QRS. There is urgent need for large, randomized clinical trials.Tabled 1DataPre-implantationPost-implantationn=10n=10pEF30±442±6≤0.001LVTDV188±78143±380.029LVTSV136±6984±310.009LVTDD63±560±70.004PQ Interval167±23121±140.030QRS107±7118±150.32Follow-up:126 ±86 days Open table in a new tab