Conduction System Pacing Improves The Outcomes On Patients With High Percentage Of Ventricular Pacing And Heart Failure With Mildly Reduced Ejection Fraction

Aims:Heart failure with mildly reduced ejection fraction(HFmr EF)occurs in 10%-20% of patients with heart failure.Previous studies demonstrated that 17% of the patients with HFmr EF transitioned to heart failure with reduced ejection fraction(HFr EF)one year after follow-up.Furthermore,patients who transitioned to HFr EF had higher heart failure rehospitalization rate and cardiovascular mortality.The risk of cardiac function deterioration increased in patients with HFmr EF and conventional right ventricular pacing(RVP).Compared with RVP,traditional cardiac resynchronization therapy(CRT),namely biventricular pacing(Bi VP),played important roles on the resynchronization and the rehospitalization reduce.However,about 30%-40% of patients did not respond to CRT.Cardiac conduction system pacing(CSP)including His bundle pacing(HBP)and left bundle branch pacing(LBBP)could maintain the electrical physiological conduction and left ventricular mechanical synchronization.Of note,the data about the effects of CSP on cardiac remodeling and function in the patients with HFmr EF was very limited.This study aimed to reveal the clinical outcome of conduction system pacing on the patients with a high percentage of ventricular pacing and heart failure with mildly reduced ejection fraction.Methods: Patients who underwent CSP for HFmr EF and ventricular pacing > 40% were consecutively enrolled from January 2018 to May 2021.All participants were followed up for at least one year.Clinical data including cardiac performance and lead outcomes were compared before and after the procedure.LBBP would be the alternative therapy in those patients with obvious infranodal atrioventricular(AV)block or the first choice of HBP failed.Regular follow-up was conducted at 1st month,3rd month,and every 6 months after operation.During follow-up,symptoms of heart failure,12-lead electrocardiogram(ECG),echocardiography,postoperative complications,and pacemaker parameters were monitored.Left ventricular ejection fraction(LVEF),mitral regurgitation(MR)and tricuspid regurgitation(TR)were measured.The improvement of cardiac function,QRS duration and pacing related parameters were evaluated before and after CSP.Results : CSP was successfully delivered in 64 cases(98.46%),including 48 cases(87.27%)with His bundle pacing(HBP)and 16 cases(94.12%)with left bundle branch pacing(LBBP).There were no significant differences in the success rate between the patients with HBP and LBBP(P = 0.43).There was no significant difference in gender,age,comorbidity,B-type natriuretic peptide level and ECG characteristics between the patients with HBP and LBBP(P > 0.05).During the follow-up period of 23.12 ± 8.17 months,no electrode dislodged,perforation,infection or thrombosis were observed.Four patients were re-hospitalized due to heart failure,and only one patient died of renal failure 2 years after surgery.QRS duration(106.83 ± 10.23 ms vs.108.50 ± 9.69 ms,P = 0.20)remained stable,NYHA classification(P < 0.001),left ventricular ejection fraction(LVEF)(42.45 ± 1.84% vs.49.97 ± 3.57%,P < 0.001),left atrial diameter(LAD)(47.13 ± 5.87 mm vs.43.84 ± 5.43 mm,P < 0.001)and left ventricular end diastolic diameter(LVEDD)(55.59 ± 6.17 mm vs.51.66 ± 3.48 mm,P < 0.001)improved significantly.In addition,mitral regurgitation and tricuspid regurgitation were also significantly improved(all with P < 0.001 vs.baseline).The threshold of CSP remained stable(1.32 ± 0.59 V @ 0.4 ms vs.1.50 ± 0.71 V @ 0.4 ms,P = 0.27)after follow-up.R wave amplitude(6.24 ± 4.73 mv vs.5.91 ± 5.76 mv,P = 0.28)was not significantly different from that at implantation.The impedance showed a significant decrease after follow-up(726.94 ± 200.50 ? vs.492.94 ± 146.51 ?,P < 0.001).The QRS duration was a little shorter(107.08 ± 10.04 ms vs.112.75 ± 7.26 ms,P = 0.04)and pacing threshold was a little higher(1.61 ± 0.71 V @ 0.4 ms vs.0.90 ± 0.27 V @ 0.4 ms,P < 0.001)in patients with HBP than those in patients with LBBP.There were no significant differences in LVEF,LVEDD,LAD,MR,TR and NYHA cardiac function classification after operation(P > 0.05).Conclusions: CSP could improve the clinical outcomes in patients with HFmr EF and a high percentage of ventricular pacing.LBBP might be a better choice because of its feasibility and safety,especially in patients with infranodal atrioventricular block.