Efficacy of left bundle branch area pacing in patients with indication for cardiac resynchronization therapy

Background

Cardiac resynchronization therapy (CRT) with biventricular pacing has demonstrated clinical benefits in heart failure patients with left bundle branch block (LBBB) and ventricular dysfunction. Left bundle branch area pacing (LBBAP) results in a relatively short QRS duration (QRSd) with fast left ventricular activation and could be considered as an alternative to conventional CRT.

Purpose

The aim of the present study was to evaluate the feasibility and outcomes of LBBAP in patients with indications for CRT.

Methods

Consecutive patients with indications for CRT were included. LBBAP was performed via transventricular septal approach (1–3). We aimed to achieve a paced QRS with right bundle branch conduction delay morphology, a stimulus to peak left ventricular activation time (S-LVAT) <100ms and/or a QRSd ≤130ms. AV delay programming was individualized in patients in sinus rhythm, taking consideration of the AV conduction, programming the one that generated the shortest QRSd at rest. Rate adaptive AV was also activated in these patients. Pacing electrical and echocardiographic parameters were recorded at baseline and during follow-up.

Results

LBBAP was achieved in 19 of 21 (90.5%) patients with indication for CRT. Indications were heart failure with LBBB and left ventricular ejection fraction (LVEF) ≤35% in 8 (42%), AV node ablation or AV block with LVEF <50% and high expected RV pacing burden in 9 (47%), 1 pacing-induced cardiomyopathy and 1 patient with biventricular pacemaker malfunction (high LV capture threshold).

The mean follow-up was 4.6±1.7 months and the percentage of ventricular pacing was 93.4±13.9%. There were no device-related complications during this period.

LBBA capture threshold was 0.6±0.3V at 0.4ms at the implantation, and remained stable (0.7±0.1 V, p=0.17). The lead impedance and R-wave amplitude at implantation were 636±106 ohms and 13.4±6.8 mV, and 541±88 ohms and 13.0±5.1 mV during the follow-up (p<0.001 and p=0.27, respectively).

Mean S-LVAT was 85.5±13.9 ms, and mean QRSd was 122±9 ms, that remained stable during follow-up (122 vs 124 ms, p=0.21). In patients with LBBB, a significant narrowing of paced QRSd was achieved (160.9±16.7 vs. 123.9±9.7 ms, p<0.001).

Mean LVEF increased by 15.9%, from 35.4±8.9% at baseline to 51.3±9.8% at follow-up (p<0.001) in the overall population, and 14.5% (from 32.7±4.8% to 47.2±10.7%, p=0.001) in patients with LBBB.

After one month, estimated time for elective replacement was 11.9±0.4 years.

Conclusions

LBBPA was successfully achieved in 90.5% of the patients with indication for CRT, with good and stable pacing electrical parameters, long estimated battery longevity and relatively narrow QRS, and was associated with improvement in cardiac function. LBBAP may be considered as a first-line option for patients with indications for CRT.

Funding Acknowledgement

Type of funding sources: None.

Heterogeneous Phenotype of Long QT Syndrome Caused by the KCNH2-H562R Mutation: Importance of Familial Genetic Testing

INTRODUCTION AND OBJECTIVES

Long QT syndrome is an inherited ion channelopathy that leads to syncope and sudden death. Because of the heterogeneous phenotype of this disease, genetic testing is fundamental to detect individuals with concealed long QT syndrome. In this study, we determined the features of a family with 13 carriers of the KCNH2-H562R missense mutation, which affects the pore region of the HERG channel.

METHODS

We identified the KCNH2-H562R mutation in a 65-year-old man with a prolonged QTc interval who had experienced an episode of torsade de pointes. Subsequently, a total of 13 mutation carriers were identified in the family. Carriers (age 48 [26] years; 46% males) underwent clinical evaluation, electrocardiography and echocardiography.

RESULTS

The mean (standard deviation) QTc in carriers was 493 (42) ms (3 [23%] showed normal QTc); 6 (46%) had symptoms (4, syncope; 1, sudden death; 1, aborted sudden death [proband]). While under treatment with beta-blockers, 11 of 12 carriers (92%) remained asymptomatic at 5 years of follow-up (1 patient required left cardiac sympathectomy). The QTc shortening with beta-blockers was 50 (37) ms. There was 1 sudden death in a patient who refused treatment.

CONCLUSIONS

Family study is essential in the interpretation of a genetic testing result. This article describes the heterogeneous and variable phenotype of a large family with the KCNH2-H562R mutation and highlights the role of genetic study for the appropriate identification of at-risk individuals who would benefit from treatment.

Multiple interatrial electrical connection after heart transplantation

A 62-year-old woman who underwent heart transplantation 6 years later presented a regular atrial tachycardia. Electrophysiologic evaluation showed an atrial arrhythmia in the recipient atrium with 2:1 conduction to the donor atrium, with a confusing electroanatomical map. With the suspect of alternant conduction through two different breakthroughs, the map was split in two concordant maps, corresponding to two connections that were successfully ablated. Later on, a third connection was detected and therefore ablated.