Clinical performance and safety of a two-lead cardiac resynchronization therapy system with a floating atrial sensing dipole
Authors: Kolb C , Zima E , Arnold M , Fedorco M , Zaman A , Deneke T , Schumacher B , Nordbeck P , Steinwender C , Storz T , Merkely B , Anneken L , Felk A , Lennerz C 
Published: May 2024

Abstract

Background
The incidence of complications after implantable cardioverter-defibrillator (ICD) and cardiac resynchronisation therapy (CRT-D) implantations is dependent on the number of implanted leads. The majority of CRT-D patients have unimpaired sinus node function and do not require atrial pacing. A two-lead CRT-D system with a floating atrial sensing dipole mounted on the right ventricular lead ((CRT-DX) allows dual chamber tachyarrhythmia detection, and atrio-ventricular sequential pacing with a reduced amount of implanted material.

Purpose
This study investigated the clinical efficacy and safety of the CRT-DX system.

Methods
This multicentre, single-arm study observed patients after de novo implantation of a CRT-DX system for 12 months. Patients were eligible for the study when chronotropic competence was proven by heart rates ≥100 bpm during exercise, premature ventricular contractions rate of &lt; 5%/h and absence of atrioventricular block ≥ II. Intraoperatively measured p-wave amplitude of ≥ 1 mV was recommended. The primary safety endpoint was the additional implantation of a right atrial (RA) lead after the initial implantation. As indicators of efficacy, we report the changes in left ventricular ejection fraction (LVEF) and New York Heart Association (NYHA) class over the follow-up period.

Results
Overall, 110 patients were implanted with the complete CRT-DX system. Mean age of study participants was 62 ± 12 years and 77 (70%) were male. The underlying heart disease was non-ischemic in 66 (60%) patients and 103 (93%) had a left bundle branch block. NYHA class was II in 60 (54.5%) and III in 50 (45.5%) patients. ICD placement was performed in 13 (11.8%) patients for the secondary prevention of sudden cardiac death. A total of 104 patients completed the follow-up, 2 patients died, 1 had the system explanted for infection, 2 withdrew consent and 1 was lost to follow-up. The primary endpoint of RA lead implantation was met in 2 (1.8%) participants (Figure 1). One patient required atrial pacing and one patient, who had shown a p-wave amplitude &lt; 1 mV at implantation, lost atrial sensing. The mean RA sensing amplitude remained stable during follow-up (4.6 ± 1.8 mV, 4.9 ± 1.8 mV and 4.6 ± 1.8 mV at 1, 6 and 12 months, respectively; Figure 2). The LVEF improved by 14.7% ± 11.0%, from 26.3% ± 6.9% to 40.8% ± 10.7% (p &lt; 0.00001). Changes in NYHA class were available in 87 patients with 35 (40.2%) improved by one class and 13 (14.9 %) by two classes. Thirty-four (39.1%) had no change and 5 (5.7%) worsened by one class (global p &lt; 0.00001).

Conclusion
The two-lead CRT-DX system showed a low requirement of subsequent RA lead implantations (1.8%) and stable RA sensing amplitudes. Our results suggest a CRT response similar to that of conventional three-lead CRT-D systems. CRT-DX systems appear to be a feasible alternative for patients with chronotropic competence.Kaplan-Meier curve for primary endpointDaily mean RA sensing amplitude