Novel ICD Lead for Conduction System Pacing Enters the Arena

A dedicated bipolar implantable cardioverter-defibrillator (ICD) lead for conduction system pacing (CSP) performed well in a first-in-human multicenter study.

Placement of the novel UltiSynq CSP ICD lead, designed for left bundle branch area (LBBA) pacing, met expectations for safety and effectiveness in over 200 patients with indications for novo ICD or cardiac resynchronization therapy defibrillator (CRT-D) implantation, according to researchers led by Robert Schaller, DO, of the Hospital of the University of Pennsylvania in Philadelphia.

In these patients, the 3-month major complication-free rate was 97.5% and the primary effectiveness endpoint (a composite of acceptable pacing capture threshold and R-wave sensing amplitude) reached 94.6%, both exceeding preset goals (88% and 80%, respectively). Additionally, lead electrical performance remained stable through 3 months, Schaller told the audience at the Heart Rhythm Society annual meeting held in Chicago.

These and other findings from the single-arm, pivotal ASCEND CSP investigational device exemption study were simultaneously published in Heart Rhythm.

“These findings support the early safety and performance of a purpose built CSP ICD lead and demonstrate that integration of physiologic pacing into ICD systems can be achieved without compromising defibrillation reliability. Continued follow-up is essential to confirm long-term durability, electrical stability, and extractability. If sustained, this approach may simplify device configurations and broaden physiologic pacing strategies within contemporary ICD and LOT [left bundle branch optimized]-CRT therapy,” wrote Schaller’s group.

LBBA pacing is a type of conduction system pacing, which directly engages the heart’s intrinsic conduction system to restore or preserve synchrony of ventricular contraction. There is evidence of improved clinical outcomes with LBBA pacing as opposed to right ventricular pacing in patients with bradycardia and heart failure; in selected settings, it can also be an alternative to conventional biventricular CRT.

Recognizing the growing role of this technique, the HRS issued in 2023 the first U.S. guidelines to address use of conductive system pacing with the intent to prevent or mitigate heart failure.

“However, incorporation of LBBA pacing into ICD systems has traditionally required either placement of an additional pacing lead or off-label adaptation of conventional ICD leads not specifically engineered for conduction system capture,” the ASCEND CSP investigators noted.

The UltiSynq CSP ICD lead was developed to allow for LBBA pacing without an additional ventricular lead.

Predicated on the commercially available Optisure ICD lead, UltiSynq was modified for implantation within the LBBA. “The CSP ICD lead is a true dedicated bipolar, stylet-driven, fixed helix lead with a dedicated sensing electrode delivered through a fixed-curve delivery catheter,” according to Schaller and colleagues.

Study operators implanted the CSP ICD with conventional stylet-driven bradycardia LBBA pacing lead placement techniques, they noted. Successful LBBA pacing lead implantation was defined as fluoroscopic confirmation of the lead tip in a deep septal location, with or without angiography.

Longer-term follow-up is warranted to confirm durability and sustained clinical benefit of this lead, the authors cautioned, as follow-up was just a mean 2.9 months in this study.

As for safety, there were five major complications adjudicated as related or probably related to the CSP ICD lead: two lead dislodgements, one intraprocedural mechanical failure of the helix disengagement mechanism, one postoperative septal perforation, and one decrease in R-wave amplitude.

ASCEND CSP was a single-arm study conducted at 32 centers in the United States, Canada, Europe, and the Asia Pacific region. Patients with an indication for ICD or CRT-D therapy were enrolled, yielding a cohort of 214 patients.

These individuals averaged 63.6 years of age and were 73.2% men. Most had a primary prevention indication for device implant (82.9%), of which 37.1% had a diagnosis of ischemic cardiomyopathy. Mean LV ejection fraction was 35.7%.

From this pool of 214 participants, 205 underwent attempted implantation of the lead. A successful lead implantation was achieved in 98.5%.

Three people had unsuccessful lead placement because of poor septal substrate, inability to penetrate the interventricular septum, or anatomical limitations leading to lead instability. In these three cases, another commercially available lead was provided instead.

Among successfully implanted patients, 74.5% got a single- or dual-chamber ICD; the mean intrinsic and paced QRS durations from the CSP ICD lead only were 119.0 ms and 128.1 ms. The remaining 25.5% received a CRT-D system; their mean intrinsic and paced QRS durations from the CSP ICD lead were 164.6 ms and 137.2 ms, respectively.

Defibrillation testing success was assessed in a prespecified cohort of 120 patients. This came out successful in 100% of cases, with 92.5% defibrillated with a single 20 J shock.