Cardiac resynchronization therapy (CRT) patients who fail to respond to conventional pacing approaches appear to have an effective new treatment option: multipoint pacing technology.
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So suggest results of the multicenter MultiPoint Pacing (MPP) IDE Study presented May 5 during the late-breaking clinical trials portion of the Heart Rhythm Society’s 37th annual scientific session.
“These findings show we have an opportunity to improve response to CRT, both among patients who were previous nonresponders to CRT and among those who responded only slightly,” says Cleveland Clinic electrophysiologist Niraj Varma, MD, PhD, who was a co-author on the study.
Why multipoint pacing?
Multipoint (multipolar) pacing approaches were designed to span greater areas of the diseased left ventricle during pacing than is possible with prior pacing modalities. “The idea is to ‘jump’ conduction barriers that result from scars and generate coordinated electrical activation and thus mechanical contraction,” Dr. Varma explains. By enabling pacing pulse delivery from multiple electrodes on a quadripolar lead, the technology allows a greater range of pacing options for patients.
This approach was introduced to the U.S. market with the FDA’s February 2016 approval of St. Jude Medical’s MultiPoint™ Pacing technology — the system assessed in the MPP IDE Study — although other multipoint pacing systems are in development as well.
Study design: Multipoint vs. biventricular
The trial was designed to compare the safety and efficacy of two pacing modalities among 506 patients with a standard indication for a CRT defibrillator (CRT-D) — i.e., heart failure or life-threatening ventricular tachyarrhythmia. All patients were implanted with a CRT-D system (Quartet™ LV lead model 1458Q with a Quadra CRT-D [St. Jude Medical]) capable of delivering either quadripolar biventricular pacing or multipoint pacing.
After initial activation of biventricular pacing following device placement, patients were assessed for response three months after implantation, at which time both responders and nonresponders were randomized to either biventricular (n = 180) or multipoint (n = 201) pacing. Randomization was 1:1 and stratified by responder status.
The primary safety end point was freedom from system-related complications at nine months after implantation. The primary efficacy end point was noninferiority in the proportion of nonresponders in the MPP arm compared with the biventricular arm between three and nine months.
All end points met, with best outcomes in a multipoint subgroup
The 93.2 percent rate of freedom from complications exceeded the objective performance criterion of 75 percent, thus meeting the study’s primary safety end point.
Likewise, the prespecified hypothesis of noninferiority of multipoint pacing to biventricular pacing was met in both intention-to-treat (P = .013) and as-treated (P = .008) analyses of the 381 randomized patients.
Analysis within the multipoint arm showed that when multipoint pacing was programmed with wide cathode spacing (≥ 30 mm) and the shortest intraventricular timing delay (5 ms), the clinical response rate to CRT was the highest (87 percent) and 100 percent of initial nonresponders were converted to responders.
Where multipoint pacing fits into practice
Cleveland Clinic enrolled 32 patients in the MPP IDE Study, making it the highest-enrolling center. Based on his experience with those patients and the overall study results, Dr. Varma suspects multipoint pacing promises the most benefit for CRT patients with left ventricular scarring and those unresponsive to standard CRT pacing.
“Nonresponders to CRT have a very poor prognosis, similar to the prognosis for some forms of cancer,” he notes. “Any intervention that can change this status is important. These results suggest that multipoint pacing promises this effect, although we need to wait and see if it works in all nonresponders, who are a heterogeneous group.”
Dr. Varma adds that multipoint pacing also shows potential to improve the degree of response among those who respond only modestly to standard pacing options. “We know that degree of response correlates with ultimate survival, so greater response is associated with better five-year survival,” he says. “The Advance CRT Registry shows that candidates for CRT in the U.S. can be especially clinically challenging compared with their counterparts outside the U.S., so we need to enhance our techniques for optimizing this therapy.”