Burst of antitachycardia pacing prior to ICD shock lowers risk for all-cause shock
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Key takeaways:
- A single burst of antitachycardia pacing (ATP) reduced risk for shocks in patients with an implantable cardioverter defibrillator for primary prevention.
- ATP did not improve shock burden vs. standard protocol.
A single burst of antitachycardia pacing before an implantable cardioverter defibrillator shock lowered risk for all-cause shock compared with a standard shock protocol, according to the results of the APPRAISE ATP trial.
However, there was no difference between the groups in total shock burden, and the antitachycardia pacing (ATP)-plus-shock group had a greater burden of ventricular tachycardia/ventricular fibrillation storm events and a greater but not significantly higher number of deaths, according to a presentation at Heart Rhythm 2024.
“We were hoping to learn the value of antitachycardia pacing in a homogenous primary prevention ICD implant population,” Claudio Schuger, MD, adjunct professor of medicine in the Clinical Cardiovascular Research Center at University of Rochester Medical Center, told Healio. “We thought there was equipoise in looking at these options in primary prevention patients.”
Antitachycardia pacing before shock
Schuger and colleagues randomly assigned 2,595 patients (mean age, 64 years; 22% women) with a transvenous Boston Scientific ICD to standard programming or programming to deliver a single burst of antitachycardia pacing consisting of eight beats at 88% of cycle length prior to shock. All patients had prior MI with left ventricular ejection fraction 30% or less or ischemic or nonischemic cardiomyopathy with LVEF 35% or less and NYHA HF class II or III.
Patients were followed for 5 years.
For the primary endpoint of time to all-cause shock, the ATP-plus-shock group had a 28% relative risk reduction compared with the shock-only group (HR = 0.72; 95.9% CI, 0.57-0.92; log-rank P = .005), representing an absolute risk reduction of 1% per year, Schuger said during a presentation.
The results were consistent in all prespecified subgroups, he said.
“We thought there was an exaggeration in the amount of ATP success rate [in prior studies], and that indeed was proven by this trial,” Schuger told Healio. “It was surprising that ATP was proven superior, because we believed it would be equivalent. However, it was superior by an amount [that was] significantly less than priorly believed. In those terms, it defines the value of ATP from the right perspective of the new programming of ICDs with higher rate cutoffs and longer therapy delays.”
The secondary endpoints of time to first appropriate shock (HR = 0.73; 95% CI, 0.56-0.95; log-rank P = .02) and time to first inappropriate shock (HR = 0.65; 95% CI, 0.44-0.97; log-rank P = .033) also favored the ATP-plus-shock group, he said.
There was no difference between the groups in all-cause mortality or time to first all-cause shock or death, but deaths were numerically higher in the ATP-plus-shock group, Schuger said.
“This is a signal that has existed in all trials of programming of ICDs, sometimes statistically significant, sometimes not,” Schuger told Healio. “Interesting is that the majority of the mortality does not relate to therapy. Now, is it a coincidence that has repeated itself over three to five trials over 20 years, we don’t know, but it is a signal we need to understand further. In this trial, deaths in the ATP arm occurred enough that the composite endpoint of time to first all-cause shock and mortality was not statistically significant,” despite time to first all-cause shock favoring the ATP arm.
There was also no difference in all-cause shock episode burden during the study period, he said.
“At the end of the day, for people that used their device frequently, there was a significant amount of interventions, so the shock burden between the arms was not reduced by the strategy of ATP,” Schuger told Healio.
Consistent with the findings of the PRAETORIAN trial, the ATP-plus-shock group had a greater burden of ventricular tachycardia/ventricular fibrillation storm events (HR = 2.39; 95% CI, 1.29-4.44), Schuger said during the presentation.
Reduction in interventions
The results, including a lower rate of syncope than in previous trials, show that “you can safely program the devices to wait to intervene,” Schuger told Healio. “This results in a reduction in inappropriate and unnecessary interventions. ATP is a useful tool, not as useful as priorly believed, but still a useful and significant part of the armamentarium for primary prevention patients. The majority of the primary prevention population that receives an ICD does not use their devices, so the absolute risk reduction was 1% per year. The conclusion to draw from that is the device platform you should use is the one that is safest for long-term complication rates.”
The results of APPRAISE ATP also suggest that the strategy from the MODULAR ATP trial, whose patients had a leadless antitachycardia pacing device implanted to communicate with a subcutaneous ICD, “should not be [used] in primary prevention patients as far as implanting both devices simultaneously,” Schuger told Healio. “I think that is an important clinical consideration. It should only be done when the patient demonstrates they need both interventions.”
For more information:
Claudio Schuger, MD, can be reached at cschuger@gmail.com.
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Schuger C, et al. Late-breaking clinical trials – CIEDs. Presented at: Heart Rhythm 2024; May 16-19, 2024; Boston.
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