Antitachycardia Pacing Reduces Shock in ICD Patients: ALTITUDE Study
Key Insights
The ALTITUDE trial demonstrated that antitachycardia pacing (ATP) prior to shock reduces the risk of first all-cause shock in primary prevention ICD recipients.
The study randomized 2,626 patients and found a 28% relative risk reduction in time to first all-cause shock with ATP plus shock compared to shock only.
While ATP reduced the initial shock risk, the overall shock burden during follow-up was not significantly different between the two treatment groups.
A recent study published in JAMA Network has demonstrated the effectiveness of antitachycardia pacing (ATP) in reducing the incidence of shocks in patients with implantable cardioverter-defibrillators (ICDs) used for primary prevention. The ALTITUDE trial, a global, prospective, double-blind, randomized clinical trial, assessed whether ATP followed by shock is clinically equivalent to a shock-only strategy in primary prevention ICD recipients programmed with long detection to therapy delays.
The study enrolled 2626 patients across 134 sites in 8 countries between September 2016 and April 2021. Participants had an indication for a primary prevention ICD, including a left ventricular ejection fraction of 35% or less. Patients were randomized 1:1 to receive either ATP plus shock or shock only. The primary endpoint was time to first all-cause shock.
Key Findings
At a mean follow-up of 38 months, the study found that ATP prior to shock reduced the relative risk of time to first all-cause shock by 28%. Specifically, first all-cause shock occurred in 129 participants in the ATP plus shock group compared to 178 in the shock-only group (HR 0.72, 95.9% CI, 0.57-0.92; P = .005). This indicates a significant benefit of using ATP as a first-line therapy in prolonging the time to the first shock.
However, the total shock burden per 100 patient-years during follow-up was not statistically different between the two groups (12.3 in the ATP plus shock group vs 14.9 in the shock-only group, P = .70). This suggests that while ATP can delay the initial shock, it does not significantly reduce the overall number of shocks experienced by patients over time.
Clinical Implications
The findings from the ALTITUDE trial support the use of ATP as an effective strategy for managing fast ventricular tachycardias (search) (VTs) in primary prevention ICD recipients. "The use of a single burst of ATP prior to shock in primary prevention ICD recipients with modern ICD detection programming prolonged the time to first all-cause ICD shock," the authors concluded.
These results are particularly relevant given the emergence of novel programming guidelines aimed at reducing premature and inappropriate therapies, as well as the development of new ICD technologies lacking traditional endocardial ATP capabilities. The study underscores the importance of reevaluating ATP as a first strategy in terminating fast VTs in primary prevention ICD recipients.
The trial's design as an equivalence trial with sequential superiority analysis of each group adds robustness to the findings. The double-blind, randomized approach minimizes bias and strengthens the validity of the results. The study's limitations include the focus on primary prevention patients and the relatively short follow-up period, which may limit the generalizability of the findings to other patient populations or longer-term outcomes.