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Periodic Repolarization Dynamics in Prophylactic ICD Implant Patients
Study Questions:
Do periodic repolarization dynamics on Holter identify patients who benefit from prophylactic implantable cardioverter-defibrillator (ICD)?
Methods:
This was a substudy of EU-CERT-ICD (EUropean Comparative Effectiveness Research to Assess the Use of Primary ProphylacTic Implantable Cardioverter Defibrillators), a prospective, nonrandomized, controlled cohort study. Patients with both ischemic and nonischemic cardiomyopathy, left ventricular ejection fraction ≤35%, and who met guideline-based criteria for primary prophylactic implantation of ICDs were included. Periodic repolarization dynamics from 24-hour Holter recordings were assessed blindly in patients the day before ICD implantation or on the day of study enrollment in patients who were conservatively managed. The primary endpoint was all-cause mortality.
Results:
A total of 1,371 patients were enrolled: 968 of these patients underwent ICD implantation, and 403 were treated conservatively. Median follow-up was 2.7 years in the ICD group and 1.2 years in the control group. During the follow-up, 138 (14%) patients died in the ICD group and 64 (16%) patients died in the control group. There was a 43% reduction in mortality in the ICD group compared with the control group (p = 0.001). Periodic repolarization dynamics significantly predicted the treatment effect of ICDs on mortality (adjusted p = 0.03). The mortality benefits associated with ICD implantation were greater in patients with periodic repolarization dynamics of ≥7.5 deg (p < 0.0001) than in those with periodic repolarization dynamics <7.5 deg (p = 0.049; p for interaction = 0.006). The number needed to treat was 18.3 in patients with periodic repolarization dynamics <7.5 deg, and 3.1 in those with periodic repolarization dynamics of ≥7.5 deg.
Conclusions:
Periodic repolarization dynamics predict mortality reductions associated with prophylactic implantation of ICDs and could help guide decisions about prophylactic ICD implantation.
Perspective:
Despite significant reductions in mortality in patients with primary prevention ICDs, many patients do not receive ICD therapies while incurring the risks associated with having an ICD. Risk stratification tools such as heart rate variability, T-wave alternans, and electrophysiologic studies have not improved risk stratification in the population of primary prevention patients. The authors of the present study use periodic repolarization dynamics to measure and explore its usefulness as a risk marker for death. Periodic repolarization dynamics use 12-lead Holter to quantify low-frequency oscillations of cardiac repolarization instability and may provide a window into coupling of sympathetic innervation and ventricular repolarization. The present study was nonrandomized and its applicability may be limited by the fact that 40% of patients were excluded due to poor Holter quality or underlying atrial fibrillation; nonetheless, it provides an intriguing hypothesis to be explored in future studies.
Clinical Topics: Arrhythmias and Clinical EP, Heart Failure and Cardiomyopathies, Prevention, Implantable Devices, SCD/Ventricular Arrhythmias, Atrial Fibrillation/Supraventricular Arrhythmias, Acute Heart Failure
Keywords: ESC 19, ESC Congress, Arrhythmias, Cardiac, Atrial Fibrillation, Cardiomyopathies, Defibrillators, Implantable, Electrophysiologic Techniques, Cardiac, Heart Failure, Hemodynamics, Myocardial Ischemia, Primary Prevention, Stroke Volume
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