Guidance on implantation of an implantable cardioverter-defibrillator (ICD) for patients who survive an out-of-hospital cardiac arrest (OHCA) is not unequivocal. This comparative study examined long-term outcomes after OHCA of cardiac origin in patients without a reversible cause and with an expected survival exceeding one year. The primary objectives were to compare early ICD use, rates of appropriate device therapy (anti-tachycardia pacing [ATP] and shocks), and 5-year mortality between patients with arrest caused by acute coronary syndrome (ACS) and those with a primary arrhythmia.
Patients resuscitated from OHCA of presumed cardiac cause were identified from the years 2007–2011. Inclusion criteria reported in the abstract were: no reversible cause for the arrest and an expected survival greater than one year. The cohort was split into two groups based on cause of arrest: ACS (n = 256) and primary arrhythmia (n = 258).
Comparisons performed were:
Covariates included in adjusted models were cause of arrest, age >65 years, left ventricular ejection fraction (LVEF) ≤35%, sex, and for the ACS subgroup, successful revascularization. Additional methodological details (for example, precise definitions of early implantation timing, source population selection, handling of missing data, or adjudication of arrhythmic events) were not reported in the abstract provided.
Early ICD implantation prior to hospital discharge differed substantially by cause of arrest: 30% of ACS patients received an ICD compared with 82% of primary arrhythmia patients.
Cumulative 5-year incidences of appropriate device therapy were similar between groups. For ATP, the cumulative incidence was 28% in ACS patients versus 27% in primary arrhythmia patients. For appropriate shocks, cumulative incidence was 22% in ACS versus 29% in primary arrhythmia patients.
Crude 5-year mortality rates differed by ICD status within groups. Among ACS patients the crude mortality was 22% for those without an ICD versus 13% for those with an ICD. Among primary arrhythmia patients the crude mortality was 66% for those without an ICD versus 16% for those with an ICD.
When comparing causes of arrest, adjusted analysis showed no significant mortality difference between ACS and primary arrhythmia patients overall (adjusted hazard ratio for ACS: 0.91; 95% confidence interval 0.50–1.67).
Importantly, early ICD implantation was independently associated with a lower 5-year mortality risk in both patient groups after adjustment for the listed covariates. Reported adjusted hazard ratios were:
In this observational cohort of OHCA survivors meeting the specified eligibility criteria, cumulative incidences of appropriate therapy delivered by ICDs (ATP and shock) did not differ meaningfully according to whether the arrest was due to ACS or a primary arrhythmia. Despite lower ICD implantation rates among ACS patients, those who received an early ICD had lower crude and adjusted 5-year mortality compared with those who did not.
Adjusted analyses indicate that early ICD implantation was associated with a statistically significant reduction in 5-year mortality for both ACS and primary arrhythmia patients, after accounting for age, sex, severely reduced LVEF, cause of arrest, and successful revascularization in ACS.
The findings reported in the abstract suggest that among selected OHCA survivors without a reversible cause and with projected survival >1 year, early ICD implantation prior to discharge was associated with improved 5-year survival regardless of whether the arrest was due to ACS or primary arrhythmia. The similar cumulative rates of appropriate ATP and shock between causes of arrest support consideration of ICD therapy in both groups when other clinical criteria are met.
These results may inform discussions about early ICD decision-making in OHCA survivors; however, application to individual patients requires careful consideration of comorbidities, LVEF, revascularization status, and patient preferences.
The summary here is based on the abstract and metadata. Several important trial and cohort details were not reported in the abstract: exact selection process, full inclusion/exclusion criteria, timing definition of “early” ICD implantation, the absolute number of ICD therapies and shocks, device programming, adverse events related to ICDs, and other potential confounders. The abstract does not report methods for event adjudication or sensitivity analyses. Readers should consult the full text for comprehensive methodology and context.
In the cohort described (2007–2011), early implantation of an ICD after OHCA was significantly and independently associated with lower 5-year mortality in both ACS and primary arrhythmia patients, while cumulative incidences of appropriate device therapy were similar between the two etiologic groups. Full-text review is required to appraise study quality, potential biases, and applicability to specific clinical settings.