Patient outcomes after ICD implantation for primary and secondary prevention: findings from a single-centre cohort in a developing region

Background Implantable cardioverter-defibrillators (ICDs) play a key role in preventing sudden cardiac death (SCD) among patients with structural heart disease. Despite their growing use, data on ICD outcomes from developing countries remain limited, particularly given differences in patient populations and healthcare resources compared to high-income settings. Purpose The objective of this study was to assess the incidence of appropriate and inappropriate ICD therapies, as well as mortality, in patients who underwent device implantation for primary or secondary SCD prevention at a tertiary cardiovascular center in a developing country. We also aimed to compare baseline clinical characteristics between subgroups, and to determine the proportion of patients who died without having received any ICD therapy. Methods We retrospectively evaluated 520 consecutive patients who received ICD or CRT-D implantation from 2017 to 2023. Patients were classified into primary or secondary prevention groups. Baseline demographic and clinical data, device therapy events (appropriate and inappropriate, anti-tachycardia pacing (ATP) and shock),and mortality were recorded for the duration of available follow-up. Results At baseline, patients in the primary prevention group had significantly lower ejection fraction (EF) and higher NYHA class than those in the secondary prevention group (p < 0.05 for both comparisons). At one year, appropriate ICD therapy ( ATP and shock) was observed in 4.5% of primary prevention patients and 16.2% of those in the secondary prevention group; by three years, these rates increased to 10.5% and 27.0%, respectively (both p < 0.001). Importantly, patients who experienced appropriate ICD therapy tended to have lower ejection fraction compared to those who did not (p = 0.006). Inappropriate therapies were infrequent at three years (5.2% for primary, 5.4% for secondary prevention). There was a strong association between atrial fibrillation (AF) and inappropriate ICD therapy: 93.8% of patients who received inappropriate therapy had AF, versus 36.7% of those who did not (p < 0.001). Mortality rates did not significantly differ between groups (17.9% vs. 14.9%, p = 0.63), though numerically, mortality was higher in the primary prevention group. Notably, 84% of patients died without receiving any ICD therapy during follow-up. Conclusions In this real-world cohort from a developing country, appropriate ICD therapies were significantly more common among secondary prevention patients, while most deaths occurred without prior ICD intervention. Our findings are broadly comparable to international experience and highlight persistent challenges in risk stratification. Further refinement and individualization of clinical selection criteria may improve patient outcomes, particularly in resource-limited healthcare settings.