Long-term mortality risk in patients with an implantable cardioverter-defibrillator: Influence of heart rate and QRS duration

Background A paucity of studies has investigated the role of autonomic cardiac regulation as well as cardiac conduction in relation to prognosis in implantable cardioverter-defibrillator (ICD) patients. Therefore, we examined the association of heart rate and QRS duration with long-term mortality risk in first-time ICD patients, adjusting also for measures of emotional distress. Methods Resting heart rate and QRS duration were assessed prior to ICD implantation in 448 patients. Primary study endpoint was all-cause mortality (up to 6.0 year follow-up, median follow-up of 5.6 years (IQR: 1.9)). The impact of heart rate and QRS duration on time to all-cause mortality was separately assessed with Cox proportional hazard regression analysis, adjusting for clinical factors and symptoms of depression and anxiety. Results Mean (SD) heart rate was 68.0 ± 13.3 bpm and mean QRS duration was 130.9 ± 36.9 ms. Heart rate of ≥ 80 bpm was associated with increased risk of mortality (HR = 1.86; 95% CI = 1.15-3.00; p =.011) in unadjusted analysis. In adjusted analyses, this relationship remained significant both with depression (HR = 1.86, 95% CI = 1.12-3.09; p =.017) and anxiety (HR = 1.82, 95% CI = 1.10-3.03; p =.021) and clinical measures as covariates. QRS duration of ≥ 120 ms was associated with impaired prognosis in unadjusted analysis (HR = 2.00, 95% CI = 1.27-3.14; p =.003), but was reduced to non-significance in adjusted analysis when medical comorbidities were included (HR = 1.15, 95% CI = 0.70-1.89; p =.60). Conclusions This study shows that increased heart rate is associated with impaired prognosis. Since heart rate is a relatively easy measurable parameter of autonomic functioning, heart rate should be included as a measure for risk stratification in daily clinical practice.

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