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Cardiorespiratory fitness and heart rate recovery predict sudden cardiac death independent of ejection fraction

Abstract

Objective To evaluate whether cardiorespiratory fitness (CRF) and heart rate recovery (HRR) associate with the risk of sudden cardiac death (SCD) independently of left ventricular ejection fraction (LVEF).

Methods The Finnish Cardiovascular Study is a prospective clinical study of patients referred to clinical exercise testing in 2001–2008 and follow-up until December 2013. Patients without pacemakers undergoing first maximal or submaximal exercise testing with cycle ergometer were included (n=3776). CRF in metabolic equivalents (METs) was estimated by achieving maximal work level. HRR was defined as the reduction in heart rate 1 min after maximal exertion. Adjudication of SCD was based on death certificates. LVEF was measured for clinical indications in 71.4% of the patients (n=2697).

Results Population mean age was 55.7 years (SD 13.1; 61% men). 98 SCDs were recorded during a median follow-up of 9.1 years (6.9–10.7). Mean CRF and HRR were 7.7 (SD 2.9) METs and 25 (SD 12) beats/min/min. Both CRF and HRR were associated with the risk of SCD in the entire study population (HRCRF0.47 (0.37–0.59), p<0.001 and HRHRR0.57 (0.48–0.67), p<0.001 with HR estimates corresponding to one SD increase in the exposure variables) and with CRF, HRR and LVEF in the same model (HRCRF0.60 (0.45–0.79), p<0.001, HRHRR0.65 (0.51–0.82), p<0.001) or adjusting additionally for all significant risk factors for SCD (LVEF, sex, creatinine level, history of myocardial infarction and atrial fibrillation, corrected QT interval) (HRCRF0.69 (0.52–0.93), p<0.01, HRHRR0.74 (0.58–0.95) p=0.02).

Conclusions CRF and HRR are significantly associated with the risk of SCD regardless of LVEF.

  • echocardiography
  • cardiac arrest
  • ECG
  • cardiac imaging and diagnostics

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