Exercise cardiac power and the risk of sudden cardiac death in a long-term prospective study

Background Little is known about exercise cardiac power and the risk of sudden cardiac death. The aim of this study was to examine the relationship of exercise cardiac power (ECP), defined as a ratio of directly measured maximal oxygen uptake with peak systolic blood pressure during exercise, with the risk for sudden cardiac death (SCD). Methods This prospective study was based on 2358 men who participated in exercise stress test at baseline. During an average follow-up of 20 years 205 SCDs occurred. Results Men with ECP (< 8.2 mL/mm Hg, lowest quartile) had a 4.6-fold (95% CI 2.8-7.5, p < 0.001) increased risk of SCD as compared to with ECP in the highest quartile (> 12.8 mL/mm Hg) after adjusting for age and examination years. Men with low ECP (< 8.2 mL/mm Hg) had markedly increased risk of SCD (RR 3.9, 95% CI 2.19-7.14, p < 0.001) after adjustment for conventional risk factors and left ventricular hypertrophy, whereas for progressive adjustment for resting systolic blood pressure, the respective risk among men with lowest ECP was 2.5 (95% CI 1.46-4.22, p < 0.001). After adding ECP in the multivariate model, the Harrell C-index increased from 0.760 to 0.778 showing the significant incremental value of ECP in predicting SCD. The integrated discrimination improvement was 0.014 (p = 0.004). Conclusions Low ECP provides a non-invasive and easily available measure for the prediction of SCD and may help in identifying men with high risk for SCD.