Background: Various indexes of 24-hour heart rate variability (HRV) have been able to predict all-cause mortality after an acute myocardial infarction (AMI), but their value in predicting specific modes of cardiac death has been limited.
Aim: The aim of this study was to assess the role of two novel spectral indexes of HRV as predictors of either sudden (SCD) or non-sudden cardiac death after an AMI. Method. We used two novel methods of spectral analysis of HRV: 1) the high-frequency (HF) spectral component, V(index), calculated as an average HF power from the most linear portion of HF power versus the R-R interval regression curve, and 2) the prevalent low-frequency oscillation of heart rate (PLF). V(index), conventional HRV measures, and PLF were analyzed from 24-hour Holter recordings of 590 patients with a recent AMI.
Results: During the mean follow-up of 39+/-14 months, SCD occurred in 3% (n = 17) and non-sudden cardiac death in 5% (n = 28) of the patients. In univariate analysis, V(index) was the most potent predictor of SCD (RR: 6.0, 95% CI: 1.7-20.7, P<0.01), also remaining the most powerful predictor of SCD after adjustment for clinical variables and ejection fraction (RR: 4.2, 95% CI: 1.2-15.2, P<0.05). PLF was a potent predictor of non-sudden cardiac death (RR: 13.9, 95% CI: 5.9-32.5, P<0.001), but it did not predict SCD.
Conclusions: Novel spectral HRV analysis methods, V(index) and PLF, provide significant information of the risk of the specific mode of death after an AMI.