HRV scaling exponent identifies postinfarction patients who might benefit from prophylactic treatment with amiodarone

Analysing the Holter recordings collected at baseline during the European Myocardial Infarction Amiodarone Trial (EMIAT), we evaluate the possibility of using alpha, the slope of the power spectrum of heart rate variability signals (HRV) in the vicinity of f = 0, for postinfarction risk stratification. We found no relevant difference in the values of alpha for the placebo population. On the contrary, in the amiodarone arm, the distinction in the survival rates of those with high or low alpha-values was highly significant. Moreover, high risk patients with respect to alpha (higher values) did not seem to benefit from amiodarone. The results suggest that alpha might convey physiologic information that is different than what is expressed by other HRV characteristics, such as the triangular index. When combining high risk patients in term of triangular index (<20) and low risk patients with respect to alpha (<median), the difference in survival on placebo and amiodarone became very substantial (24.2% mortality on placebo, 8.7% on amiodarone,p = 0.017). This might offer a possibility of selecting patients likely to benefit from a prophylactic antiarrhythmic treatment after acute myocardial infarction.