Repeat return map distinguishes patients in the chronic phase after myocardial infarction with different risk for future cardiac events

A method of nonlinear dynamics analysis of heart rate variability was applied in 65 patients in chronic phase after myocardial infarction. On the basis of clinical data, including age, mean R-R interval, standard deviation of R-R intervals, ejection fraction, the presence of ventricular premature depolarizations (VPDs) >10/hour, complex VPDs or non-sustained ventricular tachycardia, as well as ventricular late potentials, previous myocardial infarction, and survival from cardiac arrest, risk score was calculated for each patient. Patients were divided into 3 groups of different risk (H-high, n=5; M-medium, n=14; L-low, n=46). Groups were compared in respect to complexity of HRV dynamics, estimated by means of repeated return maps with increasing time-lag from 1 to 6. The authors found some quantitative measures as well as qualitative patterns, which significantly distinguished patients at high estimated risk from those with medium or low risk