Electrocardiographic alternans (ECGA), indicating an ABAB fluctuation of the electrocardiogram (ECG), may manifest as P-wave alternans (PWA), QRS-complex alternans (QRSA) and T-wave alternans (TWA). ECGA acts as cardiovascular risk index of arrhythmia predisposition. ECGA measurements may depend on the automatic method used to identify it, and identification of a risk condition requires availability of normal ranges. Normal reference values for the recently proposed enhanced adaptive matched filter (EAMF) method are not available yet. Thus, the present study aims to provide an initial reference ECGA values by analyzing ECGA in a healthy population.
The EAMF was used to characterize ECGA (in terms of: amplitude, microV; area, microV∙ms; and duration, number of beats) in 15-lead, 64-beat ECGs from 52 healthy subjects (39/13 male/female), all belonging to the PTB Diagnostic ECG Database from PhysioNet. Median ECGA values over leads and subjects were: 2 microV, 200 microV∙ms, and 17 beats for PWA; 1 microV, 80 microV∙ms, and 8 beats for QRSA; and 7 microV, 1300 microV∙ms, and 49 beats for TWA. ECGA in females (PWA: 4 microV, 350 microV∙ms, and 22 beats; QRSA: 1 microV, 80 microV∙ms, and 11 beats; TWA: 10 microV; 2000 mi-croV∙ms, and 49 beats ) was higher (* P<0.05) than ECGA in males (PWA: 2 microV*, 200 microV∙ms*, and 16 beats*; QRSA: 1 microV, 80 mi-croV∙ms, and 7 beats; TWA: 6 microV, 1150 microV∙ms, and 48 beats). Eventually, ECGA was lead-dependent. Maximum values of amplitude, area and duration were observed in the fundamental leads (PWA: 4 microV, 400 microV∙ms, and 28 beats; QRSA: 2 microV, 160 microV∙ms, and 12 beats; TWA: 10 microV, 2000 microV∙ms, and 48 beats). Although the observed initial reference ECGA values found here appears reliable since statistically lower than corresponding ECGA values previous-ly observed in pathological subjects, analysis of wider datasets are needed to confirm them.