The relationship of late potentials to assessment of heart rate variability in post-infarction patients

In order to investigate the relationship of late potential (LP) to assessme nt of heart rate variability (HRV) after acute myocardial infarction (AMI) we studied 101 Chinese patients with AMI (10+/-2.4 days) in Taiwan by colle cting 24-h ECG from a Holter tape recorder and signal-averaged ECG from a h igh-resolution ECG cart. Of the 101 patients, 36 patients had LP (LP group) and 65 patients did not (NLP group). The mean heart rate was significantly lower in the LP group than in the NLP group (P<0.05). The LP group had a s ignificantly increased high-frequency (HF) spectral component of HRV compar ed with the NLP group (P<0.005), but their low-frequency (LF) to HF ratio ( LF/HF) was lower (P<0.05). Analysis of the circadian variation of HRV revea led significant difference of morning SDRR (standard deviation of normal RR intervals) compared with noon SDRR (P<0.05 in the LP group, P<0.005 in the NLP group) and evening SDRR (P<0.05 in the LP group, P<0.005 in the NLP gr oup). In the NLP group, morning HF (normalized unit, nu) was 0.258+/-0.098 compared with noon HF (nu) of 0.219+/-0.83 (P<0.05) and evening HF (nu) of 0.225+/-0.085 (P<0.05). Nine patients died during follow-up from cardiac ca uses, three (8.3%) in the LP group and six (9.2%) in the NLP group. In post -MI patients, there was higher vagal tone in patients with late potentials compared to those without late potentials. NLP patients had more circadian change in vagal tone compared with LP patients. (C) 2000 Elsevier Science I reland Ltd. All rights reserved.