The effects of right ventricular involvement on heart rate variability andventricular late potentials in acute inferior myocardial infarction

Depressed heart rate variability and presence of ventricular late potential s in acute myocardial infarction are associated with a poor prognosis. Alth ough it is known that the abnormalities vary according to anterior or infer ior location of acute myocardial infarction, the relationship with right ve ntricular acute myocardial infarction is not clear. The effects of right ve ntricular myocardial infarction on heart rate variability and ventricular l ate potentials are studied. The study was performed with a total of 46 pati ents (38 males; aged 56 +/- 13 yr, range, 33 to 70 yr). Twenty-six patients had isolated inferior myocardial infarction while 20 patients had accompan ying right ventricular involvement. For all patients, ambulatory Holter rec ordings between 24 and 48 hours following myocardial infarction, echocardio graphy in first 48 hours, and signal-averaged electrocardiography with subm aximal exercise at average day 6 (range, 5 to 8 days) were performed. Heart rate variability and signal-averaged electrocardiography recordings were r epeated after discharge (average, 39 days). During the first 24 to 48 hr, time domain parameters (SDNN1 and SD1) were s ignificantly lower (SDNN1: 62 +/- 17 vs 100 +/- 20 ms, p = 0.001; SD: 37 +/ - 10 vs 50 +/- 16 ms, p = 0.03) in patients with isolated inferior MI than in those with right ventricular involvement, whereas root-mean-square volta ge (RMS-SD1) showed no significant difference in both groups (28 +/- 7 vs 3 5 +/- 8 ms). In post-discharge heart rate variability recordings, there wer e no significant differences (SDNN2: 86 +/- 13 vs 95 +/- 15 ms; SD2: 48 +/- 11 vs 57 +/- 13 ms; RMS-SD2: 32 +/- 14 vs 35 +/- 9 ms). In pre-discharge tests, the mean value of low-amplitude signals (LAS(1)) wa s higher (26 +/- 9 vs 33 +/- 11 ms, p = 0.03) in patients with isolated inf erior myocardial infarction than in those with right ventricular involvemen t, while other signal-averaged electrocardiography parameters were not sign ificantly different (filtered QRS(1) 102 +/- 5 vs 105 +/- 10 ms, RMS-40(1): 44 +/- 13 vs 26 +/- 10 muV; incidence of ventricular late potentials: 23% vs 30%, p = NS, respectively). In post-discharge tests, all of signal-avera ged electrocardiography parameters were similar in both groups (filtered QR S(2): 112 +/- 12 vs 114 +/- 8 ms, LAS(2): 28 +/- 9 vs 32 +/- 13 ms, RMS-40( 2): 36 +/- 10 vs 34 +/- 11 muV, and frequency of ventricular late potential s(2): 23% vs 30%, p = NS). These data suggest that right ventricular involvement in an acute inferior myocardial infarction is associated with improved heart rate variability pa rameters but not ventricular late potentials in pre-discharge period. Howev er, the influence of right ventricular involvement on heart rate variabilit y parameters fades away in the post-discharge period.