The Effects of Right Ventricular Involvement on Heart Rate Variability and Ventricular Late Potentials in Acute Inferior Myocardial Infarction

Abstract

Depressed heart rate variability and presence of ventricular late potentials in acute myocardial infarction are associated with a poor prognosis. Although it is known that the abnormalities vary according to anterior or inferior location of acute myocardial infarction, the relationship with right ventricular acute myocardial infarction is not clear. The effects of right ventricular myocardial infarction on heart rate variability and ventricular late potentials are studied. The study was performed with a total of 46 patients (38 males; aged 56 ± 13 yr, range, 33 to 70 yr). Twenty-six patients had isolated inferior myocardial infarction while 20 patients had accom panying right ventricular involvement. For all patients, ambulatory Holter recordings between 24 and 48 hours following myocardial infarction, echocardiography in first 48 hours, and signal- averaged electrocardiography with submaximal exercise at average day 6 (range, 5 to 8 days) were performed. Heart rate variability and signal-averaged electrocardiography recordings were repeated after discharge (average, 39 days).

During the first 24 to 48 hr, time domain parameters (SDNN, and SD₁) were significantly 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 voltage (RMS-SD₁) showed no significant difference in both groups (28 ±7 vs 35 ±8 ms). In post-discharge heart rate variability recordings, there were no significant differences (SDNN₂ : 86 ± 13 vs 95 ± 15 ms; SD₂: 48 ± 11 vs 57 ± 13 ms; RMS-SD ₂: 32 ± 14 vs 35 ±9 ms).

In pre-discharge tests, the mean value of low-amplitude signals (LAS₁) was higher (26 ±9 vs 33 ± 11 ms, p = 0.03) in patients with isolated inferior myocardial infarction than in those with right ventricular involvement, while other signal-averaged electrocardiography parameters were not significantly different (filtered QRS₁ 102 ±5 vs 105 ± 10 ms, RMS-40, : 44 ± 13 vs 26 ± 10 μ V; incidence of ventricular late potentials: 23% vs 30%, p = NS, respectively). In post- discharge tests, all of signal-averaged electrocardiography parameters were similar in both groups (filtered QRS₂: 112 ± 12 vs 114 ±8 ms, LAS₂: 28 ±9 vs 32 ± 13 ms, RMS-40₂: 36 ± 10 vs 34 ± 11 μV, and frequency of ventricular late potentials₂: 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 parameters but not ventricular late potentials in pre-discharge period. However, the influence of right ventricular involvement on heart rate variability parameters fades away in the post-discharge period.