Time domain heart rate variability count is improved by intravenous magnesium in anterior wall myocardial infarction receiving fibrinolysis

The effect of high-dose intravenous magnesium infusion on time-domain heart rate variability (HRV) count has been investigated in 20 patients with a first evolving anterior wall myocardial infarction (AMI) who received fibrinolytic therapy. HRV was defined as the mean 24-hour RR interval standard deviation and was derived from 24-hour Holter recordings performed in the early hours of AMI and before hospital discharge. Overall, HRV was lower in the acute vs. the subacute phase of AMI (63/spl plusmn/28 vs. 88/spl plusmn/37 msec, p=0.049). Patients who received magnesium infusion had higher HRV counts both early (80/spl plusmn/32 vs. 51/spl plusmn/15 msec, p=0.039) and late (94/spl plusmn/27 vs. 65/spl plusmn/17 msec, p=0.03) after symptom onset. Thus intravenous magnesium seems to exert a beneficial effect on cardiac autonomic activity during the hospital phase of AMI. However, no statistically significant differences regarding clinical outcome or cardiac functional status were observed between the two groups.