| Objective To study the variability of ventricular repolarization in acute myocardial infarction (AMI). And to find a new approach to predict the variability of AMI ventricular repolarization. Methods Sixty-five patients with AMI and eighty control subjects served as the study population. They were examined by 24h Holter monitoring. The computer analyzed and computed the mean and standard deviation of QT interval and RR interval. We make the stand deviation of QT interval as the QT variability(QTV), the stand deviation of RR interval as the heart rate variability(SDNN), the quotient of QTV and QT mean as the coefficient of QT variation(QTCV). Then we determined QT variability index(QTVI), which was calculated for each subject as the logarithm of the ratio of normalized QT variance to RR variance by the squared mean. Results ①QT interval and heart rate: In AMI group,the mean of heart rate (HR) in 24h was notably lower(68.02±12.01bpm vs. 73.57±7.65bpm,P<0.01), and QT was strikingly longer (382.96±37.07ms vs. 367.66±25.58ms,P<0.05)compared with the control group, while the difference of QTc between two groups was not obstructive(405.13±19.87,vs. 404.1±18.65,P>0.05). ② In AMI group, both QTV and QTCV in 24h were markedly lower than the control group(25.03±9.91ms vs. 29.95±7.27ms,P<0.01；0.066±0.03 vs.0.081±0.02,P<0.01). ③ QTVI of AMI in 24h was remarkably higher than the control group(-0.45±0.41 vs. -0.76±0.25, P<0.01). Conclusion ①QTV was not only influenced by HRV, but also was influenced by the characteristics of ventricular myocardium. ②QTV and QTCV of AMI during 24h was less than the control group, which was perhaps concerned with the damage of autonomic nervous fiber and reduction of HRV in AMI. ③But QTVI of AMI was higher than the control group, which suggested greater repolarization liability in AMI caused by myocardial ischemia and infarction. QTVI may be a new approach to predict the variability of AMI ventricular repolarization.
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