Unsuitability of corrected QT dispersion as a marker for ventricular arrhythmias and cardiac sudden death after acute myocardial infarction.

The present study investigated whether corrected QT (QTc) dispersion could play a role as a marker of ventricular arrhythmias and sudden cardiac death after acute myocardial infarction (MI). The study included 76 males and 24 females with a mean age of 60±11 years. Standard 12-lead ECGs were recorded during the recovery phase (15±9 days) after the onset of MI. The QTc was calculated according to Bazett's formula and QTc dispersion was calculated as the difference between the maximum and minimum QTc intervals. Patients were divided into 2 groups: 21 patients (group A) had a QTc dispersion of ≥80 ms, and the other 79 patients (group B) had a QTc dispersion of <80 ms in the recovery stage (15±9 days). Clinical, angiographical, and Holter monitoring data, and prognosis (mean follow-up period 29±18 months) were compared between these 2 groups. The frequencies of early coronary reperfusion and recanalization of infarct-related vessels during the recovery phase were significantly higher in group B than group A. The left ventricular ejection fraction was also higher in group B than group A (51±12 vs 43±12%, p=0.0029). There were no significant differences in the number of premature ventricular contractions, the percentage of patients with repetitive ventricular arrhythmias, or in the frequency of sudden cardiac death during the follow-up period between the 2 groups. In summary, QTc dispersion in the recovery stage is not a useful marker for ventricular arrhythmias or sudden cardiac death after acute MI, although increased QTc dispersion may correlate with an ineffective early coronary reperfusion and with the degree of depressed left ventricular function. (Jpn Circ J 1999; 63: 467 - 470)