Prolonged electrical systole in acute myocardial infarction.

Electrical systole duration has been studied in two groups of 23 patients (39 M and 7 F) admitted in the coronary care units of two different hospitals for documented acute myocardial infarction (AMI). The mean QT interval duration corrected for heart rate (QTc) was obtained from three measurements of non consecutive complexes in five different leads and compared to the ideal electrical systole duration of a normal population with the same cardiac cycle length. During the evolution of AMI, QT interval increased in both groups of patients (11.5% and 14.8% respectively) and was prolonged (17.6% and 21.5% respectively) at the 48th hour. Prolongation of electrical systole can be best measured using the ratio: QTc (according to Bazett)/normal QT (according to Ashman).