Clinical significance of body surface isochrone maps for predicting ventricular arrhythmias in patients with previous myocardial infarction.

To investigate the utility of body surface isochrone maps for estimating ventricular arrhythmias in patients with previous myocardial infarction, we compared findings of body surface isochrone maps with those of signal-averaged electrocardiograms (SAECGs) and an incidence of ventricular tachycardia (VT). Body surface isochrone mapping was performed in 50 patients with previous myocardial infarction. Eighty-seven unipolar electrocardiograms distributed over the patient's anterior chest and back were recorded simultaneously. For each lead, the activation time was measured as the duration from the onset of QRS to the peak of the R wave. SAECGs were recorded in the same patients to detect late potential (LP) which was considered to last more than 30 msec. Activation delay on isochrone maps (D) was found in 31 of 50 patients. The group D+ had a lower ejection fraction and higher incidence of VT (8/31 (25.8%) vs. 1/19 (5.3%)) and LP (13/31 (41.9%) vs. 2/19 (10.5%)) than the group D-. There were four patients with sustained VT who had both D and LP. For predicting VT, D has a sensitivity of 88.9% and a specificity of 43.8%. It was decided that abnormal delay on body surface isochrone maps indicates slow conduction of the surviving myocardium and is related to the occurrence of ventricular arrhythmias. We concluded that body surface isochrone maps can be useful in predicting life-threatening arrhythmias in patients with previous myocardial infarction.