Noninvasive determination of the activation sequence of the heart: application to patients with previous myocardial infarctions.

The uniform double layer (UDL) source model can be used to estimate the activation sequence of the heart at the ventricular surface from electrocardiogram (ECGs) measured on the body surface. Over the past decade, promising results have been obtained. However, the clinical value of the UDL model still has to be demonstrated. This paper reports on the results of experiments to validate the UDL-based method in patients who underwent open-chest surgery. The patients had previously suffered from ventricular arrhythmias after myocardial infarction. Prior to surgery, the ECG was recorded in 123 leads on the body surface at Helsinki University Central Hospital (HUCH). Based on MR images an individual volume conductor model was constructed for each patient. During surgery at HUCH, potentials were recorded invasively in 102 bipolar leads on the epicardium. Based on these data, activation maps were constructed. These maps were compared to the activation maps obtained by the UDL based inverse applied to the body-surface ECG data. The results showed that the overall pattern of the activation sequence found by the UDL corresponded well to the actual activation pattern for some patients. However, the results were poor for those patients whose heart had an infarcted region of considerable size. In a follow-up study a method was developed to take infarction into account in the UDL-based inverse procedure. The results of this study showed that one cannot expect good results from the UDL-based inverse in the presence of an old myocardial infarction unless that infarction is accounted for in the inverse procedure.