Faculty Bibliography

Noninvasive techniques, such as the signal averaged ECG, have been used to assess risk of ventricular tachyarrhythmias (VT). However, these methods produce false positive and negative results. The purpose of this study was to develop body surface map algorithms which would enhance prediction of susceptibility to VT. Fifty-three patients referred for programmed electrical stimulation were enrolled in this study. All patients underwent signal averaged ECG, body surface map, programmed electrical stimulation. Group I patients had no sustained inducible VT and group II patients had either inducible sustained VT at electrophysiology study or previously documented spontaneous, sustained VT. For body surface map analysis, the difference between extrema on isoarea maps was calculated and defined as the gradient range. An abnormal body surface map was defined as a QRST gradient range < or = 109 mv.ms. The mean QRST gradient range in group II was significantly < that in group I (P < 0.05). By logistic regression analysis, the presence of coronary artery disease, a QRST gradient range < or = 109 mv.ms, an EF < 40% and a signal averaged ECG QRS duration > 114 ms predicted VT. The sensitivity, specificity, positive and negative predictive values for predicting VT susceptibility of an algorithm which combines the signal averaged ECG QRS duration and the QRST gradients were 0.93, 0.76, 0.79, and 0.91, respectively, while those for the signal averaged ECG alone were 0.52, 0.69, 0.63, and 0.59 for VT susceptibility. A combined body surface map-signal averaged ECG algorithm was more sensitive in detecting susceptibility to VT than the signal averaged ECG alone.

The purpose of this study was to develop a simple computer-guided approach to localizing ventricular tachycardias during ventricular mapping. Six patients with sustained monomorphic ventricular tachycardia were connected to a 32-lead computer body surface mapping system. Isoarea maps of induced ventricular tachycardia were recorded. Then a pacing probe was placed in either the right or left ventricle, and maps were generated from a variety of sites. Differences between ventricular tachycardia and pace map maxima X, Y coordinates were utilized to guide catheter manipulation and localization. In 6 of 6 patients (100%) this method appeared to provide a systematic approach to ventricular tachycardia localization. Computer-generated correlations as well as the X, Y coordinates of the QRS isoarea maxima were used to determine proximity to the ventricular tachycardia foci and direct catheter manipulation. In the next three patients this method was applied prospectively to help guide catheter manipulation during ventricular tachycardia (two right ventricular outflow tract tachycardias, and one left ventricular tachycardia). After a mean of 4.0 +/- 1.7 radiofrequency applications, ventricular tachycardia was no longer inducible, and at 7 +/- 0 months follow-up there have been no arrhythmia recurrences. We conclude that online computerized body surface mapping can assist in localizing ventricular tachycardia. Differences in maxima during pace maps and in-situ ventricular tachycardias can help with catheter manipulation as well as with more precise identification of focal tachycardias. This technique appears to hold the promise of a simple computer-guided method that may facilitate radiofrequency catheter ablation.

A simple algorithm that combines QT dispersion with the signal-averaged electrocardiogram QRS duration provides an extremely sensitive method for predicting spontaneous or inducible ventricular tachyarrhythmias. This new algorithm may prove useful in determining which patients are at risk for ventricular tachyarrhythmia