SCATTER DIAGRAM ANALYSIS - A NEW TECHNIQUE FOR DISCRIMINATING VENTRICULAR TACHYARRHYTHMIAS

With the increasing flexibility allowed by implantable cardioverter de fibrillators that use tiered therapy, it is important to match the the rapy with the arrhythmia. In this article we present scatter diagram a nalysis, a new computationally efficient two-channel algorithm for dis tinguishing monomorphic ventricular tachycardia (VT) from polymorphic ventricular tachycardia and ventricular fibrillation (VF). Scatter dia gram analysis plots the amplitude from one channel versus the amplitud e from another channel on a graph with a 15 X 15 grid. The fraction (p ercentage) of the 225 grid blocks occupied by at least one sample poin t is then determined. We found that monomorphic VT traces nearly the s ame path in space and occupies a smaller percentage of the graph than a nonregular rhythm such as polymorphic VT or VF. Scatter diagram anal ysis was tested on 2,7 patients undergoing intraoperative implantable cardioverter defibrillator testing. Passages of 4.096 seconds were obt ained from rate (bipolar epicardial) and morphology (patch) leads, and digitized at 125 Hz. Scatter diagram analysis distinguished 13 episod es of monomorphic VT (28.6% +/- 4.0%) from 27 episodes of polymorphic VT or VF (48.0% +/- 8.2%) with P < 0.0005. There was overlap in only o ne monomorphic VT episode and one polymorphic VT or VF episode.