Samples above the median: a nonparametric method for intracardiac signal assessment

In this investigation, a nonparametric (distribution-free) detection scheme, Samples Above the Median (SAM), is devised as an arrhythmia discriminant for implantable cardioverter defibrillators which is highly sensitive and specific yet introduces no appreciable computational demand. No widely accepted probability density function (p.d.f.) for intracardiac electrogram signals has been determined. A nonparametric method does not utilize the p.d.f. SAM was tested on 30 patients each with documented episodes of normal sinus rhythm (NSR) and ventricular tachycardia (VT). SAM achieved an electrogram specificity of 0.992 (476/480) and an electrogram sensitivity of 0.981 (471/480). SAM achieved an arrhythmia sensitivity and specificity of 1 using a 12 of 16 (75%) electrograms per arrhythmia criterion.