DISCRIMINATION OF VENTRICULAR-TACHYCARDIA FROM SINUS TACHYCARDIA BY ANTITACHYCARDIA DEVICES - VALUE OF MEDIAN FILTERING

Rate and rate variation algorithms used by implantable devices designe d for management of life-threatening arrhythmias have major limitation s in separating physiologic sinus tachycardia (ST) from pathologic ven tricular tachycardia (VT) requiring therapy. These algorithms presentl y utilize criteria such as simple heart rate, stability of rate, or de rivative of rate (sudden onset) which assumes a gradual onset for ST a nd an abrupt onset for VT. An alternative method employing median filt ering was designed, tested, and compared to a previously published sud den onset rate algorithm using the same data set for analysis of perfo rmance. In 50 patients the onset of ST during exercise and onset of VT were analysed. To accommodate occasional outlying intervals which mig ht affect rate derived by averaging, a five-cycle median filter was us ed to smooth heart rate. Results from using a 'fixed-interval' or a 'p ercent' change in the median gave better discrimination of ST and VT t han previously published 'fixed-interval' or 'percent' change algorith ms. The superiority of median filtering performance was validated by s tatistical measures.