Median filtering as a sudden onset criterion to separate sinus tachycardia from ventricular tachycardia

Because the use of absolute rate alone to distinguish sinus tachycardia (ST) from ventricular tachycardia (VT) lacks precision, rate variation algorithms including sudden onset have been proposed to improve the detection of pathological tachycardias by implantable antitachycardia devices. In this study, a median filtering algorithm was designed, tested, and compared to these established algorithms using identical data. Onset of ST during exercise and during VT was analyzed for 50 cases each. Fixed-interval change and percent change of cardiac cycles were compared as criteria for sudden onset. Optimal performance of the five-cycle median filter was achieved using a threshold of 25% change in median ventricular rate. It successfully differentiated ST from paroxysmal VT with a sensitivity of 92% and specificity of 96%. Median filtering appears to yield better performance when compared to previously proposed onset algorithms for VT identification