The Performance of the Probability Density Function in Differentiating Supraventricular from Ventricular Rhythms

The ability of the probability density function (PDF) of an automatic implantable cardioverter defibrillator (AICD) to reject supraventricular arrhythmias being recognized as ventricular was evaluated in 12 patients who were treated with an AICD (Ventak P 1600). The PDF criterion was monitored via telemetry with the sinus rate during exercise test. PDF was satisfied in seven patients at a rate of 75-144/min (mean 109/min), and not in the remaining five patients (mean rate 141/min). PDF was fulfilled in five of ten patients at a lower heart rate than predicted by the duty cycle index, derived from the ventricular patch lead electrogram at the implantation. Thus PDF is often fulfilled already at a moderately elevated sinus rate. If used to prevent inadvertent AICD discharges during rapid supraventricular rhythms, its performance should be tested in the individual patient.