A prospective randomized-controlled trial of ventricular fibrillation detection time in a DDDR ventricular defibrillator

Implantable cardioverter defibrillators (ICDs) with dual chamber and dual c hamber rate responsive pacing may offer hemodynamic advantages for some ICD patients. Separate ICDs and DDDR pacemakers can result in device to device interactions, inappropriate shocks, and underdetection of ventricular fibr illation (VF). The objectives of this study were to compare the VF detectio n times between the Ventak AV II DR and the Ventak AV during high rate DDDR and DDD pacing and to test the safety of dynamic ventricular refractory pe riod shortening. Patients receiving an ICD were randomized in a paired comp arison to pacing at 150 beats/min (DDD pacing) or 175 beats/min (DDDR pacin g) during ICD threshold testing to create a "worst case scenario" for VF de tection. The VF detection rate was set to 180 beats/min, and VF was induced during high rate pacing with alternating current. The device was then allo wed to detect and treat VF. The induction was repeated for each patient at each programmed setting so that all patients rr ere tested at both programm ed settings. Paired analysis was performed. Patient characteristics were a mean age of 69 +/- 11 years, 78% were men, coronary artery disease was pres ent in 85%, and a mean left Ventricular ejection fraction of 0.34 +/- 0.11. Fifty-two episodes of VF were induced in 26 patients. Despite the high pac ing rate, all VF episodes were appropriately detected. The mean VF detectio n time was 2.4 +/- 1.0 seconds during DDD pacing and 2.9 +/- 1.9 seconds du ring DDDR pacing (P = NS). DDD and DDDR programming resulted in appropriate detection of all episodes of VF with similar detection times despite the " worst case scenario " tested. Delays in detection may be seen with long pro grammed ventricular refractory periods which shorten the VF sensing window and may be avoided with dynamic ventricular refractory period shortening.