PROSPECTIVE EVALUATION OF NEW AND OLD CRITERIA TO DISCRIMINATE BETWEEN SUPRAVENTRICULAR AND VENTRICULAR-TACHYCARDIA IN IMPLANTABLE DEFIBRILLATORS

This study was designed to evaluate the ability to distinguish between supraventricular tachycardias (SVTs) and ventricular tachycardias (VT s) based on onset, stability, and width criteria in an implantable def ibrillator. inappropriate detection of atrial fibrillation and sinus t achycardia is a common problem in patients with implantable defibrilla tors. The onset, stability, and width criteria were studied in 17 pati ents who underwent implantation of a Medtronic 7218C implantable defib rillator by inducing sinus tachycardia and atrial fibrillation. Additi onal data on the width criteria was obtained by pacing at separate sit es in both the left and right ventricle. Patients were studied at diff erent times for up to 6 months to determine any changes in the criteri a. The onset and stability criteria caused inappropriate detections in 36% and 12% of the episodes, respectively. The addition of the width criteria decreased the inappropriate detection using the onset and sta bility criteria to 5% and 2%, respectively. Pacing from the RV apex, R V outflow tract, and LV apex was appropriately detected as wide in 76% , 41%, and 94%, respectively. The width criteria changed over time in individual patients, but was stable by 6 months in all but one patient . No single criterion is satisfactory for distinguishing between SVT a nd VT in this patient population, but the combination of criteria seem s to provide better discrimination. The width criteria can change dram atically over time and needs to be monitored carefully. Newer algorith ms will need to be developed to allow better detection of supraventric ular tachycardias.