INITIAL CLINICAL-EXPERIENCE WITH A NEW AUTOMATIC PMT DETECTION AND TERMINATION ALGORITHM TO DISCRIMINATE BETWEEN PACEMAKER MEDIATED TACHYCARDIA DUE TO VENTRICULOATRIAL CONDUCTION AND NORMAL SINUS TACHYCARDIA

Pacemaker mediated tachycardia (PMT) algorithms based on rate alone do not discriminate between sinus tachycardia (ST) and PMT. The PMT Auto -Detect algorithm in Trilogy DR+ (Pacesetter, Inc.) uses both rate and stability of the retrograde ventriculo-atrial conduction interval (VP ) to make this distinction. Stability is determined by calculating the average VP when the rate > 100 ppm and the VP < 400 ms for four conse cutive cycles. The rhythm is considered a possible PMT if the VP inter val remains stable for four additional cycles. The next PV interval is then extended by 50 ms. The subsequent VP must remain constant (withi n 12 ms) to treat as a PMT, otherwise it is considered ST. The purpose of our research was to assess the clinical efficacy of the Auto-Detec t algorithm to discriminate between PMT and ST. The Auto-Detect algori thm was tested in 14 patients (8M, 6F, Mean age 70.5 yrs) following in itiation of sustained PMT and during exercise provoked ST > 100 ppm. P MT was initiated by temporarily programming the atrial output subthres hold at atrial drive rates above intrinsic atrial activity. Evaluation was conducted using ECG monitoring. Results: PMT identification was c onfirmed in 14 of 14 patients (100 %). A total of 19 sustained PMT wer e induced and 18 were terminated. One PMT was not terminated due to an atrial output inadvertently programmed subthreshold. ST was identifie d and ignored in all patients (100 %). Conclusions: 1.) The PMT Auto-D etect algorithm is clinically effective in discriminating between PMT and ST with a high degree of sensitivity and specificity. 2.) Inapprop riate attempts to terminate exercise induced ST can be avoided by usin g rate and VP stability detection criteria.