EVALUATION OF A NEW SENSOR-BASED ALGORITHM TO PROTECT AGAINST ATRIAL ARRHYTHMIAS

The SmarTracking (ST) algorithm (Marathon 294-09, Intermedics Inc.) us es the sensor-calculated rate (SCR) to define a ''variation band'' for the intrinsic sinus rate. If the sinus rate exceeds the upper limit o f the band, the ventricular pacing rate is limited by the ST rate (STR ) and Wenckebach behavior is observed. The present study was aimed at evaluating the behavior of the ST mechanism in patients with healthy s inus node, during exercise and at rest. Methods: Twenty-one patients ( 15 men; mean age 67.8 +/- 9.7 years) with normal sinus function were s tudied. Heart rate was recorded pia the rate profile of the implanted pacemaker (Relay 294-03, Intermedics Inc.), and STR and SCR were obtai ned via a previously calibrated strap-on pacemaker. A 15-minute protoc ol was used during which subjects alternated periods of walking with p eriods of rest; Results: The relative difference between the average S TR and the average sinus rate (DST) was calculated for each phase of t he protocol as well as the maximum number of patients showing inapprop riate Wenckebach behavior (#W). Ar nominal settings, DST was always po sitive and did not fall below 20%. #W was maximum at rest (5) and duri ng heavy exercise (3). By increasing the STR at rest to 95 ppm and the maximum pacing rate to 150 ppm, the #W was reduced to zero for all ty pes of activity except-during very fast walk where #W was 1. Conclusio n: In general, there was no competition observed between the STR and t he intrinsic rhythm. In some cases, the STR at rest and the maximum pa cing rate had to be reprogrammed for optimal performance.