SCORING METHOD FOR ASSESSING RATE-ADAPTIVE PACEMAKERS - APPLICATION TO 2 DIFFERENT ACTIVITY SENSORS

To optimize programming of rate adaptive pacemakers (RAPs), we explore d a new mathematical method to assess the performance of RAPs during d aily-life tests, using customized Windows-based software. By stepwise discriminant analysis and linear regression, this method allows calcul ation of the acceleration and deceleration capacity of pacemakers and their general behavior during effort and recovery phases, Twenty-three patients (10 females and 13 males; 68 +/- 8 years) with chronic atria l fibrillation and a slow ventricular response were evaluated. They ra ndomly received an accelerometer-controlled VVIR Dash Intermedics pace maker (10 patients) or a vibration piezoelectric-controlled VVIR Senso log III Siemens pacemaker (13 patients). All patients underwent the sa me test protocol: 6 minutes walking, 1.5 minutes climbing stairs, 1.5 minutes descending stairs, and 0.5 minutes sit-ups. By definition, the pacemaker responsiveness slope was programmed so that the heart rate response of paced patients during the walking test corresponded best t o that of healthy controls. The slope was left unchanged for the other tests. We considered four scores: an acceleration score (EA score), a n effort rate score (ER score), a deceleration score (RD score), and a recovery rate score (RR score). Scores ranged from -10 (hypochronotro pic behavior of the pacemaker) to +10 (hyperchronotropic behavior), ba sed on daily-life tests of 15 healthy controls (7 females and 8 males, 65 +/- 9 years). A score of 0 represented exact concordance with heal thy controls. During stair descent, the Sensolog III produced excessiv e acceleration (EA score = +2.9 +/- 1.1) compared to: (1) stair climbi ng (EA score = -4.0 +/- 1.9; P = 0.01, with the same pacemaker); and ( 2) the Dash (+1.8 +/- 1.9; P = 0.04) and healthy controls (P = 0.02). The sit-up tests revealed a hypochronotropic response of both pacemake rs compared to healthy controls, with a larger difference for the Sens olog III (EA score = -2.0 +/- 5.8; P = 0.04; RD score = -6.8 +/- 3.8; P = 0.02). We conclude that activity-driven pacemakers can accommodate brief activities, except for isovolumetric exercise such as sit-ups. During daily activities, accelerometer-driven pacemakers seem to provi de a heart rate response closer to th at of healthy controls. Our new mathematical analysis is a simple and reproducible meth od for evaluat ing and quantifying the efficacy of any sensor-driven pacemaker.