EFFICACY AND SAFETY OF VENTRICULAR RATE-RESPONSIVE PACING IN CHILDRENWITH COMPLETE ATRIOVENTRICULAR-BLOCK

Single chamber rate responsive pacing offers many potential advantages over the more complex dual chamber atrial tracking pacing mode in chi ldren, and the preservation of atrioventricular synchrony could be unn ecessary in selected groups of pediatric patients. Twenty-two pediatri c patients (age range 9 months to 12 years; mean 6.5 years) had implan tation of ventricular rate responsive (VVIR) pacemakers over a 2-year period. All patients had chronic third-degree atrioventricular block, and a normal ventricular function at rest. During the follow-up each p atient underwent a 24-hour Holter monitoring, and ten performed a grad ed treadmill test in both ventricular fixed rate (VVI) and rate respon sive (VVIR) pacing mode. Paced ventricular rates were found to be norm al for age in all 22 patients; maximum rate did not reach the higher p rogrammed rate during daily activities in any patient. Comparing the m ean paced ventricular rate to the mean rates of blocked P waves, six p atients showed a difference of more than 20 beats/min, which induced t he pacemaker parameters to be reprogrammed. In all patients a signific ant correlation was found between variations of paced ventricular rate and variations of spontaneous blocked atrial rhythm (P < 0.05); this correlation persisted in the subsequent Holter controls in the ten pat ients with longer follow-up. Exercise tolerance resulted normal in the ten patients who performed a treadmill test either in VVIR or VVI mod e, with increased maximal heart rates and maximal systolic blood press ure in VVIR mode (P < 0.0013). Rate responsive ventricular pacemakers seem to adequately respond to the physiological needs of daily life of this selected group of children requiring permanent pacing.