| 摘要 |
A dual-chamber heart pacer whose ventricular pacing rate is closely matched to the physiological requirements of the patient. A "true" atrial rate is determined by counting over a 3-second interval the number of sensed atrial beats, including those which occur during atrial refractory periods. When the atrial rate rises to a threshold level, the ventricular pacing rate decreases gradually from the Wenckebach rate to a fall-back rate independent of atrial sensing. During this decline, atrial pacing pulses may be generated simultaneously with ventricular pacing pulses in an effort to terminate tachycardia. The controlled decline in ventricular pacing rate begins after a 3:2 block has resulted, but before a 2:1 block would otherwise result. The fall-back rate is higher than the standby rate to compensate for the lack of atrial pacing when the system operates at the fall-back rate. |
