Takashi Usui

Prediction of Optimal Atrioventricular Delay in Patients with Implanted DDD Pacemakers

In patients with an implanted DDD pacemaker (PM), the atrial contribution may be interrupted by too short an atrioventricular (AV) delay, and filling time may be shortened by too long an AV delay. The AV delay at which the end of the A wave on transmitral flow coincides with complete closure of the mitral valve may be optimal. The subjects were 15 patients [70.3 ± 12.3 (SD) years old] with an implanted DDD PM. Cardiac output (CO) and pulmonary capillary wedge pressure (PCWP) were measured by Swan‐Ganz catheter. Transmitral flow was recorded by pulsed Doppler echocardiography. AV delay was prolonged stepwise by 25 msc. When the AV delay was set at 155 ± 26 ms, the end of the A wave coincided with complete closure of the mitral valve. When the AV delay was prolonged 25, 50, 75, and 100 ms from this AV delay, the interval between the end of the A wave and complete closure of mitral the valve was prolonged 16 ± 5, 39 ± 6, 65 ± 4 and 88 ± 5 ms, respectively (r = 0.97, P < 0.0001) and diastolic mitral regurgitation was observed during this period. Thus, the optimal AV delay may be predicted as follows: the slightly prolonged AV delay minus the interval between the end of the A wave and complete closure of the mitral valve. When the AV delay was set at 215 ms, there was a significant positive correlation between the predicted optimal AV delay (166 ± 23 ms) and the optimal AV delay (CO: 161 ± 26 msec, r = 0.93, P < 0.0001. PCWP: 161 ± 28 msec, r = 0.95, P < 0.0001). In conclusion, optimal AV delay can be predicted by this simple formula: slightly prolonged AV delay minus the interval between end of A wave and complete closure of mitral valve at the AV delay setting.

Optimal Atrioventricular Delay Setting Determined by QT Sensor of Implanted DDDR Pacemaker

ISHIKAWA, T., et al.: Optimal Atrioventricular Delay Setting Determined by QT Sensor of Implanted DDDR Pacemaker. QT interval (QTI) may change when cardiac function is improved by optimizing the AV delay. QTI is used as the sensor for rate responsive pacemakers. Evoked (e)QTI is measured as the time duration from the ventricular pace‐pulse to the T sense point, which is the steepest point of the intracardiac T wave. The relationship between AV delay and eQTI and cardiac function was studied in 13 patients (74.2 ± 9.3 [SD] years old) with an implanted QT‐driven DDDR pacemaker. A special pacemaker software module was downloaded into the pacemaker memory for eQTI data logging. AV delay was set at 100, 120, 150, 180, 210, and 240 ms. Cardiac output (CO) was measured by continuous Doppler echocardiography. eQTI was 343.3 ± 22.4, 345.1 ± 22.5, and 343.4 ± 23.2 ms (P < 0.01, repeated ANOVA) and CO was 4.2 ± 0.8, 4.6 ± 0.8, and 4.2 ± 0.8 L/min (P < 0.0001, repeated ANOVA) when AV delay was set at the AV delay shortened by one step (AV[−]) and prolonged by one step (AV[+]) from the AV delay at which QT interval was maximum (AV[max]) in seven patients, in whom the peak AV delay at which the eQTI was maximal could be identified. eQTI decreased from 341.1 ± 20.9 to 339.4 ± 21.1 ms (P < 0.0001) and CO decreased from 4.4 ± 1.4 to 4.1 ± 1.3 L/min (P < 0.005) when AV delay was prolonged from AV(max) to AV(+) in all patients. eQTI decreased from 345.1 ± 22.5 to 343.3 ± 22.4 ms (P < 0.0005) and CO decreased from 4.6 ± 0.8 to 4.2 ± 0.8 L/min (P < 0.05) when AV delay was shortened from AV(max) to AV(−) in seven patients. Thus, CO was maximal when AV delay was set at the AV delay at which eQTI was maximal. In conclusion, the optimal AV delay can be predicted from the eQTI sensed by an implanted pacemaker, and automatic setting of the optimal AV delay can be achieved by the QT sensor of an implanted pacemaker.

Long-term follow-up in patients with intra-Hisian atrioventricular block

Long-term follow-up was performed in patients with intra-Hisian atrioventricular (AV) block who were implanted with permanent pacemakers. Subjects were 14 consecutive patients (3 men and 11 women, 65.4±9.7 [SD] years old), who exhibited intra-Hisian block at the time of pacemaker generators were replaced due to battery depletion. Electrophysiological examinations were performed at both the initial implantation and pacemaker replacement. The mean duration from the initial implantation to the replacement was 9.4±4.3 years. All patients had severe symptoms such as syncope, dizziness, or dyspnea, and these symptoms were relieved by pacemaker implantation. Seven patients had complete AV block, and the other seven had advanced or paroxysmal AV block at the time of implantation. Seven patients, who had advanced AV block at the time of implantation, developed complete AV block. Five of the seven patients who had complete AV block at the time of implantation remained in complete AV block, one patient had advanced AV block, and one patient of complete AV block increased significantly from 50% to 93% during the two electrophysiological examinations (P<0.05). A mean heart rate of 40.3±7.5 beats/min was observed during complete AV block. At the time of implantation, two patients were misdiagnosed as having AH block, and the other two patients were misdiagnosed as having HV block. In conclusion, intra-Hisian AV block gradually developed from advanced or paroxysmal AV block into complete AV block. Because the diagnosis of intra-Hisian block is sometimes difficult, we should always consider the possibility of intra-Hisian block in patients with severely symptomatic AV block.