Sinus node recovery time assessment by the overdrive suppression test employing an intravenous injection of disopyramide phosphate.

Although sinus node recovery time (SNRT) assessment by the overdrive suppression test (ODST) is important in detecting sick sinus syndrome (SSS), its sensitivity is still inadequate. We have evaluated the effect of intravenous injection (i.v.) of disopyramide phosphate (DP) in ODST. The subjects were 30 SSS patients (64.9 +/- 10.0 years old). If SNRT was <2,000 ms or the corrected SNRT (CSNRT) was < 1,000 ms, ODST was repeated after DP i.v. (2 mg. kg(-1), < or = 100 mg in total). Eleven normal subjects (59.3 +/- 9.0 years old) were also studied. Although SNRT was <2,000 ms or the CSNRT was < 1,000 ms in 13 of the 30 SSS patients (43%), SNRT was prolonged from 1,510 +/- 300ms to 3,400 +/- 1,160 ms (P<0.01), and CSNRT from 510 +/- 190 to 2,470 +/- 1,470 ms (P<0.01) after DP i.v. in these patients. Thus, SNRT was > or = 2,000 ms and the CSNRT was > or = 1,000 ms in 27 of 30 SSS patients (90%) after DP i.v. Using a combination of overdrive suppression and intravenous injection of disopyramide phosphate, the corrected sinus node recovery time was diagnostic (>525 ms) in 29 of the 30 patients (97%). In contrast, SNRT and CSNRT were shortened in the normal subjects during ODST after DP i.v. (P<0.01). The plasma concentration of DP estimated in nine patients was 4.1 +/- 1.0 microg.ml(-1). No serious side effect occurred. ODST employing DP i.v. is safe and seems to be highly effective in diagnosing SSS.

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.

Improvement of cardiac function by short atrioventricular delay and diastolic mitral regurgitation in patients implanted with DDD pacemakers

Efficacy of short atrioventricular (AV) delay and diastolic mitral regurgitation (MR) were studied in 16 patients (70.2 mais ou menos 10.5 SD years old) with implanted DDD pacemakers. AV delay was set at 0.215 and 0.115 sec. In 10 of the 16 patients, diastolic MR was not observed when the AV delay was set at both 0.215 and 0.115 sec. Cardiac output (CO) and pulmonary capilary wedge pressure (PCWP) did not change.In 6 of the 16 patients, diastolic MR was observed when the AV delay was set a 0.215 se However, diastolic MR was not observed when the AV delay was set at 0.115 sec. CO increased from 3.6 mais ou menos 0.7 to 3.9 mais ou menos 0.8 I/min (p menor que 0.05). PCWP was decreased in 5 of the 6 patients (83 por cento, p menor que 0.05 vs. 10 por cento in patients without diastolic MR at 0.215 sec of AV delay). Cardiac function may be improved by shortening AV delay when the diastolic MR was observed. On the other hand, short AV delay may not be effective for patients in whom diastolic MR was ntobserved.