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 < 2000ms or the corrected SNRT (CSNRT) was <1000 ms, ODST was repeated after DP i.v. (2 mg.kg(-1), less than or equal to 100 mg in total). Eleven normal subjects (59.3 +/- 9.0 years old) were also studied. Although SNRT was < 2000 ms or the CSNRT was <1000 ms in 13 of the 30 SSS patients (43%), SNRT was prolonged from 1510 +/- 300 ms to 3400 +/- 1160 ms (P < 0.01), and CSNRT from 510 +/- 190 to 2470 +/- 1470 ms (P < 0.01) after DP i.v. in these patients. Thus, SNRT was greater than or equal to 2000ms and the CSNRT was greater than or equal to 1000 ms in 27 of 30 SSS patients (90%) after DP i.v. Using a combination bf overdrive suppression and intravenous injection elf disopyramide phosphate, the corrected sinus node recovery time was diagnostic (>525 ms) in 23 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 mu g.ml(-1). No serious side effect occurred. ODST employing DP i.v. is safe and seems to be highly effective in diagnosing SSS. (C) 2000 The European Society of Cardiology.