Disopyramide: a promising new approach to the medical treatment of the hypercyanotic spell complicating tetralogy of Fallot.

Under continuous ECG and oxygen saturation (SpO2) monitoring, the following measurements were taken by Doppler echocardiography in 6 consecutive patients with tetralogy of Fallot (TF) before and after intravenous administration of disopyramide (2mg/kg): left ventricular shortening fraction (LVSF); peak velocities in the right ventricular outflow tract (RVOT); diastolic and systolic internal diameters of the right ventricular outflow tract (dRVOT, sRVOT); and systolic blood pressure. SpO2 increased (p<0.01) from 78 to 98 (89 +/- 7, mean +/- standard deviation)% to 86-99 (94 +/- 5)%. LVSF decreased (p<0.05) from 0.34-0.56 (0.42 +/- 0.08) to 0.22-0.54 (0.33 +/- 0.13). The systolic blood pressure fell slightly (p<0.05) from 68-92 (79 +/- 8) to 64-92 (71 +/- 11)mmHg. The sRVOT increased (p<0.05) from 2.1-4.8 (2.7 +/- 1.5)mm to 3.0-8.1 (4.9 +/- 2.4)mm, while RVOT peak velocity decreased (p<0.05) from 2.20-4.88 (3.70 +/- 0.97)m/sec to 2.05-4.07 (2.92 +/- 0.72)m/sec. Disopyramide alleviates hypoxia in patients of TF through its negative inotropic action on right ventricular outflow obstruction.