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

The use of pethidine as pre-medication to prevent anoxic spells in patients with tetralogy of Fallot

OBJECTIVE

The aim of this study was to determine whether morphine-HCl or pethidine-HCl differ as pre-medication to prevent anoxic spell in patients with tetralogy of Fallot (TOF) at catheterization.

METHODS

A 3 year retrospective case notes review study of 46 consecutive patients who underwent cardiac catheterization from 1998 to 2001 was conducted. In a prospective 1 year randomized control study, 10 patients diagnosed as TOF and admitted to Tokyo Women's Medical University, The Heart Institute of Japan, Tokyo, in 2002 were randomized to receive morphine or pethidine as pre-medication for cardiac catheterization. The incidence of anoxic spell before and after cardiac catheterization was investigated in both studies.

RESULTS

In the case notes review, a total of 10 out of the 46 patients showed anoxic spell study: eight out of 24 patients in the morphine group and two out of 22 in the pethidine group. The difference in the incidence was statistically significant (P < 0.05, Fisher's exact test). Four patients in the prospective study showed anoxic spell: three out of six in the morphine group and one out of four in the pethidine group (odds ratio = 3.0). Overall, 14 out of 56 patients had anoxic spell: 11 out of 30 in the morphine group and three out of 26 in the pethidine group (P = 0.03).

CONCLUSION

The incidence of hypoxic spells in patients with TOF undergoing cardiac catheterization is reduced by the use of pethidine-HCl as pre-medication compared to morphine. This has important clinical implications.

Failure of Disopyramide to Improve Right Ventricular Outflow Tract Obstruction After Living-Donor Lobar Lung Transplantation

Right ventricular (RV) outflow tract obstruction (RVOTO) is an uncommon complication of lung transplantation in patients with pulmonary hypertension (PH) and both medical management and surgical intervention are required. A 28-year-old female with primary PH was referred and because she did not respond to medical treatment, living-donor lobar lung transplantation was performed. The operation was successful, but dyspnea and exercise intolerance developed during rehabilitation and transthoracic echocardiography revealed RVOTO. Intravenous disopyramide during cardiac catheterization reduced the pressure gradient from 35 mmHg to 16 mmHg without decreasing RV systolic pressure. However, electrical and hemodynamic parameters were adversely affected by disopyramide and thus, after cardiac catheterization, administration of fluid and a low dose of atenolol was started, and her symptoms improved. Transthoracic echocardiography showed improvement in the RVOTO. This case suggests that disopyramide should be avoided for patients with RVOTO following lung transplantation and that other negative inotropic agents, such as beta-blockers, are more effective for relief of RVOTO.

Disopyramide improves hypoxia in patients with tetralogy of Fallot through a negative inotropic action

The hemodynamic and right ventricular volumetric effects of disopyramide were investigated in patients with tetralogy of Fallot (TF). Intracardiac pressure and oxygen saturation were measured, before and after intravenous administration of disopyramide (2 mg/kg) in 7 patients who had not had previous surgery. Right ventricular volume and the diameter of its outflow tract were analyzed in these 7 and in a further 4 patients with a previous shunt. Aortic oxygen saturation increased from 90.4+/-7.5 (mean+/-SD) to 94.1+/-5.5% (p<0.05) with an increase in pulmonary blood flow and pressure. The systolic pressure gradient between the main pulmonary artery and the right ventricle decreased from 59+/-8 to 42+/-9 mmHg (p<0.01). Aortic pressure fell from 77+/-5 to 67+/-4 mmHg (p<0.05). Systemic vascular resistance increased from 15.3+/-2.2 to 19.4+/-3.3 u x m2 (p<0.05). Pulmonary vascular resistance remained unchanged. The diastolic and systolic diameter indices of the right ventricular outflow tract increased from 17.8+/-3.8 to 20.5+/-3.4 and from 6.5+/-3.0 to 10.4+/-2.2 mm/m2, respectively (p<0.01), whereas the right ventricular ejection fraction decreased. Disopyramide improves systemic oxygen saturation in patients with TF through its negative inotropic action on the right ventricle.