The palliative Mustard operation: rationale and results.

The tendency toward development of severe pulmonary vascular obstructive disease in patients with complete transposition of the great arteries and associated large ventricular septal defect has been well documented. The physiologic consequence of this process is a significant reduction in intercirculatory mixing, resulting in increasingly severe levels of systemic arterial hypoxemia, compensatory polycythemia and an associated significant increase in symptoms. Data indicate that definitive surgical correction in patients with pulmonary arteriolar resistance of more than 10.0 units m2 is associated with a prohibitive operative mortality. However, the "palliative" Mustard operation (that is, intraatrial baffle repair, leaving the ventricular septal defect open) can be accomplished with relatively low risk and substantial hemodynamic benefits to the patient. It is erroneous to assume that the result of the operation will be a mere "reversal" of the preoperative systemic arterial and pulmonary arterial saturations, as shown by a review of the hemodynamic changes attributable to the operation. After the operation, systemic arterial saturations of 80 to 93 percent have been achieved, with a concomitant significant reduction in hemoglobin concentration, to a near normal level in some. Although the long-term prognosis in such patients is unknown, the reduction in symptoms and increase in exercise tolerance soon after operation are most gratifying.