Steal phenomenon from mammary side branches: When does it occur?

Background. The hemodynamic significance of patent mammary graft side branc hes is still controversial. This study was designed to evaluate the potenti al for flow steal of patent mammary side branches in different hemodynamic conditions. Methods. Echo-Doppler measurement of mammary graft flow was performed at re st and after dipyridamole-induced coronary vasodilatation in 10 patients wi th angiographic demonstration of evident mammary graft side branches (study group) and in 10 matched control patients (control group). Concomitant tha llium-201 myocardial scintigraphy was performed to assess the adequacy of m ammary flow to the myocardial oxygen demand. Patients of the study group we re also submitted to flow evaluation in condition of selective muscular or combined systemic and coronary relaxation. Results. No difference in mammary flow and adequacy to myocardial oxygen de mand was detected between patients of the study and control groups both at rest and after dipyridamole infusion. In patients with patent side branches the systolic-to-diastolic flow ratio was maintained in case of combined co ronary and peripheral vasodilatation, whereas selective muscular relaxation led to an increase in the systolic and a reduction in the diastolic flow. Conclusions. Flow steal from patent mammary graft side branches is possible only in case of selective muscular vasodilatation. As this situation is un likely to occur in the clinical setting, the potential for flow steal of ma mmary side branches in cardiac surgery patients seems to be minimal. (C) 19 98 by The Society of Thoracic Surgeons.