Analysis of Y-graft blood flow and flow reserve in conditions of increased myocardial oxygen consumption.

BACKGROUND: It is not well established whether early following surgery the blood flow of arterial composite Y-grafts may efficiently meet the flow demand of the coronary system. The aim of this study was to evaluate whether early after surgery arterial composite Y-grafts may increase the blood flow in response to an increase in myocardial oxygen consumption (MVO2). METHODS: Twenty-seven patients who received complete arterial myocardial revascularization using the left internal thoracic artery (LITA) and the radial artery (RA) as composite Y-graft gave their consent to a pre-discharge coronary angiography and intravascular flow velocity measurements using a Doppler guidewire. Flow measurements were performed in the LITA main stem, the distal LITA and the RA, both at rest and during atrial pacing at 85% of the patient age-predicted maximum heart rate. The heart rate-systolic blood pressure product was considered as an indirect index of MVO2. Hyperemic flow was determined after injection of adenosine. The flow reserve was defined as the ratio of blood flow during maximal hyperemia (Qmax) to baseline flow (Qbasal). RESULTS: Atrial pacing significantly increased MVO2 (p < 0.000). None of the patients developed ischemic ST-segment modifications or complained of chest pain. Qbasal increased significantly in the LITA main stem (p = 0.001), distal LITA (p = 0.041) and RA (p = 0.004) while Qmax did not change significantly. As a consequence the flow reserve decreased in the LITA main stem (p = 0.002), distal LITA (p = 0.000) and RA (p = 0.000) but was not completely exhausted. CONCLUSIONS: Early after surgery arterial composite Y-grafts may significantly increase blood flow in response to conditions of increased MVO2 and maintain a normal myocardial oxygen supply-to-demand ratio.