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OBJECTIVE:
The majority of coronary artery bypass surgery is performed with the use of cardiopulmonary bypass (CPB) and transit time flow (TTF) measurement is the most widely used method for intraoperative graft quality control.
The purpose of this study was to determine the effect of CPB and cardioplegic arrest on the native coronary artery flow.
METHODS:
In six healthy swine, TTF was measured in the pulmonary artery, left anterior descending (LAD), circumflex (Cx), right coronary artery (RCA), right common carotid artery and left internal mammary artery along with left and right ventricular pressure (LVP, RVP). After baseline measurements CPB with cardioplegic arrest was applied for 103 ± 39 minutes with aortic cross clamping for 32 ± 22 minutes.
Simultaneous measurements of all parameters were repeated at 5, 10, 15, 30, 45 and 60 minutes post removal of the aortic cross clamp.
RESULTS:
Baseline Total Coronary Flow (TCF = LAD + Cx + RCA blood flow, 77 ± 18 ml/min) increased precipitously and significantly after the aortic clamp removal and remained significantly higher than baseline (ranging between 108 ± 37 ml/min, 140% of baseline, p<0.05 up to 154 ± 61, 200% of baseline, p<0.05) throughout the 60 minutes of measurements while cardiac output did not change significantly from baseline. TCF returned back to baseline at 126 ± 39 minutes post aortic clamp removal.
CONCLUSIONS:
CPB and the associated cardiac ischemia and reperfusion have a significant impact on coronary blood flow even without performing any surgical procedure.
This must be considered when assessing the graft flow by TTF as it may misrepresent graft quality. Possible increased graft flow may be the result of the CPB induced myocardial ischemia and the associated increased myocardial demand during reperfusion.