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OBJECTIVE: The physiologic goal of revascularization, either by CABG or PCI, is to improve myocardial perfusion to the heart. As surgeons, we assume that myocardial regions perfused by target vessels with “critical” anatomic stenoses require grafting. This anatomic construct for surgical revascularization has recently been questioned by the PCI experience with Fractional Flow Reserve (FFR), and the results of the DEFER and FAME trials. These studies demonstrated that PCI intervention should be based on BOTH anatomy and functionality, namely the presence of chronic stable angina (CSA) ischemia in the region supplied by that vessel. Extrapolating these findings to CABG, successful grafting would then provide: 1) an angiographically competent bypass graft to the epicardial target vessel, and 2) improvement in regional myocardial perfusion that relieves the CSA ischemia.
METHODS: We have modified the Vascular Fluorescence Angiography technology to measure regional myocardial perfusion (RMP) before and after multi-vessel revascularization (62% OPCAB, 38% on-pump, beating heart). This intraoperative imaging system uses a standardized data acquisition protocol (90 sec total/graft) to reliably collect the arteriographic and microvascular phases of angiography in the image datafile (34-sec DICOM sequence, 1020 frame video loop), thus capturing both complex angiographic (i.e., competitive flow) and perfusion data. Then, customized image meta-data analytical and display software (SPY-QC) quantifies in real time the increase in RMP (post-vs-pre-grafting) that results from the bypass graft to the target epicardial vessel (> 70% stenosis) under these physiologic conditions.
RESULTS: 80 consecutive patients undergoing non-emergent multivessel CABG had all grafts evaluated with this new technology. For each graft, the difference in RMP as a result of bypass grafting was quantified for the anterior, lateral and inferior regions of the heart in each patient in real-time at CABG. These image meta-data were then aggregated into 2-D and dynamic 3-D representations of the change in perfusion as a result of bypass grafting, including the influences of collateral flow and competitive flow on regional and global perfusion changes.
CONCLUSIONS: Changes in RMP as a result of bypass grafting can be readily quantified and displayed, highlighting the ability of surgical revascularization to change perfusion to relieve CSA ischemia.