For Isolated Left Main Coronary Artery Stenoses Are Grafts Needed For Both Left Anterior Descending And Circumflex Systems?
Krish Chaudhuri1, Zeke Pullan1, Nicolas P. Smith2.
1Green Lane Cardiothoracic Surgical Unit at Auckland City Hospital, Auckland, New Zealand, 2Auckland Bioengineering Institute, The University of Auckland, Auckland, New Zealand.
BACKGROUND: It is not known whether grafting both left anterior descending (LAD) and circumflex (CIRC) coronary artery systems is necessary in isolated left main coronary artery (LMCA) stenoses, especially for ostial stenoses. Wide separation of the territories may mandate dual grafting, however, debate remains whether these grafts will have flow competition. METHODS: 62 hemodynamic scenarios were investigated using CT coronary angiography scans of five patients of whom two had a ramus intermedius (trifurcating LMCA). A novel personalised predictive hemodynamic flow solver ("COMCAB") introduced an isolated 90% LMCA stenosis of varying lengths at the ostium, mid or distal LMCA. Different graft configurations utilising left and right internal mammary arteries (LIMA, RIMA) and radial arteries (RA) (Figure 1) were evaluated by calculating mean graft flow (MGF) and pulsatility index (PI) as well as regional myocardial perfusion. Hemodynamic comparisons included LMCA lesion location, single versus dual graft configurations, site of LAD graft and impact of a trifurcating LMCA. RESULTS: A single graft to LAD versus dual grafting LAD and OM led to less myocardial perfusion in both CIRC (55.6 ± 7.1 vs 72.2 ± 10.6 ml/min, P<0.001) and LAD territories (87.3 ± 10.2 vs 93.2 ± 9.4 ml/min, P=0.04). Grafting very proximally on the LAD in an ostial LMCA stenosis did not significantly increase LAD perfusion (84.7 ± 10.1 vs 89.9 ± 11.3 ml/min, P=0.46) or CIRC perfusion (57.3 ± 6.7 vs 53.8 ± 8.2 ml/min, P=0.48). In one patient a composite Y-graft to LAD had highly unsatisfactory MGF 3.6 ml/min with PI 21.8. For a trifurcating LMCA, when the second graft targeted the ramus intermedius instead of the OM, there was slight increase in LAD perfusion (101.8 ± 4.7 vs 105.8 ± 5.7 ml/min, P<0.001) but significant decrease in CIRC perfusion (69.7 ± 15.2 vs 59.3 ± 8.1 ml/min, P=0.016). CONCLUSIONS: Coronary surgeons should graft both LAD and CIRC territories, irrespective of isolated LMCA stenosis location. In patients with a ramus intermedius, the second graft should be placed on the OM to avoid poor CIRC territory perfusion. Composite Y-grafting causes competitive flow in certain patients who may be identified using personalised predictive hemodynamics. 
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