Abstract
BackgroundQuantitative myocardial perfusion mapping using cardiovascular magnetic resonance (CMR) is validated for myocardial blood flow (MBF) estimation in native vessel coronary artery disease (CAD). Following coronary artery bypass graft (CABG) surgery, perfusion defects are often detected in territories supplied by the left internal mammary artery (LIMA) graft, but their interpretation and subsequent clinical management is variable.MethodsWe assessed myocardial perfusion using quantitative CMR perfusion mapping in 38 patients with prior CABG surgery, all with angiographically-proven patent LIMA grafts to the left anterior descending coronary artery (LAD) and no prior infarction in the LAD territory. Factors potentially determining MBF in the LIMA–LAD myocardial territory, including the impact of delayed contrast arrival through the LIMA graft were evaluated.ResultsPerfusion defects were reported on blinded visual analysis in the LIMA–LAD territory in 27 (71%) cases, despite LIMA graft patency and no LAD infarction. Native LAD chronic total occlusion (CTO) was a strong independent predictor of stress MBF (B = − 0.41, p = 0.014) and myocardial perfusion reserve (MPR) (B = − 0.56, p = 0.005), and was associated with reduced stress MBF in the basal (1.47 vs 2.07 ml/g/min; p = 0.002) but not the apical myocardial segments (1.52 vs 1.87 ml/g/min; p = 0.057). Extending the maximum arterial time delay incorporated in the quantitative perfusion algorithm, resulted only in a small increase (3.4%) of estimated stress MBF.ConclusionsPerfusion defects are frequently detected in LIMA–LAD subtended territories post CABG despite LIMA patency. Although delayed contrast arrival through LIMA grafts causes a small underestimation of MBF, perfusion defects are likely to reflect true reductions in myocardial blood flow, largely due to proximal native LAD disease.
Highlights
Despite improved outcomes associated with surgical revascularisation using coronary artery bypass grafting (CABG) [1], a large proportion of patients with coronary artery disease (CAD) experience recurrent symptomsSeraphim et al J Cardiovasc Magn Reson (2021) 23:82[2]
The deconvolution algorithm deployed for quantitative perfusion mapping includes assumptions about the maximum delay time, meaning that a true delay in contrast delivery transit time— for myocardium supplied by the long left internal mammary artery (LIMA) graft—may result in inaccurate estimations of myocardial blood flow (MBF) [9]
This study confirms that perfusion defects in the left anterior descending coronary artery (LAD) territory are common in patients referred for perfusion cardiovascular magnetic resonance (CMR) despite LIMA to LAD graft patency and no infarction, and that these defects are predominantly located in the basal and mid rather than apical segments and are associated with native vessel chronic total occlusion (CTO)
Summary
Despite improved outcomes associated with surgical revascularisation using coronary artery bypass grafting (CABG) [1], a large proportion of patients with coronary artery disease (CAD) experience recurrent symptomsSeraphim et al J Cardiovasc Magn Reson (2021) 23:82[2]. Post CABG, the increased length of graft conduits plausibly results in a prolonged contrast transit time (arterial time delay), potentially distorting the first pass kinetics of the contrast bolus and the subsequent estimation of myocardial blood flow in graft-subtended territories [8]. This is often proposed as an explanation for the presence of perfusion defects in the LIMA territory, evidence to support this is lacking. Following coronary artery bypass graft (CABG) surgery, perfusion defects are often detected in territories supplied by the left internal mammary artery (LIMA) graft, but their interpretation and subsequent clinical management is variable
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
