Background
Serial perfusion cardiovascular magnetic resonance (CMR) in symptomatic patients undergoing coronary artery bypass grafting (CABG) may provide mechanistic insight into dynamic abnormalities of the myocardium.

Objectives
To assess how changes in cardiac reperfusion and remodelling associate with symptom improvement in patients undergoing CABG

Methods
Patients awaiting elective CABG completed serial quality of life questionnaires and detailed CMR at baseline and at 6-12 months post CABG as per protocol. Automated fully quantitative stress and rest myocardial blood flow was calculated, alongside assessment of the visual ischaemic burden. Findings were correlated with changes in symptomatology.

Results
Of 40 patients who underwent serial evaluation with CMR (mean age 62.1±9.3, median LVEF 68% [IQR: 62-73%]), there was improvement in the median visual ischaemic burden (42% [IQR: 27-51] vs 18% [IQR: 11-21], P<0.001), mean global stress myocardial blood flow (1.34±0.5 ml/min/g vs 1.59±0.5 ml/min/g, P=0.002) and median global myocardial perfusion reserve (1.85±0.6 vs 2.4±0.9, P<0.001) following CABG. Greater improvement in the SAQ-7 summary score was associated with a greater decrease in the visual ischaemic burden following CABG (ρ=-0.38, P=0.02). Quantitative MBF metrics did not associate with baseline or change in SAQ-7 summary score.

Conclusion
Serial perfusion CMR identifies dynamic changes in markers of myocardial perfusion in patients following CABG. Greater reduction of visually assessed ischaemia associated with improvement in SAQ-7 score. Quantitative perfusion indices were not associated with symptom improvement in this study. The results also suggest residual inducible ischaemia post CABG requiring further studies to elucidate its clinical relevance.