Abstract
Coronary artery bypass graft (CABG) surgery effectively relieves symptoms and improves outcomes. However, patients undergoing CABG surgery typically have advanced coronary atherosclerotic disease and remain at high risk for symptom recurrence and adverse events. Functional non-invasive testing for ischaemia is commonly used as a gatekeeper for invasive coronary and graft angiography, and for guiding subsequent revascularisation decisions. However, performing and interpreting non-invasive ischaemia testing in patients post CABG is challenging, irrespective of the imaging modality used. Multiple factors including advanced multi-vessel native vessel disease, variability in coronary hemodynamics post-surgery, differences in graft lengths and vasomotor properties, and complex myocardial scar morphology are only some of the pathophysiological mechanisms that complicate ischaemia evaluation in this patient population. Systematic assessment of the impact of these challenges in relation to each imaging modality may help optimize diagnostic test selection by incorporating clinical information and individual patient characteristics. At the same time, recent technological advances in cardiac imaging including improvements in image quality, wider availability of quantitative techniques for measuring myocardial blood flow and the introduction of artificial intelligence-based approaches for image analysis offer the opportunity to re-evaluate the value of ischaemia testing, providing new insights into the pathophysiological processes that determine outcomes in this patient population.
Highlights
Coronary artery bypass surgery is the most frequently performed cardiac surgical procedure, with ∼200,000 patients undergoing isolated coronary artery bypass surgery each year in the US [1]
Despite improved post-operative survival [2] among high risk groups [3, 4], patients undergoing surgical revascularisation represent the severe end of coronary artery disease spectrum and comprise a high risk group
With long term survival of patients undergoing Coronary artery bypass graft (CABG) approaching that of the general population [5,6,7], a significant number of patients with prior CABG surgery are expected to experience symptom recurrence requiring re-intervention [8]
Summary
Coronary artery bypass surgery is the most frequently performed cardiac surgical procedure, with ∼200,000 patients undergoing isolated coronary artery bypass surgery each year in the US [1]. Advances in image quality across all modalities has meant that noninvasive tests are becoming increasingly capable of detecting microvascular disease, thereby providing additional insights into the pathophysiological mechanisms of reduced myocardial blood flow Quantitative perfusion indices such as stress MBF and MPR have been used to help differentiate epicardial coronary disease and microvascular dysfunction in the context of native vessel disease [73], but whether a similar assessment can be performed in patients with prior surgical revascularisation is unclear. In patients with prior CABG, the increased length of graft conduits results in a prolonged tracer transit time, potentially distorting the first pass kinetics of the contrast bolus complicating both the visual interpretation of relative perfusion defects and the subsequent estimation of myocardial blood flow in graftsubtended territories [75] Such delay in contrast arrival, small, is thought to affect longer conduits, such as internal mammary (LIMA) grafts [53]. Arnold et al demonstrated that the hyperaemic MBF in response to TABLE 1 | Non-invasive myocardial blood flow assessment post-surgical revascularisation
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