Stress Perfusion Cardiac Magnetic Resonance for Ischaemia and Viability Detection in Patients With Coronary Chronic Total Occlusions

A total chronic occlusion (CTO) is defined as a coronary obstruction with TIMI 0 flow lasting at least 3 months.The prevalence of CTO in patients with coronary disease is about 10-40%. Coronary collateralizations may supply sufficient perfusion to retain tissue viability, but do not protect from myocardial ischaemia. In fact, percutaneous revascularization (PCI) of CTO lesions leads to improved symptoms, functional class, quality of life, higher left ventricular ejection fraction and improved survival in several observational studies. However, due to the higher rate of procedural complications and lower success rate of PCI than in other settings, it is attempted in only 10% of all CTO lesions. Myocardial viability/ischaemia assessment should be performed before PCI to avoid potential PCI-related complications and identify patients who might benefit most from myocardial revascularization, individualizing the risk-to-benefit ratio. In this regard, patients with stable coronary artery disease who have moderate-to-severe ischaemia are at higher risk of event rates (death or MI of ~5%/year) and plausibly represent the best target for PCI.

Cardiac MRI (CMR) provide a reliable assessment of both myocardial ischaemia and viability. Using late gadolinium enhancement (LGE) sequences, myocardial segments with LGE >75% of transmurality do not show any improvement in contractility even after revascularization, representing a subset of patients in which CTO PCI may be futile. Viability assessment by CMR may be also performed with low dose dobutamine infusion; in patients with CTO and akinetic segments, contractility improvement at low dose dobutamine may predict functional recovery in the follow-up. Myocardial ischaemia may be assessed by CMR with high accuracy, identifying perfusion defects during pharmacological-induced hyperemia and/or regional wall motion abnormalities during inotrope infusion.

This study is designed to verify the hypothesis that myocardial ischaemia and viability assessed by CMR could identify patients who are more likely to benefit from PCI in terms of improvement in left ventricular remodeling, functional recovery and clinical outcome.