Cardiovascular magnetic resonance of acute and chronic myocardial ischaemia

Abstract

BACKGROUND: Ischaemic heart disease is the leading cause of mortality and morbidity in the developed world. Cardiovascular magnetic resonance (CMR) is a non-invasive imaging modality providing in vivo myocardial tissue characterisation and quantification. We aimed to validate CMR in the field of interventional cardiology as a tool for guiding patient selection and management to the assessment of the results of interventions both in the acute and chronic settings. METHODS AND RESULTS: We investigated the impact of primary angioplasty delay on the presence and extent of myocardial salvage, microvascular obstruction and infarct size. We found that “time is muscle”, and that shorter time to reperfusion was associated with smaller infarct size (p=0.05), less microvascular obstruction (p=0.04) and a greater amount of salvaged myocardium (p=0.003). Microvascular obstruction was then used as an endpoint in a prospective randomised trial assessing the impact of a thrombectomy device as adjunctive therapy in primary PCI. The incidence and extent of microvascular damage was significantly reduced in the thrombectomy group compared to standard primary PCI (p=0.0005). CMR can identify 2 degrees of microvascular damage: early or persistent microvascular dysfunction. The latter was the strongest predictor of LV remodelling (p=0.03), it was predicted by infarct size (p=0.002), and infarct healing (shrinkage) occurred to a greater extent (p<0.006). We validated the clinical use of CMR perfusion in a cohort of patients with chronic coronary occlusion whose management is currently controversial. CMR identified myocardial viability and inducible myocardial ischaemia in a significant percentage of patients, guided revascularisation that reduced ischaemic burden (p<0.0001) with improvements in left ventricular function (p<0.0001) and health outcome measures (p<0.0001). Finally, improved CMR perfusion image quality was pursued with a new imaging protocol but this demonstrated increased incidence of artefacts (p<0.001) and lower diagnostic accuracy compared to the standard technique. CONCLUSIONS: Cardiovascular magnetic resonance provides in vivo myocardial tissue characterisation that can potentially not only guide treatment but also assess its effects. The result of this work suggests that CMR could emerge as a clinical valuable technique in numerous interventional clinical settings within acute to chronic myocardial ischaemia, in addition to providing surrogate endpoints for clinical trials.