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Introduction Non-ST-segment elevation myocardial infarction (NSTEMI) results in approximately 50,000 hospital admissions in the UK every year with up to 90% undergoing invasive coronary angiograms (ICA). A non-invasive strategy using cardiovascular magnetic resonance (CMR) before ICA in suspected NSTEMI has the potential to diagnose non-ischaemic pathologies and obviate the need for ICA. Furthermore, in cases of acute myocardial infarction (MI) with multi-vessel coronary artery disease (CAD), it can identify the infarct related artery (IRA), which can help guide revascularisation strategies. This study aimed to assess the diagnostic utility of early multi-parametric CMR before ICA in suspected acute NSTEMI. Methods We recruited 100 consecutive patients admitted to our hospital for suspected NSTEMI (70% male, age 62±11 years) into the Oxford Acute Myocardial Infarction Study (OxAMI). They underwent CMR pre-ICA; the protocol included cine, T2-weighted imaging, T1-mapping and late gadolinium enhancement, all with full short-axis coverage of the left ventricle (LV). CMR images were interpreted by experts blinded to ICA findings. The clinicians performing the ICA and those in charge of the patients' care were blinded to CMR findings until post-ICA. Results The acute CMR protocol was successfully completed in 96% of patients at 20–48 hours post-admission and at a median of 4 2–6 hours pre-ICA. It showed acute MI in 67%, non-ischemic pathologies in 18%, normal findings in 11%, and was uninterpretable in 4%. Patients with MI, when compared to those with non-ischaemic pathologies and normal findings, had similar frequency of ischaemic changes on ECG (48 vs 24 vs 46%; p = 0.218) but larger rise in Troponin-I levels (51(12–155) vs 19 (5–77) vs 8 (2–10) fold; p = 0.003) and lower LV ejection fraction (51±9% vs 50±12% vs 61±5%; p = 0.004) (table 1). In patients with obstructive CAD on ICA (73/100; of whom 85% received revascularisation and 15% were medically managed for MI), CMR confirmed MI in only 84% (61/73), reclassifying the diagnosis in 15% (11/73: 7 non-ischemic pathologies, 4 normal). In patients with non-obstructive coronary arteries (NOCA) (27/100), CMR reclassified the presumed diagnosis of NSTEMI in 67% (18/27: 11 non-ischemic pathologies, 7 normal), confirming MI in only 22% (6/27); i.e. true myocardial infarction with non-obstructive coronary arteries (MINOCA) (figure 1). In patients diagnosed with MI on both ICA and CMR (61/100), CMR identified a different IRA in 11% (7/61). Conclusion In patients presenting with suspected NSTEMI, a CMR-first strategy has the potential to change management in at least 36%; by reclassifying the presumed diagnosis (29%) and offering a new IRA in CMR-confirmed MI (7%), to guide clinical decision-making, including the need for ICA and revascularisation strategies. Multi-centre randomised clinical trials are needed to test the clinical and cost-effectiveness and long-term prognostic implications of a CMR-first strategy when compared to an ICA-first strategy in patients with suspected NSTEMI. Conflict of Interest NONE
Shanmuganathan et al. (Mon,) studied this question.