Discussion

In the era of high-sensitivity cardiac troponin assays, the aetiology of myocardial injury can be difficult to ascertain. In this case, myocardial infarction with non-obstructed coronary arteries1 due to plaque erosion was the probable cause of the index presentation, given the typical presentation and left anterior descending (LAD) atheroma. Stress cardiomyopathy was unlikely given the lack of a trigger, regional wall motion abnormality on echocardiography or ECG changes.2 Mild myocarditis was less likely in the absence of an infective prodrome and a clinical presentation most in keeping with acute ischaemia, although cardiac magnetic resonance (CMR) may be a useful test when there is clinical uncertainty. Microvascular dysfunction is a recognised cause of ischaemia3 but typically presents with a history of angina rather than a discrete episode of myocardial infarction. Similarly, coronary artery spasm usually presents with episodic chest pain of diurnal variation that responds rapidly to nitrates. If an ECG is taken during an acute episode, transient ST-segment deviation can be seen, not present in in this case.4 In situations of diagnostic ambiguity, the use of adjunctive tools such as intravascular imaging or CMR5 should be considered to clarify the underlying pathology and guide therapies.

However, myocarditis was felt to be the most likely diagnosis by the treating team. Preventative therapies were stopped and the patient was discharged. He continued to smoke. Six months later, he re-presented with severe chest pain and anterior ST elevation. Emergent coronary angiography demonstrated a thrombotic occlusion of the mid-LAD artery (figure 2A,B). Primary percutaneous intervention was undertaken (figure 2C,D). The patient recovered well.

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Figure 2

Angiography at re-presentation. (A–D) Right anterior oblique–caudal/cranial views showing mid-left anterior descending artery occlusion with progression of proximal left anterior descending artery disease and thrombus extending into the large second diagonal branch. (C,D) Post-percutaneous intervention views from the same projections demonstrating a recanalised left anterior descending artery.