ST segment elevation myocardial infarction with normal coronary arteries

A middle-aged patient presented to the emergency department with intermittent chest pain of 4-hour duration. The patient had been recently diagnosed with metastatic adenocarcinoma of the colon and was receiving 5-fluorouracil (5-FU)-based chemotherapy at the time of presentation. The ECG at presentation showed 1 mm ST segment elevation in leads II, III and aVF, with reciprocal changes in leads aVL, V1 and V2 (figure 1A). Serum cardiac troponin I level was elevated at 0.11 ng/mL (normal: 0.00-0.02 ng/mL). The patient was given sublingual nitrate and loading doses of aspirin, clopidogrel and atorvastatin, and was taken up for coronary angiography with an intent to perform primary percutaneous coronary intervention.Figure 1(A) 12-lead ECG done at presentation to the emergency department. (B) 12-lead ECG done 30 min after coronary angiography.The images of the coronary angiogram are shown in figure 2. The patient was angina-free by this time. A repeat ECG done 30 min after coronary angiography is shown in figure 1B. Two-dimensional transthoracic echocardiogram revealed normal left ventricle (LV) systolic function and no regional wall motion abnormality.Figure 2Images of the coronary angiogram of the patient. (A) Right anterior oblique view with a caudal angulation showing left anterior descending (LAD) artery and left circumflex (LCx) artery. (B) Left anterior oblique view with a cranial angulation showing right coronary artery (RCA).

What is the likely mechanism of myocardial infarction in this patient?In situ coronary artery thrombosis with spontaneous recanalisation.Epicardial coronary artery vasospasm.Coronary artery embolism.Coronary microvascular dysfunction.