Initial Presentation    
A 39-year-old Japanese man presented with a half-month history of intermittent chest pain at rest and during activity. After a severe 15-minute chest pain episode one night, he sought medical attention. Workup revealed a moderate stenosis in the proximal left anterior descending (LAD) artery and positive troponin levels, leading to a diagnosis of unstable angina. He was started on aspirin, statins, and calcium channel blockers. Despite treatment, intermittent chest pain persisted.

Sudden Collapse and Resuscitation    
Twenty-nine days after his initial hospital visit, he collapsed at work. On arrival, the emergency team found him in ventricular fibrillation. After defibrillation and CPR, he converted to pulseless electrical activity. Spontaneous circulation was restored five minutes after hospital arrival. An ECG post-resuscitation showed ST-segment elevation in leads I, aVL, and V2–V6, and ST depression in lead III—raising concern for an acute coronary event.

Differential Diagnoses Considered    
Given the sudden cardiac arrest and ECG findings, several urgent possibilities were explored:
•    Acute coronary syndrome (ACS) was suspected due to chest pain history, ECG changes, and known LAD stenosis.
•    Coronary artery spasm was suspected in the context of persistent symptoms and risk for arrhythmias.
•    Spontaneous coronary artery dissection (SCAD) was considered due to the patient’s young age and sudden collapse.
•    Aortic dissection and pulmonary embolism were also evaluated due to overlapping symptoms with ACS.

Imaging and Intervention    
CT scans ruled out aortic dissection and pulmonary embolism. Emergency coronary angiography confirmed a critical LAD stenosis, and primary percutaneous coronary intervention (PCI) was performed. Optical coherence tomography (OCT) revealed features consistent with intraplaque hemorrhage (IPH), including low signal intensity and cholesterol crystals—marking the plaque as rupture-prone. A drug-eluting stent was placed successfully.
To investigate persistent chest pain and suspected vasospasm, an acetylcholine (ACh) provocation test was performed. It confirmed coronary spastic angina, with diffuse LAD and obtuse marginal branch spasms, reproducing the patient’s symptoms and ST-segment changes. Spasm was also noted in the right coronary artery without symptoms.

Outcome and Long-Term Management    
For secondary prevention of sudden cardiac death, an implantable cardioverter-defibrillator (ICD) was placed. The patient was discharged on dual antiplatelet therapy, statins, and a combination of vasodilators, including calcium channel blockers and nitrates. Over a follow-up period exceeding three years, he remained free of cardiac events.