Sleeping with the unknown: coronary vasospasm in an anomalous right circumflex artery mimicking in-stent restenosis

Coronary vasospasm represents a transient, reversible constriction of coronary arteries that often goes unrecognised in patients with established coronary artery disease or anomalous coronary anatomy. When combined with prior percutaneous coronary intervention (PCI), vasospasm can closely mimic in-stent restenosis, leading to delayed diagnosis and unnecessary repeat interventions. We describe a 55-year-old male with prior PCI to an anomalous right circumflex artery (RCx) who presented with recurrent nocturnal chest pain and asymptomatic transient ST-segment elevation (STE) during sleep. Despite FFR-guided PCI to the left anterior descending artery (LAD) and subsequent repeat intervention for suspected RCx in-stent restenosis, symptoms persisted. A probable diagnosis of nocturnal coronary vasospasm was established based on the clinical presentation, characteristic nocturnal ECG changes, response to diltiazem, and exclusion of alternative structural pathology on cardiac magnetic resonance imaging; however, the diagnosis remains inferential in the absence of invasive provocation testing. This case illustrates the diagnostic complexity of probable coronary vasospasm in a male patient with structural coronary disease and anomalous coronary anatomy. Several factors may have contributed to diagnostic delay, including anchoring toward structural disease, angiographic ambiguity, anomalous anatomy, and the unusual nocturnal presentation. The differential response to calcium channel blocker subclasses in this patient is presented as a clinically relevant, hypothesis-generating observation rather than evidence of therapeutic superiority. Clinicians should maintain a high index of suspicion for probable coronary vasospasm in patients with recurrent nocturnal ST elevation following PCI, particularly when symptoms, telemetry findings, and coronary physiology are discordant with fixed obstructive disease. Careful reassessment, transparent acknowledgement of diagnostic uncertainty, and thoughtful use of non-invasive monitoring and targeted medical therapy may help avoid unnecessary repeat intervention.