Decoding cardiac masquerade: Arrhythmogenic cardiomyopathy camouflaging as acute myocardial infarction

Arrhythmogenic cardiomyopathy, a rare inherited heart condition, can mimic acute coronary syndrome, presenting diagnostic challenges. This case also highlights the utility of a CT coronary angiogram over an invasive angiogram, allowing for a degree of tissue differentiation and thus early diagnosis. A 76 year old male presented with a sudden onset retrosternal chest pain associated with shortness of breath and diaphoresis, resembling his previous myocardial infarction 25 years ago. He reported that he had an angiogram at the time which did not show any coronary artery disease. His past medical history apart from a MI, included hypertension, BPH and small bowel obstruction. In the Emergency Department, he had broad complex tachycardia (187 bpm), tachypnoea (24 bpm), unrecordable blood pressure, hypoxaemia (77% on room air), and a GCS of 15. He denied any palpitations or syncope and there were no signs of peripheral fluid overload on examination. Due to his haemodynamic instability, he was cardioverted with a single 200 J synchronised shock. Initial blood results revealed an AKI stage 1, normal full blood count, serum electrolytes, liver function tests and pro-bnp levels. His first cardiac troponin level was 56 ng/L. The patient's initial ECG revealed broad complex tachycardia indicative of monomorphic ventricular tachycardia (Image 1), later resolving to sinus rhythm post-cardioversion with diffuse ischaemic changes. Notably, a positive deflection after a QRS complex was observed in right-sided precordial leads. Decision was made for medical management considering absence of persistent ST elevations and chest pain. Serial troponin levels peaked at 554 ng/L without further chest pain. Echocardiogram displayed normal left ventricular size but impaired systolic function (EF 45–50%) with hypokinesis of apical and anterior walls, akinetic apical inferior wall segment, and normal right ventricles and atria. No significant valvular abnormalities or pericardial effusion were noted. Post-cardioversion, patient received IV magnesium sulfate and dual antiplatelets plus fondaparinux for a presumed acute coronary syndrome. CT angiogram revealed normal coronaries but extensive fatty metaplasia, mostly within the left ventricular myocardium which suggested arrhythmogenic cardiomyopathy (Image 2). He underwent a cardioverter defibrillator implantation. On clinic follow-ups, the patient remains asymptomatic and well. Arrhythmogenic ventricular cardiomyopathy (AVC) is a rare