An unsual cascade of events in a young patient: from Cardiac Arrest, Cardiogenic Shock, HCM to MINOCA

Description of Clinical Presentation: A 17-year-old male athlete with no prior cardiac history suffered cardiac arrest during a basketball game. Cardiopulmonary resuscitation was initiated with five shocks delivered. Subsequently, PEA and pulseless VT were documented, with ROSC achieved after adrenaline, amiodarone, and defibrillation. On admission, rapid hemodynamic deterioration required ECMO support. Initial echocardiography suggested non-obstructive HCM, confirmed by 2D echocardiography showing marked anterior and septal hypertrophy (maximum 38 mm at mid-anterior wall) with severe mitral regurgitation due to restricted posterior leaflet motion. Coronary angiography showed no significant stenosis (Figure 1). Haemodynamic stability enabling ECMO weaning was achieved only after surgical mitral valve repair.

Diagnostic Techniques and Their Most Important Findings: A comprehensive cardiac magnetic resonance (CMR) study was performed eight weeks after the acute event, including cine, T2 mapping and LGE images. The study revealed asymmetric LVH (maximum 22 mm at basal anterior wall) with no LVOT obstruction or septal anterior motion (SAM) at rest. There was extensive myocardial oedema and LGE in the basal-to-mid hypertrophied septum with a large hypointense core, along with papillary muscle LGE. The mitral valve ring was in situ with no residual regurgitation. Overall, CMR findings were consistent with HCM phenotype with extensive acute myocardial infarction in the proximal LAD/septal territory and a large intramyocardial haemorrhage core (Figure 2).

At one-year follow-up, CMR showed reduced septal and anterior wall thickness (maximum 16 mm) and improved systolic function (EF 55%) with nearly transmural LGE of basal-mid anterior and septal walls, in keeping with non-obstructive HCM with anterior infarction (Figure 3).

Learning Points from this Case: Acute myocardial infarction with non-obstructed coronary arteries (MINOCA) has been described in patients with HCM, having multiple underlying mechanisms such as small-vessel disease, septal perforator compression, myocardial bridging, inadequate capillary density, and coronary spasm.

This case highlights the pivotal role of CMR in this setting: from accurate assessment of the maximal wall thickness to identify the causes for the acute presentation and the extent of myocardial injury, once the patient is stabilised. Beyond confirming asymmetric hypertrophy, CMR delineated the extent of the infarction and intramyocardial haemorrhage. In addition, CMR showed papillary muscle displacement and infarction, causing posterior mitral leaflet restricted motion, resulting in haemodynamic instability that prevented weaning from mechanical support. Interestingly, the large septal infarction ultimately served a similar role to alcohol septal ablation, resulting in reduced wall thickness on follow-up CMR. Nevertheless, it remains unclear if the cause of the cardiac arrest was arrhythmias from HCM with the acute infarction representing a complication of the resuscitation.

Figure 1. Coronary angiography. (A) Left main stem, left anterior descending and circumflex arteries without significant stenosis. (B) Right coronary artery of small caliber, without stenosis.
Figure 2. CMR performed eight weeks after the acute event. (C) T2 mapping, short-axis basal slice. (D) Late gadolinium enhancement (PSIR), short-axis basal slice.
Figure 3. (E), (F) CMR performed eight weeks after the acute event. (E) Cine short-axis basal slice showing maximum wall thickness of 22 mm; (F) Late gadolinium enhancement (PSIR), short-axis basal slice. (G), (H) One-year follow-up CMR. (G) Cine short-axis basal slice showing maximum wall thickness of 16 mm; (H) Late gadolinium enhancement (PSIR), short-axis basal slice.