Clinical introduction A 48-year-old man presented with cardiorespiratory arrest while swimming. An automated external defibrillator was attached displaying a non-shockable rhythm. Cardiopulmonary resuscitation was commenced by the lifeguard with return of circulation and ventilation.

He had previously been investigated for atypical chest pain, including with an exercise treadmill test that was stopped due to marked hypertensive response.

Initial examination revealed bilateral crepitations throughout the lung fields and a loud systolic murmur, heard throughout the precordium, but loudest at the left sternal edge. ECG was unremarkable. Manually assessed QTc was 420 ms.

Troponin T (high-sensitivity assay) measured 6 hours apart were 21 and 32 ng/L, respectively (normal <14 ng/L).

A full echo study performed at the bedside by an experienced echo sonographer reported: suboptimal window, mild concentric left ventricular hypertrophy (LVH), dilated left ventricle (LV), preserved LV ejection fraction and mild aortic incompetence. Due to lack of definitive explanation on echocardiography, he was referred for cardiac MRI (CMR) to further elucidate the cause of dilated LV and cardiac arrest (figure 1).

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Figure 1

(A) Sagittal oblique cine MRI. Right ventricle (RV), mean pulmonary artery (MPA) and descending aorta (Des Ao). (B) Contrast-enhanced MRI. Left atrium (LA) and left ventricle (LV).

Question What is the most likely cause of his cardiac arrest?

1. Aortic regurgitation

2. Hypertensive heart disease

3. Infiltrative cardiomyopathy

4. Long QT syndrome

5. Patent ductus arteriosus

Question