Clinical introduction A 32-year-old man referred to the cardiology clinic for palpitations was found to have paroxysmal supraventricular tachycardia (SVT) on 24-hour Holter monitoring. His general and cardiac examinations were unremarkable. A transthoracic echocardiographic study to exclude structural heart disease was performed and showed an abnormal structure in relation to the right ventricular (RV) free wall; however, poor echocardiographic windows precluded proper characterisation. Cardiac MR (CMR) was therefore performed. Cine images (figure 1 and online supplementary videos 1 and 2) demonstrated the abnormal structure. Dynamic pass of contrast (rest perfusion module) showed the sequence of intracavitary enhancement across different cardiac chambers in the horizontal long-axis plane (figure 1 and online supplementary video 3).

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Figure 1

Still frames from balanced steady state free precession images in the horizontal long-axis plane (A,B). Still frames from the dynamic pass of contrast in the horizontal long-axis and the short axis following contrast injection into the right arm (C,D). Images in the horizontal long-axis plane at the basal level using T2-weighted short-tau inversion recovery (E) and half Fourier single-shot turbo spin echo (F).

Question The abnormal structure is most likely which of the following?

1. Pericardial cyst

2. Right atrial appendage aneurysm

3. Right ventricular aneurysm

4. Juxtaposed left atrial appendage

5. Accessory right ventricular chamber

Question