Double-chambered right ventricle or sub-infundibular stenosis assessed by cardiovascular magnetic resonance.

This paper presents magnetic resonance findings in four adults with double-chambered right ventricle or sub-infundibular stenosis, a condition that is treatable by surgery, but which can be difficult to assess echocardiographically. Four patients referred for cardiovascular magnetic resonance in the last 2 years were identified from CMR findings, although not necessarily from previous echocardiography, as having sub-infundibular stenosis. We used multislice spin echo imaging, cine imaging in oblique sagittal planes, and phase velocity mapping. We performed spin echo imaging of a post-mortem heart without known structural abnormality to illustrate right ventricular myocardial morphology. Results in patients showed evidence of sub-infundibular muscular obstruction separating the hypertrophied inlet and apical portions of the right ventricle from a thin-walled, unobstructed infundibular region in each case, with a systolic jet originating at least 15 mm beneath the unstenosed pulmonary valve. In addition to previously described structural components contributing to stenosis--enlargement and/or displacement of the septomarginal trabeculation, septoparietal trabeculations or the moderator band--CMR suggested additional components: a right ventricular papillary muscle in one, an anteriorly bulging aortic sinus in one, and hypertrophied muscular ridges of the parietal wall of the right ventricle. Even in this small group of patients, the causes of sub-infundibular stenosis appeared to be varied and multi-factorial. The abilities of magnetic resonance to give unrestricted, multi-planar views of right ventricular anatomy, movement and flow make it well suited for diagnosis and characterization of sub-infundibular stenosis, especially in adults.