RV volume was measured by either CMR (n=6) or gated cardiac MSCT (n = 44). The cardiac MSCT scanning protocol was developed specifically for this study as previously reported [9 (link)]. Patients were scanned on a GE Lightspeed 16-slice scanner (n = 13) or GE VCT 64-slice scanner (n=31) (General Electric Healthcare; Milwaukee, WI). Multiplanar reformatted images and 3D and 4D whole heart volume renderings were performed on a free standing workstation (GE ADW version 4.3, GE Healthcare, Milwaukee, Wisconsin). RV function was measured utilizing standard summation of slab volume technique as has been used in evaluating left ventricular volumes. The endoluminal borders of the RV in each slice were manually traced from apex to the tricuspid valve plane in both end-systole and end-diastole. CMR was performed by dedicated CMR technologists with a 1.5T Siemens Magnetom Espree (Siemens Medical Solutions, Erlangen, Germany) and a 32 channel phased array cardiovascular coil. The CMR scans included standard breath held segmented cine imaging with steady state free precession (SSFP) and prospective ECG gating [10 (link)]. RV volumes were measured using Simpson’s rule without geometric assumptions from short axis stacks of end diastolic and end systolic cine frames (slices 6 mm thick, 4 mm gap, 30 frames per cardiac cycle) by physicians experienced in CMR [10 (link)].