Background—: Both transthoracic echocardiography (TTE) and cardiac magnetic resonance (CMR) imaging allow quantification of chronic aortic regurgitation (AR) and mitral regurgitation (MR). We hypothesized that CMR measurement of regurgitant volume (RVol) is more reproducible than TTE. Methods and Results—: TTE and CMR performed on the same day in 57 prospectively enrolled adults (31 with AR, 26 with MR) were measured by 2 independent physicians. TTE RVol _AR was calculated as Doppler left ventricular outflow minus inflow stroke volume. RVol _MR was calculated by both the proximal isovelocity surface area method and Doppler volume flow at 2 sites. CMR RVol _AR was calculated by phase-contrast velocity mapping at the aortic sinuses and RVol _MR as total left ventricular minus forward stroke volume. Intraobserver and interobserver variabilities were similar. For AR, the Bland–Altman mean interobserver difference in RVol was −0.7 mL (95% confidence interval [CI], −5 to 4) for CMR and −9 mL (95% CI, −53 to −36) for TTE. The Pearson correlation was higher ( P =0.001) between CMR (0.99) than TTE readers (0.89). For MR, the Bland–Altman mean difference in RVol between observers was −4 mL (95% CI, −21 to 13) for CMR compared with 0.7 mL (95% CI, −30 to 32) for the proximal isovelocity surface area and −10 mL (95% CI, −76 to 56) for TTE volume flow at 2 sites. Correlation was similar for CMR (0.94) versus TTE readers (0.90 for the proximal isovelocity surface area). Conclusions—: Compared with TTE, CMR has lower intraobserver and interobserver variabilities for RVol _AR , suggesting CMR may be superior for serial measurements. Although RVol _MR is similar by TTE and CMR, variability in measured RVol by both approaches suggests that caution is needed in clinical practice.

Sphingolipid deposition in Fabry disease causes left ventricular (LV) hypertrophy, of which the accurate assessment is essential. Cardiovascular magnetic resonance (CMR) has been proposed as the gold standard. However, there is debate in the literature as to whether papillary muscles and trabeculations (P&T) should be included in LV mass (LVM). We examined the accuracy of 2 CMR methods of assessing LVM and LV volumes, including (M inc P&T) or excluding (M ex P&T) P&T, in a cohort of Fabry disease subjects (n = 20) compared to a matched control group (n = 20). Significant differences between the two measurement methods were observed for LV end-diastolic volume, LV end-systolic volume, LVM, and LV ejection fraction (LVEF) in both groups. These differences were significantly greater in the Fabry group compared to controls, except for LVEF. P&T contributed to a greater percentage of LVM in Fabry subjects than controls (20 ± 1% vs 13 ± 2%, p = 0.01). In the control group, both volume-derived methods (M inc P&T or MexP&T) provided accurate SV measurements compared with the internal reference of velocity-encoded aortic flow. In the Fabry group, inclusion of P&T (M inc P&T) resulted in good concordance with phase contrast flow imaging (difference between flow and volume techniques: 1 ± 3 ml, p = 0.7). The volumetric contribution of P&T in Fabry disease is markedly increased relative to healthy controls. Failure to account for this results in significant underestimation of LVM and results in misclassification of a proportion of subjects.