A disproportionate contribution of papillary muscles and trabeculations to total left ventricular mass makes choice of cardiovascular magnetic resonance analysis technique critical in Fabry disease

BACKGROUND: 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). METHODS/RESULTS: 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 M(ex)P&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). CONCLUSION: 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.