Left Ventricular Papillary Muscles and Trabeculae Are Significant Determinants of Cardiac MRI Volumetric Measurements: Effects on Clinical Standards in Patients with Advanced Systolic Dysfunction

Background: Left ventricular (LV) mass and ejection fraction are of diagnostic and therapeutic importance in patients with systolic dysfunction. Cardiac MRI (CMR) has been proposed as a standard for these indices. Prior studies have variably included papillary muscles and trabeculae in either intracavitary or myocardial volumes. Quantitative effects and clinical implications of this methodological difference in patients with systolic dysfunction are unknown.

Methods: Fifty consecutive patients with known systolic dysfunction (EF<40%) underwent CMR. LV volumes were determined using previously established methods: Method 1 included papillary muscles and trabeculae in cavity volume, method 2 included these in myocardial volume. Both methods were used for each patient with tracings superimposed to isolate papillary/trabecular volume and insure consistency of other endocardial contours. Readers applied methods in random order blinded to clinical findings and results of the other method.

Results: LV mass differed substantially by method (p<0.001) with absolute difference of 16.6%. Ejection fraction differed by 3 points (p<0.001) with absolute differences of > or =5 points in 16% of patients. Mean differences in LV mass and ejection fraction were produced by consistent methodological differences on a per-patient basis. Methodology used produced differences in patients meeting established criteria for LV hypertrophy (28% vs. 60%, p<0.001) and ICD implantation (64% vs. 48%, p<0.01).

Conclusions: LV mass and ejection fraction differ significantly between commonly employed CMR methods. Alternative inclusion of papillary muscles and trabeculae in either cavity or myocardial volumes produces significant differences in clinical and therapeutic indices that can affect management of patients with advanced systolic dysfunction.