Purpose To evaluate the relationship between left ventricular (LV) twist, shear, and twist-per-volume and the severity of mitral regurgitation (MR). Primary MR is a valvular disorder that induces LV dysfunction. There exist several measures of LV rotational mechanics, but it remains unclear which measure of LV dysfunction best accords with the severity of MR. We hypothesized that LV systolic twist-per-volume slope would decrease with increasing severity of MR because of both decreases in rotational mechanics and increases in stroke volumes. Materials and Methods Normal subjects (n-=-54), moderate MR patients (n-=-29), and severe MR patients (n-=-54) were studied. Magnetic resonance imaging (MRI) was performed on a 1.5T scanner and grid-tagged LV images were collected at the LV base and LV apex. Measures of LV rotational mechanics were derived from tagged images using Fourier Analysis of STimulated echoes (FAST). Results Peak systolic twist-per-volume slope was significantly different for all pairwise comparisons (P-<-0.0001) and compared to normal subjects (-0.14-±-0.05°/mL) was decreased in moderate MR (-0.12-±-0.04°/mL) and further decreased in severe MR (-0.07-±-0.03°/mL). Conclusion Peak systolic twist-per-volume slope significantly decreased with increasing severity of MR and is therefore a suitable quantitative imaging biomarker for LV dysfunction in patients with MR.