Relationship between systolic and diastolic function with improvements in forward stroke volume following reduction in mitral regurgitation

Efforts to improve mitral regurgitation (MR) are often performed in conjunction with coronary revascularization. However, the independent effects of a reduced MR area (MRa) are difficult to quantify. Using a previously-developed cardiovascular model, ventricular contractility (elastance 1-8 mmHg/ml) and relaxation (τ=40-150 ms) were independently adjusted for four grades of MR orifice areas (0.0-0.8 cm ²). Improvements in forward stroke volume (fSV) were determined for the permutations of reduced MRa. For all conditions, left ventricular (LV) end-diastolic pressure and volumes ranged from 7.3-24.2 mmHg and 64.8-174.3 ml, respectively. Overall, fSV ranged from 36.0-89.4 (mean: 64.2±12.8) ml, improved between 6.4 and 35.3% (mean: 15.6±8.1%), and was best predicted (r=0.97, p<0.01) by %Δ(fVS) = 34[MRa_inital] - 46[MRa_final] 0.5[elastance]. Thus, it is concluded that reduced MRa, independent of relaxation and minimally influenced by contractility, yielded improved fSVs