Changes in diastolic function during development and correction of chronic LV volume overload produced by mitral regurgitation.

Abstract

Background. Mitral regurgitation (MR) causes an augmentation in left ventricular (LV) diastolic function, increasing early diastolic filling rate and decreasing LV stiffness. Whether these changes in diastolic function persist, return to normal, or become abnormal after mitral valve replacement (MVR) is unknown.Methods and Results. Simultaneous LV echocardiography and catheterization studies were performed in six dogs in the baseline state (baseline), 3 months after creation of MR (chronic MR), and 3 months after MVR. Chronic MR caused LV dilation (end-diastolic dimension increased from 4.5±0.1 cm in baseline to 5.8+0.1 cm in chronic MR,p<0.05) and eccentric LV hypertrophy (LV-to-body weight ratio increased from 3.6±0.2 g/kg in baseline to 4.9±0.4 g/kg in chronic MR, p<0.05). Chronic MR caused an increase in LV early diastolic filling rate (peak rate of increase in minor-axis dimension increased from 11±1 cm/sec in baseline to 18+1 cm/sec in chronic MR,p<0.05), did not change the time constant of myocardial relaxation (T was 31±4 msec in baseline and 30±2 msec in chronic MR), and caused a decrease in the modulus of regional chamber stiffness from 7.7± 1.2 in baseline to 2.4±0.03 in chronic MR,p<0.05. MVR caused the resolution of LV dilation (end-diastolic dimension returned to normal [4.8±0.2 cm]), but three months after MVR, regression of LV hypertrophy was incomplete (LV-to-body weight ratio remained

Novel Mechanistic Insights Into Atrial Functional Mitral Regurgitation – 3-Dimensional Echocardiographic Study –

“…Also, patients with chronic MR have preserved LV relaxation and decreased LV stiffness to compensate for the volume overload. 32 These previous findings may be consistent with the findings of the present study. LA remodeling and AF are surrogate markers of LV diastolic dysfunction.…”

Progressive nature of chronic mitral regurgitation and the role of tissue Doppler-derived indexes

“…In a similar chronic canine model (22,36), chamber dilatation is also seen without a reduction in EF. However, in this model, there is no progressive change in the severity of the MR.…”

Adaptive mechanisms of left ventricular diastolic function to the physiologic load of pregnancy

“…Zile et al have demonstrated a shift to the right of the pressure-volume curve in dogs with mitral regurgitation. 33 They also found that chamber stiffness decreased in response to the volume load. Fragata and Areias 34 showed that smallto-moderate volume load induced by infusion of saline to dogs resulted in an increase in early filling and improved compliance, while severe acute volume load resulted in a shift in filling toward late diastole and decreased compliance.…”