Changes in systemic sympathetic nervous system activity after mitral valve surgery and their relationship to changes in left ventricular size and systolic performance in patients with mitral regurgitation

Background We have shown that the systemic sympathetic nervous system (SNS) is activated in patients with chronic mitral regurgitation (MR). However, the fate of systemic SNS activity after surgical correction of MR is currently unknown. Methods We examined 14 patients with MR who had normal sinus rhythm with an investigational, preoperative cardiac catheterization, including arterial norepinephrine (NE) sampling and [3H]-NE infusions and arterial blood sampling to determine NE kinetic parameters using a 2-compartment modeling analysis. The arterial NE and NE kinetic parameters were determined in all patients after mitral valve surgery (MVS) at a mean of 12 months. A 2-dimensional echocardiographic examination was also performed before and after MVS. Results The average extravascular NE release rates (NE2) before and after MVS were 1.89 ± 0.66 and 2.26 ± 0.82 μg/min/m2 (P = .24), respectively. The average left ventricular (LV) end-diastolic dimension, fractional shortening, and ejection fraction decreased, whereas the mean LV end-systolic dimension did not change between the pre- and post-MVS echocardiographic studies. However, these group averages were comprised of patients with MR in whom the NE2 and echocardiographic values both increased and decreased. This lack of homogeneity was a reflection of our new observation that the pre- to post-MVS changes in NE2 were directly proportional to the changes in LV end-systolic dimension (r = 0.91, P <.001) and inversely related to the changes in LV fractional shortening (r = −0.82, P <.001) and ejection fraction (r = −0.78, P <.001). Conclusions The response in systemic SNS activity in patients with MR after MVS is not homogeneous, and these changes are concordant with the post-MVS changes in LV size and systolic performance. These data further support our earlier observations and extend them to suggest that systemic SNS activation in patients with chronic MR is related to LV remodeling and impaired systolic performance.