Submitted on February 16, 2007
Accepted on May 6, 2007
Contribution of mitral annular dynamics to LV diastolic filling with alteration in preload and inotropic state
Carl Johan Carlhall1, Katarina Kindberg2, Lars Wigstrom3, George T. Daughters4, D. Craig Miller4, Matts Karlsson2, and Neil B. Ingels5*
1 Cardiothoracic Surgery, Stanford University School of Medicine, Stanford, California, United States; Clinical Physiology, Linköping University Hospital , Linköping, Sweden
2 Biomedical Engineering, Linköping University, Linköping, Sweden
3 Clinical Physiology, Linköping University Hospital, Linköping, Sweden
4 Cardiothoracic Surgery, Stanford University School of Medicine, Stanford, California, United States
5 Laboratory of Cardiovascular Physiology and Biophysics, Research Institute of the Palo Alto Medical Foundation, Palo Alto, California, United States; Cardiothoracic Surgery, Stanford University School of Medicine, Stanford, California, United States
* To whom correspondence should be addressed. E-mail: ingels{at}stanford.edu.
Mitral annular (MA) excursion during diastole encompasses a volume that is part of total left ventricular filling volume (LVFV). Altered excursion or area variation of the MA due to changes in preload or inotropic state could affect LV filling. We hypothesized that changes in LV preload and inotropic state would not alter the contribution of MA dynamics to LVFV. Six sheep underwent marker implantation in the LV wall and around the MA. After 7-10 days, biplane fluoroscopy was used to obtain three-dimensional (3-D) marker dynamics from sedated, closed-chest animals during: control conditions; inotropic augmentation with calcium (Ca); preload reduction with nitroprusside (N) and vena caval occlusion (VCO). The contribution of MA dynamics to total LVFV was assessed using volume estimates based on multiple tetrahedra defined by the 3-D marker positions. Neither the absolute nor the relative contribution of MA dynamics to LVFV changed with Ca or N, although MA area decreased (Ca: P<0.01, and N: P<0.05) and excursion increased (Ca: P<0.01). During VCO the absolute contribution of MA dynamics to LVFV decreased (P<0.001), based on a reduction in both area (P<0.001) and excursion (P<0.01), but the relative contribution to LVFV increased from 18±4 to 45±13 % (P<0.001). Thus, MA dynamics contribute substantially to LV diastolic filling. Although MA excursion and mean area change with moderate preload reduction and inotropic augmentation, the contribution of MA dynamics to total LVFV is constant with sizeable magnitude. With marked preload reduction (VCO), the contribution of MA dynamics to LVFV becomes even more important.
