Resetting of regional preload due to ventricular shape change alters diastolic and systolic performance

Abstract

The diastolic and systolic pressure of one ventricle is increased by an increase in volume and/or pressure of the opposite ventricle; however, a mechanism for the ventricular interaction remains unclear. We hypothesized that the shape change of one ventricle elicited by the opposite ventricle would lead to resetting of the regional length, which may explain the ventricular interaction. We used 15 cross-circulated isovolumically contracting canine hearts in which both ventricular volumes were independently controlled. Diastolic regional segment area was calculated by multiplying circumferential and longitudinal lengths on right ventricular free wall (RVFW; n = 6), interventricular septum (IVS; n = 11), and left ventricular (LV) FW (n = 12). The regional area at relatively small volumes of both ventricles were expressed as 100%. With constant RV volume, increasing LV from 7 to 19 ml increased RV diastolic and systolic pressures by 2.7 and 5.5 mmHg, respectively. Conversely, increasing RV volume increased LV diastolic and systolic pressures by 2.3 and 7.5 mmHg, respectively. Increasing LV volume increased RVFW regional area from 121.0 to 124.6% (P < 0.01) and increased IVS regional area from 103.3 to 108.7% (P < 0.01), whereas the RV volume was held constant. Increasing RV volume also increased LVFW and IVS regional areas from 109.9 to 111.6% (P < 0.01) and from 106.8 to 108.9% (P < 0.05), respectively. Ventricular shape change elicited by ventricular interaction will increase the regional wall area, even though the volume of the chamber is unchanged. The increase in the regional area alters the position of the tissue on its resting and active length-tension relations and, thus, leads to enhancement of the chamber pressure.

Assessment of left ventricular cardiac shape by the use of volumetric curvature analysis from 3D echocardiography

“…It influences not only the cardiac shape and performance but also patient's prognosis. Deformation of left ventricular shape may also occur in the patient with left and right ventricular pressure and volume overloading [6][7][8][9]. Accordingly, the shape of heart is an important diagnostic and therapeutic index for evaluating a variety of cardiac diseases.…”

Impaired distensibility of the left ventricle after stiffening of the right ventricle

“…The models (14,15,22) imply that all interactions occur through the septum and are not influenced through the ventricular free walls. We reported that ventricular interdependence not only altered septal position but also caused regional myocardial stretch in the whole ventricle (30,31). For example, increasing RV volume enhanced regional LV diastolic dimensions in the septum and LV free wall, even at constant LV volume and increased LV chamber pressures (30).…”

“…For example, increasing RV volume enhanced regional LV diastolic dimensions in the septum and LV free wall, even at constant LV volume and increased LV chamber pressures (30). The augmented myocardial diastolic stretch, that is, the increased regional preload, results in the increased resting and active regional forces under the same LV volume, and then the increased forces inevitably elevate LV intracavitary pressure (30,31). Although the septum is important in ventricular interdependence, ventricular interdependence affects the whole heart: the RV free wall, the LV free wall, and the septum (7,30).…”

“…We reported that ventricular interdependence not only altered septal position but also caused regional myocardial stretch in the whole ventricle (30,31). For example, increasing RV volume enhanced regional LV diastolic dimensions in the septum and LV free wall, even at constant LV volume and increased LV chamber pressures (30). The augmented myocardial diastolic stretch, that is, the increased regional preload, results in the increased resting and active regional forces under the same LV volume, and then the increased forces inevitably elevate LV intracavitary pressure (30,31).…”

“…The augmented myocardial diastolic stretch, that is, the increased regional preload, results in the increased resting and active regional forces under the same LV volume, and then the increased forces inevitably elevate LV intracavitary pressure (30,31). Although the septum is important in ventricular interdependence, ventricular interdependence affects the whole heart: the RV free wall, the LV free wall, and the septum (7,30). However, it is unclear whether changes in mechanical properties of one ventricle alter the myocardial dimension of the other ventricle when both ventricular volumes are fixed.…”