Compression of interventricular septum during right ventricular pressure loading

Abstract

The interventricular septum, which flattens and inverts in conditions such as pulmonary hypertension, is considered by many to be an unstressed membrane, in that its position is assumed to be determined solely by the transseptal pressure gradient. A two-dimensional finite element model was developed to investigate whether compression and bending moments (behavior incompatible with a membrane) exist in the septum during diastole under abnormal loading, i.e., pulmonary artery (PA) constriction. Hemodynamic and echocardiographic data were obtained in six open-chest anesthetized dogs. For both control and PA constriction, the measured left ventricular and right ventricular pressures were applied to a residually stressed mesh. Adjustments were made to the stiffness and end-bending moments until the deformed and loaded residually stressed mesh matched the observed configuration of the septum. During PA constriction, end-bending moments were required to obtain satisfactory matches but not during control. Furthermore, substantial circumferential compressive stresses developed during PA constriction. Such stresses might impede septal blood flow and provoke the unexplained ischemia observed in some conditions characterized by abnormal septal motion.

Evaluation of Right Ventricular Tei Index (Index of Myocardial Performance) in Healthy Dogs and Dogs with Tricuspid Regurgitation

“…PH was assumed on the basis of the following echocardiographic findings: essential parameters were maximal TR jet velocity of not less than 2.8 m/sec and no existence of RV outflow tract stenosis. In addition, relative dilation of the main pulmonary artery as compared with the aorta, appearance of another peak or notch in the latter half of RV outflow profiles and maximal pulmonary regurgitant jet velocity of not less than 2.2 m/sec were referred [3,14,20,21,29,41]. Diagnostic ultrasound machines, Nemio (SSA-550A, Toshiba Medical Systems, Tokyo, Japan) and EUB-565A (Hitachi Medical Corporation, Tokyo, Japan), were used for the echocardiographic measurements.…”

A 2D FE model of the heart demonstrates the role of the pericardium in ventricular deformation

“…At this point, the cross-sectional area of the heart would become virtually fixed, and any increase in the area (and thus volume) of one ventricle would have to be accompanied by a concomitant decrease in the other-a relation that we defined as direct ventricular interaction (7). Given this role, the pericardium may be important in the structural responses of the LV and RV free walls and septum when subjected to abnormal pressure loading, particularly at end diastole, when the pericardium is taut.Using finite element (FE) analysis, our group studied the behavior of the interventricular septum during diastole with acute pulmonary artery constriction (PAC) (17,18). Under control conditions, the septum behaved as part of the LV and was under slight circumferential tension; the dominant stress was a low radial compression over the width of the septum.…”

“…Using finite element (FE) analysis, our group studied the behavior of the interventricular septum during diastole with acute pulmonary artery constriction (PAC) (17,18). Under control conditions, the septum behaved as part of the LV and was under slight circumferential tension; the dominant stress was a low radial compression over the width of the septum.…”

Pericardial Fat Is Associated With Impaired Lung Function and a Restrictive Lung Pattern in Adults

“…RV diastolic pressure has been shown to be positively associated with epicardial fat in humans, 6 and in anesthetized dogs, constriction of the pulmonary artery increased RV diastolic pressure. 7 Pericardial fat may indeed compress the pulmonary artery, thereby increasing pulmonary artery systolic pressure (PASP) and contributing to a restrictive lung pattern. A study of obese subjects undergoing autopsy demonstrated a higher frequency of pulmonary edema and pulmonary hypertensive changes, including venous hypertension and capillary hemangiomatosis, than healthy age-matched control subjects.…”

“…Given the close proximity of pericardial fat to the pulmonary outfl ow tract and lungs, pericardial fat may have similar effects on the lungs. First, epicardial fat deposits 6 and pulmonary artery constriction 7 have been shown to increase RV end-diastolic pressure. Pericardial fat may compress the pulmonary artery, thereby increasing RV pressure and impairing lung function.…”