Biventricular systolic function in young lambs subject to chronic systemic right ventricular pressure overload

Abstract

In various clinical situations of congenital heart disease, the right ventricle (RV) is subject to a chronic systemic pressure overload which affects biventricular function and may progress to the development of RV failure. Young lambs (2-3 wk old) underwent adjustable pulmonary artery banding (PAB) at systemic (aortic) level for 8 wk. Biventricular function was determined by using load-independent indexes of global ventricular contractile performance by the end-systolic pressure-volume relationship (ESPVR) using the conductance catheter at baseline and during dobutamine infusion. PAB resulted in a significant fivefold increase in RV end-systolic pressure (12-64 mmHg) and a doubling of the RV-to-left ventricular (LV) wall thickness ratio (P < 0.01). RV global contractile performance increased significantly, as indicated by an increased slope of the ESPVR. Compared with age-matched control lambs, cardiac output decreased from 2.6 to 1.6 l/min (P < 0.05) whereas heart rates were equal. In contrast with RV volume, LV volume decreased significantly after PAB (P < 0.01), whereas the LV-ESPVR slope was unchanged. In the PAB group, the RV, but not the LV, showed a reduced response to dobutamine. We concluded that chronic RV pressure overload for 8 wk results in diminished pump function despite compensatory increased RV global contractile performance.

Normal Right Ventricular Three‐Dimensional Architecture, as Assessed with Diffusion Tensor Magnetic Resonance Imaging, is Preserved During Experimentally Induced Right Ventricular Hypertrophy

“…Surprisingly, this did not occur because of simultaneous development of left ventricular hypertrophy. While previous bi-ventricular conductance catheter studies in lambs showed impairment of left ventricular function during right ventricular hypertrophy (Leeuwenburgh et al, 2001), our findings showing that banded animals displayed significant bilateral hypertrophy, with potential biventricular increase of systolic function in terms of myocardial systolic thickening. The design of our study, however, however, does not permit us to speculate regarding the mechanism responsible for this phenomenon.…”

“…Other experimental models have been proposed (Leeuwenburgh et al, 2001). It is not surprising, therefore, that we were able to develop our model on the basis of growth-induced relative stenosis.…”

Magnetic Resonance Imaging Analysis of Right Ventricular Pressure-Volume Loops

“…Interestingly, both RV and LV chamber volumes were diminished in this group of patients. These findings are similar to experimental studies performed in sheep after 2 months of pulmonary stenosis, 3 whereas studies involving adult patients with prolonged increased RV afterload demonstrated a progressive dilation of RV volumes. 27 Although further studies are needed to elucidate underlying mechanisms, it may be hypothesized that small RV volumes, as noted in the present study, are due to a combination of limited diastolic filling in the presence of eccentric myocardial hypertrophy and enhanced myocardial contractile performance.…”

“…16 More recently, several animal and human conductance catheter studies were reported for analysis of RV function. 3,5,7 However, the assessment of the trapezoidal RV or morphologically deformed ventricle, existent in many patients with congenital heart disease, can be problematic because of field inhomogeneities and mismatch between catheter segments and the RV cavity. In addition, the use of conductance catheters is time consuming and requires added radiation exposure; therefore, conductance catheters are used predominantly as a research tool, not in routine clinical practice.…”

“…1,2 Pressure-volume relations yield information about ventricular pump performance, mechanical interaction of the ventricle with the pulmonary vascular system, and the contractile state of the myocytes and thus may provide important insight into the pathophysiology of the pressure-loaded RV. [3][4][5][6][7] MRI analysis of RV and left ventricular (LV) volumes does not rely on geometrical assumption. 8 -10 MRI is widely considered the "gold standard" to assess ventricular pump function but is limited in its ability to determine cardiovascular pressures required for assessment of more loadindependent parameters of ventricular function.…”