Biomechanical and Hemodynamic Measures of Right Ventricular Diastolic Function: Translating Tissue Biomechanics to Clinical Relevance

Abstract

Background Right ventricular ( RV ) diastolic function has been associated with outcomes for patients with pulmonary hypertension; however, the relationship between biomechanics and hemodynamics in the right ventricle has not been studied. Methods and Results Rat models of RV pressure overload were obtained via pulmonary artery banding ( PAB ; control, n=7; PAB, n=5). At 3 weeks after banding, RV hemodynamics were measured using a conductance catheter. Biaxial mechanical properties of the RV free wall myocardium were obtained to extrapolate longitudinal and circumferential elastic modulus in low and high strain regions (E 1 and E 2 , respectively). Hemodynamic analysis revealed significantly increased end‐diastolic elastance (E ed ) in PAB (control: 55.1 mm Hg/mL [interquartile range: 44.7–85.4 mm Hg/mL]; PAB : 146.6 mm Hg/mL [interquartile range: 105.8–155.0 mm Hg/mL]; P =0.010). Longitudinal E 1 was increased in PAB (control: 7.2 kPa [interquartile range: 6.7–18.1 kPa]; PAB : 34.2 kPa [interquartile range: 18.1–44.6 kPa]; P =0.018), whereas there were no significant changes in longitudinal E 2 or circumferential E 1 and E 2 . Last, wall stress was calculated from hemodynamic data by modeling the right ventricle as a sphere: <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mfenced close=")" open="(" separators=""> <mml:mtext>stress</mml:mtext> <mml:mo>=</mml:mo> <mml:mfrac> <mml:mrow> <mml:mtext>Pressure</mml:mtext> <mml:mo>×</mml:mo> <mml:mtext>radius</mml:mtext> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> <mml:mo>×</mml:mo> <mml:mtext>thickness</mml:mtext> </mml:mrow> </mml:mfrac> </mml:mfenced> </mml:math> . Conclusions RV pressure overload in PAB rats resulted in an increase in diastolic myocardial stiffness reflected both hemodynamically, by an increase in E ed , and biomechanically, by an increase in longitudinal E 1 . Modest increases in tissue biomechanical stiffness are associated with large increases in E ed . Hemodynamic measurements of RV diastolic function can be used to predict biomechanical changes in the myocardium.