Magnetic resonance imaging assisted detection of hypoxia induced right ventricular hypertrophy in mice

Abstract

It is well known that chronic hypoxia induces pulmonary hypertension resulting in right ventricular hypertrophy (RVH). Previously, heart histopathology has been the standard assessment tool for assessing right ventricular enlargements in rats and mice. The purpose of our study was to non‐invasively image, with Magnetic Resonance (MR) RVH in mice. Mice were housed in the hypoxia (10% O2) chambers for 2, 3, 5, and 8 wks. Age matched mice housed under the normal room air condition were included as controls. Serial short‐axis MR images of mouse right ventricle (RV) were captured in real time. The volume, wall thickness and ejection fraction (EF) of the RV was assessed using MR. Preliminary results showed that right ventricular volume and wall thickness were not altered after 2 or 3 wks of hypoxia in mice. Following 5 wks of hypoxia, mice showed increased RV wall thickness compared with controls (0.34±0.01 vs. 0.25±0.02 mm, p<0.05) without altering the RV volume and EF. By 8 wks of hypoxia, mice continued to show increased RV wall thickness. In addition, the RV ejection fraction was significantly reduced in hypoxia treated mice (52±1 vs. 69±2%, p<0.01). Our data demonstrated that hypoxia induced RVH in mice can be detected following at least 5 wks of continuous exposure to hypoxia using MR imaging. MR imaging can be applied to monitor heart morphological and functional changes in small animals such as mice.