Abstract 12077: Speckle Tracking Echocardiography and MRI Identify Both Right and Left Ventricular Dysfunction in a Large Animal Model of Severe Pulmonary Hypertension
Right ventricular (RV) failure in pulmonary hypertension (PH) is usually blamed for poor outcomes, but PH also affects left ventricular (LV) function. Prior research has focused on LV septal mechanics and diastolic dysfunction from decreased filling. We hypothesize that PH causes global biventricular systolic dysfunction which can be quantified with 2-dimentional strain imaging. We developed a large animal model of PH by exposing calves to a hypobaric hypoxic environment (PB = 430 mmHg) for 2 weeks. Hypoxic animals (HA) develop severe PH compared to controls (mean pulmonary artery pressure of 109±34 vs. 25±4 mmHg). Echocardiograms with speckle tracking analysis were performed in awake calves. Tricuspid annular systolic excursion (TAPSE) and longitudinal strain (LS) were measured from sub-costal long axis images. Circumferential (CS) and radial strains (RS) were obtained from lateral short axis images at the papillary muscles. Segments from the anterior, lateral, posterior and inferior walls were averaged to obtain non-septal LV strain. A subset of animals was anaesthetized with propofol and isoflurane to evaluate cardiac performance with MRI. In awake animals, RV strain was markedly depressed in HA relative to controls. There was also a decrease in non-septal LV strain in HA vs. controls, but this result did not reach statistical significance. With anesthesia, a dramatic decrease in LV dysfunction was seen in HA relative to controls; these findings are consistent with biochemical changes in the myofilament where decreases in phosphorylation of Troponin I, Troponin T and Myosin Light Chain 2 are evident in both the RV and LV. We conclude that speckle tracking imaging is possible in this unique model of severe PH. We were able to quantify global RV dysfunction and identify vulnerabilities in the left ventricle which were confirmed with MRI.
- © 2012 by American Heart Association, Inc.