Abstract 3631: Validation of Two Non-invasive Imaging Methods, High-resolution Echocardiography (ECHO) and Magnetic Resonance Imaging (MRI) for Assessment of Pulmonary Hemodynamics in Rats With Pulmonary Arterial Hypertension
Introduction: Pulmonary arterial hypertension (PAH) is a lethal disease. An accurate, non-invasive method for diagnosing the severity of PAH and treatment stages is crucial. A good correlation between echo and catheterization (cath), and MRI and cath has been shown for some hemodynamic measurements in both humans and animals. However, the 2 non-invasive imaging methods have not been simultaneously analyzed and validated by cath in animal models of PAH.
Methods: We have compared pulmonary artery (PA) hemodynamics in 23 Sprague Dawley adult rats: 4 controls and 19 with PAH induced by monocrotaline. Three methods were used to assess hemodynamics: high-resolution 2-D and Doppler echo (Vevo 770 ultrasound system and a 30 MHz transducer), phase-contrast cine MRI (9.4T Bruker Biospec system), and right heart cath (1.4F Millar micromanometer catheter). All methods were performed within 0 –2 days of each other. Cardiac output (CO) was measured using the geometric PA flow approach in echo and MRI and by the thermodilution on catheterization. PA acceleration time (PAAT) (the interval from onset of forward flow to the moment of maximal flow velocity - a measure inversely proportional to PA pressure) was measured by echo and MRI. Right ventricular free wall (RVFW) thickness was assessed by echo, right ventricular (RV) mass by MRI, RV weight postmortem.
Results: There was strong positive correlation between the CO assessed by MRI vs cath (R2=0.85, P<0.001), echo vs cath (R2=0.75, P<0.0001), and echo vs MRI (R2=0.76, P<0.0001). For PAAT, an inverse correlation was found between MRI vs systolic PA pressure on cath (sPAP) (R2=0.74, P<0.0007), echo vs sPAP (R2=0.68, P<0.0001) and direct correlation was between echo vs MRI (R2=0.76, P<0.0001). Strong positive correlations were detected between RVFW thickness by echo and RV mass on MRI (R2=0.70, P=0.0004), RV mass on MRI and RV weight postmortem (R2=0.86, P<0.0001), and RVFW thickness on echo and postmortem RV weight (R2=0.73, P<0.0001).
Conclusion: There is excellent correlation between 2 non-invasive techniques and both correlate well with high-fidelity catheterization. Non-invasive imaging methods can be used in longitudinal studies to determine the severity of experimental PAH and evaluate experimental therapies.