Rationale: Pulmonary hypertension (PH) is a complex disease and can be best described with various parameters involving the right ventricle (RV). Echocardiographic measurement of these RV parameters (dimension, diastolic and systolic functions) during normobaric hypoxia may be an ideal noninvasive simulation approach for studies on PH treatment options. Thus, we correlated RV parameters under hypoxia with critical PH values and built a generic algorithm to evaluate these parameters.
Methods: Our protocol was developed for 20 healthy young subjects with continuous echocardiography monitoring under hypoxia below 11% (˜4500–5000m) for 2.5h. Echocardiographic data were recorded during different stages (0, 30, 60, 100, 150 minutes) under hypoxia and data are reported as means±SD. The parameter framework includes measures describing RV dimensions as RV mid cavity diameter (RVD1), RV basal diameter (RVD2), RV longitudinal diameter (RVD3), RV outflow tract diameter (RVOT) and RV enddiastolic area (RVEDA). Based on the Tricuspid Regurgitation Velocity (TRV) and the Right Atrial Pressure (RAP) we calculated the Right Ventricular Systolic Pressure (RVSP). Global RV systolic and diastolic functions are described with Myocardial Performance Index (MPI), Acceleration Time (AcT), Tricuspid Annular Plane Systolic Excursion (TAPSE) and by means of Tissue Doppler Imaging (TDI) the parameters of Tricuspid Annular Systolic Velocity (TASV) and peak diastolic E' and A'.
Results: There was a significant increase regarding to all RV dimension (RVD1 +29mm, RVD2 +42mm, RVD3 +41mm, RVOT +13mm, RVEDA +18mm) parameters classifiable with a high PH likelihood score. MPI (+0.38), AcT (-11ms), TAPSE (-4mm) and TDI with TASV (-5m/s), E' (-1m/s), A' (-0.9m/s) were reliable echocardiographic measures and achieved medium PH likelihood scores. RSVP (+9mmHg) had a moderate increase, but at 3 subjects TRV were hardly to access.
Conlusion: Strong and weak parameters within the PH correlation framework have been found. The easily accessible noninvasive measured physiologic results in normobaric hypoxia point toward the presented method as a feasible method for anti-PH drug testing based on these evaluated parameters.
