Pulmonary 4D flow CMR imaging in Landrace pigs under rest and stress

Introduction: CMR 4D flow is a promising technique for assessing vessel hemodynamics. However, its current utilization is limited due to the lack of reference values, particularly for pulmonary vessels, generally understudied. With the purpose to serve for future research studies, we have analysed the pulmonary flow and velocity in Landrace pigs at both rest and stress by utilizing the software MEVISFlow. Methods: Nine (n=9) healthy Landrace pigs were acutely instrumented closed-chest and transported to the CMR facility for evaluation. After baseline (BL) measurements, dobutamine (Dob) was administrated to achieve a 25% increase in heart rate compared to baseline values. 4D flow images from the pigs during both rest and stress states have been analysed through MEVISFlow software by two independent observers. In detail, we examined peak flow and peak velocity of the pulmonary trunk (PT) and both left and right pulmonary arteries (LPA and RPA, respectively). Results: A significant difference between BL and Dob regarding both peak flow and peak velocity in all the pulmonary vessels was observed. Peak flow changed from 0.09 L/min to 0.14 L/min in PT, from 0.04 L/min to 0.07 L/min in LPA and from 0.05 L/min vs 0.07 L/min in RPA. Peak velocity changed from 0.90 m/s to 1.40 m/s in PT, from 0.80 m/s to 1.40 m/s in LPA and from 0.80 m/s to 1.33 m/s in RPA. Conclusions: The current study showed that peak flow and peak velocity assessed through pulmonary 4D flow follow the physiological alterations during systole and diastole and after stress induced by dobutamine.