Page 114 - Assessing right ventricular function and the pulmonary circulation in pulmonary hypertension Onno Anthonius Spruijt

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patient with severe PH. Several studies showed that single MRI parameters of the RV are related to hemodynamic parameters and disease severity. For instance, two independent studies showed that MRI-measured RV ejection fraction is inversely related to NT-proBNP [6, 7] and that RV mass is related to pulmonary arterial pressure [18, 19]. In a group of 64 idiopathic PAH patients, van Wolferen et al. showed that RV end-diastolic volume, stroke volume and LV end-diastolic volume all measured at baseline conditions were strong predictors for first year mortality [20]. It has been shown that baseline RV ejection fraction and the change in RV ejection fraction after one year of PAH specific treatment are strong predictors of survival [21]. Furthermore, a recent study by Swift et al. found that, when corrected for age, sex and body surface area, RV end-systolic volume was an independent predictor of mortality [22].
Several studies have demonstrated the possibilities of MRI to monitor the effects of PAH therapy on the RV over time [16, 20, 23-25]. In these studies, an increased RV stroke volume and a decrease in RV wall mass was associated with improvement of symptoms and 6-minutes walking distance. In addition, it was shown that a progressive dilation of the RV during therapy accompanied with a decrease in stroke volume is associated with a poor outcome [20, 26].
The potential of MRI-derived parameters to be used as a primary end-point to compare different treatment strategies was demonstrated in the Seraph study; a randomized prospective study aimed to measure the different effects of bosentan and sildenafil on RV mass [27]. This study demonstrated that sildenafil, in contrast to bosentan, reduces RV mass. This finding is of interest; since it underlines that MRI provides additional insights in comparison to the functional parameters currently used to evaluate the efficacy of medication.
Finally, the volume of the RV might be considered as an additional treatment goal since a recent study showed that progressive dilatation of the RV in clinical stable PH patients predict worse outcome whereas a stable RV volume during the first year of treatment predicts a long term survival [28].
Advanced techniques to characterize the right ventricle
The MRI protocol can be extended with more advanced techniques that recently have been used in the study of the RV in PH. These techniques include delayed contrast enhancement to measure the presence of scar tissue in the RV wall, myocardial tagging to analyze regional myocardial shortening and measurement of coronary artery flow to the RV.