Prolonged right ventricular post-systolic isovolumic period in pulmonary arterial hypertension is not a reflection of diastolic dysfunction

Background In pulmonary arterial hypertension (PAH) a prolonged time interval between pulmonary valve closure and tricuspid valve opening is found. This period is interpreted as prolonged right ventricular (RV) relaxation, and thus a reflection of diastolic dysfunction. This concept recently has been questioned, since it was shown that RV contraction continues after pulmonary valve closure causing a post-systolic contraction period. Objectives To investigate in PAH whether the increased RV post-systolic isovolumic period is caused by either an additional post-systolic contraction period, or an increased relaxation period (diastolic dysfunction). Methods 23 patients with PAH (mean pulmonary arterial pressure 54+/-12 mm Hg), and 18 healthy subjects were studied using cardiac MRI. In a RV two-chamber view, times of pulmonary valve closure (T-PVC) and tricuspid valve opening (T-TVO) were measured, defining the total post-systolic isovolumic period. Time to peak of RV free wall contraction (TpeakRV) was determined with myocardial tagging. Post-systolic contraction and relaxation periods were defined as the time intervals between T-PVC and TpeakRV and between TpeakRV and T-TVO, respectively. These periods were normalised to an RR interval. Results The total post-systolic isovolumic period was longer in patients than in healthy subjects (0.15+/-0.04 vs 0.04+/-0.02, p<0.001), but the relaxation period was not different (0.06+/-0.02 vs 0.05+/-0.02, p=0.09). The post-systolic contraction period in patients was strongly related to the total post-systolic isovolumic period (y=0.98x-0.05; r=0.89, p<0.001), and was associated with disease severity. Conclusion In PAH, the prolonged post-systolic isovolumic period is caused by an additional post-systolic contraction period, rather than by an increased relaxation period.