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

Abstract

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. 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). 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 (T(peak)RV) was determined with myocardial tagging. Post-systolic contraction and relaxation periods were defined as the time intervals between T(PVC) and T(peak)RV and between T(peak)RV and T(TVO), respectively. These periods were normalised to an RR interval. 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. In PAH, the prolonged post-systolic isovolumic period is caused by an additional post-systolic contraction period, rather than by an increased relaxation period.