PURPOSE: This study sought to determine whether cardiac magnetic resonance imaging (CMRI) parameters correlate with right heart hemodynamics, and whether changes in CMRI parameters after initiation of bosentan predict changes in six minute walk distance (6MWD) among patients with pulmonary arterial hypertension (PAH).
METHODS: 16 patients with confirmed PAH underwent evaluation with CMRI, right heart catheterization and 6MWD at baseline and after 12 months of treatment with bosentan. Add on therapy was required in nine patients.
RESULTS: Patients had severe pulmonary hypertension with a baseline mean pulmonary arterial pressure (mPAP) of 54±14 mmHg. At 12 months, cardiac index (CI) increased from 2.9±1 to 3.2±0.8 L/min/m2, p=0.03 and pulmonary vascular resistance decreased from 8.9±4 to 6.5±2.5 Wood units, p=0.01. There was no significant change in mPAP or right atrial pressure. 6MWD increased from 280±153 to 340±92m, p=0.04. Abnormal CMRI findings at baseline included markedly increased right ventricular end diastolic volume (RVEDV), right ventricular (RV) end systolic volume and reduced right ventricular ejection fraction (RVEF). After one year of treatment with bosentan, there was a trend towards an increase in RV stroke volume (70±27 to 81±30 ml, p=0.08) while there was no change in RVEF (44±13 to 46±11%; p=0.64) and RVEDV (164±57 to 179±50 ml; p=0.19). Among patients in whom RVEF increased, change in 6MWD was significantly greater than among patients in whom RVEF was stable or decreased (+97.5 vs. -36.5 meters respectively; p=0.01). Finally, RVEF, RV stroke volume and LV end diastolic volume correlated significantly with CI at both baseline and follow-up, with correlations ranging from r=0.56 to r=0.77, p<0.05.
CONCLUSION: After one year of treatment with bosentan, patients with PAH showed improvement in 6MWD and hemodynamics as well as stability in CMRI parameters. CMRI parameters correlated with invasive hemodynamics. CMRI changes in right heart function (RVEF) predicted improvement in exercise capacity (6MWD).
CLINICAL IMPLICATIONS: These findings suggest that CMRI may have an important role in evaluating response to treatment in patients with PAH.
DISCLOSURE: Kelly Chin, No Product/Research Disclosure Information; Consultant fee, speaker bureau, advisory committee, etc. Dr. Fernando Torres, Dr. Kelly Chin and Martha Kingman have participated in advisory boards, clinical research and speaker's bureau with Actelion.