Background: Progressive right ventricular (RV) dysfunction in pulmonary arterial hypertension (PAH) which is contributed by RV ischemia leads to adverse clinical outcomes. Oxygen-sensitive (OS) cardiovascular magnetic resonance (CMR) has been used to determine the in vivo myocardial oxygenation of the left ventricle (LV). The aims of the present study were therefore to determine the feasibility of RV targeted rest/stress OS-CMR imaging in PAH patients and healthy volunteers.
Methods: We prospectively recruited 20 patients with right heart catheter proven PAH and 9 healthy age matched controls (NC). The CMR examination involved standard functional imaging and OS-CMR imaging. An OS-CMR signal intensity (SI) index (stress/rest SI) was acquired at RV anterior, RV free-wall and RV inferior segments. In the LV, the OS-CMR SI index was acquired globally.
Results: Reliable OS SI changes were only obtained from the RV inferior segment. As RV dysfunction in PAH is a global process, hence this segment was used in both patients and NC for further comparison. RV OS-CMR SI change between rest and stress in the NC was 17%±5% (mean ± SD). Nine of 20 (45%) of the PAH patients had a mean OS SI change of less than 9% (or ≥2 SD different from the mean values in NC). Overall, RV OS SI index between the PAH patients and NC was 11%±9% vs. 17%±5% (P=0.045) in the RV inferior segment. In the LV, the global OS-CMR SI index between the PAH patients and NC was 11%±7% vs. 21%±9% (P=0.019). There was a strong correlation between RV Inf OS-CMR SI and LV OS-CMR SI (r=0.86, P<0.001).
Conclusions: In this small pilot study, pharmacological induced OS-CMR is a feasible and safe technique to identify and study myocardial oxygenation in the RV of PAH patients.
Keywords: Pulmonary artery hypertension; cardiac magnetic resonance (CMR); microcirculation; microvascular ischemia; oxygen-sensitive cardiac magnetic resonance.
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