CMR protocol

The full protocol has been described elsewhere [18]; in brief, CMR was performed using a 3 T clinical CMR scanner (MAGNETOM Skyra, Siemens Healthineers, Erlangen, Germany) with 18 channel torso phased array coil in conjunction with a spinal coil posteriorly). Electrographically (ECG) gated balanced steady-state free precession (bSSFP) sequence was used to acquire cine images in vertical and horizontal long-axis, and ten short-axis images covering the entire RV and LV. For OS imaging, a single mid-ventricular slice was acquired at mid-diastole using a single-shot T2-prepared ECG-gated bSSFP sequence (FOV of 340 × 340 cm, matrix 168 × 192 m, slice thickness 6 mm, producing a voxel size 2.02 × 1.77 mm. The repetition time (TR) was 256 ms and with echo time (TE) of 1.21 ms, flip angle 44˚). Each OS-CMR image was acquired during a single breath-hold over six heart beats. Prior to adenosine infusion, four resting OS-CMR images were acquired. Stress OS-CMR stress images acquisition commenced 2 min after adenosine infusion. Four to six OS-CMR images were acquired over the stress period with the typical duration of stress OS-CMR image acquisition was 3 min with the total adenosine infusion duration of about 5 min (Fig. 1).

CMR Imaging Protocol. Cine, Oxygen sensitive cardiovascular magnetic resonance (OS-CMR) and native T1 mapping imaging protocol for pulmonary artery hypertension (PAH) and healthy control groups

Native T1 mapping were acquired using Shortened Modified Look-Locker Inversion recovery (ShMOLLI) on a single mid-ventricular short-axis slice as previously described [19]. The ShMOLLI sequence was performed with prospective ECG triggering performed until optimal image quality was obtained. This sequence has a FOV of 360 × 360 cm, matrix 192 × 144, slice thickness 8 mm, producing an interpolated voxel size 0.9 × 0.9 mm. The TR was 379.40 and with TE of 1.07. Typically, the flip angle was set to 35 degrees and IPAT (GRAPPA) factor of 2, with inversion time (TI) of 260 ms. The T1 maps were acquired after the resting OS-CMR images prior to adenosine infusion (Fig. 1). The mid-ventricular slice location selected was matched to the selected mid-ventricular resting OS-CMR images. Stress heart rate and blood pressure were obtained every minute of adenosine infusion. Patients were monitored throughout the study by ECG, sphygmomanometry and pulse oximetry.