1356368 - Pulmonary Hypertension is associated with Decreased 4D flow MRI quantified Vena Cava Blood Flow

In patients with pulmonary hypertension (PH), elevated pulmonary artery and right heart pressures impact caval pressure and flow [1, 2]. 4D flow MRI can non-invasively measure these changes in the superior and inferior vena cava (SVC and IVC). The purpose of this study is to evaluate differences in 4D flow-derived SVC and IVC blood flow in patients with pulmonary hypertension and controls and correlate these changes with invasive hemodynamic assessment.

Methods:

In this IRB-approved retrospective study, cardiac MRI including gradient recalled echo 4D flow previously obtained as part of a prior prospective study were included. The study cohort included adult patients with pulmonary hypertension who had cardiac MRI within 28 days from right heart catheterization (RHC). Healthy volunteers who had same cardiac MRI protocol were included. Prospective ECG gated 4D flow MRI was performed with spatial resolution of 2.3 x 2.3 x 2.9 mm, temporal resolution of 40.0 msec, and VENC of 1.20 m/sec [3]. Net flow (in ml), and peak velocity (in cm/s) were measured in the superior vena cava (SVC) and inferior vena cava (IVC) in 3 different planes (high, middle, low) in each vessel (Figure1). Mann-Whitney test and Pearson’s correlation were used to compare 4D flow parameters between patients and controls and to assess correlation between 4D flow parameters and RHC in patients with PAH. A p value of less than 0.05 was considered statistically significant different.

Results:

Fifteen PH patients (8 male; mean age 55 ± 14.5; mean BMI 31.2 ±6.7 kg/m and 15 healthy volunteers (8 male; mean age 52 ± 14.6; mean BMI 24.6 ±4.7 kg/m²) were included.  Net flow was lower in the PH cohort compared to the control cohort in both SVC and IVC (p< 0.05) at each plane except for SVC low (Table 1). No significant differences were found in peak velocities between the PAH cohort compared to the control cohort at each level (Table 1). Net flow in the SVC and IVC had moderate to high correlation with the mean right atrial pressure (r=0.53, 0.73, 0.605 at the SVC middle, SVC low, and IVC high respectively, p< 0.05) (Figure 2). Peak velocity and IVC had high correlation with the pulmonary capillary wedge pressure (r=0.62, p< 0.05)

Conclusion:

Preliminary findings suggest that 4D flow can identify changes in vena cava blood flow in patients with pulmonary hypertension. Our study is currently limited by small cohort size and the use of prospectively-gated 4D flow MRI. If our findings are supported by larger studies, this non-invasive technique has the potential to be used as a biomarker for both diagnosis and treatment response in PH.