Flow characteristics of the proximal pulmonary arteries and vena cava in patients with chronic thromboembolic pulmonary hypertension: correlation between 3.0 T phase-contrast MRI and right heart catheterization

PURPOSE

We aimed to determine the correlation between flow characteristics of the proximal pulmonary arteries and vena cava obtained by 3.0 T phase-contrast magnetic resonance imaging (MRI) and hemodynamic characteristics by right heart catheterization in patients with chronic thromboembolic pulmonary hypertension.

MATERIALS AND METHODS

Twenty consecutive patients with chronic thromboembolic pulmonary hypertension and 20 sex- and age-matched healthy volunteers were included prospectively. All patients and controls underwent phase-contrast MRI to determine the flow characteristics including peak velocity, mean velocity, and mean blood flow of the proximal pulmonary artery and vena cava. All patients underwent right heart catheterization to determine the hemodynamics.

RESULTS

Peak velocity and mean velocity of the proximal pulmonary artery were significantly lower in the patient group. In patients, both peak velocity and mean blood flow were sequentially decreased in the main pulmonary artery, left and right pulmonary arteries, and left and right interlobar pulmonary arteries. Inferior vena cava had higher peak velocity, mean velocity, and mean blood flow than superior vena cava. Peak velocity of the main pulmonary artery correlated with mean and diastolic pulmonary artery pressure. Peak velocity of both inferior and superior vena cava strongly correlated with the pulmonary vascular resistance index (PVRI) (r=−0.68, P < 0.001 and r=−0.74, P < 0.001, respectively). Mean velocity of the main pulmonary artery and right pulmonary artery strongly correlated with PVRI and mean pulmonary artery pressure. Mean velocity of the superior vena cava and mean blood flow of the main pulmonary artery strongly correlated with PVRI and right cardiac work index.

CONCLUSION

Blood flow in the proximal pulmonary artery and vena cava evaluated by phase-contrast MRI correlate with hemodynamic parameters of right heart catheterization and can be used to noninvasively evaluate the severity of chronic thromboembolic pulmonary hypertension and, potentially, to follow up the treatment response.Chronic thromboembolic pulmonary hypertension (CTEPH) develops as a result of obstruction of pulmonary arterial vessels by organized thromboembolic material and subsequent vascular remodeling in small unobstructed vessels, and it is associated with significant morbidity and mortality (1). Right heart catheterization remains the reference standard to diagnose CTEPH, assess the hemodynamic disturbance, and follow up the treatment response; but it is invasive, delivers radiation, and is associated with recognized complications (2, 3).Magnetic resonance imaging (MRI) is considered not only as the reference standard for evaluation of ventricular function, but it also provides a reproducible and noninvasive assessment of hemodynamics changes in pulmonary hypertension (4). In a separate validation study, cardiac MRI-derived parameters showed a strong correlation with invasive determinations (5).In a study by Mohiaddin et al. (6), phase-contrast MRI was used to confirm reduced diastolic peak velocity of the inferior vena cava (IVC) in patients with pulmonary hypertension. Only one study reported blood flow conditions in the proximal pulmonary arteries and vena cava in healthy children (7). To our knowledge, no study has assessed proximal pulmonary artery and vena cava flow or evaluated correlation of the flow determined by phase-contrast MRI and hemodynamics by right heart catheterization in CTEPH.We performed a prospective study to observe the flow change in the proximal pulmonary artery, superior vena cava (SVC) and inferior vena cava (IVC) in patients with CTEPH by phase-contrast MRI, and to evaluate the correlation of the proximal pulmonary artery and vena cava flow with hemodynamics derived by right heart catheterization in patients with CTEPH.