Non - invasive right ventricular efficiency using 4D flow MRI

AbstractWe used 4D-flow MRI to investigate circulation, an area integral of vorticity, in the main pulmonary artery (MPA) as a new hemodynamic parameter for assessing patients with a repaired Tetralogy of Fallot (TOF). We evaluated the relationship between circulation, right ventricular (RV) function and the pulmonary regurgitant fraction (PRF). Twenty patients with a repaired TOF underwent cardiac MRI. Flow-sensitive 3D-gradient sequences were used to obtain 4D-flow images. Vortex formation in the MPA was visualized, with short-axis and longitudinal vorticities calculated by software specialized for 4D flow. The RV indexed end-diastolic/end-systolic volumes (RVEDVi/RVESVi) and RV ejection fraction (RVEF) were measured by cine MRI. The PR fraction (PRF) and MPA area were measured by 2D phase-contrast MRI. Spearman ρ values were determined to assess the relationships between circulation, RV function, and PRF. Vortex formation in the MPA occurred in 15 of 20 patients (75%). The longitudinal circulation (11.7 ± 5.1 m2/s) was correlated with the RVEF (ρ = − 0.85, p = 0.0002), RVEDVi (ρ = 0.62, p = 0.03), and RVESVi (ρ = 0.76, p = 0.003) after adjusting for the MPA size. The short-axis circulation (9.4 ± 3.4 m2/s) in the proximal MPA was positively correlated with the MPA area (ρ = 0.61, p = 0.004). The relationships between the PRF and circulation or RV function were not significant. Increased longitudinal circulation in the MPA, as demonstrated by circulation analysis using 4D flow MRI, was related to RV dysfunction in patients with a repaired TOF.

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Sildenafil Administration Improves Right Ventricular Function on 4D Flow MRI in Young Adults Born Premature

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.00824.2020 ◽

2021 ◽

Author(s):

Philip A Corrado ◽

Gregory P Barton ◽

Christopher J François ◽

Oliver Wieben ◽

Kara N Goss

Keyword(s):

Heart Rate ◽

Young Adults ◽

Kinetic Energy ◽

Right Ventricular ◽

Right Atrial ◽

4D Flow Mri ◽

4D Flow ◽

Direct Flow ◽

Flow Mri ◽

Rv Function

Background: Extreme preterm birth conveys an elevated risk of heart failure by young adulthood. Smaller biventricular chamber size, diastolic dysfunction, and pulmonary hypertension may contribute to reduced ventricular-vascular coupling. However, how hemodynamic manipulations may affect right ventricular (RV) function and coupling remains unknown. Methods: As a pilot study, 4D flow MRI was used to assess the effect of afterload reduction and heart rate reduction on cardiac hemodynamics and function. Young adults born premature were administered sildenafil (a pulmonary vasodilator) and metoprolol (a beta blocker) on separate days, and MRI with 4D flow completed before and after each drug administration. Endpoints include cardiac index (CI), direct flow fractions, and ventricular kinetic energy including E/A wave kinetic energy ratio. Results: Sildenafil resulted in a median CI increase of 0.24 L/min/m2 (P=0.02), mediated through both an increase in heart rate (HR) and stroke volume. Although RV ejection fraction improved only modestly, there was a significant increase (4% of end diastolic volume) in RV direct flow fraction (P=0.04), consistent with hemodynamic improvement. Metoprolol administration resulted in a 5-bpm median decrease in HR (P=0.01), a 0.37 L/min/m2 median decrease in CI (P=0.04), and a reduction in time-averaged kinetic energy (KE) in both ventricles (P<0.01), despite increased RV diastolic E/A KE ratio (P=0.04). Conclusions: Despite reduced right atrial workload, metoprolol significantly depressed overall cardiac systolic function. Sildenafil, however, increased CI and improved RV function, as quantified by the direct flow fraction. The preterm heart appears dependent on HR, but sensitive to RV afterload manipulations.

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