Effect of General Anesthesia on Cardiac Magnetic Resonance-Derived Cardiac Function in Repaired Tetralogy of Fallot

Comparison of 2D and 4D Flow MRI in Neonates Without General Anesthesia

BACKGROUND

Neonates with critical congenital heart disease require early intervention. Four-dimensional (4D) flow may facilitate surgical planning and improve outcome, but accuracy and precision in neonates are unknown.

PURPOSE

To 1) validate two-dimensional (2D) and 4D flow MRI in a phantom and investigate the effect of spatial and temporal resolution; 2) investigate accuracy and precision of 4D flow and internal consistency of 2D and 4D flow in neonates; and 3) compare scan time of 4D flow to multiple 2D flows.

STUDY TYPE

Phantom and prospective patients.

POPULATION

A total of 17 neonates with surgically corrected aortic coarctation (age 18 days [IQR 11-20]) and a three-dimensional printed neonatal aorta phantom.

FIELD STRENGTH/SEQUENCE

1.5T, 2D flow and 4D flow.

ASSESSMENT

In the phantom, 2D and 4D flow volumes (ascending and descending aorta, and aortic arch vessels) with different resolutions were compared to high-resolution reference 2D flow. In neonates, 4D flow was compared to 2D flow volumes at each vessel. Internal consistency was computed as the flow volume in the ascending aorta minus the sum of flow volumes in the aortic arch vessels and descending aorta, divided by ascending aortic flow.

STATISTICAL TESTS

Bland-Altman plots, Pearson correlation coefficient (r), and Student's t-tests.

RESULTS

In the phantom, 2D flow differed by 0.01 ± 0.02 liter/min with 1.5 mm spatial resolution and -0.01 ± 0.02 liter/min with 0.8 mm resolution; 4D flow differed by -0.05 ± 0.02 liter/min with 2.4 mm spatial and 42 msec temporal resolution, -0.01 ± 0.02 liter/min with 1.5 mm, 42 msec resolution and -0.01 ± 0.02 liter/min with 1.5 mm, 21 msec resolution. In patients, 4D flow and 2D flow differed by -0.06 ± 0.08 liter/min. Internal consistency in patients was -11% ± 17% for 2D flow and 5% ± 13% for 4D flow. Scan time was 17.1 minutes [IQR 15.5-18.5] for 2D flow and 6.2 minutes [IQR 5.3-6.9] for 4D flow, P < 0.0001.

DATA CONCLUSION

Neonatal 4D flow MRI is time efficient and can be acquired with good internal consistency without contrast agents or general anesthesia, thus potentially expanding 4D flow use to the youngest and smallest patients.

EVIDENCE LEVEL

1 TECHNICAL EFFICACY: Stage 2.

High Variability of Right Ventricular Volumes and Function in Adults with Severe Pulmonary Regurgitation Late After Tetralogy of Fallot Repair

Our aim was to assess changes of right ventricular end-diastolic volumes (RVEDVi) and right ventricular ejection fraction (RVEF) in asymptomatic adults with repaired tetralogy of Fallot, with native right ventricular outflow tract and severe pulmonary regurgitation by serial cardiac magnetic resonance imaging (CMR). The study included 23 asymptomatic adults who underwent ≥3 CMR studies (total of 88 CMR studies). We compared changes in RVEDVi and RVEF between first and last study (median follow-up: 8.8 years, interquartile range: 6.3 to 13.1 years) and between all study pairs. Variability of measurements between study pairs (65 consecutive and 139 nonconsecutive CMR study pairs) were assessed using Bland-Altman analysis and intraclass correlation coefficients. On average, there were no significant changes of RVEDVi or RVEF over the study period (change in RVEDVi: +0.4 ± 17.8 ml/m², change in RVEF: -1.0 ± 5.5%). Assessment of variability of measurements between study pairs demonstrated no systematic change in RVEDVi and RVEF between study pairs with limits of agreement within the range of previously published studies (RVEDVi -29.1 to +27.2 ml/m²; RVEF -11.5% to 10.2%). High intraclass correlation coefficients for RVEDVi (0.943, 95% CI 0.906 to 0.965, p <0.001) and RVEF (0.815, 95% CI 0.697 to 0.887, p <0.0001) indicate high reliability of reported measurements. In conclusion, in asymptomatic adults with repaired tetralogy of Fallot with native right ventricular outflow tracts and severe pulmonary regurgitation, CMR measurements of RV volumes and RVEF remain stable during follow-up with variability between CMR studies in individual patients, as expected for interobserver and interstudy variability. Measurements derived from a single CMR study or changes occurring between 2 CMR studies should be used with caution for clinical decision-making.