• Cardiac catheterization MRI congenital heart

Abstract
Background and aims
Congenital Heart Disease (CHD) affects six in every 1000 newborns and with current medical and surgical treatment survival to adult age is common. Current radiographic techniques, especially fluoroscopy, hinder effective intervention due to poor soft-tissue visualization, prolonged procedures, and increased radiation exposure. Concerns about X-ray doses' long-term effects have emerged, revealing a heightened risk of chromosomal damage in children. Cardiovascular Magnetic Resonance (CMR) emerges as a radiation-free, accurate alternative, providing superior soft-tissue visualization for congenital heart disease patients. Traditional methods for assessing hemodynamics, like thermodilution and the Fick principle, face inaccuracies. In contrast, CMR's velocity-encoded phase contrast accurately measures stroke volume, informing diagnoses and treatment decisions. However, invasive catheter-derived measurements remain crucial for calculating pulmonary vascular resistance (PVR). Notably, CMR-guided catheterization, particularly in adult populations, has shown feasibility and safety, offering a promising direction for improving interventions in congenital heart disease cases.
Our study aims to validate the efficacy of calculating cardiac output and vascular resistance by integrating invasive hemodynamic values with MRI-derived flows. We seek to establish the safety and feasibility of combining cardiac catheterization and magnetic resonance imaging to minimize radiation exposure in congenital heart disease patients.
Methods
We conducted a left and right cardiac catheterization guided by MRI. We measured invasively pulmonary artery pressure, oxygen saturations, and left atrial or pulmonary artery wedge pressure, and in the same exam we conducted MRI phase-contrast through-plane flow analysis. Cardiac and pulmonary index were computed using both Fick's method and MRI, then we calculated the pulmonary resistance using both of these results.
Results
From May 2022 to October 2023, 13 patients with congenital heart disease underwent MRI-guided cardiac catheterization, achieving a procedural success rate of 92%. The procedure included left heart catheterization, CMR imaging, and baseline RHC, with a median total department time of 122 minutes. Factors like severe PH and RV dysfunction correlated with longer catheter times.
Baseline index LV end diastolic volume was 83 mL/mq (IQR 59-96), LV end-systolic volume was 33 mL (IQR 22-49) and LV ejection fraction was 51 % (IQR 42-58). Baseline index RV end diastolic volume was 77 mL/mq (IQR 62-86)), RV end-systolic volume was 39 mL (IQR 24-52) and RV ejection fraction was 42 % (IQR 39-57).
Baseline cardiac index was 2,65 L/min/m2 (IQR 2,45-3,02) vs. 3 (IQR 2,7-3,9) L/min/m2 by CMR flow vs. Fick.

Conclusions
The analysis compared cardiac index, pulmonary vascular resistances, and pulmonary index between Fick method and CMR, revealing varying degrees of correlation and systematic biases. While cardiac index demonstrated a weak correlation, PVR exhibited a trend of positive association, and the pulmonary index displayed a moderate positive relationship. Bland-Altman analyses highlighted systematic biases between the Fick method and cardiac magnetic resonance, emphasizing the importance of considering methodological differences in the interpretation of results. Fick consistently underestimated pulmonary blood flow (Qp) and overestimated PVR compared to CMR, while the calculations for systemic blood flow (Qs) exhibited an opposite trend.
Subgroup analysis based on cardiac anatomy emphasized the importance of considering specific characteristics in assessing parameters.
Further research is vital to establish correlations between single ventricle and biventricular patients in the CMR environment. The determination of pulmonary vascular resistance (PVR) remains crucial for risk stratification in congenital heart disease, impacting intervention decisions. The study's modest sample size emphasizes its exploratory nature, providing a foundation for future, more extensive research to enhance our understanding of complex hemodynamic parameters in patients undergoing MRI-guided cardiac catheterization.