First experience with real-time magnetic resonance imaging-based investigation of respiratory influence on cardiac function in pediatric congenital heart disease patients with chronic right ventricular volume overload.

Background: Congenital heart disease (CHD) is often associated with chronic right ventricular (RV) volume overload. Real-time magnetic resonance imaging (MRI) enables the analysis of cardiac function during free breathing.

Objective: To evaluate the influence of respiration in pediatric patients with CHD and chronic RV volume overload.

Methods And Materials: RV volume overload patients (n=6) and controls (n=6) were recruited for cardiac real-time MRI at 1.5 tesla during free breathing. Breathing curves from regions of interest reflecting the position of the diaphragm served for binning images in four different tidal volume classes, each in inspiration and expiration. Tidal volumes were estimated from these curves by data previously obtained by magnetic resonance-compatible spirometry. Ventricular volumes indexed to body surface area and Frank-Starling relationships referenced to the typical tidal volume indexed to body height (TTVi) were compared.

Results: Indexed RV end-diastolic volume (RV-EDVi) and indexed RV stroke volume (RV-SVi) increased during inspiration (RV-EDVi/TTVi: RV load: + 16 ± 4%; controls: + 22 ± 13%; RV-SVi/TTVi: RV load: + 21 ± 6%; controls: + 35 ± 17%; non-significant for comparison). The increase in RV ejection fraction during inspiration was significantly lower in RV load patients (RV load: + 1.1 ± 2.2%; controls: + 6.1 ± 1.5%; P=0.01). The Frank-Starling relationship of the RV provided a significantly reduced slope estimate in RV load patients (inspiration: RV load: 0.75 ± 0.11; controls: 0.92 ± 0.02; P=0.02).

Conclusion: In pediatric patients with CHD and chronic RV volume overload, cardiac real-time MRI during free breathing in combination with respiratory-based binning indicates an impaired Frank-Starling relationship of the RV.