Thorac Cardiovasc Surg 2016; 64 - OP13
DOI: 10.1055/s-0036-1571854

Classification of Fontan Hemodynamics by Respiration Using Real-Time Phase-Contrast Magnetic Resonance

K. T. Laser 1, K. Müller 1, P. Barth 2, E. Klusmeier 1, J. Gieseke 3, N. A. Haas 1, D. Kececioglu 1, W. Burchert 2, H. Körperich 2
  • 1Ruhr-Universität Bochum/HDZ-NRW Bad Oeyhausen, Zentrum für Angeborene Herzfehler, Bad Oeynhausen, Germany
  • 2Ruhr-Universität Bochum/HDZ-NRW Bad Oeyhausen, Institut für Radiologie und Nuklearmedizin, Bad Oeynhausen, Germany
  • 3Philips Healthcare, Hamburg, Germany

Objective: Outcome of Fontan patients is often complicated by impaired hemodynamics caused by increased pulmonary vascular resistance and/or ventricular stiffness. The influence of respiration and vasodilative agents on vessel flow might be of value to investigate their quality of hemodynamics. Cardiac magnetic resonance (CMR) is highly accurate and can measure flow in realtime by generation of respiratory-dependent stroke volumes.

Methods: Body-surface indexed respiratory-related stroke volumes (SVi's) were obtained by using real-time phase-contrast CMR in the ascending aorta and both caval veins under room air, forced respiration and after 100% oxygen inhalation. 29 Fontan patients (age:17.2 ± 7.5years;15 males) and 32 weight/height matched healthy volunteers (roomair;13.4 ± 3.7years;14m) were investigated, Fontan hemodynamics was classified using a thirteen parameters risk-score. Respiration curve was divided into four segments: expiration, end-expiration, inspiration and end-inspiration.

Results: Mean aortic SVi was 46.1 ± 11.1mL/m2 in good Fontans compared with 30.4 ± 6.2mL/m2 in failing Fontans (p = 0.002) and 51.1 ± 6.9mL/m2 (controls,p = n.s.). In all Fontans forced respiration was followed by increased amplitudes of SVi in the SVC (6.4 ± 3.2mL/m2vs. 13.3 ± 5.8mL/m2,p = 0.0001) and IVC (43.0 ± 23.4m/m2 vs. 68.3m/m2, p = 0.0001), whereas aortic SVi remained constant (6.12 ± 2.92mL/m2 vs 6.78 mL/m2, p = n.s.). Only failing Fontans showed a reduction of mean SVi in the IVC (18.5 ± 6.0mL/m2vs. 15.8 ± 6.2mL/m2,p = 0.020). After oxygen inhalation mean aortic SVi increased to 48.7 ± 12.7mL/m2 (“good”;p = 0.045) whereas remained unchanged in failing Fontans (31.1 ± 5.8mL/m2,p = n.s.). Simultaneously, heart rates decreased from 75.2 ± 15.9bpm to 70.8 ± 16.4bpm (“good”;p = 0.000) but were not affected in impaired circulation (p = n.s.). Excellent diagnostic accuracy was obtained using end-expiratory aortic SVi's(AUC = 0.920;LR + = 14.5).

Conclusion: Aortic end-expiratory SVi's are particularly suitable to classify quality of Fontan circulation based on ROC statistics resulting in a cutoff-value of 32.1mL. Although higher amplitudes of flow can be achieved under forced respiration no increase of aortic flow can be detected in Fontan patients, in the IVC a decrease of mean SVi revealed a failing Fontan hemodynamic. Results support the hypothesis that hyperoxygenation reduces pulmonary resistance by vasodilation in Fontan patients with adequate hemodynamics but had no impact on failing Fontan circulation.