Magnetic resonance investigation of blood flow after aortic valve bypass (apicoaortic conduit).

Background: Aortic valve bypass (AVB, apicoaortic conduit) is an alternative to aortic valve replacement (AVR) for high-risk patients with aortic stenosis (AS). The redistribution of blood flow after AVB has been poorly characterized. In order to understand cardiovascular physiology after AVB, we performed cardiac magnetic resonance (CMR) imaging of AVB recipients.

Methods: Fifteen patients with symptomatic AS underwent beating-heart AVB. Electrocardiography-gated two-dimensional phase-contrast velocity mapping CMR imaging was conducted on each patient. Instantaneous flow was acquired at discrete intervals within the cardiac cycle and ventricular function and volumes were evaluated. Five age-matched patients without aortic valve disease served as controls.

Results: Conduit flow (as a percent of total cardiac output) was 65% ± 5%. Ejection fraction was unchanged compared with before AVB (50% ± 17% versus 57% ± 13%; p = 0.91). Ventricular volumes and cardiac indices were within normal limits and similar to those values in controls (cardiac index 2.9 ± 1.0 versus 2.3 L/min/m(2); p = 0.26; end-diastolic volume index 59 ± 17 mL versus 55 ± 20 mL; p = 0.66; end-systolic volume index, 25 ± 12 versus 25 ± 18 mL; p = 0.91; stroke volume index, 33 ± 11 versus 30 ± 6 mL; p = 0.57 for AVB and control patients, respectively). There was a small degree of retrograde blood flow in the descending aorta above the level of the conduit insertion (10% ± 8% of cardiac output).

Conclusions: Aortic valve bypass results in a predictable blood flow distribution between the native aorta and conduit and is associated with normal ventricular volumes and function.