Postsurgical hemodynamics of the aortic valve bypass operation evaluated with phase contrast magnetic resonance.

Purpose: To characterize the postsurgical hemodynamics in aortic valve bypass (AVB) patients, and to determine the relationship between presurgical native aortic valve pressure gradient and postsurgical hemodynamics. Materials and Methods: Twenty patients scheduled for AVB surgery underwent presurgical transthoracic Doppler echocardiography to assess the degree of aortic stenosis and postsurgical cardiac magnetic resonance imaging (MRI) to acquire phase contrast magnetic resonance (PCMR) flow values along the ascending and descending aorta, and in the conduit. Net flow values were calculated from the PCMR images and compared to presurgical aortic valve pressure gradient measurements. Results: PCMR showed that: 1) The blood flow split between the aorta and the conduit was 35%: 65% of cardiac output and 2) 60% of patients had net retrograde blood flow in the superior thoracic aorta over the cardiac cycle. Patients with presurgical pressure gradient (Delta P) > 45 mmHg had significantly less blood flow out of the native aorta than patients with Delta P < 45 mmHg, and had significantly more retrograde flow in the superior thoracic aorta postsurgery. Conclusion: In patients undergoing AVB, presurgical aortic valve pressure gradient is associated with the volume of blood flow out the aorta and the direction of blood flow in the superior thoracic aorta after conduit addition as measured by PCMR.