The Feasibility of Cardiovascular Magnetic Resonance Imaging in Monitoring the Long-term Outcomes of Aortic Valve Bypass Surgery Patients
Mohamad Rabbani1, Lin-Rui Guo1, Ali Islam1, Christopher Harle1, Bob Kiaii2
1London Health Science Centre, London, ON, Canada, 2UC Davis Medical Center, Sacramento, CA, USA
BACKGROUND: Aortic valve bypass (AVB) (apico-aortic conduit) is an alternative surgical treatment for patients with aortic valve stenosis in whom surgical aortic valve replacement and transcatheter aortic valve implantation is not feasible. The role of ECG-triggered MRI in monitoring the long-term outcomes of this procedure is poorly understood. The aim of this study is twofold. First to determine the long term follow-up of patients who have undergone aortic-valve bypass. Second to investigate the role of MRI in evaluating patientís postoperative anatomy and understand the cardiovascular physiology after almost 10 years post aortic valve bypass surgery. METHODS: Between November 2010 and May 2015, a total of 8 patients (5 males, 3 females) had aortic-valve bypass surgery using the Correx automated coring and apical connector system (Correx, Waltham, MA). After 10 years, based on the comorbidity of the patients, only two patients, who were operated on November 2010 and January 2013, were still alive. These patients had follow-up and were examined with a 1.5 Tesla Heart MRI. Qualitative assessment of flow patterns in the left ventricle, aorta and conduit was performed. Quantitative analysis included measurement of net flow, peak flow, retrograde flow, and time-to-peak flow in the aorta and conduit lumina. Also data looking at left ventricle deformation and aortic deformation were studied. Differences in flow through the aorta and conduit were compared with the 2-tailed, paired Student t test. RESULTS: One patientís apico-aortic conduit proved to be open with a maximum flow velocity of 130 cm/s whereas the other patient conduit was occluded with a maximal flow velocity of 5 cm/s. The anatomy was able to be evaluated in both patients and myocardial function was able to be assessed based on the deformation analysis. In the patient with the patent conduit (10 years post-op) more than 60% of the stroke volume was bypassed as measured by magnetic resonance. There was a small degree of retrograde blood flow in the descending aorta above the level of the conduit insertion. CONCLUSIONS: The long-term outcome of patients with aortic valve bypass is very poor with only 25% alive and of two patients alive only one of the conduits was patent. ECG-triggered MRI is a reliable method for the evaluation of the long-term outcomes of aortic valve bypass with respect to anatomical and functional data.