Transcatheter and Surgical Aortic Valve Replacement for Severe Aortic Stenosis: Insights from Cardiovascular Magnetic Resonance Imaging

Background: Surgical aortic valve replacement (SAVR) remains first-line treatment for symptomatic severe aortic stenosis, whereas transcatheter aortic valve implantation (TAVI) is indicated in patients who are inoperable or considered too high-risk for surgery. Current focus is centred on differences in the impact of valve replacement upon cardiovascular function to guide patient selection and the development of novel prosthetic valves to improve outcomes. Cardiovascular Magnetic Resonance (CMR) imaging is the investigative modality of choice for such a purpose.
Objectives:
To compare the impact of SAVR and TAVI upon aortic stiffness, right ventricular function and myocardial strain, and to compare two vendor designs in the quantity of post-TAVI aortic regurgitation and reverse remodelling.
Methods: A prospective study of patients with severe aortic stenosis under surveillance and subsequently requiring SAVR or TAVI, recruited between September 2009 and December 2015. A 1.5 Tesla CMR study was performed pre and 6 months post SAVR, and pre, immediately and 6 months post implantation of Medtronic CoreValve and Boston Lotus TAVI. Aortic distensibility (AD), pulse wave velocity (PWV), right ventricular (RV) volumes, myocardial strain and aortic regurgitation (AR) were quantified.
Results: At 6 months, SAVR was associated with a significant worsening in PWV (6.38±4.47 vs. 11.01±5.75ms-1, p=0.001) and ascending AD (1.95±1.15 vs. 1.57±0.68x10-3mmHg-1, p=0.044), whereas no change was seen following TAVI. A significant reduction in RV ejection fraction (58±8 vs. 53±8%, p=0.005) was seen flowing SAVR, with no change following TAVI. A significant and comparable decline in LV torsion and twist was observed. Baseline circumferential strain was significantly associated with all-cause mortality (hazard ratio, 1.03; 1.01–1.05; p=0.009). Significantly less AR was seen immediately following Lotus than CoreValve TAVI (4.3±3.4 vs.11.7±8.4%, p=0.001) with equivalent degrees of reverse remodelling observed at 6 months.
Conclusion: Compared with TAVI, SAVR is more detrimental upon aortic stiffness and right ventricular function at 6 months. CMR derived circumferential strain is associated with survival following SAVR and TAVI.