Magnetic Resonance Imaging in the Assessment of Surgical and Transcatheter Aortic Valve Replacement: The impact on neurocognitive function and myocardial reverse remodelling

Background: Aortic valve stenosis is the most common degenerative valve disease affecting the Western elderly population. Medical therapy is ineffective at treating the mechanical obstruction of blood flow. Surgical Aortic Valve Replacement (SAVR) is the current recommended treatment for symptomatic severe AS but often high risk patients are declined for this. Transcatheter Aortic Valve Implantation (TAVI) allows the percutaneous delivery of the prosthetic valve but this novel approach is associated with complications. Aims: This thesis aims to focus on the effects of TAVI and contemporary SAVR on patients’ quality of life, neurocognitive function and the left ventricular reverse remodelling. Methods: High risk patients with symptomatic aortic stenosis were studied at baseline, 30 days, 6 month and 12 months after intervention. Cerebral MRI with diffusion weighted imaging for micro-embolism was conducted before and after intervention and again at 6 months. Cardiac MR was conducted at baseline and 6 months. Health related quality of life and a comprehensive battery of neurocognitive functional assessments were also conducted across 3 and 4 time points respectively. Results: The incidence (54(77%) vs. 17(43%), p=0.001) and number (3.4±4.9 vs. 1.2±1.8, p=0.001) of new micro-infarcts was greater after TAVI compared to SAVR. Physical component scores (PCS) in TAVI increased after 30 days (32.1±6.6 vs. 38.9±7.0, p<0.0001) and 6m (40.4±9.3, p<0.0001); the improvement occurred later in SAVR (baseline: 34.9±10.6, 30d: 35.9±10.2, 6m: 42.8±11.2, p<0.001). At 12 months, the majority of neurocognitive function tests did not show a significant change in the proportion of patients categorised as having impaired NCF compared to baseline in the TAVI or SAVR groups. After 6 months, there were significant improvements in indexed end-diastolic volumes (TAVI: 100±25mls vs. 87±26mls, p<0.001; SAVR 91±28mls vs. 82±17mls, p<0.05) Extracellular volumes were similar for both groups at baseline (range 22.8 to 24.6%). There was no significant change in ECV after 6 months (TAVI, 24.0±9% vs. 29.3±11%, SAVR, 23.8±7 vs. 23.5±9, p= 0.76). Conclusions: TAVI patients experience higher numbers of cerebral micro-infarcts than contemporary SAVR patients, but this appears to have no effect on HRQoL; TAVI patients experienced earlier improvements in quality of life than SAVR patients. There was also no evidence of neurocognitive functional decline after TAVI using a battery of very sensitive neurocognitive function tests. Both TAVI and SAVR improved cardiac imaging parameters with evidence of reverse LV remodelling but no change in diffuse myocardial fibrosis after 6 months.