The effects of transcatheter aortic valve replacement and conventional aortic valve replacement on cardiac mechanics and function in patients with confirmed severe aortic stenosis. Insights from a national echocardiographic core lab

Kuyt, Katherine (2020) The effects of transcatheter aortic valve replacement and conventional aortic valve replacement on cardiac mechanics and function in patients with confirmed severe aortic stenosis. Insights from a national echocardiographic core lab. Doctoral thesis (PhD), Manchester Metropolitan University.

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Abstract

Aortic Stenosis (AS) is a progressive disease characterised by increasing aortic valve calcification and thickening, leading to escalating left ventricular afterload, and myocardial damage. This sub-study of the UK TAVI trial investigated myocardial functional recovery post-intervention in subjects with severe AS and intermediate surgical risk, randomised to surgical aortic valve replacement (AVR) or transcatheter aortic valve insertion (TAVI). Speckle tracking echocardiography (STE) was used to assess the deformation of the myocardial wall (strain) in trans-thoracic echocardiographic images (TTE’s). Strain was measured pre-intervention (baseline), 6weeks post-intervention(6W), and 12-months post-intervention (12M) in the left ventricle (LV, n≤142), right ventricle (RV, n=25) and left atrium (LA, n=74). Additionally, strain-volume loops were constructed to explore how the haemodynamic relationship between volume and longitudinal strain in the LV changed pre- to post-intervention after AVR and TAVI (n=48). The improvement seen from baseline to 12M in TAVI was non-inferior AVR (P<0.05) for LV global longitudinal strain, and LA maximum volume, pre-A volume, total emptying fraction and active emptying fraction. Overall, there was evidence of global recovery of the myocardium. Strain volume loops (SVL) for both AVR and TAVI saw a decrease in LV end-diastolic volume at 12M compared to baseline, but only the TAVI SVL saw a reduction in LV end-systolic volume. Overall systolic-diastolic uncoupling recovered in both SVL’s but the changes in early vs late diastolic uncoupling varied between the treatment groups; suggesting different myocardial changes. This work was limited by the sample sizes for many of the analyses. A review of the UK TAVI image acquisition and analysis procedures was performed, providing feedback regarding improvements that may initiate greater quality TTE’s. Conclusions centred around improving communication pathways and ensuring consistent training of staff. It has previously been established that LV GLS is a sub-clinical predictor of heart function, and long-term outcomes for patients with AS. LA volume is also a well-established predictor of cardiovascular risk. Therefore, the findings of this work that recovery of both LV GLS and LA maximum volume is non-inferior in TAVI compared the AVR suggest that the long-term outcomes will also be non-inferior and supports the use of TAVI to treat severe AS.