Author: Dylan Jones
Jones, Dylan, 2021 Review of current practices for the assessment of patients with severe aortic stenosis and predicting poor symptom recovery after aortic valve intervention, Flinders University, College of Medicine and Public Health
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The work presented in this thesis explores the perioperative evaluation and management of patients with severe symptomatic aortic stenosis (AS), an increasing common calcific degenerative cardiac valvular disease, and further investigates novel mechanisms of residual symptoms of dyspnoea post-intervention.
The first three research chapters used a retrospective design to examine current practices. We first examined the effect of the introduction of a structural heart program with an accompanying multidisciplinary team on mortality in a tertiary hospital. We found that although no differences in mortality existed between the existing surgical valve replacement and the new transcatheter valve replacement, there was a significant mortality benefit in the AS population, attributed to the expansion of services and the use of multidisciplinary care.
We then analysed the use of balloon aortic valvuloplasty (BAV) as a temporizing measure in patients with severe AS. While BAV had previously fallen out of favour due to a lack of benefit long-term, we found a significant short to medium term mortality benefit, which may allow rapid relief of valvular obstruction, time for further investigation of comorbidities, improvement in cardiac function and safer subsequent procedures.
We then sought to clarify timing of intervention in patients with a discordant number of severe AS criteria. We found that patients with an increasing number of criteria had increased mortality without intervention, and that those with fewer criteria had a delay in intervention. Despite this, we found that the effect of intervention was similar for all groups, indicating that earlier intervention may be beneficial.
The last three research chapters used a prospective design to examine residual dyspnoea in patients who had undergone intervention. We examined left ventricular strain in severe AS and found that patients with severe AS had reduced strain, indicating a degree of remodeling had already occurred. After intervention, patients who had an improvement in strain had a significantly greater improvement in symptoms than those who did not improve or worsened, implicating this as a cause of residual symptoms.
We then used a non-invasive bedside tool to measure the augmentation index, a marker of arterial stiffness. Since the valvuloarterial impedance is the combined obstruction to flow from the left ventricle due to both valvular disease and reduced systemic compliance, we measured the arterial stiffness after the valvular obstruction had been relieved, finding that those with a higher degree of arterial stiffness were more likely to suffer from residual dyspnoea, likely due to increased myocardial work.
Lastly, we examined the use of a commonly used frailty assessment and found that after intervention frailty improves significantly after intervention, indicating that frailty, as currently measured, may be more a symptom than a comorbidity.
Our research supports that careful consideration, but early action, may prevent irreversible cardiovascular injury leading to residual symptoms, despite intervention.
Keywords: Aortic stenosis, Symptoms, TAVR, SAVR, Multidisciplinary Heart Team, Balloon Valvuloplasty, Global Longitudinal Strain, Augmentation Index, Valvuloarterial impedance, Frailty
Subject: Medicine thesis
Thesis type: Doctor of Philosophy
Completed: 2021
School: College of Medicine and Public Health
Supervisor: Dr Sam Lehman