Mitral Regurgitation in Heart Failure: Burden, Treatment Options and Outcomes

Victor, Kelly Jayne (2021) Mitral Regurgitation in Heart Failure: Burden, Treatment Options and Outcomes. Doctoral thesis (PhD), Manchester Metropolitan University.

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Abstract

Heart failure (HF) affects an estimated 900 000 people within the United Kingdom (UK), resulting in approximately 60 000 hospital admissions each year (1). Mortality at one year is estimated at as high as 40%, with the risk of death rising with age (1). A common consequence of HF is mitral regurgitation (MR). MR is one of the most common valvular lesions worldwide. The prevalence within Europe is estimated at 4 million making MR the second most common valve lesion requiring surgery (2, 3). By nature of the disease, severity also worsens with advancing age, and as such by 2030, prevalence is expected to more than double (4). MR in HF can occur as a consequence of organic leaflet disruption (primary MR) or secondary to annular dilation (secondary MR), with both mechanisms ultimately resulting in geometric changes to the left atrium (LA) and left ventricle (LV), and concomitant symptoms. HF is commonly seen in patients with chronic long standing MR and also those who present in the acute setting. Patients with symptomatic primary MR typically undergo surgery which offers a survival benefit. Recommended treatment options for patients with secondary MR and symptoms focus on the optimisation of medical therapy, cardiac resynchronisation therapy and conventional open heart surgery. However more recently, transcatheter mitral valve repair (TMVR) has been recognised as a novel technique for MR patients with a high surgical risk and multiple comorbidities, LV systolic dysfunction, and persistent symptoms despite optimal medical therapy (OMT). Currently, there remains a dearth of information regarding the number of HF patients with MR, and the proportion of these patients who despite OMT remain symptomatic with MR and an LV ejection fraction (EF) <50%. Additionally whether or not these individuals meet suitability criteria for TMVR, and the effectiveness of TMVR in reducing the degree of MR, improving symptoms and quality of life is largely unknown. This thesis therefore aimed to identify the prevalence of MR within the HF population as well as assess the degree of change as a result of OMT. It also investigated thepopulation considered eligible for TMVR based on risk and echocardiography criteria. The thesis then focussed on using current literature and a systematic review to identify predictors of outcomes for patients who have undergone TMVR. Employing these findings, the project then prospectively assessed the usefulness of predictors in relation to quality of life and symptoms. The thesis concludes that one fifth of all patients presenting with HF have moderate or more MR and that patients with moderate or more MR have a greater risk of mortality. Patients who received OMT do see an element of relief from symptoms and a proportion also experience a reduction in the severity of MR. However, one half of patients with LV systolic dysfunction and MR still remain symptomatic despite OMT. When further evaluating the risk status for these patients, the thesis determines that a significant number of these patients are eligible for TMVR based on echocardiographic and risk criteria. From a functional assessment perspective, the results of a systematic review demonstrated that six minute walk test (6MWT) may be predictive of outcome for patients who undergo TMVR. Exercise stress echocardiography may also play a role in determining patients with early stage exercise induced severe MR. The prospective study, although limited, demonstrated variation in quality of life and echocardiography outcomes across the recruited population of eight patients. Further recruitment is needed prior to the provision of more solid conclusions. More broadly, these findings suggest the burden of MR within the HF population is significant and although medical optimisation can assist in reducing the degree of MR and symptoms, a portion of high risk patients with LV systolic dysfunction remain symptomatic and should be considered for TMVR eligibility assessment. The thesis findings suggest that when identifying patients who have the potential for improvement with MV intervention, the value of 6MWT distance, exercise stress echo, LV volume, the LV/MR ratio, and the degree of LA dilation should be assessed and examined. Further studies should also focus on clarifying recommendations for TMVR in a variety of clinical settings.