Electronic Thesis and Dissertation Repository

Thesis Format

Integrated Article

Degree

Doctor of Philosophy

Program

Epidemiology and Biostatistics

Supervisor

John-Baptiste, Ava.

2nd Supervisor

Cheng, Davy.

Co-Supervisor

Abstract

The objective of this doctoral was three-fold: 1) to systematically review frailty measures and prognosis of frail patients undergoing TAVI, 2) to examine the performance of frailty indices in predicting clinical outcomes after TAVI, and 3) to examine the performance of frailty indices in predicting one-year costs of TAVI and high-cost TAVI patients.

For the first objective, we systematically reviewed the literature published in 2006 or later. We found that frailty instruments varied across studies, leading to a wide range of frailty prevalence estimates for TAVI recipients and substantial heterogeneity.

For the second objective, we utilized data from the CorHealth Ontario TAVI registry and administrative databases housed at the Institute for Clinical Evaluative Sciences (IC/ES), Canada. Two administrative database frailty indices, the Johns Hopkins Adjusted Clinical Group (ACG) frailty indicator and the Hospital Frailty Risk Score (HFRS), were used to assign frailty status. We found that the agreement between the Johns Hopkins ACG frailty indicator and the HFRS was fair. Both the Johns Hopkins ACG frailty indicator and the HFRS were significantly associated with one-year mortality and rehospitalization following TAVI. We found that both the Johns Hopkins ACG frailty indicator and HFRS improved performance in predicting one-year mortality and rehospitalization.

For the third objective, we analyzed cost data from the same Ontario TAVI cohort. We found that frail patients incurred significantly increased one-year healthcare costs. The HFRS was a significant predictor for high-cost patients. We found that the HFRS improved the performance of the model in predicting high-cost patients.

Summary for Lay Audience

Transcatheter aortic valve implantation (TAVI) has emerged as an alternative, less invasive treatment option for patients with severe symptomatic aortic stenosis who are at high or intermediate risk for poor outcomes with surgical aortic valve replacement (SAVR). Frailty is a biological syndrome characterized by an increased vulnerability to illnesses, and has been recognized as a predictor for poor outcomes after TAVI.

In this study, we reviewed and analyzed existing literature that reported outcomes of frail patients undergoing TAVI. We also compared the predictive performance of two frailty indices: 1) the Johns Hopkins Adjusted Clinical Groups (ACG) frailty indicator and 2) the Hospital Frailty Risk Score (HFRS). We analyzed data in 3,866 patients who underwent a TAVI procedure in Ontario, Canada from 2012 to 2018. We found that the prevalence of frailty in patients undergoing TAVI ranged widely across the literature, due to the variety of frailty definitions. Pooling prognosis of frail patients, we found very low or low confidence in the overall estimates due to inconsistency of frailty measures identified in the studies. Drawing on data from the Ontario TAVI registry, we found similar proportions of frail patients diagnosed. We found a fair agreement between the Johns Hopkins ACG frailty indicator and the HFRS, due to key differences amongst the two frailty indices. Both the Johns Hopkins ACG frailty indicator and the HFRS were associated with increased risk of death and rehospitalization at one year following TAVI. Both the Johns Hopkins ACG frailty indicator and the HFRS added incremental predictive value when predicting death and rehospitalization at one year. Analyzing cost data in the cohort, we found that frail patients incurred dramatically increased one-year healthcare costs after TAVI. The HFRS was identified as a powerful predictor for high-cost patients, and added incremental predictive value when predicting high-cost patients undergoing TAVI. Our study suggests that preoperative frailty assessment may add predictive value for outcomes after TAVI.

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