Title

Clinically Meaningful Change in Heart Failure: The Six-Minute Walk Test and Daily Activity

Date of Award

4-2012

Degree Name

Doctor of Philosophy

Department

Interdisciplinary Health Sciences

First Advisor

Dr. Amy B. Curtis

Second Advisor

Dr. Eric Vangsnes

Third Advisor

Dr. Michael Dickinson

Abstract

The purpose of this three-paper dissertation was to determine thresholds for clinically meaningful change in two important measures related to the rehabilitation of individuals with chronic heart failure (CHF).

The objective of the first paper was to provide a preliminary estimate of the minimum detectable difference (MDD) and minimum clinically important difference (MCID) of the six-minute walk test (6MWT) and daily activity in outpatients with CHF. The results of this prospective study suggested that the MDD at the 95% confidence level for the 6MWT was 32.4 meters. The MCID for the 6MWT was 31.4 (CI95% 21.7, 41.2) meters. There was poor alignment of the MDDand MCID for daily activity suggesting that either daily activity may be robust to changes in disease status or that accelerometer-based measures of daily activity are burdened by excessive measurement error.

The second paper is a systematic review which sought to utilize existing, published data to provide an estimate of the amount of change in 6MWT distance (Δ6MWT) that represents a clinically meaningful change in individuals with CHF. The mean (standard deviation) MDD calculated based on the published ICCs was 43.1(16.8) meters. A Δ6MWT of 40-45 meters was associated with at least moderate aerobic capacity and health-related quality of life effect sizes in the intervention groups.

The third paper is a retrospective review of 102 medical records that sought to determine whether there is an association between daily activity measured by implanted cardiac defibrillators (ICDs) and mortality/mean life expectancy as predicted by the Seattle Heart Failure Model (SHFM) in individuals with CHF, and to provide an estimate of the MCID for daily activity. A moderate correlation was found between baseline daily activity and each of the SHFM prognostic indicators: 1-year mortality (r=.36, p

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