Abstract 64: Echocardiographic Determinants of Change in Cardiorespiratory Fitness in Response to Exercise Training: The DREW Study

Abstract

Background: Although exercise training is associated with an improvement in cardiorespiratory fitness (CRF), there is substantial individual heterogeneity in the response to exercise training. To our knowledge, the contribution of baseline left ventricular structure to the variability in exercise training response has not been studied. Methods: We included 147 subjects from the Dose Response to Exercise in Women (DREW) study cohort who were randomized to 4, 8, 12 kilocalories/kg/week of aerobic training for 6 months and had a baseline transthoracic echocardiogram. CRF was evaluated at baseline and 6 month follow up using a cycle ergometer and quantified as peak absolute oxygen consumption (VO2abs L O2/min) and peak relative oxygen consumption (mLO2/kg/min). Change in CRF was defined as the difference in VO2abs between the two examinations. Baseline demographic, clinical and echocardiographic characteristics were compared among subjects across tertiles of CRF change. Multivariable adjusted linear regression analysis was used to determine the association between echocardiographic measures at baseline and the change in CRF in response to exercise training. Results: Participants were middle age (mean age: 57), obese (mean BMI: 31), and with low baseline CRF (average METs: 4.3). As expected, lower baseline CRF and a higher exercise training dose were associated with a greater increase in CRF. In addition, posterior wall thickness (PWT), interventricular septal thickness (IVST), and indexed left ventricular mass (LVmi) were all found to be inversely associated with change in CRF in response to exercise training after adjustment for age, body mass index, baseline CRF, blood pressure and exercise training dose (see Table). Other echocardiographic measures (i.e. systolic and diastolic function) were not associated with change in CRF. Conclusions: Both left ventricular mass and wall thickness are independent predictors of CRF change in response to exercise training among obese, sedentary postmenopausal females.