Exercise capacity is known to be an important prognostic factor in patients with cardiovascular disease and in healthy subjects. While structural heart disease is found in a relatively small proportion, other factors are likely responsible for reduced exercise tolerance in these patients. Indices of left ventricular (LV) diastolic filling variably correlated with exercise time in select patient populations including hypertensives and the elderly. Moreover, no study has specifically addressed the contribution of LV systolic and diastolic functional abnormalities to both exercise duration and perceived effort. The objectives of the study were to determine echocardiographic correlates of exercise capacity and of perceived exertion in patients without structural heart disease.
We studied 111 consecutive patients, age 53+/-13 years, who were referred for echocardiographic stress testing. Patients underwent symptom limited treadmill exercise testing according to Bruce protocol in all cases. Standard blood pressures and 12 channel electrocardiograms were performed. Baseline 2 dimensional and Doppler echocardiographic images were recorded immediately prior to exercise. The primary end points were maximal exercise tolerance defined by mets and peak RPE.
Age was directly correlated with mets (r=.38, p=.<.001) but not with RPE (r=.21,p=.51). On univariate analysis, mets also correlated with: hemoglobin (r=.39, p=.001), E/A (r=.33, p=.019) E/Vp (r=-.41, p=.004) and E/E’ (r=-.41, p=.004). Multiple regression analysis showed that independent predictors of mets were: age and gender (r2=.58,p<.001). There was a direct correlation between RPE and LA size (r=.35, p=.013) and a trend towards a correlation between RPE and LV mass index (r=.24, p=.09). On multivariate analysis, LA size remained the sole independent predictor of RPE (r2=.17, p=.021).
This study showed reduced exercise capacity measured by metabolic equivalents (mets) is related to advanced age and female gender whereas perceived exertion is related to left atrial size.
There are age and gender related differences in functional capacity but not in preceived exertion. The specific mechanism by which LA size modulates perceived exertion is unknown but merits further study.
Jason Lazar, None.