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An appraisal of echocardiography as an epidemiological tool. The Strong Heart Study
Richard B Devereux1, Mary J Roman, Jennifer E Liu
1The New York Hospital-Cornell Medical Center, New York, NY 10021, USA. rbdevere@med.cornell.edu
Purpose:
Despite the prognostic importance of left ventricular (LV) mass (LVM) by M-mode echocardiography, concern exists about bias introduced by missing data. The American Society of Echocardiography has made recommendations for linear measurements of LV wall thickness and internal dimension used to calculate LVM, but it is unknown whether their substitution for suboptimal M-modes improves measurement yield and reduces bias.
Methods:
LVM measurement yield and associations of missing data with risk factors were assessed in 3487 American Indian participants in Strong Heart Study (SHS) Phase II and compared to data from other large-scale studies.
Results:
In SHS, LVM was measurable in 3188 (91%) participants compared to 4947/6148 (80%) Framingham participants studied by classic M-mode technique, with less decrease in measurement yield with age in SHS. In univariate SHS analyses, missing LVM was significantly associated with male gender, older age, greater height, body mass index, fat-free mass, waist/hip ratio, fibrinogen and, marginally, diabetes but not smoking, blood pressure, or lipids. In logistic regression analysis, missing LVM was independently associated with male gender, older age, greater body mass index and lower forced expiratory volume (FEV(1)) (with a low multiple R(2) [.04]), but not other risk factors. Doppler stroke volume, a measure of hemodynamic volume load, was measurable in 96% of SHS participants; missing values were weakly associated with older age, higher creatinine and lower FEV(1). During 48 +/- 11 months of follow-up, inability to measures LV mass or stroke volume was not associated with higher rates of cardiovascular events or death (p = 0.25 to 0.96).
Conclusions:
Improvements in echocardiographic methods have increased the yield of LVM in middle-aged and older adults and allow even more consistent assessment of cardiac volume load. Despite small persistent biases, due to associations of missing LVM and Doppler stroke volume data with male gender, greater obesity, lower FEV(1) and (for LVM only) older age, individuals with missing measurement are not at higher risk of cardiovascular events.