Why do exercise-induced ventricular arrhythmias increase with age? Role of M-mode echocardiographic aging changes

BACKGROUND: Although advancing age is associated with a higher prevalence and complexity of exercise-induced ventricular arrhythmias (EIVA), the role of age-associated cardiac anatomic and functional characteristics in this relationship has not been explored. METHODS: We performed both M-mode echocardiography and maximal treadmill exercise testing within two consecutive visits in 366 healthy volunteers ages 20 to 90 years from the Baltimore Longitudinal Study of Aging. RESULTS: Simple (i.e., isolated) EIVA were detected in 79 subjects (21%) and complex EIVA (i.e., EIVA comprising > or = 10% of beats in any minute or occurring in runs) in another 17 (5%). Univariate predictors of any EIVA, whether simple or complex, were older age (p < .0001), greater LV mass index (p < .0001), male gender (p < .001), higher peak exercise systolic blood pressure (p = .003), and larger body surface area (p = .005). By multiple logistic regression analysis, only age (p = .0001) independently predicted the occurrence of EIVA. For complex EIVA alone, the strongest univariate predictors were age (p = .004), male gender (p = .008), lower maximal heart rate (p = .01), greater left atrial size (p = .03), and larger LV posterior wall thickness (p = .04); on multiple logistic regression, only older age (p = .03) and larger left atrial size (p = .04) independently predicted the presence of complex EIVA. CONCLUSION: In healthy volunteers undergoing maximal treadmill exercise, greater LV wall thickness and mass are associated with the development of EIVA but they do not independently predict EIVA once the powerful effect of age is considered. The association between complex EIVA and left atrial dilatation may be mediated by higher LV end diastolic pressure and volume during exercise in subjects with larger left atria.