Abstract 8649: Aerobic Exercise Training Improves Heart Rate Variability, as Reflected by PD2i, in Individuals with Low PD2i
Point Correlation Dimension (PD2i) is a non-linear measure of heart rate variability complexity that has been shown to be able to predict the risk of sudden arrhythmic death, such that a value ≤ 1.4 increases risk substantially, with a value ≤2 denoting the presence of autonomic dysfunction. It is unclear, however, if exercise, a lifestyle behavior recommended to sedentary individuals, can favorably alter PD2i. The purpose of this study was to determine if 16 weeks of moderate intensity aerobic exercise training would raise PD2i in sedentary lean and obese, middle aged men and women (age 40-57 yr). PD2i was measured at rest and in response to 5 min of upright tilt pre and post the 16 week exercise training regimen. Subjects were stratified into 2 groups according to their pre-regimen resting PD2i: low PD2i≤ 2 (lPD2i, n=14) and normal PD2i >2 (nPD2i, n=45 ). At rest, there was a training by group interaction such that PD2i increased substantially with exercise training in the lPD2i group but not in the nPD2i group (lPD2i pre 1.94±0.2, post 2.46±0.2; nPD2i pre 2.95±0.1, post 3.0±0.09, P=0.02). In response to the sympathetic stress of upright tilt (known to acutely lower PD2i), both groups had an appropriate decrease in PD2i (P<0.001) and an overall effect of training (P=0.04), but there was no training by group interaction on this response. During recovery from tilt, the lPD2i group had a significant improvement in PD2i with training (lPD2i pre 2.21±0.2, post 2.92±0.2; nPD2i pre 3.26±0.1, post 3.22±0.1, P=0.009), while there was no change in the nPD2i group. In conclusion, a 16 wk moderate intensity training program improves resting and recovery PD2i in those with low initial resting values, and this improvement may reduce their risk of sudden arrhythmic death.
- © 2011 by American Heart Association, Inc.