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Wednesday, 9 July 2008
Learning Objective 1: describe the association between blood pressure dipping and physical activity among patients with heart failure.
Learning Objective 2: understand applications of ambulatory blood pressure monitoring for the heart failure patient population in the community.
Fluctuation in ambulatory blood pressure (BP) is due in part to physical activity (PA) corresponding to wake and sleep. BP declines during sleep (“dipping”) as protection from consistent BP load. Patients with heart failure (HF) undergo constant neurohumoral activation, which may suppress or even eliminate dipping. The aims of this study were to estimate the correlation between BP dipping and PA among patients with HF and to compare degree of BP dipping between HF patients with no limitation of PA (New York Heart Association [NYHA] functional class I) and those with limitation of PA but no discomfort at rest (NYHA class II or III). BP at 30-minute intervals (SpaceLabs 90207) and minute-by-minute PA (Basic Motionlogger) were measured over a 24-hour period to investigate BP dipping and PA levels in community-based individuals with HF. Thirty-eight patients completed ambulatory monitoring of both BP and PA; 15 had NYHA class I and 23 had class II or III HF. There were 17 men and 21 women, aged 49 to 82 years (66.0±11.3). The results indicated that there were significant positive correlations of awake PA with BP dipping (r = 0.31, 0.60, and 0.46 for systolic BP [SBP], diastolic BP [DBP], and mean arterial pressure [MAP], respectively). There was no significant difference in BP dipping, however, between class I and class II HF subjects (6.3±5.5% vs 5.9±7.4%; 10.4±6.8% vs 10.72±8.8%; 8.9±5.4% vs 7.9±7.9% in SBP, DBP, and MAP dipping, respectively). These preliminary findings suggest a positive association of PA while awake with level of BP dipping in this patient population. Further research in a larger sample of patients is warranted.