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Hindlimb unloading results in loss of circadian control of heart rate and increased incidence of spontaneous ventricular arrhythmias
Author(s) -
Welliver Kathryn C,
Jepson Amanda J,
Moffitt Julia A
Publication year - 2010
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.24.1_supplement.625.12
Subject(s) - circadian rhythm , medicine , deconditioning , autonomic nervous system , heart rate , cardiology , heart rate variability , endocrinology , autonomic function , incidence (geometry) , blood pressure , physics , optics
Hindlimb unloading (HU) in rats, a model of cardiovascular deconditioning, has been found to result in cardiac sympathovagal imbalance. Previous data indicate that derangement in circadian control of heart rate may lead to increased risk for acute cardiac events via alterations in autonomic function. We hypothesized that attenuated circadian control of HR and increased incidence of spontaneous premature ventricular complexes (PVC) would occur over the course of 10–14 days of HU vs casted control (CC) condition. Radiotelemetry probes for electrocardiographic analysis were implanted in male, Sprague‐Dawley rats 10 days prior to manipulations. Data were collected for 5 consecutive minutes at the top of each hour, separated into light and dark cycles and statistically compared. Circadian differences in HR in CC (n=4) and HU (n=6) rats were similar and significantly different over 48h of baseline and 72h of HU adaptation. While loss of this difference and tachycardia occurred initially in both groups, HR and circadian control returned to baseline levels by 6 days in CC rats but not in HU rats. In addition, 27 spontaneous PVCs and one run of salvo were observed in a subset of HU rats (n=3) as compared to only 4 spontaneous PVCs in a subset of CC (n=2) rats. These data indicate that deconditioning leads to loss of circadian control of HR and increased incidence of ventricular arrhythmias, likely due to autonomic dysfunction.