Relationship between Daily Activity Levels and Cardiac Ambulatory Monitoring (Introduced BY SW Davies)

Abstract

calculated. The high (HF) and low (LF) frequency components of heart rate variability were measured from a concomitant 5-minute segment of a 24 hour Holter ECG recording. LF, HF and the L F k F ratio were taken as indices of sympathetic, parasympathetic and sympathovagal balance, respectively. RESULTS: All 3 measures of autonomic tone were related to QT dispersion as follows: for LF: QT Disp (R=+0.56, p<O.OI), A.QT (R=+0.56, p<O.OI) and SD QT (R=+0.53, p<O.OI); for HF: QT Disp (R=-0.45, p<0.05), A.QT (R=-0.47, p<0.05) and SD QT (R=-0.41, p=0.05) and for the LF/HF ratio: QT Disp (R=+0.51, p<0.05), A.QT (R=+0.53, p<O.OI) and SD QT (R=+0.50, p<0.05). CONCLUSIONS: Our results suggest that increased sympathetic tone is associated with increased QT dispersion and that increased vagal tone may have the opposite effect. This may help to explain the link between Q T dispersion and sudden death and it suggests a role for both anti-adrenergic therapy and vagomimetic therapy in reducing QT dispersion in CHF and its attendant risk of sudden cardiac death.