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Changes in heart rate and heart rate variability before ambulatory ischemic events¹

Willem J. Kop, PhD^* , Ralph J. Verdino, MD, FACC , John S. Gottdiener, MD, FACC, Shaun T. O’Leary, MD, PhD^||, C. Noel Bairey Merz, MD, FACC^¶ and David S. Krantz, PhD^*

^* Department of Medical and Clinical Psychology, Uniformed Services University of the Health Sciences Bethesda, Bethesda, Maryland, USA
Division of Cardiology, Department of Medicine, Georgetown University Medical Center Washington, DC, USA
Division of Cardiology, University of Pennsylvania, Philadelphia, Pennsylvania, USA
Noninvasive Cardiology, Saint Francis Hospital, Roslyn, New York, USA
^|| Department of Neurosurgery, Henry Ford Hospital, Detroit, Michigan, USA
^¶ Division of Cardiology, Department of Medicine, Cedar Sinai Research Institute, Los Angeles, California, USA

View larger version (14K): [in a new window]   Figure 1 Decrease in heart rate variability (HRV) before ischemic events. Top: A significant decrease in high frequency (hf) (p = 0.04) occurred in the period from 60 min to 10 min before the ischemic event, followed by a further depression during the 4 min preceding the event. Low frequency (lf) HRV decreased significantly at 4 min before the ischemic event but not at earlier time points. Lower: Changes in heart rate (HR) in the hour surrounding ischemic events. *p < 0.05; **p < 0.01, unadjusted p levels comparing target and preceding HRV or HR level.

View larger version (16K): [in a new window]   Figure 2 Depressed high-frequency heart rate variability (HRV) during elevated mental activities before ischemic events. High frequency (hf) HRV was significantly depressed during high levels of mental activity compared with events occurring at low mental activity. The difference emerged 10 min before the ischemic event (p = 0.060) and persisted until 4 min (p = 0.038) and 2 min before ischemia (p = 0.045). Heart rates (HR) tended to be elevated during high mental stress at onset of ischemia and 10 min before ischemia. *p < 0.05; p < 0.10 (unadjusted p values for high versus low mental activity comparisons). Solid circle = high mental activity; open circle = low mental activity.

View larger version (12K): [in a new window]   Figure 3 Relation between ischemic heart rate (HR) and heart rate variability (HRV) changes. Both low (p = 0.001) and high frequency (p = 0.003) HRV components were significantly depressed at ischemic events occurring at high HRs (>100 beats/min; 35 episodes) compared with events occurring at low heart rates (33 episodes. Heart rate variability measures did not differ between high versus low heart rate events for assessments before the ischemic events (at 10, 4 and 2 min; pinteraction < 0.01). **p < 0.005 ischemic events occurring at high versus ischemic events at low HRs. Open circle = high HR event; solid circle = low HR event.