White-Coat Effect is Related to Decreased Heart Rate Variability in Treated Type II Diabetic Patients

Wednesday, 9 July 2008
Mei-Yeh Wang, MSN , Graduate Institute of Medical Science, College of Medicine, Taipei Medical University; Cardinal Tien College of Healthcare and Management, Taipei, Taiwan
Pei-Shan Tsai, PhD , College of Nursing, Taipei Medical University, Taipei, Taiwan

Learning Objective 1: describe the association of heart rate variability (HRV) with white-coat effect (WCE) in treated type II diabetics

Learning Objective 2: describe the changes in heart rate variability in treated type II diabetics

Objectives: This study examined the association of heart rate variability (HRV) with white-coat effect (WCE) in treated type II diabetics.

Methods: Included in this study were 34 type II diabetics, aged 23 – 70 years. All participants underwent a morning laboratory session during which anthropometric measurements, clinic blood pressure (BP), 5-min HRV, and cardiovascular responses to handgrip exercise were collected. Ambulatory blood pressure (ABP) was recorded during a 48-hour period. The WCE was defined as the systolic clinic–daytime BP difference. Participants who showed a WCE of 5mmHg and above were assigned to the WCE group; those who showed a WCE of between -5 and 5mmHg were assigned to the no white-coat effect (NWCE) group; those who exhibited a WCE of -5mmHg and lower were assigned to the reverse white-coat effect (RWCE) group.

Results: The systolic day–night BP difference was lower in the WCE group compared to the RWCE group (p = 0.011). In addition, the WCE correlated to the systolic day–night BP difference (r = -0.43, p = 0.011). The NWCE group had higher high-frequency HRV than the WCE (p = 0.04) and RWCE groups (p = 0.008). Similarly, the NWCE group had higher total HRV power than the WCE (p = 0.032) and RWCE groups (p = 0.028).

Conclusions: Treated type II diabetics with WCE are characterized by sympathetic predominance and decreased HRV suggesting that the WCE phenomenon may be of prognostic value. In addition, reverse WCE is associated with elevated metabolic risk and decreased HRV, which may in turn favor the development of cardiovascular morbidity.