Defensive active coping responses (being-in-control, acceptance of the stressor as reality) have been associated with vascular hyper-responsiveness in urban Africans. However, the association between active coping responses, blood pressure (BP), and ECG-derived left-ventricular hypertrophy (LVH) responses is unknown.
Associations between BP, silent ischaemia and ECG Cornell product LVH were assessed in 161 African and Caucasian men with active coping responses identified by the Amirkhan Coping Strategy Indicator. BP, ECG and silent ischaemia data were obtained from 24-h ambulatory monitoring. Beat-to-beat BP was continuously recorded during stress testing and fasting resting blood samples obtained for biochemical analyses.
Enhanced ß-adrenergic central cardiac responses were evident in active coping Caucasians as opposed to a predomination of α-adrenergic vascular responses in active coping Africans. Active coping African men displayed higher 24-h BP and prevalence of silent ischaemia events compared to the Caucasian men. Regression analyses revealed that α-adrenergic responses were associated with silent ischaemic events, adjusted R2 0.21 [ß 1.07, 95% confidence interval (CI) 0.29–1.85] and that ischaemic events predicted LVH in active coping Africans (adjusted R2 0.12, ß 0.35, 95% CI 0.11–0.59). Receiver-operated characteristic (ROC) analyses indicated a defensive pathway cut point of 16 in Africans as opposed to 32 in Caucasians predicting silent ischaemia with sensitivity/specificity 100/96%.
A defensive pathway revealed disturbed vascular function showing dissociation between behavioural and physiological ß-adrenergic active coping responses in Africans. Vascular responsiveness facilitated silent ischaemia events and structural LVH changes which potentially explain the increased risk for incident ischaemic stroke in black Africans.
aHypertension in Africa Research Team (HART), School for Physiology, Nutrition and Consumer Sciences, North West University, Potchefstroom, South Africa
bDepartmentof Epidemiology and Public Health, University College of London, UK
cNeurovascular Hypertension & Kidney Disease and Human Neurotransmitters laboratories, Baker IDI Heart and Diabetes Institute, Melbourne, Australia
dUnit for Drug Research and Development, Division of Pharmacology, School of Pharmacy, North-West University, Potchefstroom, South Africa
eDepartment of Neurology, Medical Faculty Carl Gustav Carus, Dresden University of Technology, Dresden, Germany
fDepartment of Biological Psychology, Vrije Universiteit, Amsterdam, The Netherlands
gThe Renal Hypertension Unit, Nelson Mandela School of Medicine, University of Kwa-Zulu Natal, Durban, South Africa
Correspondence to Professor Leoné Malan, RN, PhD, Hypertension of Africa Research Team (HART), School for Physiology, Nutrition and Consumer Sciences, North-West University, Potchefstroom Campus, Private Bag X6001, Corner of Hoffman and Meyer streets, Potchefstroom, 2520, South Africa. Tel: +27 18 299 2438; fax: +27 18 299 1053; e-mail: email@example.com
Abbreviations: γ-GT, gamma glutamyl transferase; ABPM, ambulatory blood pressure monitoring; BSA, body surface area; CO, cardiac output; CVD, cardiovascular disease; Cw, Windkessel arterial compliance; DBP, diastolic blood pressure; ECG, electrocardiogram; hs-CRP, ultra-high-sensitive C-reactive protein; LVH, left-ventricular hypertrophy; SBP, systolic blood pressure; SV, stroke volume; TPR, total peripheral resistance
Received 19 August, 2011
Revised 4 November, 2011
Accepted 29 November, 2011