Heritability of hemodynamic reactivity to laboratory stressors in a homogenous Arab population: 'Oman Family Study'.

Background: Exaggerated cardiovascular reactivity to stressful stimuli may be a risk factor for the development of hypertension. The genetic influence on blood pressure (BP) reactivity to stress and its control mechanisms has been receiving considerable support. This study aims at examining the heritability of BP and its intermediate hemodynamic phenotypes to acute stress in a homogeneous Arab population.

Methods: Parameters were computed from continuous BP, electrocardiography and impedance cardiography measurements, during rest, word conflict (WCT) and cold pressor (CPT) tests. Heritability estimates (h(2)) were obtained using the variance components-based approach implemented in the SOLAR software package.

Results: Reactivity scores for WCT and CPT increased significantly (P < .05) for systolic (SBP), diastolic (DBP), heart rate (HR), cardiac output (CO), and total peripheral resistance (TPR). They decreased significantly (P < .05) for stroke volume (SV), left ventricular ejection time (LVET), end diastolic (EDI) and cardiac contractility (IC) indices. Univariate analysis detected heritability estimates that ranged from 0.19-0.35 for rest, 0.002-0.40 for WCT and 0.08-0.35 for CPT.

Conclusion: In this unique cohort, resting as well as challenged cardiovascular phenotypes are significantly influenced by additive genetic effects. Heritability estimates for resting phenotypes are in a relatively narrow range, while h(2) for their reactivity is somewhat broader with lower estimates. Further analyses of this study may offer important opportunities for gene finding in hypertension. WHAT IS KNOWN ABOUT THE TOPIC: (1) cardiovascular reactivity to stress predicts cardiovascular disease; (2) genetic susceptibility plays an important role in stress reactivity. Family studies using the cold pressure test reported significant heritability for blood pressure.

What This Study Adds: (1) this cohort is from five highly consanguineous isolated Arab pedigrees with genetically verified genealogical records and environmental homogeneity; (2) This is the first study to estimate heritability of detailed intermediate hemodynamic phenotypes that make up normal blood pressure.