Cardiovascular Measures of Allostatic Load

Summary prepared by Thomas Pickering in collaboration with the Allostatic Load Working Group. Last revised June, 1997.

Blood Pressure

• Both genetically and environmentally determined; interventions in early life may have permanent effects.
• Tends to track in a predictable way in individuals, but course may be altered by environmental factors.
• Can be conceptualized as tonic and phasic components; hypertensives show elevated tonic level, without much change in phasic (variability).
• Adverse effects thought to be largely due to tonic component; phasic may contribute to triggering of acute events, e.g. atherosclerotic plaque rupture.
• Chronic environmental stress (e.g. job strain) can reset tonic component (i.e. BP raised to same extent throughout 24 hours in men with high strain jobs).
• Conventional clinic or casual measurement of BP gives imprecise estimate of true BP level, for several reasons: few readings, taken in unrepresentative setting; confounding effect of observer (white coat effect).
• Ambulatory monitoring (ABPM) can give accurate estimate of true (tonic) BP level, and limited information about phasic component. Beat-to-beat ABPM is available, but cumbersome & expensive.
• Sympathetic NS is likely mediator of environmental effects on BP, including calories (obesity), sodium, and stress.

Left Ventricular Structure Function (Echocardiography)

• Left ventricular mass can be reliably assessed by echo, and represents cumulative effects of BP on the heart.
• Also influenced by other genetic environmental factors.
• Is an independent risk factor for cardiovascular morbidity.
• Cardiac function can be assessed as cardiac output, peripheral resistance, and ejection fraction, all of which are dynamic rather than structural measures.