Age Hemodynamics and Exercise in Essential Hypertension

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The hemodynamic disturbances behind increased blood pressure (BP) differ widely and depend on the patient's age as well as on the severity of the hypertensive state. During the last 20 years we have studied central hemodynamics with the same invasive methods in groups of hypertensive patients at rest and exercising. [BP recorded intra-arterially in the brachial artery and cardiac output (CO) measured by dye dilution method, Cardiogreen.] In elderly hypertensive subjects (60-69 years) with almost the same mean resting arterial BP [mean arterial pressure (MAP) = 113 mm Hg] as a young group (17-29 years, MAP = 114.1 mm Hg) cardiac index (CI) was 2.17 L/min m2 (or 42% lower), and total peripheral resistance index (TPRI) was 4,223 dyn/s cm-5m2 (or 69% higher). The increase in MAP during exercise was much steeper in the older group. During 150 W exercise TPRI was about twice as high whereas CI was only about half of that in the younger group. Arteriovenous oxygen (AVO2) difference was markedly increased and stroke index fell when subjects were in transition from submaximal to maximal work, probably early markers of incipient heart insufficiency during work. Most data on drug effects are based on studies in middle aged subjects. The typical response to nonselective or selective beta-blockers without intrinsic sympathomimetic activity (ISA) (agents such as propranolol, timolol, atenolol and metoprolol) is a BP reduction through a fall in CI and heart rate (HR) of approximately 20-25% when subjects were at rest and exercising. Initially there is an increase in TPRI that prevents BP from falling, but with time TPRI is downregulated, and BP falls.(ABSTRACT TRUNCATED AT 250 WORDS)