Age Hemodynamics and Exercise in Essential Hypertension

SUMMARY 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 β-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 ∼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. However, TPRI rarely falls below pretreatment level. AVO2 difference increases, and the venous reserve of O2 falls. In contrast, calcium antagonists of the dihydropyridine (DHP) type (such as nifedipine, nitrendipine, nisoldipine, and felodipine) reduce TPRI during chronic use whereas CO, HR, and stroke index (SI) remain unchanged, and AVO2 difference is not increased. From a pathophysiological viewpoint, the dihydropyridine calcium antagonists would seem to be more suitable than β-blockers for active elderly hypertensive patients. Long-term clinical studies to prove this are not yet available.