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Age hemodynamics and exercise in essential hypertension: difference between beta-blockers and dihydropyridine calcium
1Department of Medicine, University of Bergen School of Medicine, Haukeland Hospital, Norway.
Insights
Elderly hypertensive patients exhibit significantly lower cardiac index and higher total peripheral resistance compared to younger individuals. Beta-blockers reduce blood pressure by decreasing cardiac index and heart rate.
Area of Science:
- Cardiovascular Physiology
- Hypertension Research
Background:
- Hemodynamic disturbances contributing to elevated blood pressure vary with patient age and hypertension severity.
- Central hemodynamics in hypertensive patients have been investigated using invasive methods over two decades.
Purpose of the Study:
- To compare central hemodynamics between young and elderly hypertensive patients at rest and during exercise.
- To investigate the effects of beta-blockers on hemodynamics in hypertensive individuals.
Main Methods:
- Intra-arterial blood pressure (BP) measurement in the brachial artery.
- Cardiac output (CO) measurement using the dye dilution method (Cardiogreen).
- Invasive assessment of central hemodynamics at rest and during graded exercise (150 W).
Main Results:
- Elderly hypertensive subjects (60-69 years) showed a 42% lower cardiac index (CI) and 69% higher total peripheral resistance index (TPRI) compared to young subjects (17-29 years) at similar mean arterial pressures.
- During 150 W exercise, the older group exhibited a steeper increase in mean arterial pressure (MAP), with TPRI being twice as high and CI half that of the younger group.
- Beta-blockers (without ISA) typically reduce BP by decreasing CI and heart rate (HR) by 20-25%, with an initial increase in TPRI followed by downregulation.
Conclusions:
- Age significantly impacts hemodynamic profiles in hypertension, with elderly individuals demonstrating impaired cardiac function and increased vascular resistance.
- Beta-blockers effectively lower blood pressure, primarily through reductions in cardiac output and heart rate, though initial vascular resistance changes occur.
Abstract:
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)