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Hemodynamic changes during long-term thiazide treatment of essential hypertension in responders and nonresponders
Insights
Hydrochlorothiazide effectively lowers blood pressure in patients with essential hypertension. However, its long-term effects on cardiac output and peripheral resistance differ between responders and non-responders.
Area of Science:
- Cardiology
- Pharmacology
- Nephrology
Background:
- Essential hypertension is a common condition requiring effective pharmacologic management.
- Diuretics, such as hydrochlorothiazide, are frequently used to treat hypertension.
- Understanding the hemodynamic effects of hydrochlorothiazide is crucial for optimizing treatment strategies.
Purpose of the Study:
- To investigate the hemodynamic effects of hydrochlorothiazide in patients with essential hypertension.
- To compare the responses between patients who significantly lowered their blood pressure and those who did not.
Main Methods:
- 13 patients with essential hypertension received hydrochlorothiazide (100 mg daily) or placebo.
- Measurements included blood pressure, cardiac output, plasma volume, renin, and aldosterone at various time points (1, 4, 12, 24, and 36 weeks).
Main Results:
- Hydrochlorothiazide significantly lowered mean arterial pressure.
- Cardiac output initially decreased but returned to baseline in responders, while remaining reduced in non-responders.
- Plasma volume decreased, renin was consistently elevated, and aldosterone increased during the initial treatment phase.
- Total peripheral resistance decreased only in responders, suggesting different compensatory mechanisms.
Conclusions:
- Hydrochlorothiazide effectively reduces blood pressure in essential hypertension.
- Hemodynamic responses, particularly to cardiac output and peripheral resistance, differ between blood pressure responders and non-responders.
- Plasma volume reduction and neurohormonal activation (renin-angiotensin-aldosterone system) may play a role in the elevated peripheral resistance observed in non-responders.
Abstract:
Blood pressure, cardiac output, plasma volume, renin, and aldosterone were measured in 13 patients with essential hypertension on placebo and after 1, 4, and 12 wk on hydrochlorothiazide 100 mg daily. In 9 patients the same variables were also measured after 24 and 36 wk. Hydrochlorothiazide lowered mean arterial pressure (p less than 0.01). Cardiac output was reduced after 4 and 12 wk of treatment, followed by a return to placebo levels. Stroke volume changed in the same way but heart rate and total peripheral resistance did not differ from placebo values. Plasma volume was reduced after 1 and 24 wk. Renin was permanently elevated (p less than 0.01), but aldosterone rose only during the first 12 wk of treatment. A comparison between responders (greater than 10% fall in mean arterial pressure) and nonresponders (less than 10% fall) revealed different hemodynamic patterns. In responders the initial fall in cardiac output was followed by a return to pretreatment levels, whereas in nonresponders it was permanently reduced. Consequently, total peripheral resistance was lowered only in responders. Nonresponders tended to show a greater degree of plasma volume depletion and greater stimulation of renin and aldosterone, which probably contributed to elevated peripheral resistance. It is concluded that changes in cardiac output are unlikely to be of decisive importance in the ultimate reduction of peripheral resistance in responders to thiazide therapy.