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Haemodynamics during long-term thiazide treatment in essential hypertension: differences between responders and
Insights
Hydrochlorothiazide effectively lowers blood pressure in essential hypertension. However, its long-term impact on cardiac output and peripheral resistance differs between responders and non-responders.
Area of Science:
- Cardiology
- Pharmacology
- Hypertension Research
Background:
- Essential hypertension is a common cardiovascular condition requiring effective treatment.
- Thiazide diuretics, like hydrochlorothiazide, are widely used for hypertension management.
- Understanding the hemodynamic effects of hydrochlorothiazide is crucial for optimizing treatment strategies.
Purpose of the Study:
- To investigate the long-term hemodynamic effects of hydrochlorothiazide in patients with essential hypertension.
- To differentiate the responses between patients who significantly lower their blood pressure (responders) and those who do not (non-responders).
- To assess the role of cardiac output changes in determining the sustained antihypertensive effect.
Main Methods:
- A study involving 13 patients with uncomplicated essential hypertension.
- Measurements included blood pressure, systemic hemodynamics, plasma volume, renin, and aldosterone.
- Data collected during placebo treatment and at multiple time points (1, 4, 12, 24, and 36 weeks) during hydrochlorothiazide administration.
Main Results:
- Hydrochlorothiazide significantly lowered mean arterial pressure, with notable differences between responders and non-responders.
- Cardiac output decreased, particularly after 12 weeks, with responders showing a return to baseline and reduced peripheral resistance.
- Non-responders exhibited persistently reduced cardiac output and elevated total peripheral resistance.
- Plasma volume, renin, and aldosterone changes were not significantly different, though non-responders showed trends towards greater volume depletion and aldosterone increase.
Conclusions:
- The initial decrease in cardiac output is unlikely to be the primary determinant of the long-term hemodynamic effects of thiazide diuretics.
- Individual hemodynamic responses to hydrochlorothiazide vary, influencing long-term efficacy.
- Further research may elucidate the mechanisms behind differential responses in essential hypertension.
Abstract:
1. Blood pressure, systemic haemodynamics, plasma volume, renin and aldosterone were measured during placebo treatment and after 1, 4 and 12 weeks of hydrochlorothiazide in 13 patients with uncomplicated essential hypertension. Nine of these patients were also studied after 24 and 36 weeks of treatment. 2. Mean arterial pressure was lowered significantly during hydrochlorothiazide treatment. In seven patients the fall in mean arterial pressure was lowered significantly during hydrochlorothiazide treatment. In seven patients the fall in mean arterial pressure was greater than 10% (responders); four of these were studied for 36 weeks. The remainder were considered non-responders. 3. Hydrochlorothiazide lowered cardiac output. The maximal decrease was observed after 12 weeks of treatment (P less than 0.01). In responders this was followed by a return to pretreatment values and a significant decrease in total peripheral resistance, whereas in non-responders cardiac output remained reduced and total peripheral resistance was permanently elevated. 4. Changes in plasma volume, renin and aldosterone were not significantly different in responders and non-responders although non-responders tended to show a greater degree of plasma volume depletion and a more pronounced increase in plasma aldosterone. 5. Thus it is unlikely that the initial decrease in cardiac output is an important determinant of the long-term haemodynamic effect of thiazide diuretics.