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Enalapril in hypertension with renal artery stenosis: long-term follow-up and effects on renal function
Insights
Enalapril effectively controlled hypertension in patients with renal artery stenosis, causing minor increases in creatinine and urea. Long-term use is suitable for non-surgical candidates, but short-term use is advised for those awaiting surgery.
Area of Science:
- Nephrology
- Cardiovascular Medicine
- Pharmacology
Background:
- Renal artery stenosis (RAS) can lead to renovascular hypertension.
- The renin-angiotensin-aldosterone system (RAAS) plays a crucial role in regulating blood pressure in RAS.
- Converting enzyme inhibitors like enalapril impact the RAAS.
Purpose of the Study:
- To evaluate the long-term efficacy and safety of enalapril in patients with renal artery stenosis.
- To assess the effects of enalapril on systemic blood pressure, renal function, and hormonal markers in RAS patients.
Main Methods:
- A long-term study (mean follow-up 19 months) involving patients with renal artery stenosis treated with enalapril (10-40 mg once daily).
- Monitoring of systemic blood pressure, serum creatinine, urea, peripheral plasma angiotensin II, and plasma active renin concentration.
- Analysis of renin secretion and extraction by stenotic and contralateral kidneys.
Main Results:
- Enalapril effectively controlled systemic hypertension long-term with no serious side effects observed.
- Modest increases in serum creatinine and urea were noted.
- Significant reduction in plasma angiotensin II and a 20-fold increase in plasma active renin concentration were maintained.
- The stenotic kidney secreted both active and inactive renin, while the contralateral kidney extracted active renin.
Conclusions:
- Enalapril is an effective long-term treatment for hypertension in patients with renal artery stenosis, particularly those unsuitable for surgery.
- Short-term enalapril therapy (≤1 month) is recommended before corrective surgery to maximize blood pressure reduction without compromising the stenotic kidney.
- Inhibition of the renin-angiotensin system by enalapril can counteract important intrarenal compensatory mechanisms in RAS.
Abstract:
Enalapril alone, 10-40 mg given once-daily, controlled systemic hypertension long-term (mean follow-up time 19 months) in patients with renal artery stenosis. Significant, but usually modest, increases in serum creatinine and urea were observed. No serious side-effects were seen. A highly significant reduction in peripheral plasma angiotensin II was maintained 24 h after the previous dose of enalapril. Plasma active renin concentration rose 20-fold with long-term enalapril, when the stenotic kidney showed significant secretion of inactive, as well as of active renin. With enalapril therapy, the contralateral kidney showed net extraction of active renin. In unilateral renal artery stenosis, circulation on the affected side is diminished and is mainly via the juxtamedullary nephrons, which become rich in associated renin. Important intrarenal compensatory actions of the renin-angiotensin system include support of glomerular filtration, enhancement of vasa recta-mediated counter-current exchange, sustained urea excretion and maintenance of renal artery pressure distal to the stenosis. These compensatory effects are lost with converting enzyme inhibition. Thus in patients who are candidates for operation, enalapril should usually be given for no more than one month before proceeding to corrective surgery, to allow maximum blood pressure reduction without endangering the stenotic kidney for too long. Enalapril can nevertheless be given effectively long-term in patients unsuitable for corrective surgery.