EDITOR--The editorial by Kumar et al reminds us that treatment with angiotensin converting enzyme inhibitors can cause harm in patients with unilateral or bilateral renal artery stenosis. Their suggestion, however, that patients at high risk should undergo screening with duplex ultrasonography is impracticable and would restrict its use in those for whom there is proved benefit.
Kumar et al's definition of high risk includes most patients who are currently being treated with angiotensin converting enzyme inhibitors--elderly people with hypertension, and patients with diabetes or coronary heart disease. Implementing the recommendations of Kumar et al would have substantial clinical and financial implications. Duplex ultrasonography requires considerable technical skill, is not available in every centre, and is not currently thought to be sufficiently sensitive to be an effective screening method, even in patients with a technically adequate scan. Most patients with heart failure and almost all other patients have started treatment with angiotensin converting enzyme inhibitors in the community. What are the implications, therefore, for general practitioners without easy access to screening facilities?
Evidence from multiple randomised clinical trials shows that it is neither necessary nor possible to screen these patients. In the evaluation of losartan in the elderly study, treatment with either losartan or captopril was associated with only a 10.5% incidence of renal dysfunction, defined as a rise in serum creatinine of 26.5[micro]mol/1, despite patients' advanced years (two thirds of patients aged over 70) and high incidence of diabetes (25%), hypertension (57%), and previous myocardial infarction (50%). Data from the fourth international study of infarct survival show that early oral treatment with angiotensin converting enzyme inhibitors after myocardial infarction was safe and associated with an additional 1.5 lives saved per 1000 patients treated within the first 24 hours. Screening this unstable population would be impossible. All these patients have coronary artery disease, and many have concomitant diabetes mellitus or peripheral vascular disease.
There is no evidence that angiotensin converting enzyme inhibitors are detrimental in unilateral renal artery stenosis. In a recent study of elderly patients with heart failure, many of whom had unilateral renal artery stenosis, angiotensin converting enzyme inhibitors were tolerated excellently. Furthermore, no evidence exists that relief of unilateral stenosis is associated with an improved outlook. What is, therefore, to be done with patients with unilateral stenosis? Are they to be denied the proved benefits of angiotensin converting enzyme inhibitors in the absence of evidence of harm? Kumar et al have not fully considered the implications of their recommendations. Currently, screening for unilateral renal artery stenosis cannot be justified.
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David R Murdoch Specialist registrar in cardiology
Department of Cardiology, Hairmyres Hospital,
East Kilbride G75 8RG
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