Biomedical subjects
Publications and source records attributed to C T Postma.
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OBJECTIVE: To investigate methods to diagnose renal artery stenosis (RAS) among the general hypertensive population. METHODS: We studied the value of clinical and biochemical characteristics at the outpatient clinic to identify subjects with a renal artery narrowing of more than 50% of the luminal surface among 1047 hypertensive patients. Included in the analysis were: blood pressure, age, sex, body mass index, endogeneous creatinine clearance, smoking and plasma renin activity. RESULTS: Among the 1047 patients, 355 were selected for angiography. In this subgroup 104 patients (29%) had RAS. The subjects with RAS had significantly higher diastolic and systolic blood pressures than did those without stenosis. Forward stepwise logistical regression analysis showed that systolic blood pressure, stimulated plasma renin activity and smoking were the most predictive independent screening variables for the presence of RAS. Yet, none of these characteristics or their combinations were sufficiently sensitive to distinguish reliably between patients with essential hypertension and those with RAS. Sytolic blood pressure > 160 mmHg or diastolic blood pressure > 100 mmHg on automatic (Dinamap) recording as criteria selected a subgroup of patients with a RAS prevalence of 30%. CONCLUSIONS: By using blood pressure screening criteria a subgroup of hypertensive patients with a high prevalence of RAS can be formed in whom further invasive tests for RAS are indicated and efficient.
BACKGROUND: Recent studies have reported elevated prostaglandin levels in patients with renal artery stenosis and hypertension. To investigate whether a distinction between essential hypertension and hypertension with renal artery stenosis is possible by measuring eicosanoid excretion, we studied the excretion of these compounds in patients with essential hypertension and in hypertensives with concomitant renal artery stenosis. METHODS: The 24-h urinary excretion of metabolites of prostaglandin I2, prostaglandin E2 and metabolites of thromboxane A2 was sampled under standardised conditions, in 15 patients with essential hypertension and in 15 patients with unilateral renal artery stenosis with hypertension. Also clinical and biochemical characteristics of the subjects were analysed. RESULTS: The patients with renal artery stenosis had significantly lower excretion of prostaglandin I2 than did the essential hypertensive patients. However, the overlap in the values was large, thus not allowing a diagnostic differentiation according to urinary prostaglandin I2 levels. The excretion of prostaglandin E2 and of metabolites of thromboxane A2 showed no significant differences among the groups. CONCLUSIONS: Measurement of urinary prostaglandin or prostaglandin metabolite excretion did not contribute to the non-invasive detection of the presence of a renal artery stenosis in the patients in this study.
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The diagnostic accuracy of Doppler ultrasound in the detection of renal arterial disease has been assessed in a prospective study of 61 hypertensive patients. The findings of Doppler ultrasound were compared with the results of renal angiography. In 15 patients (24.5%) no accurate Doppler signs could be obtained and the Doppler ultrasound examination was considered a technical failure. Of the remaining 46 patients, 24 had renal artery stenosis. Nine of the stenoses were not detected by Doppler ultrasound and in three patients a false positive diagnosis of renal artery stenosis was made. The sensitivity of Doppler ultrasound was 62.5%, the specificity 86.4% and the overall diagnostic accuracy was 73.9%. By comparing the 15 patients in whom Doppler ultrasound failed with the 46 in whom it was successful, age appeared to be higher and creatinine clearance lower in the failure group. By comparing the 34 patients with true positive and true negative results with the 12 patients with false results, no significant differences were found. In a multivariate analysis, higher age showed a significant relation to failure of Doppler ultrasound. Doppler ultrasound has limited value in the screening of hypertensive patients for renal artery stenosis.
We have studied prospectively the acute blood pressure lowering effect on an oral dose of captopril, 25 mg in 240 hypertensive patients. The mean relative reduction of systolic and diastolic BP was 16 and 15% respectively and the mean time to the mean arterial pressure nadir was 59 minutes. Systolic BP fell by more than 30% in 4.6% of patients and diastolic BP and mean arterial pressure dropped by more than 30% in 4.2 and 3.3% of patients respectively. Patients over 60 years of age showed a significantly larger fall in systolic and diastolic BP. Patients with renal artery stenosis reached the BP nadir in a significantly shorter time compared with patients with essential hypertension (50.5 vs. 59.7 minutes, P less than 0.05) and showed a significantly larger fall in systolic BP (20.7 vs. 15.4%, P less than 0.05). A forward stepwise regression analysis showed that only baseline plasma renin activity had a significant relation to the fall in BP (P less than 0.01, R = 0.57). We conclude that according to our definition of a greater than 30% decrease of the mean arterial pressure, a first dose hypotension after captopril was seen in 3.3% of 240 patients. Captopril treatment should be introduced carefully since not all those patients at risk of hypotension can be identified in advance.
The aim of this study was to investigate whether caffeine stimulates selectively renal vein renin levels at the side of unilateral stenosis in patients with renovascular hypertension. In this study seven of the involved patients had renal arterial stenosis and four had no stenosis. Four of the seven patients with a stenosis had retrospectively-proven renovascular hypertension. Renal vein renin sampling was performed before and after intravenous administration of caffeine. Caffeine did not induce any consistent effect on plasma renin activity in the renal veins, either on the stenotic side or on the contralateral side in patients with renovascular hypertension. There were no consistent caffeine mediated changes in systemic plasma renin activity.
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The aim of this study was to evaluate tests predicting renovascular hypertension. This was done by relating the results of renal vein renin tests, the captopril test, and renal scintigraphic tests to the blood pressure outcome 12 months after relief of renal artery stenosis by percutaneous transluminal renal angioplasty in 31 patients. Cure was seen in eight (26%). Improved blood pressure was obtained in 12 patients (39%), and in 11 patients (35%), the result for blood pressure was a failure. The accuracies of the two mathematical models used to analyze the renal vein renin assays were 44% and 60%. The captopril test showed a sensitivity of 36% and an accuracy of 43%. Renal captopril technetium Tc 99m-labeled pentetic acid scintigraphy gave a sensitivity of 60%. Stepwise logistic regression analysis of clinical variables in relation to blood pressure response revealed age as the only factor significantly related to blood pressure outcome. We conclude that the tests used are unfit for helping select patients for percutaneous transluminal renal angioplasty and that age may have an important influence on outcome.
A number of reports share the conclusion that the captopril test is an adequate screening procedure for the detection of renovascular disease among hypertensive patients. Therefore, we prospectively studied the value of this test in 149 consecutive hypertensive patients. The test was considered positive if plasma renin activity, after an oral dose of 25 mg of captopril, rose by more then 4.44 ng.L-1.s-1 (16.0 ng/mL per hour). The sensitivity of the test was 39%, the specificity was 96%, the positive predictive value was 81%, and the negative predictive value was 79%. No clinically important cutoff point identifying patients with renal artery stenosis could be detected in the values of baseline and stimulated plasma renin activity nor in baseline blood pressure or changes after captopril testing. The low sensitivity makes the captopril test unfit to be used as a screening procedure in an unselected hypertensive population.
In a group of 269 untreated hypertensive patients the effect of a single oral dose of captopril (25 mg) on blood pressure was studied for 90-120 minutes. The systolic blood pressure decreased by more than 20% in 9.5% and by more than 30% in 1.1% of the patients. In 22.6% the diastolic blood pressure decreased by more than 20%; in 4.5% it fell more than 30%. The calculated mean arterial pressure (MAP) was reduced by more than 20% in 12.3% of the patients and by more than 30% in 3%. Three patients showed transient neurological deficits. Factors related to a strong blood pressure drop were: renal artery disease and resistant hypertension. However, a potentially dangerous fall in blood pressure, i.e. an acute fall of MAP of over 30%, was also observed in the absence of these risk factors. Therefore not all patients at risk can be identified in advance, and treatment with ACE-inhibitors has to be started under well-controlled circumstances especially in elderly patients.
In 78 patients we studied retrospectively the occurrence of occlusion in unilateral renal artery stenosis during antihypertensive drug treatment. Complete occlusion occurred in 14 patients (18%). In a multivariate analysis the following characteristics were included: blood pressure, aetiology of the stenosis, serum creatinine, the degree of the stenosis, anti-hypertensive medication, standing renal vein renin ratio and age. In this analysis the combination of a diuretic and an ACE-inhibitor, during the observation period, showed an independent relation to the development of an occlusion (P less than 0.05). Also the ACE-inhibitor alone showed a relation (P = 0.06). In the 14 patients who developed an occlusion only three showed a significant rise in serum creatinine. We conclude that special attention should be given to the follow-up of patients with renal artery stenosis who have ACE-inhibitors in their treatment regimen, especially when in combination with a diuretic.
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Explore the source record for details and available documents.
Explore the source record for details and available documents.
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BACKGROUND: Atherosclerotic renal artery stenosis (ARAS) is associated with progressive loss of renal function and is one of the most important causes of renal failure in the elderly. Current treatment includes restoration of the renal arterial lumen by endovascular stent placement. However, this treatment only affects damage caused by ARAS due to the stenosis and ensuing post-stenotic ischemia. ARAS patients have severe general vascular disease. Atherosclerosis and hypertension can also damage the kidney parenchyma causing renal failure. Medical treatment focuses on the latter. Lipid-lowering drugs (statins) could reduce renal failure progression and could reduce the overall high cardiovascular risk. The additional effect on preserving renal function of stent placement as compared to medical therapy alone is unknown. Therefore, the STAR-study aims to compare the effects of renal artery stent placement together with medication vs. medication alone on renal function in ARAS patients. METHOD: Patients with an ARAS of > or = 50% and renal failure (creatinine (Cr) clearance < 80 mL/min/1.73 m2) are randomly assigned to stent placement with medication or to medication alone. Medication consists of statins, anti-hypertensive drugs and antiplatelet therapy. Patients are followed for 2 yrs with extended follow-up to 5 yrs. The primary outcome of this study is a reduction in Cr clearance > 20% compared to baseline. This trial will include 140 patients.