Magnetic resonance angiography versus duplex sonography for diagnosing renovascular disease.
Noninvasive testing for renovascular disease is required to identify patients who may benefit from revascularization procedures without exposing an unnecessary amount of patients to the risks of catheter angiography. All available methods of diagnosing renal artery stenosis have significant limitations. We compared a new technique, contrast-enhanced magnetic resonance angiography, with an established technique, duplex ultrasonography, for the detection of renal artery stenosis using catheter angiography as the standard of reference. Eighty-nine patients with clinically suspected renovascular disease underwent duplex renal scanning and contrast-enhanced magnetic resonance angiography. Sixty of these also underwent catheter angiography. All studies were interpreted for the presence of renal artery stenosis blinded to the results of the other imaging modalities. For detection of hemodynamically significant (>/=60% diameter reduction) main renal artery stenosis, sensitivity and specificity were 90% and 86%, respectively, for magnetic resonance angiography and 81% and 87% for duplex sonography. Most false readings involved differential grading of stenoses detected with all 3 techniques. When patients with fibromuscular dysplasia were excluded from the analysis, the sensitivity of magnetic resonance angiography increased to 97%, with a negative predictive value of 98%. Magnetic resonance angiography detected 96% and duplex 5% of accessory renal arteries seen at catheter angiography. Contrast-enhanced magnetic resonance angiography is a useful technique for diagnosing atherosclerotic renovascular disease. It overcomes the major limitations of duplex renal scanning. However, duplex has the advantage of providing hemodynamic information and appears better suited for the assessment of patients with suspected fibromuscular dysplasia. (+info)
Kidney aminopeptidase A and hypertension, part II: effects of angiotensin II.
Aminopeptidase A (APA) is the principal enzyme that metabolizes angiotensin II (Ang II) to angiotensin III. Previously, we showed that kidney APA was elevated in spontaneously hypertensive rats and was reduced after angiotensin-converting enzyme inhibition. In the present study, we sought to determine whether kidney APA expression was altered after chronically elevated Ang II, either exogenously delivered via osmotic minipumps or endogenously produced in two-kidney, one clip (2K1C) hypertensive rats. Ang II (200 ng. kg-1. min-1) was infused subcutaneously for 1 or 2 weeks by osmotic minipumps, and 2K1C rats were tested 4 weeks after unilateral renal artery clipping. Blood pressure was not significantly elevated in the Ang II-infused animals but was significantly increased at 3 and 4 weeks in the 2K1C animals. APA was significantly elevated approximately 2-fold in kidney cortical membranes from Ang II-infused animals but was decreased 45% in the clipped kidney and 18% in the nonclipped kidneys from 2K1C animals. Isolated glomeruli from Ang II-infused animals and the nonclipped kidneys from 2K1C animals had markedly higher APA activity and immunoreactivity. Likewise, histochemical and immunohistochemical studies indicated that APA levels were increased in glomeruli from angiotensin-infused animals and in both nonclipped and clipped kidneys from 2K1C animals. In contrast, tubular APA was decreased in tubular elements from 2K1C animals, most markedly in the clipped kidneys. Thus, despite the increase in glomerular APA expression in kidneys from 2K1C animals, the decrease in tubular APA expression is more extensive and accounts for the measured reduction in total APA in cortical homogenates. Because clipped kidneys are not exposed to high blood pressure, these results suggest that glomerular APA expression is positively regulated and tubular APA negatively regulated by Ang II. These results further suggest that changes in kidney APA expression could influence the progression of angiotensin-dependent hypertension. (+info)
Epidermal growth factor: a potent vasoconstrictor in experimental hypertension.
We have tested the hypothesis that growth factor signaling pathways are augmented in hypertension, a disease associated with vascular smooth muscle cell growth. Thoracic aorta was dissected from deoxycorticosterone acetate-salt (DOCA-salt) and one kidney, one clip (1K, 1C) hypertensive rats and from sham normotensive rats for use in isolated tissue bath experiments. Systolic blood pressure was significantly higher in DOCA-salt and 1K, 1C than in normotensive sham rats: 192 +/- 7, 185 +/- 10, and 117 +/- 4 mmHg, respectively. Although virtually no contraction to epidermal growth factor (EGF) was observed in endothelium-denuded sham rat aorta [1 +/- 1% phenylephrine (PE) (10 micromol/l)-induced contraction], the maximal EGF-induced contraction was 45 +/- 7% in endothelium-denuded aorta from DOCA-salt hypertensive rats and 39 +/- 7% in aorta from 1K, 1C rats. Although slightly attenuated, a contraction to EGF was still observed in endothelium-intact aortic strips from 28-day DOCA-salt hypertensive rats. We also conducted concentration-response curves to EGF on days 1, 3, 5, 7, 14, and 21 of DOCA-salt therapy. A significant contraction to EGF in aorta from DOCA-salt rats was observed on day 14, when DOCA-salt rats had significantly higher blood pressure than sham rats: 188 +/- 6 and 122 +/- 3 mmHg, respectively. Transforming growth factor-alpha, an agonist of the EGF receptor, contracted DOCA-salt rat aorta (30 +/- 7% PE-induced contraction) but not sham aorta (3 +/- 3%). The EGF receptor tyrosine kinase inhibitor 4,5-dianilinophthalimide (10 micromol/l), the mitogen-activated protein kinase kinase inhibitor PD-098059 (10 micromol/l), and the L-type voltage-gated calcium channel inhibitor diltiazem (1 mol/l), but not the cyclooxygenase inhibitor indomethacin (10 micromol/l), virtually abolished EGF-induced contraction (85, 98, and 99% reduction, respectively). These data support a striking difference in EGF signaling between normotensive and hypertensive animals. Furthermore, they provide evidence that growth factors should be considered vasoconstrictors as well as growth modulators in hypertension. (+info)
Effects of praeruptorine C on the intracellular free calcium in normal and hypertrophied rat ventricular myocytes.
AIM: To study the intracellular free calcium ([Ca2+]i) in normal and hypertrophic left ventricular myocytes isolated from adult rat hearts and the effects of praeruptorine C (Pra-C) on them. METHODS: [Ca2+]i of single myocyte was measured with Fura 2-AM. RESULTS: The resting [Ca2+]i was 87 +/- 4 nmol.L-1 in normal left ventricular myocytes, 123 +/- 7 nmol.L-1 in hypertrophied myocytes. After exposure to KCl (20, 40, and 60 mmol.L-1), the [Ca2+]i were increased by 66%, 141%, and 268% in normal myocytes, and 77%, 185%, and 243% in hypertrophic myocytes, respectively. Pra-C (1, 10, and 100 mumol.L-1) concentration-dependently inhibited the [Ca2+]i elevation caused by KCl (35 mmol.L-1) or norepinephrine (20 mumol.L-1) in both normal and hypertrophied myocytes. All of the effects of Pra-C were similar to that of nifedipine. CONCLUSION: [Ca2+]i of hypertrophied myocytes was higher than that of normal ones and Pra-C decrease the [Ca2+]i elevation in left ventricular myocytes resulted from its calcium channel blockade. (+info)
Hypotensive response to captopril: a potential pitfall of scintigraphic assessment for renal artery stenosis.
A characteristic pattern seen on captopril renography is described that is due to systemic hypotensive response. Most patients with these findings on captopril renography do not receive renal artery angiograms in our clinic because it is usually recognized. However, this pattern has received little attention in the medical literature and may be misinterpreted as being due to physiologically significant renal artery hypertension. METHODS: Over the last 3 y, renal artery angiograms were performed on three patients with systemic hypotensive response pattern on captopril renography. This allowed a unique opportunity to correlate the results of the captopril renogram with the renal artery angiograms in this patient population. Captopril renography was performed with a glomerular filtration agent, diethylenetriamine pentaacetic acid (DTPA), and a tubular agent, o-iodohipurate (OIH). RESULTS: Renal artery angiograms showed no evidence of renal artery stenosis in three patients with systemic hypotensive response pattern on captopril renography. Systemic hypotension on captopril renograms results in preserved uptake of both DTPA and OIH and hyperconcentration in the cortex and collecting system. CONCLUSION: The systemic hypotensive response pattern seen on captopril renography is a distinctive pattern that does not represent physiologically significant renal artery stenosis. (+info)
Value of captopril renal scintigraphy in hypertensive patients with renal failure.
The aims of this study were to show the value of captopril renal scintigraphy for detecting a renovascular cause in hypertensive patients with renal failure and to assess the ability to predict the beneficial effect of revascularization on renal function. METHODS: Thirty-eight patients with renal failure (mean glomerular filtration rate = 35 mL/min) underwent renal scintigraphy after injection of 99mTc-mercaptoacetyltriglycine. Baseline scintigraphy was performed, and the test was repeated 24 h later after oral administration of 50 mg captopril given 60 min before the test. RESULTS: In 5 of 6 patients with a renovascular cause for renal failure, and 2 of 3 patients with a probable arterial pathology, scintigraphy had a high probability. The result was indeterminate in the other 2 patients. In 5 of 11 patients with negative arteriography and 14 of 18 patients with probable absence of renovascular pathology, we found a low probability of functional renal artery stenosis. Six revascularization procedures were performed and were predictive of a beneficial effect in 5 patients. Time of peak activity was an effective predictor in each case. CONCLUSION: In hypertensive patients with renal failure, captopril renal scintigraphy can detect hemodynamic dysfunction downstream from a renal artery stenosis and can predict the beneficial effect of revascularization in some cases. (+info)
Renal artery stenosis treated with stent deployment: indications, technique, and outcome for 108 patients.
From January 1993 to May 1996, 108 patients (64 men, 44 women; mean age, 72 years; age range, 37 to 87 years) underwent 125 percutaneous transluminal angioplasties and stent implantations primarily for atherosclerotic lesions of the renal artery. Sixty-four patients underwent treatment for renovascular hypertension (two antihypertensive medications or more), 32 patients underwent treatment for a combination of hypertension and renal failure (serum creatinine level >/=1.6 mg/dL), and a small group of six patients (5%) without hypertension or diminished renal function underwent treatment to prevent the progression to renal artery occlusion and kidney loss. Thirty-three patients (31%) had renovascular hypertension that was classified as severe on three or more medications, 31 patients (29%) had renovascular hypertension that was classified as moderate on two medications, and 38 patients (35%) had renovascular hypertension that was classified in the mild group on a single antihypertensive agent. Stenotic lesions were located at the ostium of the renal artery in 82 cases (65%) and were ostial-adjacent (<5 mm from renal ostium) in the other 43 cases (34%). A total of 125 stents were deployed in 125 arteries (procedural success 97.6%). Renovascular hypertension either was cured or was improved in 73 patients (68%), with 14 patients (13%) considered cured (normotensive on no medications). The conditions of 29 patients (27%) were unchanged, and 6 patients (5%) had worsening hypertension after surgery. We were unable to demonstrate a statistically significant improvement in serum creatinine levels after renal artery balloon angioplasty/stenting. Complications occurred in a total of nine cases (7.2%), six of which were related to technical problems. One patient had worsening renal insufficiency caused by contrast agent, and another patient had a perinephric hematoma develop that necessitated evacuation. There were four postoperative deaths (30-day mortality). Two of these deaths were caused by postoperative myocardial infarction. The other two patients had progressive renal failure develop that necessitated dialysis. These patients later died of the disease process despite supportive care. Follow-up renal artery duplex scan studies and angiograms were available on 96 patients (76%). The mean peak systolic renal/aortic ratio on duplex scanning was 2.2. Life-table analysis yielded a 74% primary patency rate and an 85% secondary patency rate at 36 months. This retrospective analysis showed the effectiveness of combining percutaneous transluminal angioplasty with stent deployment for significant renal artery stenosis to treat renovascular hypertension. (+info)
Chronic ETA receptor blockade attenuates cardiac hypertrophy independently of blood pressure effects in renovascular hypertensive rats.
In isolated cardiac myocytes, the direct effects of angiotensin II on cellular growth and gene expression were shown to be mediated by endothelin via the endothelin subtype A (ETA) receptor. To determine whether this pathway is also involved in the cardiovascular adaptations to a chronic activation of the renin-angiotensin system in vivo, the effects of a selective ETA receptor antagonist (LU 127043) were investigated in adult rats with renal artery stenosis. Four groups of rats (n=107) were studied over a period of 10 days after surgery: (1) sham-operated animals with saline administration, (2) rats subjected to left renal artery clipping with saline administration, (3) sham-operated rats with LU 127043 administration, and (4) rats subjected to left renal artery clipping with LU 127043 administration. LU 127043 (50 mg/kg) or saline was given by gavage twice daily starting 1 day before the operation. In clipped rats with saline administration, plasma renin activity, the ratio of left ventricular weight to body weight, and mRNAs for beta-myosin heavy chain and atrial natriuretic peptide were significantly elevated as early as 2 days after surgery. Blood pressure started to rise on the third postoperative day and attained a steady state hypertensive level by day 6. Blockade of ETA receptors had no effects on plasma renin activity or the time course of hypertension in clipped animals but completely prevented left ventricular hypertrophy and the re-expression of the beta-myosin heavy chain and atrial natriuretic peptide genes on day 2. While the expressions of the beta-myosin heavy chain and atrial natriuretic peptide genes were not different from saline-treated, clipped animals after day 4, the development of left ventricular hypertrophy remained markedly blunted (-50%) during ETA receptor blockade until day 10. These results show that a continuous blockade of ETA receptors significantly attenuates the development of left ventricular hypertrophy and, more transiently, fetal gene expression in the early phase of renovascular hypertension. Since neither blood pressure nor the increase in plasma renin activity was significantly altered by ETA receptor blockade, the inhibitory influences of the ETA receptor antagonist on left ventricular hypertrophy and gene expression were mediated most likely through a direct blockade of myocardial ETA receptors. (+info)