Safety of CO(2)- and gadodiamide-enhanced angiography for the evaluation and percutaneous treatment of renal artery stenosis in patients with chronic renal insufficiency

OBJECTIVE

The objective of our study was to evaluate the safety of CO(2) and gadodiamide angiography for diagnosing and percutaneously treating renal artery stenosis in patients with chronic renal insufficiency and presumed ischemic nephropathy.

SUBJECTS AND METHODS

One hundred forty-six consecutive patients with chronic renal insufficiency (serum creatinine > 1.5 mg/dL) were examined for renal artery stenosis using CO(2) and gadodiamide as the angiographic contrast agents. If renal artery stenosis was detected, percutaneous balloon angioplasty with or without stenting was performed. In patients for whom 48-hr creatinine levels were available, we performed an analysis to determine the incidence of contrast-involved nephropathy (increase in serum creatinine of 0.5 mg/dL at 48 hr without identifiable cause). Major complications were reported up to 1 week, and mortality was reported up to 30 days after the procedure.

RESULTS

Ninety-five patients had serum creatinine levels available at 48 hr. An increase in creatinine of greater than 0.5 mg/dL at 48 hr occurred in three patients (3.2%), presumably caused by CO(2), by gadodiamide, or by both. Neither diabetes nor the degree of preexisting chronic renal insufficiency was a predictor of worsening renal function 48 hr after the procedure. The volumes of CO(2) and gadodiamide used for diagnostic studies alone versus the volume used for interventional studies was not significantly different (for CO(2), p = 0.09; for gadodiamide, p = 0.30). Eleven major complications occurred in eight patients (5.5%). Two deaths (1.4%) occurred within 30 days. One death was due to cholesterol embolization and the other was not believed to be related to the procedure.

CONCLUSION

Angiography and percutaneous treatment of renal artery stenosis in patients with chronic renal insufficiency and suspected ischemic nephropathy can be performed relatively safely using CO(2) and gadodiamide as angiographic contrast agents without an increased risk of complications. Contrast-induced nephropathy potentially occurred in 3.2% of patients. Neither the degree of underlying renal insufficiency nor diabetes was a risk factor for predicting a greater likelihood of renal function worsening at 48 hr of follow-up. The volumes of CO(2) and gadodiamide used in this study did not result in an increased risk of contrast-involved nephropathy.

New diagnostic inroads in hypertension and atherosclerosis

In the past two to three decades, the practice among hypertension specialists has been to lower blood pressure with the strong assumption that morbidity and mortality would be reduced. This was largely based on large clinical trials done in the 1960s and 1970s that did not include angiotensin-converting enzyme inhibitors or calcium-channel blockers. Performing large clinical trials is expensive and the results often do not apply to individual patients. Until recently, noninvasive methods to monitor end-organ effects of elevated blood pressure and other cardiovascular risk factors were limited. The development of high-resolution ultrasound and evolving magnetic resonance technology will allow early detection of heart and blood vessel changes and will make monitoring of the progression and regression of disease possible. This will allow better selection of treatment programs for each patient.

Elevated serum lipoprotein(a) is a risk factor for clinical recurrence after coronary balloon angioplasty

BACKGROUND

Elevated lipoprotein (Lp) (a) concentrations are associated with coronary artery disease and myocardial infarction. Lp(a) is structurally related to proteins involved in lipid transport, fibrinolysis, coagulation, and cellular mitogenesis and is known to have important physiological interactions with the coagulation and fibrinolytic systems. Because these processes may be important to arterial healing after balloon injury, we hypothesized that elevated Lp(a) concentrations may be associated with recurrence of symptoms and restenosis after balloon angioplasty.

METHODS AND RESULTS

We assessed 240 consecutive patients undergoing coronary balloon angioplasty with measurements of Lp(a), total cholesterol, triglycerides, HDL cholesterol, LDL cholesterol, apolipoprotein A-I, and apolipoprotein B-100 concentrations from fresh specimens. Patients were evaluated 4 to 6 months after angioplasty for clinical recurrence by repeat angiography if angina had returned or by maximal exercise treadmill testing with thallium imaging if patients remained asymptomatic. Ninety-seven patients (40%) had clinical recurrence; 143 (60%) did not. Patients with recurrence had significantly greater Lp(a) concentrations compared with those without (median, 29 versus 14; P < .0001). Each patient quintile stratified by increasing Lp(a) concentrations had incrementally greater recurrence rates ranging from 27% (lowest quintile) to 60% (highest quintile). By multivariate logistic regression analysis, Lp(a) concentration was the only predictor of recurrence (P < .0001). A subset of frozen, stored serum samples showed a significant decrease in measured Lp(a) concentration over time (mean, 605 days; P < .01).

CONCLUSIONS

An elevated Lp(a) concentration was a risk factor for clinical recurrence after percutaneous transluminal balloon coronary angioplasty. Other lipid levels or clinical characteristics were not significantly associated with recurrence. When serum was frozen and stored for a prolonged period, Lp(a) concentration decreased over time.

Assessment of the reliability of the determination of carotid artery lumen sizes by quantitative image processing of magnetic resonance angiograms and images

In order to use MR imaging to assess progression or regression of atherosclerosis, one must have an idea of the reproducibility of the imaging and image processing techniques. The ability of dark-blood MRI and semiautomated image processing to reproducibility measure the inner boundary of the carotid arteries was evaluated and compared with results obtained using bright-blood MRA. MRI and MRA images were obtained for two normal and two diseased volunteers six times each over a short period of time (6 months). The carotid bifurcation was used to align slices from different imaging sessions. The area for each vessel (right and left common, internal and external carotid artery) was determined for the six imaging sessions. The standard deviations of each lumen area normalized to the average area were computed for each vessel segment for each volunteer. For the common, internal, and external carotids, the averaged normalized standard deviations for MRI were 8, 12, and 17% and for MRA were 6, 8, and 13%. Lumen sizes obtained by MRI and MRA were found to be not statistically different. Eccentric plaques not seen on MRA were visualized by MRI. In conclusion, dark-blood MRI with semiautomated image processing yields reliable lumen areas that are in agreement with those obtained by MRA.

Hemodynamic and metabolic correlates of dipyridamole-induced myocardial thallium-201 perfusion abnormalities in multivessel coronary artery disease

The mechanisms responsible for the development of reversible thallium-201 (TI-201) defects with dipyridamole stress in patients with coronary artery disease (CAD) is not well understood. Previous experimental animal studies have demonstrated coronary steal characterized by an absolute decrease in subendocardial flow distal to a stenosis in response to dipyridamole infusion. Accordingly, the purpose of this study was to determine if reversible TI-201 defects in response to dipyridamole infusion are reflective of myocardial ischemia or secondary to regional differences in flow reserve. Dipyridamole (0.56 mg/kg) TI-201 imaging was performed in 23 patients in whom serial electrocardiographic, hemodynamic, aortic and coronary sinus lactate, and coronary sinus adenosine measurements were obtained. All patients with CAD had TI-201 redistribution (3.8 +/- 2.0 defects/patient), and all patients without CAD had normal scans. Mean aortic pressure was similar in both groups and did not change in response to dipyridamole (non-CAD 103 +/- 11 vs CAD 99 +/- 15 mm Hg, p = NS). Pulmonary capillary wedge pressure was similar at baseline (non-CAD 11 +/- 4 vs CAD 13 +/- 5 mm Hg, p = NS) and did not change in response to the drug (non-CAD 14 +/- 3 vs CAD 15 +/- 7 mm Hg, p = NS). Lactate extraction fraction was similar at baseline (non-CAD 0.22 +/- 0.09 vs CAD 0.17 +/- 0.14, p = NS) and decreased similarly in both groups (non-CAD 0.08 +/- 0.06 vs CAD 0.05 +/- 0.12, p = NS).(ABSTRACT TRUNCATED AT 250 WORDS)

Noninvasive quantitative evaluation of atherosclerosis using MRI and image analysis

A new medical image analysis system to quantify atherosclerosis in the lower abdominal aorta using magnetic resonance imaging is described. This medical image analysis and display system permits the quantification of the three-dimensional (3D) properties of the vessel wall and lumen cross-sectional area and volumes. Preliminary results of employing this medical image analysis capability on magnetic resonance images demonstrated a twofold increase in wall volume per unit vessel length, corresponding to intimal thickening, before luminal narrowing was detected. This work demonstrated the feasibility and usefulness of quantitatively evaluating the 3D properties of the vessel lumen and wall by using a combination of magnetic resonance imaging and image analysis. The demonstration that intimal wall thickening is observed in images before observable occlusion of the lumen can be expected to provide an important early indicator of the future development of atherosclerosis. Such capability will permit detailed and quantitative studies to assess the effectiveness of therapies, such as drug, exercise, and dietary regimens.

The precise radioimmunoassay of adenosine: minimization of sample collection artifacts and immunocrossreactivity

Anti-adenosine antibodies were produced in rabbits immunized with N6-carboxymethyladenosine conjugated to methyl albumin. 125I-N6-Aminobenzyladenosine was synthesized and used as a high-specific-activity, high-affinity ligand. A radioimmunoassay (RIA) was developed that can detect 6.25 nM (312.5 fmol) of underivatized adenosine and cross-reacts less than 0.02% with adenine nucleotides and guanosine and not at all with 1 mM inosine. The sensitivity of the RIA can be increased to a detection limit of 0.125 nM (6.25 fmol) by derivitizing samples with benzyl bromide to form N6-benzyladenosine. The assay was adapted to an automated RIA procedure. Assay precision was increased by: (i) inhibiting slight adenosine deaminase activity present in anti-sera; (ii) treating buffers and albumin used in the RIA with charcoal to remove contaminating adenosine; and (iii) correcting for a small but variable component of immunoreactivity not attributable to adenosine. A second antibody prepared with a 2',3'-disuccinyladenosine-albumin conjugate was also found to detect some non-adenosine-mediated immunoreactivity in plasma samples. Immunointerference in human plasma was eliminated in samples treated with ZnSO4/Ba(OH)2 or partially purified over C18 Sep Paks to remove nucleotides and assayed after sample benzylation or succinylation. Human blood was mixed with a novel "stop" solution that was optimized to inhibit adenosine formation from AMP by greater than 99% and to inhibit adenosine uptake into red cells and degradation by greater than 94%. Human plasma/stop solution was assayed by RIA and HPLC with equivalent results.

Improved detection of ischemia-induced increases in coronary sinus adenosine in patients with coronary artery disease

Attempts to monitor coronary sinus adenosine as a clinical marker of myocardial ischemia in humans have been disappointing. Accordingly, procedures have been developed for detecting adenosine in blood collected from the human coronary sinus. Collection involves using a double-lumen metabolic catheter, which allows blood to be mixed with a stop solution at the catheter tip, thereby minimizing adenosine formation and degradation. A five-component stop solution almost completely arrests adenosine formation and degradation. Adenosine analysis is improved by using both boronate and C18 Sep-Pak columns to purify and concentrate adenosine in human plasma before HPLC. Plasma adenosine in the coronary sinus of patients with and without coronary artery disease, measured before and during peak atrial pacing, showed a twofold atrial pacing-induced increase in adenosine in the patients with coronary artery disease (n = 9, P less than 0.001) but no change in the patients with normal epicardial coronary arteries (n = 6). These preliminary results indicate that coronary sinus adenosine may provide an index of myocardial ischemia in patients with coronary artery disease.

Image analysis and quantification of atherosclerosis using MRI

This paper describes an image processing, pattern recognition, and computer graphics system for the noninvasive identification and evaluation of atherosclerosis using multidimensional Magnetic Resonance Imaging (MRI). Particular emphasis has been placed on the problem of developing a pattern recognition system for noninvasively identifying the different plaque classes involved in atherosclerosis using minimal a priori information. This pattern recognition technique involves an extension of the ISODATA clustering algorithm to include an information theoretic criterion (Consistent Akaike Information Criterion) to provide a measure of the fit of the cluster composition at a particular iteration to the actual data. A rapid 3-D display system is also described for the simultaneous display of multiple data classes resulting from the tissue identification process. This work demonstrates the feasibility of developing a "high information content" display which will aid in the diagnosis and analysis of the atherosclerotic disease process. Such capability will permit detailed and quantitative studies to assess the effectiveness of therapies, such as drug, exercise, and dietary regimens.

Radiographic contrast agents and platelet function: a quenched-flow study

Radiographic contrast media (RCM) may alter platelet behavior at concentrations achieved during cardiac angiography. We used quenched-flow aggregometry coupled to single-particle counting to study the influence of RCM on the kinetics of platelet aggregation (less than 5.0 sec) induced by adenosine diphosphate (ADP, 2.86 microM). At a concentration in platelet-rich plasma (PRP) of 5 per cent RCM by volume, platelet aggregation was inhibited by diatrizoate, iopamidol and ioxaglate either directly or following incubation of each contrast agent with PRP for 20 minutes. Diatrizoate inhibited more than did iopamidol or ioxaglate (56 +/- 6, versus 39 +/- 3 and 40 +/- 9 per cent respectively; P less than 0.003, p less than 0.009, n = 20 normal subjects). A small reduction (about 16 per cent) in aggregation velocity occurred within 5 seconds of exposure of PRP to all 3 RCM and the onset time (t) or lag period before aggregation begins was significantly prolonged by diatrizoate (p less than 0.03). The RCM vehicles alone (iodinated moiety removed, osmolality readjusted) had no effect on the ADP-induced aggregation. Platelet counts fell significantly after incubation with diatrizoate (12%; p = 0.04). Our data therefore show that early platelet aggregation was inhibited by 3 commonly-used ionic and nonionic contrast agents. Inhibition was apparently caused by the iodinated contrast molecule, began within seconds of platelet-RCM contact and was independent of vehicle composition. Since diatrizoate inhibited aggregation more than iopamidol or ioxaglate, its use may be of additional value during angiographic procedures in clinical situations involving enhanced platelet activation.

Platelet calcium and quenched-flow aggregation kinetics in essential hypertension

Abnormal platelet function may contribute to the complications of essential hypertension. We have studied the kinetics of platelet aggregation induced by adenosine diphosphate (ADP) or epinephrine, plasma beta-thromboglobulin, and basal, cytosolic, and free calcium, as correlates of platelet function. Fifteen untreated patients with essential hypertension and without detectable atherosclerosis, 18-40 years old, were compared with 30 matched normotensive control subjects. Maximal rates of platelet aggregation (Vmax) with ADP and epinephrine were significantly higher in patients than in control subjects (p less than 0.03), as assessed by quenched-flow aggregometry. However, significance was lost when Vmax was corrected for the platelet count. Paradoxically, the activation constants (Ka) for ADP were higher in patients than in control subjects (p less than 0.03). With ADP as the inducing agent, onset time (t) or lag period before aggregation begins was longer in patients than in control subjects (p less than 0.02). beta-thromboglobulin levels, an index of in vivo platelet activation, were not significantly different between the two groups (p = 0.13). The mean platelet cytosolic free calcium concentration was higher in patients (213 +/- 19 nM) than in control subjects (172 +/- 14 nM), but this difference was not statistically significant (p = 0.07). However, there was a close correlation between the free calcium level and systolic, diastolic, and mean blood pressure (p less than 0.003, p less than 0.04, p less than 0.004, respectively). No difference in platelet volume between the two groups was found. Our data suggest that platelets in the early stages of essential hypertension display an overall increased aggregation potential but a diminished sensitivity to ADP.(ABSTRACT TRUNCATED AT 250 WORDS)

Plasma renin activity and albumin excretion in teenage type I diabetic subjects. A prospective study

Plasma renin activity (PRA) may be high among teenage and young adult insulin-dependent diabetic subjects. Supine PRA and stimulated PRA were therefore measured in 50 female and 50 male diabetic subjects, 13-20 years old, diagnosed before the age of 16. Fifty percent have been restudied after 4.6 +/- 0.2 (mean +/- SEM) years. Initially, 43% had high PRA (supine 4.0 +/- 0.37, stimulated 12.02 +/- 0.8 ng/ml/hr angiotensin I), 45% had normal activity (supine 2.89 +/- 0.26, stimulated 6.47 +/- 0.34 ng/ml/hr/angiotensin I), and 12% had low activity (supine 1.57 +/- 0.05, stimulated 3.09 +/- 0.08 ng/ml/hr/angiotensin I). Levels were directly associated with prepubertal duration of diabetes and were inversely associated with duration of diabetes after onset of puberty but not with total duration or patient age. Within 4.6 +/- 0.2 years the percentage of subjects with high PRA fell to 13%, and the percentage of those with low PRA rose to 35%. Initially 51% of the cohort had normal albumin excretion rates (AER) at rest and during exercise equal to or less than 10 micrograms/min/m2; 32% had elevated rates only during exercise of 39 +/- 5 micrograms/min/m2; 13% had elevated rates at rest of 41 +/- 8 micrograms/min/m2 and during exercise of 116 +/- 21 micrograms/min/m2; and 4% had clinical proteinuria at rest and during each exercise period equal to or greater than 150 micrograms/min/m2. After 5 years, 58% continued to have normal AER, or their AER improved.(ABSTRACT TRUNCATED AT 250 WORDS)

Atrial natriuretic factor in essential hypertension

We measured circulating levels of immunoreactive atrial natriuretic factor (ANF) in 10 patients with untreated, uncomplicated mild to moderate essential hypertension and in 15 normotensive controls. ANF concentrations were significantly higher in the hypertensive group than in the control group (38.4 +/- 6.9 pg/ml versus 18.3 +/- 1.8 pg/ml, p less than 0.02). A positive correlation between ANF levels and systolic, diastolic and mean blood pressure was noted in the total study population (p less than 0.008, r = 0.52; p less than 0.005, r = 0.55; p less than 0.02, r = 0.46, respectively). Thus, plasma ANF concentrations are elevated in essential hypertension and may result from increased intraarterial pressure.

High-resolution 1H NMR spectral signature from human atheroma

Coronary artery disease due to atherosclerosis takes the lives of approximately 550,000 Americans each year--an enormous toll. Put in economic terms, the cost to the United States alone has been estimated to exceed 60 billion dollars annually. We have found that well-resolved proton (1H) NMR spectra can be obtained from human atheroma (fatty plaque), despite its macroscopic solid appearance. The fraction of the total spectral intensity corresponding to the sharp 1H NMR signals is temperature dependent and approaches unity at body temperature (37 degrees C). Studies of the total lipids extracted from atheroma and cholesteryl esters were conducted to identify the chemical and physical origin of the spectral signature. The samples were characterized through assignment of their chemical shifts and by measurement of their T1 and T2 relaxation times as a function of magnetic field strength. The results suggest that the relatively sharp 1H NMR signals from human atheroma (excluding water) are due to a mixture of cholesteryl esters, whose liquid-crystalline to isotropic fluid phase transition is near body temperature. Preliminary applications to NMR imaging of human atheroma are reported, which demonstrate early fatty plaque formation within the wall of the aorta. These findings offer a basis for noninvasive imaging by NMR to monitor early and potentially reversible stages of human atherogenesis.

Identification and 3-D quantification of atherosclerosis using magnetic resonance imaging

Cardiovascular disease due to atherosclerosis is a leading cause of death in the United States as well as other developed countries. This paper describes the development of image processing, pattern recognition, and graphical display techniques to non-invasively quantify the atherosclerotic disease process using magnetic resonance imaging (MRI). We have demonstrated the ability to identify the soft tissue classes of (1) normal, smooth muscle wall, (2) fatty plaque, (3) complex, fibrous plaque, and (4) calcified plaque. The objective of this work has been to combine functional information, such as plaque tissue type, with structural information, represented by 3-D display of vessel structure, into a single composite display. The results of this work provide a "high information content" display which will aid in the diagnosis and analysis of the atherosclerotic disease process, and permit detailed and quantitative studies to assess the effectiveness of therapies (e.g. changes in diet, exercise and drug administration).

High-resolution proton NMR spectra of human arterial plaque

Well-resolved proton (1H) NMR spectra of solid human arterial plaque can be acquired. Studies have been carried out of human fatty plaque obtained postmortem (ex vivo), the total lipids extracted from human atheroma, and a model mixture of cholesteryl esters whose lipid composition resembles that of human atheroma. In each case, well-resolved 1H NMR spectra were obtained at body temperature (37 degrees C), with little or no underlying broad signal. Such sharp 1H NMR spectra are typical of isotropic fluids, whereas solid and liquid-crystalline materials give rise to much broader spectral lines. The results suggest the sharp 1H NMR spectra of human atheromatous lesions at body temperature are due largely to the presence of intracellular and extracellular droplets of cholesteryl esters in the isotropic liquid phase. These findings provide a necessary basis for use of 1H NMR techniques to image quantitatively the lipid constituents of human atheroma in vivo, and to study their chemical and physical properties.

Limitation of deuterium labelled methoximes as internal standards in the mass spectral analysis of prostaglandins

A reported method for the preparation of d3-methoxime derivatives as internal standards for prostaglandin assays by gas chromatography-mass spectrometry was evaluated. Sample derivatization resulted in 1.5-86% exchange of the d3-methoxime in a series of prostaglandins. Exchange was minimal when the methoxime was on the 5-membered ring; whereas, acyclic methoximes exhibited extensive exchange. Induced strain energy due to the steric interaction of the hydroxyl group and the C13-C20 alkyl side chain with the gem-dimethoxylamine transition state is offered as an explanation for the unusual stability of PGE2. The use of 18O exchange of the carboxylic acid function is presented as an alternative for the preparation of unavailable labelled eicosanoids.

Enalapril maleate versus captopril. A comparison of the hormonal and antihypertensive effects

24 hypertensive patients were randomised into 2 groups to compare the antihypertensive effects of enalapril and captopril over a 10-week period. In the hydrochlorothiazide run-in period, blood pressure was reduced from 171 +/- 4/109 +/- 1mm Hg to 160 +/- 4/103 +/- 1mm Hg (p less than 0.05). Angiotensin-converting enzyme (ACE) inhibition decreased blood pressure to 132 +/- 3/87 +/- 2mm Hg. Captopril decreased diastolic blood pressure significantly more after 3 hours than enalapril (-24 versus -17mm Hg, p less than 0.05). After 10 weeks of therapy, this antihypertensive response was maintained at 134 +/- 3/83 +/- 1mm Hg. There was no difference between the captopril and enalapril treated groups. Acute and chronic responses of plasma renin activity, plasma aldosterone and ACE were determined. There was an acute positive correlation between the rise in plasma renin activity and the fall in blood pressures with captopril but not with enalapril. With chronic treatment there was no difference in the ability of either of the 2 drugs to reduce blood pressure, inhibit ACE, reduce aldosterone or stimulate plasma renin activity.

The dopamine agonist bromocriptine induces hypotension by venous and arteriolar dilation

Acute bromocriptine administration reduced sitting and standing blood pressure and produced severe orthostatic hypotension in 12 normal subjects. Concomitantly, there was an increase in venous distensibility and basal blood flow, and a decrease in peripheral vascular resistance, as determined by forearm plethysmography. After administration of bromocriptine, plasma norepinephrine concentration decreased. Bromocriptine lowers blood pressure by dilating arterioles and veins, at least in part by means of dopaminergic inhibition of sympathetic nervous system activity.

Dilation of forearm blood vessels after angiotensin-converting-enzyme inhibition by captopril in hypertensive patients

In eight hypertensive patients, forearm vascular tone was assessed by water plethysmography following inhibition of angiotensin II-converting-enzyme (ACE) activity with captopril. Acute captopril administration increased venous distensibility (VV30) and decreased forearm vascular resistance (FVR), while it lowered systemic blood pressure (BP). Alpha-one adrenergic receptor blockade by prazosin did not prevent captopril from decreasing vascular tone or lowering blood pressure (BP). Thus, captopril dilated both veins and arterioles. The primary mechanism of captopril's acute antihypertensive action did not involve inhibition of alpha1-adrenergic receptor activity. Moreover, captopril and prazosin together produced a greater reduction in BP and peripheral resistance than occurred with either agent alone.

Effects of percutaneous transluminal angioplasty on renal plasma flow

Percutaneous transluminal angioplasty is being used with increasing frequency for the treatment of renal artery stenosis. Several noninvasive techniques that utilize radioactive tracers have been used for monitoring the effects of angioplasty and progression of disease. Forty-one patients were studied before and after renal angioplasty by using renograms and fractionated measurements of effect renal plasma flow. Although there were striking examples of improvement in effective renal plasma flow following angioplasty, this was not a consistent finding. There was a tendency for effective renal plasma flow to revert to the baseline level on follow-up studies. Cure of hypertension was more likely in patients without renal insufficiency and in patients with shorter periods of sustained hypertension. Fractionated effective renal plasma flow studies did not reliably differentiate patients who were cured from those who were improved nor were we able to delineate clearly those requiring repeat dilatation. Nevertheless, this technique is useful for noninvasively measuring fractionated renal function in the immediate postoperative or postdilatation recovery period and for detecting the difference between occlusion of the renal artery and transient renal insufficiency due to contrast material. Also, long-term measurement of fractionated function has value in following potential progression of the basic disease process.

Relation of therapeutic response to nifedipine to coronary anatomy and motion of S-T segment during unstable angina pectoris

Of 77 patients hospitalized for unstable angina pectoris and failure of oral, dermal, or intravenous nitrates and/or beta blockade, 81 percent with negligible or single-vessel disease and 55 percent with two- or three-vessel disease showed response (p less than 0.05) to nifedipine therapy. Patients with either S-T elevation or no change during pain responded better (31 of 45) than those with any S-T depression (16 of 32; p less than 0.05). Patients with negligible or single-vessel disease had a higher prevalence of S-T elevation (13 of 16) than patients with two- or three-vessel disease (15 of 31; p = 0.004). S-T motion did not predict response in patients with two- or three-vessel disease, but did predict response in patients with negligible or single-vessel disease. On follow-up study at 9 +/- 8 (range one to 33) months, 39 of 42 who had shown response were free from pain. Three died from infarction without unstable angina. (range one to 33) months, 39 of 42 who had shown response were free from pain. Three died from infarction without unstable angina. Five who showed response had elective bypass surgery. The addition of nifedipine abolished or reduced pain episodes by more than 50 percent in 61 percent of patients with refractory unstable angina pectoris. Patients with negligible or single-vessel disease with S-T elevation benefit most. In patients with two- or three-vessel disease, the type of S-T motion did not predict response. Follow-up of all those with response indicated sustained amelioration by nifedipine therapy. Failure of nifedipine therapy should not be accepted until a dose of 120 mg per day has been achieved, or until intolerable side effects appear.

Measurement of plasma prostaglandin E2 using capillary gas chromatography negative ion chemical ionization mass spectrometry

A stable isotope dilution assay for the measurement of plasma prostaglandin E2 (PGE2) employing capillary column gas chromatography-negative ion chemical ionization mass spectrometry (GC-NICIMS) is described. PGE2 was extracted from plasma using C18 and silica SEP-PAKS. Further purification and separation was accomplished by thin layer chromatography. The prostaglandin was analyzed as its pentafluorobenzyl ester-methoxime-trimethyl-silyl ether, using fragment ions at m/e 524 (protium) and m/e 528 (deuterium) for quantitation. The mean plasma concentration of PGE2 determined in 8 healthy volunteers was 2.8 +/- 2.0 pg/ml.

Percutaneous transluminal angioplasty: the treatment of choice for renovascular hypertension due to fibromuscular dysplasia

Twenty-three renal artery stenoses in 21 hypertensive patients, caused by fibromuscular dysplasia, were treated with percutaneous transluminal angioplasty (PTA). Follow-up over a period of 1 to 30 months, including angiography, renal vein renin assay, and radionuclide flow studies, was performed in 8 patients, each with one stenosis. Dilatation was initially successful in all cases and was successfully repeated in 1 case. The mean systolic pressure decreased by 61.81 mm Hg and the mean diastolic pressure by 36.28 mm Hg in response to treatment. Thirteen patients were cured, 8 were felt to have better control of blood pressure on medication, and there was no failures. This study demonstrates that PTA is a clinically effective method of treating renovascular hypertension due to fibromuscular dysplasia.

Left ventricular mural thrombus in a patient with thrombocytosis and agnogenic myeloid metaplasia

The two factors responsible for the development of left ventricular mural thrombi are endocardial injury secondary to old or recent anterior myocardial infarction and left ventricular dysfunction. Endothelial damage also is thought to be the initial event in the development of arterial thrombi. However, arterial thrombi may develop in patients with thrombocytosis secondary to myeloproliferative disorders in the absence of endothelial injury. A patient had thrombocytosis secondary to agnogenic myeloid metaplasia and a left ventricular mural thrombus developed in the absence of clinical or laboratory evidence of old or coronary angiogram and left ventricular function. To our knowledge, this is the first such case reported.

Acute and chronic intrarenal alpha- and beta- adrenergic receptor stimulation of renin release in the conscious dog

The effect of continuous intrarenal infusion of norepinephrine, isoproterenol, and methoxamine on renin release was studied in the uninephrectomized conscious dog. Chronic intrarenal infusion of norepinephrine produced a biphasic curve of plasma renin activity (PRA) and a sustained 25 mm Hg increase in mean arterial pressure (MAP). The initial increase in PRA peaked at 3 hours, after which PRA returned to control levels. Alpha- or beta-adrenergic antagonists did not attenuate the initial rise in PRA. The PRA increased again after 48 hours of chronic intrarenal norepinephrine infusion and remained elevated thereafter. The second rise in PRA was increased by 30% with alpha-adrenergic blockade. Chronic intrarenal isoproterenol administration produced a similar increase in PRA, which peaked at 3-5 hours and then returned to control levels. In contrast to norepinephrine, chronic isoproterenol administration did not result in a second increase in PRA. At the end of the chronic isoproterenol infusion period, beta-adrenergic receptor refractoriness was demonstrated, as PRA did not increase significantly in response to a fourfold increase in the dose of isoproterenol. An increase in PRA was produced by acute intrarenal infusion of methoxamine. This increase in PRA was blocked by phentolamine, suggesting a vascular alpha-adrenergic receptor-mediated release of renin.

Percutaneous transluminal angioplasty in patients with renal artery stenosis: follow-up studies

Fifty renal artery stenoses in 38 hypertensive patients were treated with percutaneous transluminal angioplasty. Follow-up over a period of 1 to 24 months (mean, 9 mo.), including angiography, renal vein renin determinations, and radionuclide flow studies, were performed in 24 patients (32 stenoses). The initial dilatation was successful in 90% of stenoses and redilatation was necessary in 22% with a success rate of 84%. The mean systolic pressure decreased by 65.83 mm Hg and the mean diastolic pressure by 35.88 mm Hg in response to the treatment. Sixteen patients were cured, 18 were felt to have better control of blood pressure on medication, and 4 were not helped. Percutaneous transluminal angioplasty appears to be a technically feasible and clinically effective method of treating renovascular hypertension.

Percutaneous transluminal dilatation of the renal arteries: techniques and results

The techniques and results of percutaneous transluminal angioplasty (TPA) of the renal arteries were evaluated in 20 hypertensive patients with 25 renal artery stenoses. Follow-up angiograms have been obtained in nine patients. Many patients had evidence of both essential and angiotensinogenic hypertension. Eleven patients had evidence of severe diffuse atherosclerotic disease, and nine patients had evidence of renal insufficiency. The mean systolic pressures before and after PTA were 203.80 and 150.30, respectively. The mean diastolic pressures before and after PTA were 117.45 and 85.95, respectively. Ten patients were cured. Six patients with long histories of hypertension and a recent increase in blood pressure were classified as having blood pressure easier to control with antihypertensive medication following PTA. Three patients failed to respond to PTA, and one patient was a technical failure. The advantages of this technique include avoidance of general anesthesia and a major surgical procedure, decreased cost, and a shortened hospital stay. The technique can be easily repeated if necessary, and future surgical intervention is not precluded if the method is unsuccessful.

Ischemic cardiovascular complications concurrent with administration of captopril. A clinical note

Administration of potent vasodepressor agents such as the angiotensin converting enzyme inhibitor, captopril, may precipitate myocardial ischemic events in patients with coronary artery disease, particularly if this treatment is preceded by a discontinuation of beta-blocking drugs such as propranolol. In one case studied, a patient experienced three episodes of angina pectoris under these conditions; in another, acute anterior myocardial infarction was suspect.

Identification and differentiation of surgically correctable hypertension due to primary aldosteronism

During a protocol study for the evaluation of patients with primary aldosteronism, a variety of diagnostic studies were employed in an attempt to identify patients with primary aldosteronism and to differentiate patients with adrenal adenoma from patients with idiopathic adrenal hyperplasia. In this study, we are able to demonstrate the utility of (1) absent postural increase in plasma aldosterone concentration, (2) adrenal scanning and (3) normalization of blood pressure with spironolactone therapy in identifying patients with primary aldosterone excess who have an adrenal adenoma, surgical removal of which results in eliminating their hypertension.

Hemodialysis-resistant hypertension: control with an orally active inhibitor of angiotensin-converting enzyme

In two patients with end stage renal disease and dialysis-resistant hypertension, the orally active inhibitor of angiotensin-converting enzyme, captopril (SQ14,225; 2-D-methyl-3-mercaptopropranoyl-L-proline, dramatically lowered blood pressure both before and during dialysis. This agent holds promise as an alternate to bilateral nephrectomy in such patients.

Activity of [des-aspartyl1]-angiotensin II in primary aldosteronism

This study describes the effects of [des-Aspartyl(1)]-angiotensin II ([des-Asp]-AII) on blood pressure and aldosterone production in patients with primary aldosteronism due to aldosterone-producing adrenal adenoma (APA) and idiopathic adrenal hyperplasia (IHA), and in normotensive control subjects. 10 patients with primary aldosteronism, 7 with APA and 3 with IHA, and 6 normotensive control subjects were placed on a constant 150-meq sodium diet for 4 days. [des-Asp]-AII was infused for 30 min at 6, 12, and 18 pmol/kg per min. Three groups of patients were identified on the basis of aldosterone response to [des-Asp]-AII. Group I, composed of normotensive control subjects, showed incremental increases in plasma aldosterone concentration from 6+/-1 to 14+/-3 ng/100 ml (P < 0.01) with [des-Asp]-AII infusion. Group II, composed of patients with primary aldosteronism, showed incremental increases in plasma aldosterone concentration from 33+/-8 to 65+/-13 ng/100 ml (P < 0.05) with 12 pmol/kg per min of [des-Asp]-AII. Group III, also composed of patients with primary aldosteronism, showed no increase of plasma aldosterone concentration with [des-Asp]-AII. Groups I and II showed similar percentage increases in plasma aldosterone concentration (P = NS). Group III showed significantly lower aldosterone responses than group I (P < 0.01). Group II included all patients with IHA and two patients with APA. Group III included only patients with APA. The blood pressure responses to [des-Asp]-AII of subjects in group I did not differ significantly from those of groups II or III.Thus, patients with IHA and a subgroup of patients with APA showed responsiveness to [des-Asp]-AII which was limited to adrenal cortical stimulation of aldosterone biosynthesis. This suggests that adrenal responsiveness to angiotensin is a major control mechanism in some forms of primary aldosteronism. The differential adrenal responsiveness to [des-Asp]-AII in patients with APA indicates either that there are two distinct subpopulations of APA, or that alteration in tumor response to angiotensin occurs during the natural progression of the disease history.

The immediate pressor effect of saralasin in man

An immediate pressor response to [Sar1-Ala8]-angiotensin II (saralasin) is described in all of 16 hypertensive subjects. Blood pressure rose within 1-3 min, peaked at 4-6 min, then returned toward baseline. Plasma norepinephrine and dopamine beta-hydroxylase activity were unchanged by saralasin, indicating that the pressor response is not mediated by saralasin-induced catecholamine release. Ten normal renin hypertensives had diastolic pressor responses of 19.4 +/- 3.3 mm Hg. After 5 weeks of diuretic therapy, the diastolic pressor responses to saralasin were decreased to 4.9 +/- 2.4 mm Hg. Six low renin hypertensives had diastolic pressor responses of 26.2 +/- 6.2 mm Hg, but 5 weeks of diuretic therapy did not decrease these pressor responses significantly. In two normal and two low renin hypertensives, the diastolic blood pressure rose to levels greater than 150 mm Hg. The amplitudes of the immediate pressor responses were inversely correlated with the base-line plasma renin activities, r = -0.46. The data support the concept that the agonist activity of saralasin occurs at the angiotensin II vascular receptor level with clinical expression mediated by sodium and/or volume changes.

Activity of (des-Aspartyl1)-angiotensin II and angiotensin II in man. Differences in blood pressure and adrenocortical response during normal and low sodium intake

This study was designed to compare the effect of [des-Aspartyl(1)]-angiotensin II ([des-Asp]-A II) and angiotensin II (A II) on blood pressure and aldosterone production in man under conditions of normal and low sodium (Na) intake. Seven normal male subjects in balance on constant normal Na intake (U(Na) V 160.3+/-5.0 meq/24 h) for 5 days received A II and [des-Asp]-A II infusions on two consecutive days; 1 mo later they were restudied after 5 days of low Na intake (U(Na) V 10.5+/-1.6 meq/24 h). Each dose was infused for 30 min, sequentially. During normal Na intake, [des-Asp]-A II from 2 to 18 pmol/kg per min increased mean blood pressure from 85.2+/-3 to 95.3+/-5 mm Hg and plasma aldosterone concentration from 5.2+/-1.1 to 14.3+/-1.9 ng/100 ml. During low Na intake, the same dose of [des-Asp]-A II increased mean blood pressure from 83.7+/-3 to 86.7+/-3 mm Hg and plasma aldosterone concentration from 34.4+/-6.0 to 51.0+/-8.2 ng/100 ml. In contrast, A II from 2 to 6 pmol/kg per min during normal Na intake increased mean blood pressure from 83.3+/-4 to 102.3+/-4 mm Hg and plasma aldosterone concentration from 7.0+/-2.2 to 26.8+/-2.0 ng/100 ml; during low Na intake, A II increased mean blood pressure from 83.0+/-3 to 96.0+/-4 mm Hg and plasma aldosterone concentration from 42.0+/-9.7 to 102.2+/-15.4 ng/100 ml. A II and [des-Asp]-A II were equally effective in suppressing renin release. Plasma cortisol and Na and K concentration did not change. The effects of two doses (2 and 6 pmol/kg per min) of each peptide on blood pressure and aldosterone production were evaluated. During normal Na intake, [des-Asp]-A II had 11-36% of the pressor activity and 15-30% of the steroidogenic activity of A II. Na deprivation attenuated the pressor response and sensitized the adrenal cortex to both peptides, but the increase in steroidogenesis was greater with [des-Asp]-A II than with A II. The dose-response curves for [des-Asp]-A II with respect to blood pressure and aldosterone production were not parallel, and although no maximum was established for A II, [des-Asp]-A II was less efficacious.In summary, (a) [des-Asp]-A II has biologic activity in man, (b) [des-Asp]-A II is less efficacious than A II in stimulating aldosterone production, (c) Na deprivation sensitizes the adrenal cortex more markedly to [des-Asp]-A II than A II, and (d) dose-response curves for the two peptides differ, suggesting the possibility that they act at different receptor sites in vascular smooth muscle and the adrenal cortex.

Clinical experience with saralasin infusion in hypertensive patients

Renal arteriography gives a reliable anatomic delineation of the renal vasculature. However, the presence of renal arterial disease does not determine the physiologic significance of the lesion. The intravenous infusion of saralasin, a specific angiotensin II antagonist, has been investigated as a method for identifying patients with hypertension dependent upon excessive angiotensin II activity. Correlations between the blood pressure response to saralasin infusion, peripheral and differential renal vein plasma renin levels and renal angiography have been obtained in 35 hypertensive patients. The results suggest that a hypotensive response to saralasin infusion provides an adjunct to renin determinations for recognizing angiotensinogenic renovascular hypertension. However, false negative responses to saralasin occur. The reasons for these negative responses need to be determined before saralasin infusion can be employed as the sole screening test for renovascular hypertension.

Production of sustained hypertension by chronic intrarenal norepinephrine infusion in conscious dogs

The purpose of this study was to determine whether increased sympathetic nervous system activity with proportionally greater stimulation to the kidney could result in sustained hypertension. This was simulated by continuous intrarenal norepinephrine infusion. Effects of chronic infusion of norepinephrine (0.285 microng/kg per min) into the renal artery and inferior vena cava were compared in uniephrectomized conscious dogs. Ten days of intrarenal norepinephrine infusion produced a sustained rise in mean arterial pressure (25 mm Hg), and a 32-mEg positive sodium balance occurred. Inferior vena caval infusion caused a transient rise, lasting 24 hours, in mean arterial pressure which was associated with a 54-mEq natriuresis. With renal artery infusion, peripheral plasma renin activity rose from 1.0 +/- 00.2 to 4.4 +/- 0.8 ng angiotensin I/ml per hour at 1 hour (P less than 0.002) and fell to 1.4 +/- 0.4 at 24 hours (not significant). Inferior vena caval infusion produced a similar result. [Sar1,ala8]angiotensin II (6 MICrong/kg per min) produced no significant change in arterial blood pressure. (alpha-Adrenergic blockade with phentolamine normalized the blood pressure. Renal plasma flow was chronically decreased by about 25% in dogs given intrarenal norepinephrine; no significant change in glomerular filtration rate occurred. The cardiac output decreased from a control of 7.2 +/- 0.6 to 4.8 +/- 0.1 liters/min (P less than 0.01) and total peripheral resistance was increased from a control of 13 +/- 1 to 26 +/- 1 resistance units (RU) (P less than 0.0005) in dogs given intrarenal norepinephrine. The data indicate that chronic intrarenal infusion of norepinephrine in uninephrectomized conscious dogs results in sustained hypertension characterized by decreased renal plasma flow, normal glomerular filtration rate, positive sodium balance, and increased total peripheral resistance due to norepinephrine-dependent vasoconstriction.

Intrarenal renin-angiotensin-sodium interdependent mechanism controlling postclamp renal artery pressure and renin release in the conscious dog with chronic one-kidney Goldblatt hypertension

We studied postclamp renal artery pressure and renin release in eight conscious dogs with one-kidney Goldblatt hypertension. On normal sodium intake, intrarenal blockade of angiotensin II with Sar1-Ala8-angiotension II (P-113, saralasin acetate) markedly decreased postclamp renal artery pressure and increased renin release during the first 5 days after renal artery constriction. We found that 10-14 days after renal artery constriction, the maintenance of postclamp renal artery pressure and negative feedback on renin release became markedly less dependent on angiotensin II, as shown by almost no change in postclamp renal pressure or renin release with intrarenal blockade of angiotensin II. At this stage of our study the dogs were given a sodium diet of less than 5 mEq/day and we found that within 5-10 days intrarenal blockade of angiotensin II once again markedly decreased postclamp renal artery pressure and increased renin release. These observations support the concept of an angiotensin II-sodium interdependent negative feedback mechanism for renin release.

Effect of intrarenal angiotensin II blockade on renal function in conscious dogs

The effects of intrarenal infusion of 1-sar-8-ala angiotension II (P 113) and a converting enzyme inhibitor, SQ 20881, at doses that did not affect systemic blood pressure (2.0 mug/kg per min) were studied in conscious, uninephrectomized dogs. In dogs receiving approximately equal to 5 mEq/day of sodium, intrarenal infusion of P 113 increased renal blood flow (RBF) from 219.8 +/- 32.3 to 282.7 +/- 20.0 ml/min (P less than 0.004), and with intrarenal SQ 20881 infusion from 215.3 +/- 14.2 to 278.0 +/- 22.2 ml/min (p less than 0.005). In sodium-restricted dogs (approximately equal to 5 mEq/day), glomerular filtration rate (GFR) also increased with intrarenal P 113 infusion from 57.9 +/- 5.7 to 66.3 +/- 6.6 ml/min (P less than 0.05), and with SQ 20881 infusion from 43.1 +/- 2.1 to 55.7 +/- 4.5 ml/min (P less than 0.01). Dogs on approximately equal to 5 mEq/day of sodium showed significant increases in plasma renin activity (PRA) with intrarenal infusion of the peptides, unmasking a negative feedback inhibition of renin release by angiotensin II. No increases in RBF, GFR, or PRA were seen with infusion without inhibitors, or in dogs give P 113 or SQ 20881 while on approximately equal to 80 mEq/day of sodium. In addition, angiotensin II inhibition increased sodium excretion during sodium restriction. These findings suggest that intrarenal angiotensin II is intimately involved in renal responses to sodium restriction which result in conservation of sodium and water.

The Charlottesville Blood-Pressure Survey. Value of repeated blood-pressure measurements

The population of a community of 29,608 adults was screened door-to-door for elevated blood pressure. Of 12,371 adults screened, 20% were classified as hypertensive. After repeated blood-pressure measurement, however, there were only 9% with sustained hypertension, while 11% had labile hypertension. Sixty percent of the cases of sustained hypertension had been either undiagnosed, untreated, or inadequately treated. Eighty-two percent who initially were unaware of hypertension had labile hypertension after repeated blood-pressure measurement, and 18% were unaware of having, sustained hypertension. Labile hypertension was most prevalent in the young and decreased with age. In contrast, sustained hypertension was least prevalent in the young and increased with age. Labile hypertension was most prevalent in white men, and sustained hypertension was more prevalent in blacks than in whites. Labile hypertension represents a large segment (52%) of the population initially identified as having hypertension in a home blood-pressure survey.