A prospective study of carbon dioxide-digital subtraction vs standard contrast arteriography in the evaluation of the renal arteries

Renal denervation using carbon dioxide renal angiography in patients with uncontrolled hypertension and moderate to severe chronic kidney disease

Background

Chronic kidney disease (CKD) is the most common cause of secondary hypertension. More than half of the patients have uncontrolled hypertension (≥140/90 mmHg on three or more antihypertensive agents at optimum doses). Renal sympathetic denervation (RSDN) has been shown to reduce blood pressure (BP) in patients with resistant hypertension. Although patients with CKD have high sympathetic drive, all major clinical trials have excluded patients with estimated glomerular filtration rates (eGFRs) <45 mL/min/1.73m² for risk of contrast-induced nephropathy.

Methods

In this pilot study, carbon dioxide (CO₂) was used as the sole contrast agent to carry out renal angiography and RSDN in patients with moderate to severe CKD (eGFR 15–44 mL/min/1.73m²) and uncontrolled hypertension.

Results

Eleven patients (eight males) underwent RSDN. The median age was 57 years [interquartile range (IQR) 49–66]. The median number of antihypertensives being taken at baseline was 4 (IQR 3–4). No statistically significant difference was observed in serum creatinine in the serial follow-ups until at 6 months[median difference 0.25 mg/dL (IQR 0.09–0.53); P = 0.008]. There was a non-significant reduction in median clinic BP from baseline to 6 months [−14 mmHg (IQR −24–5)] and a significant increase in daytime ambulatory systolic BP [7 mmHg (IQR −2–12); P= 0.045]. A trend towards a serial reduction in albuminuria was observed. Procedure-related complications included a groin haematoma (n = 1) and reported flank (n = 1) and groin pain (n = 1).

Conclusions

This pilot study shows that CO₂ renal angiography can be used to perform RSDN in patients with significant renal impairment and may lead to associated improvements in clinic BP and albuminuria.

Percutaneous Endovascular Therapy of Renal Artery Stenosis: Technical and Clinical Developments in the past Decade

Renal artery stenosis may initiate or exacerbate arterial hypertension and/or renal insufficiency. During the last decade, technical improvements of diagnostic and interventional endovascular tools have led to more widespread use of endoluminal renal artery revascularization and broader indications for this type of therapy. Since the first renal artery angioplasties performed by Felix Mahler and Andreas Grüntzig in 1978, numerous single-center studies have documented the benefits of percutaneous renal revascularization. In the early 1990s, stent implantation was added to the interventionist's armamentarium for treating renal artery stenosis due to atherosclerosis or fibromuscular dysplasia. The metaanalysis of 3 randomized studies comparing balloon angioplasty with best medical therapy found intervention to be beneficial for blood pressure control but not for preservation of renal function. Despite the absence of randomized studies, there is mounting evidence that stenting of hemodynamically relevant atherosclerotic renal artery stenosis has a positive impact on blood pressure control and renal function. This article summarizes the technical improvements in these endovascular tools during the last decade and gives an overview concerning their clinical impact on renal artery revascularization.

Contrast-Induced Acute Kidney Injury in Patients Undergoing Carotid Artery Stenting: An Underestimated Issue

Carotid artery stenting (CAS) is increasingly offered to patients with carotid artery stenosis. Although CAS is a less invasive (and thus more attractive) alternative compared with carotid endarterectomy, it requires the use of contrast material. A possible side effect from the use of contrast material during CAS is the development of contrast-induced acute kidney injury (CI-AKI). This review discusses the incidence/prevalence and clinical significance of CI-AKI developing after CAS. We also discuss possible measures to reduce the incidence of CI-AKI after CAS.

Renal artery stenosis

Fibromuscular dysplasia (FMD) and aortoarteritis are the most frequent causes of secondary hypertension induced by renal artery stenosis (RAS). Revascularization of this disease entity usually cures arterial hypertension. Demographic evolution leads to an increasing incidence of atherosclerotic RAS, one of the major causes of end-stage renal failure. Furthermore, atherosclerotic RAS leads to deterioration of primary hypertension, progression of atherosclerosis manifestation such as occlusive and aneurysmatic peripheral artery disease, and chronic or acute organ damage such as left ventricular hypertrophy and recurrent flash pulmonary edema. Despite the lack of sufficiently powered randomized controlled trials, each hemodynamically relevant RAS (eg, > or = 70%) should be considered for stent angioplasty in patients without end-stage ischemic nephropathy or limited life expectancy due to concomitant disease (eg, cancer). Drug-eluting stents will probably reduce the overall low in-stent restenosis rate of 10% to 20%. Interventions in patients with dialysis-dependent end-stage nephropathy are left to appropriate clinical study protocols.

Carbon dioxide digital subtraction angiography-assisted endovascular aortic aneurysm repair in the azotemic patient

OBJECTIVE

This report analyzes the safety and efficacy of carbon dioxide digital subtraction angiography (CO(2)-DSA) for EVAR in a group of patients with renal insufficiency compared with a concurrent group of patients with normal renal function undergoing EVAR with iodinated contrast angiography (ICA).

METHODS

Between 2003 and 2005, 100 consecutive patients who underwent EVAR using ICA, CO(2)-DSA, or both were retrospectively reviewed, and preoperative, intraoperative, postoperative, and follow-up variables were collected. Patients were divided into two groups depending on renal function and contrast used. Group I comprised patients with normal renal function in whom ICA was used exclusively, and group II patients had a serum creatinine >or=1.5 mg/dL, and CO(2)-DSA was used preferentially and supplemented with ICA, when necessary. The two groups were compared for the outcomes of successful graft placement, renal function, endoleak type, and frequency, and the need for graft revision. Comparisons were made using chi(2) analysis, Student t test, and the Fisher exact test.

RESULTS

A total of 84 EVARs were performed in group I and 16 in group II. Patient demographics and risk factors were similar between groups with the exception of serum creatinine, which was significantly increased in group II (1.8 mg/dL vs 1.0 mg/dL P < .0005). All 100 endografts were successfully implanted. Patients in group II had longer fluoroscopy times, longer operative times, and increased radiation exposure, and 13 of 16 patients required supplemental ICA. Mean iodinated contrast use was 27 mL for group II vs 148 mL in group I (P < .0005). Mean postoperative serum creatinine was unchanged from baseline, and 30-day morbidity was similar for both groups. No patient required dialysis. No patients died. Perioperatively, and at 1 and 6 months, the endoleak type and incidence and need for endograft revision was no different between groups.

CONCLUSIONS

CO(2)-DSA is safe, can be used to guide EVAR, and provides outcomes similar to ICA-guided EVAR. CO2-DSA protects renal function in the azotemic patient by lessening the need for iodinated contrast and associated nephrotoxicity, but with the tradeoff of longer fluoroscopy and operating room times and increased radiation exposure.

Contrast medium use

Various properties of iodinated contrast media (osmolality, ionic versus nonionic, and viscosity) may contribute to contrast-induced nephropathy (CIN). Therefore, the choice of contrast medium affects the risk for CIN. There is good evidence that low-osmolar contrast media are less nephrotoxic than high-osmolar contrast media in patients at increased risk for CIN who receive intra-arterial iodinated contrast. Current evidence suggests that nonionic isosmolar contrast presents the lowest risk for CIN in patients with chronic kidney disease (CKD), particularly in those patients with diabetes mellitus. Intra-arterial administration of contrast media may be associated with a greater risk for CIN above that observed with intravenous administration. The use of gadolinium or CO(2) as alternative contrast media to avoid the risk of nephrotoxicity cannot be substantiated by clinical trials and therefore cannot be recommended. Most studies show that, within a class, higher volumes (>100 mL) of iodinated contrast medium are associated with a higher risk for CIN. However, in patients at high risk, such as those with CKD and diabetes, even small volumes of contrast medium can have adverse effects on renal function.

Atherosclerotic renal artery stenosis and renovascular hypertension: clinical diagnosis and indications for revascularization

Atherosclerotic renal artery stenosis (RAS) is relatively common and often associated with reversible hypertension, progressive renal insufficiency, and/or coronary-independent pulmonary edema. Not all RAS is associated with renovascular hypertension. Historical and physical findings may suggest renovascular hypertension and warrant investigation for RAS. Noninvasive diagnostic imaging options include renal artery duplex ultrasonography, magnetic resonance angiography, computed tomographic angiography, and CO2 angiography, with each method having its own advantages and limitations. Functional tests of renal flow, which characterize RAS significance, include captopril-stimulated plasma renin activity and captopril renography. To date, no single approach has shown clear superiority either in diagnosis or identification of patients most likely to benefit from revascularization. Revascularization of RAS is recommended for severe/drug-refractory hypertension, preservation of renal function, recurrent flash pulmonary edema, or recurrent severe heart failure. Intervention response is variable, but the ongoing Cardiovascular Outcomes in Renal Atherosclerotic Lesions (CORAL) trial, comparing medical therapy with and without stenting, should provide management guidance.

Renal artery stenosis: epidemiology, clinical manifestation, and percutaneous endovascular therapy

Renal artery stenosis may cause or deteriorate arterial hypertension and/or renal insufficiency. Technical improvements of diagnostic and interventional endovascular tools have lead to a more widespread use of endoluminal renal artery revascularization and extension of the indications for this type of therapy. Since the first renal artery angioplasties performed by Felix Mahler and Andreas Grüntzig in 1978, numerous single-center studies have reported the beneficial effect of percutaneous transluminal renal angioplasty, and since the early 1990's stenting of renal artery stenosis caused either by atherosclerosis or by fibromuscular dysplasia. This article summarizes the impact of technical improvements of endovascular tools on interventional techniques during the last decade and gives an overview concerning the clinical impact of renal artery revascularization. Despite the absence of sufficient randomized studies, there is nonetheless evidence that stenting of hemodynamically relevant atherosclerotic renal artery stenosis has an impact on blood pressure control, renal function, and left ventricular hypertrophy.

Percutaneous endovascular therapy of renal artery stenosis: technical and clinical developments in the past decade

Renal artery stenosis may initiate or exacerbate arterial hypertension and/or renal insufficiency. During the last decade, technical improvements of diagnostic and interventional endovascular tools have led to more widespread use of endoluminal renal artery revascularization and broader indications for this type of therapy. Since the first renal artery angioplasties performed by Felix Mahler and Andreas Gruntzig in 1978, numerous single-center studies have documented the benefits of percutaneous renal revascularization. In the early 1990s, stent implantation was added to the interventionist's armamentarium for treating renal artery stenosis due to atherosclerosis or fibromuscular dysplasia. The meta-analysis of 3 randomized studies comparing balloon angioplasty with best medical therapy found intervention to be beneficial for blood pressure control but not for preservation of renal function. Despite the absence of randomized studies, there is mounting evidence that stenting of hemodynamically relevant atherosclerotic renal artery stenosis has a positive impact on blood pressure control and renal function. This article summarizes the technical improvements in these endovascular tools during the last decade and gives an overview concerning their clinical impact on renal artery revascularization.

Estudo angiográfico de fístula arteriovenosa utilizando gás carbônico como meio de contrante

OBJETIVO: Este estudo tem por finalidade obter um método diagnóstico angiográfico alternativo que possa ser utilizado em doentes com alto risco ao uso de meio de contraste iodado. MATERIAIS E MÉTODOS: Foram estudados 26 doentes com insuficiência renal crônica, que tiveram suas fístulas analisadas, submetidos à angiografia digital - na primeira fase, utilizando o meio de contraste iodado e, na segunda fase, gás carbônico como meio de contraste, com registro em filme angiográfico. A angiografia foi avaliada por dois médicos independentes, que analisaram a opacificação, o diagnóstico radiológico e o calibre dos vasos; a análise comparativa das medidas da artéria, da veia e da freqüência respiratória antes e após a injeção de contraste foi realizada pelo autor. RESULTADOS: Os resultados obtidos pela analise estatística utilizando coeficiente kappa apresentaram concordância entre os dois médicos, referente à opacificação, de 0,3217, referente ao diagnóstico radiológico, de 0,5583, e referente à analise de calibre dos vasos, de 0,4298. A análise das medidas da artéria e da veia não apresentou diferença significativa pela medida de posição e dispersão, mostrando concordância na regressão linear, com p-valor de 0,3657 e de 0,2041; para a freqüência respiratória, as análises das medidas de posição e dispersão não apresentaram diferença significativa. CONCLUSÃO: Concluímos ser este método uma alternativa no estudo angiográfico em pacientes com antecedente alérgico ou com risco nefrotóxico.

Current endovascular management of atherosclerotic renal artery stenosis

The recent advances in stent technology and renal endovascular management have provided a technically reproducible method of percutaneously treating atherosclerotic renal artery stenosis (RAS). In many centers, this has resulted in endovascular management being the primary therapy for atherosclerotic RAS. Although still controversial, it appears that endovascular management of RAS by primay stent deployment provides better blood pressure control than that afforded by best medical management. The impact on renal function is less than that found for hypertension, but there is evidence to suggest that the use of protection devices and primary stenting may enhance renal function outcomes. Whether the ultimate benefit of enhanced survival follows remains an important question and should be the subject of future prospective studies.

Comparison of carbon dioxide and iodinated contrast for cavography prior to inferior vena cava filter placement

BACKGROUND

The use of iodinated contrast in the critically ill trauma patient has been associated with the development of acute renal failure. The low incidence of nephrotoxicity associated with carbon dioxide (CO(2)) makes it an ideal contrast agent for cavography. However, the use of CO(2) has been limited, because reportedly it underestimates the diameter of the inferior vena cava (IVC).

METHODS

During a 6-month period (January 2000 through June 2000), 25 adult trauma patients required IVC filter placement. Bedside cavagrams using CO(2) followed by iodinated contrast were employed to determine the diameter of the IVC and the anatomy of the renal veins.

RESULTS

Using CO(2) injection for cavography, we were able to determine the diameter of the IVC and the anatomy of the renal veins in all patients. Furthermore, when CO(2) cavography was compared with the results obtained with iodinated contrast, the difference in diameter of the IVC was within 1 mm.

CONCLUSIONS

Based on these data, it was determined that CO(2) cavagrams accurately reflect the diameter of the IVC and the anatomy of the renal veins. Additionally, CO(2) cavagrams can be safely performed in the intensive care unit during bedside placement of IVC filters.

Demonstration of renal arterial anatomy and tumour neovascularity for vascular mapping of renal cell carcinoma: the value of CO2 angiography

The aim of this study was to compare the efficacy of CO(2) angiography with that of iodinated contrast angiography for vascular mapping prior to partial nephrectomy for presumed renal cell carcinoma. 13 consecutive patients were studied and all patients underwent selective renal angiography using both CO(2) and iodinated contrast medium. Digitally subtracted images were acquired and compared. Seven male and six female patients, with a median age of 58 years (range 46-74 years), were examined. On comparing images the main renal artery was visualized in all cases with both contrast agents. The segmental vessels were seen in 7 of 13 CO(2) studies and 12 of 13 iodinated contrast studies. CO(2) was also inferior in the depiction of tumour circulation, showing it in 4 of 13 cases compared with 9 of 13 cases using iodinated contrast. It therefore appears that CO(2) angiography offers no diagnostic advantage and is also inferior to iodinated contrast angiography in the pre-operative vascular mapping of renal tumours.

Neurotoxicity of angiographic carbon dioxide in the cerebral vasculature

RATIONALE AND OBJECTIVES

This study was undertaken to resolve conflicting evidence about the neurotoxicity of carbon dioxide gas as an angiographic contrast medium within the cerebral vasculature.

MATERIALS AND METHODS

Single intracarotid injections or five consecutive intracarotid injections, at 2-minute intervals, of carbon dioxide, iopromide or saline, were given to 32 rabbits under clinically relevant conditions. Extravasation of Evans blue and Tc-pertechnetate was used to determine blood-brain barrier damage at 30 minutes or 6 hours after injection. At 6 hours after multiple injections, brains were removed for histologic examination.

RESULTS

A single intracarotid injection of carbon dioxide caused minimal blood-brain barrier breakdown, whereas multiple injections caused significant breakdown that was still present at 6 hours after the injections. All carbon dioxide-injected brains that underwent histologic examination showed evidence of irreversible brain damage in the injected hemisphere.

CONCLUSIONS

The study confirms the neurotoxicity of carbon dioxide within the cerebral vasculature and its unsuitability for clinical use in cerebral angiography.

Magnetic resonance angiography for the diagnosis of renal artery stenosis: a meta-analysis

AIM

To review the published literature comparing the diagnostic accuracy of magnetic resonance angiography (MRA) with and without gadolinium in diagnosing renal artery stenosis, using catheter angiography as reference.

MATERIALS AND METHODS

A meta-analysis was performed of English language articles identified by computer search using PubMed/MEDLINE, followed by extensive bibliography review from 1985 to May 2001. Inclusion criteria were: (1) blinded comparison with catheter angiography; (2)indication for MRA stated; (3) clear descriptions of imaging techniques; and (4) interval between MRA and catheter angiography < 3 months and only the largest of all studies from one centre was selected in the analysis.

RESULTS

A total of 39 studies were identified, of which 25 met the inclusion criteria. The number of patients included in the meta-analysis was 998: 499 with non-enhanced MRA and 499 with gadolinium-enhanced MRA. The sensitivity and specificity of non-enhanced MRA were 94% (95% CI: 90-97%) and 85% (95% CI: 82-87%), respectively. For gadolinium-enhanced MRA sensitivity was 97% (95% CI: 93-98%) and specificity was 93% (95% CI: 91-95%). Thus, specificity and positive predictive value were significantly better for gadolinium-enhanced MRA (P < 0.001). Accessory renal arteries were depicted better by gadolinium-enhanced MRA (82%; 95% CI: 75-87%) than non-gadolinium MRA (49%; 95% CI: 42-60%) (P < 0.001).

CONCLUSIONS

Gadolinium-enhanced MRA may replace arteriography in most patients with suspected renal artery stenosis, and has major advantages in that it is non-invasive, avoids ionizing radiation and uses a non-nephrotoxic contrast agent.

Accuracy of CO(2) angiography in vessel diameter assessment: a comparative study of CO(2) versus iodinated contrast material in a porcine model

PURPOSE

To compare, with use of intravascular ultrasound (IVUS) as an internal reference standard in a porcine model, arterial diameters measured from arteriograms obtained with use of CO(2) to those obtained with use of iodinated contrast material (ICM).

MATERIALS AND METHODS

In nine pigs, digital subtraction angiograms (DSAs) were obtained in the aorta and iliac arteries to compare vessel diameters measured with use of CO(2) to those measured with use of ICM. These measurements were divided by measurements made with use of intravascular ultrasound (IVUS) to yield a DSA/IVUS ratio. Differences between ICM and CO(2) were compared with analysis of variance to assess the effect of location (aorta vs iliac), contrast material used (ICM vs CO(2)), and position (posteroanterior, right anterior oblique, or left anterior oblique). Secondary analysis compared measurements of dependent and nondependent iliac arteries and compared the use of hand-injected CO(2) to that of CO(2) injected by an injector.

RESULTS

The DSA/IVUS ratio was 70.7% +/- 4.4% with ICM use and 69.6% +/- 6.3% with CO(2) use, which did not represent a significant difference (P =.311). Animal position had no effect (P =.477). Underestimation was worse in the iliac arteries than in the aorta (67.4% +/- 1.5% vs 71.4% +/- 1.7%; P =.038). There was no difference in nondependent (P =.163) arteries, but CO(2) underestimated dependent iliac artery size more than ICM did (66.3% +/- 4.8% vs 70.3% +/- 5.4%; P =.051). Vessel diameter was underestimated more with the CO(2) injector than with hand-injected CO(2) (64.3% +/- 2.3% vs 71.7% +/- 1.7%; P <.0001).

CONCLUSION

There is no difference in diameter underestimation between CO(2) and ICM in this animal model. Hand-injection of CO(2) causes less underestimation of vessel diameter than does the CO(2) injector.

Carbon dioxide angiography for endovascular grafting in high-risk patients with infrarenal abdominal aortic aneurysms

Allergic reactions to contrast media, preexisting renal dysfunction, and hyperthyroidism are relative contraindications for angiography with conventional contrast medium. Carbon dioxide (CO(2)) angiography is an alternative method in high-risk patients because CO(2) is nontoxic, without allergic potential, and not iodic. CO(2)-related complications are extremely rare. Because renal insufficiency often occurs in vascular patients, this method will become increasingly important for endovascular surgery. We report on three consecutive patients with asymptomatic infrarenal aortic aneurysm and concomitant renal dysfunction or allergic reactions to standard contrast media. Aortic stent grafts were deployed under CO(2) angiographic control without complications or worsening of renal function.

Accuracy of CO2 angiography in vessel diameter assessment: a comparative study of CO2 versus iodinated contrast material in an aortoiliac flow model

PURPOSE

Precise vessel sizing prior to endovascular intervention is critical to achievement of technical success. Diameter measurements obtained with CO2 and iodinated contrast material in an aortoiliac flow model were compared.

MATERIALS AND METHODS

Aortoiliac flow was simulated in a compliant, silicone elastomer phantom of the aortoiliac system using an autoperfusion pump (flow volume, approximately 1100 mL/min; mean arterial pressure, 70-80 mm Hg at 80-90 cycles/minute) and a glycerol solution (40% by weight; viscosity 3.7 centipoise at 20 degrees C). Digital subtraction angiography was performed with the phantom in the anteroposterior (AP) plane and in three oblique planes with both CO2 and iodinated contrast material. Five sets of images for both CO2 and iodinated contrast material were obtained for each projection. Two readers independently performed vessel diameter measurements at seven sites (distal abdominal aorta, bilateral proximal and distal common iliac, and mid-external iliac arteries). The model was then evaluated with intravascular ultrasound (IVUS) using a 20-MHz imaging catheter. Actual diameter measurements were taken from the inner wall to inner wall in orthogonal planes at the same locations within the model, as described previously. Analysis was performed to determine local difference in measurements (t tests), difference when compared to the standard AP projection with iodinated contrast material (Dunnett's test) and inter-reader variability (Pitman's test).

RESULTS

The contralateral iliac vessel segment did not opacify when imaging with CO2 in the 45 degrees obliquities; thus, 22 of 28 sites were available for comparison. At 18 of 22 (81.8%) sites, there was significant difference in vessel measurements (P < .01), with CO2 yielding a significantly larger diameter at 17 of 22 (77.3%) of the sites. The difference in mean diameter ranged from -1.28 to 4.47 mm. With use of the AP iodinated contrast material run as the standard, there were significant differences (P < .05) in vessel diameter at 17 of 22 (77.3%) and four of 21 (19%) sites for CO2 and iodinated contrast material respectively, with CO2 tending toward greater diameter measurements. Significant differences (P < .05) in variance between the two readers were present but occurred primarily with CO2 in the AP projection and iodinated contrast material in the 45 degrees left obliquity. With use of IVUS as the standard, there were significant differences (P < .05) in the measured vessel diameters with CO2 at nine of 22 (40.9%) of the sites and with iodinated contrast material at 17 of 28 (60.7%) of the sites. Of the measurements made with CO2, seven of nine (77.8%) of the measurements were of larger diameter than those obtained with IVUS. By contrast, of the measurements made with iodinated contrast material angiography, IVUS measured larger diameters in 16 of 17 (94.1%).

CONCLUSION

CO2 angiography consistently yielded significantly larger vessel measurements when compared to both iodinated contrast angiography and WVUS. These results have important implications in regards to planning intervention based solely on CO2 angiography. Further evaluation is needed before recommending CO2 for vessel sizing in clinical practice.

Renal angiography using carbon dioxide

The many advantages of carbon dioxide (CO2) angiography in the investigation of renal arterial disease include an absence of both nephrotoxicity and allergic reactions. An automated delivery system facilitates injection of CO2 whilst ensuring that there is no contamination of the injection with air. We report our initial experience using a prospective study of this delivery system in 47 patients referred for renal angiography, and assess diagnostic image quality and adverse reactions to CO2 angiography using the automated delivery system. The majority (37/47; 79%) of angiograms were of diagnostic quality and there were no significant adverse reactions in response to the CO2 contrast agent.