Gadolinium-enhanced elliptically reordered three-dimensional MR angiography in the assessment of hand vascularization before radial artery harvest for coronary artery bypass grafting: first experience

Radial artery cannulation: a comprehensive review of recent anatomic and physiologic investigations

Consistent anatomic accessibility, ease of cannulation, and a low rate of complications have made the radial artery the preferred site for arterial cannulation. Radial artery catheterization is a relatively safe procedure with an incidence of permanent ischemic complications of 0.09%. Although its anatomy in the forearm and the hand is variable, adequate collateral flow in the event of radial artery thrombosis is present in most patients. Harvesting of the radial artery as a conduit for coronary artery bypass grafting, advances in plastic and reconstructive surgery of the hand, and its use as an entry site for cardiac catheterization has provided new insight into the collateral blood flow to the hand and the impact of radial arterial instrumentation. The Modified Allen's Test has been the most frequently used method to clinically assess adequacy of ulnar artery collateral flow despite the lack of evidence that it can predict ischemic complications in the setting of radial artery occlusion. Doppler ultrasound can be used to evaluate collateral hand perfusion in an effort to stratify risk of potential ischemic injury from cannulation. Limited research has demonstrated a beneficial effect of heparinized flush solutions on arterial catheter patency but only in patients with prolonged monitoring (>24 h). Conservative management may be equally as effective as surgical intervention in treating ischemic complications resulting from radial artery cannulation. Limited clinical experience with the ultrasound-guided arterial cannulation method suggests that this technique is associated with increased success of cannulation with fewer attempts. Whether use of the latter technique is associated with a decrease in complications has not yet been verified in prospective studies. Research is needed to assess the safety of using the ulnar artery as an alternative to radial artery cannulation because the proximity and attachments of the ulnar artery to the ulnar nerve may potentially expose it to a higher risk of injury.

The value of Allen's test in harvesting a radial forearm flap: correlation of ex-vivo angiography and histopathological findings

The radial forearm flap is one of the most commonly raised free flaps. In most cases an Allen's test is sufficient for preoperative assessment of the palmar arch, but an intact palmar arch does not imply that the radial artery is suitable for microvascular anastomosis. For a patient operated for oral squamous cell carcinoma, reconstruction was planned with a radial forearm flap. The flap had to be discarded because of advanced atherosclerosis in the presence of a negative Allen's test. The correlation of an ex-vivo angiography and the histopathologic findings was assessed. In cases of expected vascular disease, further examinations like color flow Doppler ultrasound are recommended to ensure sufficient perfusion of the radial artery.

Can the modified Allen's test always detect sufficient collateral flow in the hand? A computational study

Blood flow in the largest arteries of the arm up to the digital arteries is numerically modelled using the one-dimensional equations of pressure and flow wave propagation in compliant vessels. The model can be applied to different anatomies of arterial networks and can simulate compression of arteries, these allowing us to simulate the modified Allen's test (MAT) and to assess its suitability for the detection of sufficient collateral flow in the hand if radial blood supply is interrupted. The test measures blood flow in the superficial palmar arch before and during compression of the radial artery. The absence of reversal flow in the palmar arch with the compression indicates insufficient collateral flow and is referred to as a positive MAT. This study shows that small calibres of the superficial palmar arch and insufficient compression of the radial artery can lead to false-positive results. Measurement of the drop in digital systolic pressures with compression of the radial artery has proved to be a more sensitive test to predict the presence of sufficient ulnar collateral flow in networks with small calibres of the superficial palmar arch. However, this study also shows that digital pressure measurements can fail in detecting enough collateral flow if the radial artery is insufficiently compressed.

Graft harvesting for revascularization in the head and neck

The techniques for revascularization in the neurocranium, skull base, and neck continue to evolve at an exciting pace. In this body of literature, however, techniques for harvesting radial artery and saphenous vein grafts are mainly reported using traditional open techniques. Minimally invasive procedures are fast becoming an alternative to open techniques in many fields and have the potential to become the standard of care. The cardiovascular literature is replete with reports of endoscopically harvested vascular grafts. This article reviews both methods, since the current state of the art involves knowledge of open and endoscopic harvesting techniques.

Time-resolved contrast-enhanced magnetic resonance angiography of the carotid arteries: diagnostic accuracy and inter-observer variability compared with selective catheter angiography

RATIONALE AND OBJECTIVES

To assess the diagnostic accuracy and interobserver variability of contrast-enhanced magnetic resonance angiography (CE-MRA) in a time-resolved technique compared with digital subtraction angiography (x-ray DSA) in patients with suspected stenoses of the internal carotid artery.

MATERIALS AND METHODS

A total of 43 patients were enrolled in this prospective study. All patients underwent selective x-ray DSA involving a total of 84 carotid arteries. CE-MRA was performed in a time-resolved technique with a fast gradient-echo sequence on a 1.5 T MR scanner: TR 3.8 milliseconds, TE 1.49 milliseconds. Four consecutive measurements, each a duration of 10 seconds, were performed with omission of measuring bolus transit time. Four independent radiologists scored the degree of stenosis. The interobserver variability was calculated for CE-MRA and x-ray DSA.

RESULTS

In the 43 cases, at least one MRA measurement showed arterial contrast without venous degradation. Compared with x-ray DSA the mean sensitivity and specificity for grading stenosis > or = 70% were 98% and 86%, respectively. The interobserver agreement was substantial with no significant difference between CE-MRA (kappa value 0.794) and x-ray DSA (kappa value 0.786).

CONCLUSIONS

The short acquisition time of a fast CE-MRA sequence allows a selective visualization of the internal carotid arteries without degradation from venous enhancement. It is a reliable method with a good interobserver agreement.

Double-blind, efficacy evaluation of gadobenate dimeglumine, a gadolinium chelate with enhanced relaxivity, in malignant lesions of the brain

BACKGROUND AND PURPOSE

The diagnostic efficacy of gadobenate dimeglumine (Gd BOPTA) was compared with that of gadodiamide (Gd DTPA-BMA) in patients with primary malignant tumors or metastases of the brain.

METHODS

A subset of patients was evaluated from the 410 enrolled in the United States in phase III central nervous system clinical trials with gadobenate dimeglumine. From these trials, there were 82 patients with intraaxial malignant neoplasms of the brain, the focus of the current study. Patients were randomized to one of three incremental dosing regimens. Imaging with gadodiamide at doses of 0.1 and 0.3 mmol/kg was compared with gadobenate dimeglumine at doses of 0.05 and 0.15 mmol/kg and at doses of 0.1 and 0.2 mmol/kg. The on-site physician, patient, and all off-site reviewers were blinded to the agent injected and the administered dose. Scans were obtained before contrast administration and within 5 minutes after administration of each dose. The two contrast injections in any one patient were separated by 15 minutes. An independent laboratory performed signal intensity measurements. The magnetic resonance (MR) films were evaluated for level of diagnostic information, number of lesions detected, and confidence in MR imaging diagnosis by two independent board-certified neuroradiologists unaffiliated with any study site.

RESULTS

The lesion-to-brain signal intensity ratio after a dose of 0.1 mmol/kg gadobenate dimeglumine was higher than that after a dose of 0.1 mmol/kg gadodiamide, with this result statistically significant (P = 0.02). After the second dose of contrast, results were comparable in all three groups. The level of diagnostic information contained on the MR films increased significantly for all three groups from pre- to postcontrast for both the first and second administered doses. In between-group comparisons, the level of diagnostic information was similar after the first contrast dose for all three dosing regimens. This was also true after the second contrast dose. For all three groups, the number of lesions detected increased significantly postdose (whether first or second). Confidence in MR diagnosis increased from predose to postdose for all three groups, with no statistically significant difference between groups.

CONCLUSION

Gadobenate dimeglumine, used at slightly lower doses, is comparable to gadodiamide in terms of efficacy in imaging of malignant intraaxial brain lesions. As with other gadolinium chelates, higher doses (0.15 and 0.2 mmol/kg) of gadobenate dimeglumine offer greater diagnostic information.