Surgery News - September 2007 - (Page 7) SEPTEMBER 2007 • SURGERY NEWS TRAUMA 7 Cerebrovascular Injury Screening Tools Scrutinized BY BRUCE JANCIN Else vier Global Medical Ne ws C O L O R A D O S P R I N G S — CT angiography has significant false-positive and false-negative rates for the diagnosis of blunt carotid/vertebral artery injury, according to results of a new single-center prospective comparative study. The finding raises serious questions about whether CT should replace conventional angiography, Dr. Ajai K. Malhotra said at the annual meeting of the American Surgical Association. “Before accepting CT for blunt carotid/vertebral artery injury screening, caution is warranted. Each institution should perform its own quality assurance to ensure its own results are accurate,” said Dr. Malhotra of Virginia Commonwealth University, Richmond, and an ACS Fellow. Diagnosis of blunt cerebrovascular injury is a major challenge for surgeons managing trauma, because these injuries are uncommon and symptoms are generally nonspecific. Yet delay in diagnosis and initiation of prophylactic antithrombotic therapy often leads to devastating stroke. Conventional digital subtraction angiography has long been considered the gold standard for diagnosis of blunt carotid/vertebral artery injuries, but it has major shortcomings. It is invasive, challenging to perform in acutely injured patients, and not widely available in smaller hospitals. In contrast, CT angiography is noninvasive, rapid, complication-free, and readily available—all of which account for its increasing popularity for the diagnosis of blunt cerebrovascular injury. Dr. Malhotra reported on a head-tohead comparison of 16-channel CT angiography and digital subtraction angiography (DSA) in the evaluation of 92 patients. The patients were suspected of having blunt carotid/vertebral artery injury based on symptoms and/or facial or cervical spine fractures. The results of CT angiography were not evaluable in three patients. Six of 62 patients who had negative findings by CT angiography had positive findings with DSA, whereas 10 of 27 who had positive findings by CT angiography had negative findings with DSA. That translates to a false-negative rate of 10% and a false-positive rate of 37% for the noninvasive imaging procedure. CT angiography had a diagnostic sensitivity of 74%, a specificity of 84%, a positive predictive value of 63%, and a negative predictive value of 90%. There was a significant learning curve with CT angiography. The false-negative interpretation rate was 17% during the first half of the roughly 3-year study and zero in the second half, he noted. Discussant Dr. Timothy C. Fabian, an ACS Fellow, found the Virginia Commonwealth study unpersuasive. His interpretation of Dr. Malhotra’s data is that DSA is no longer the gold standard, and CT angiography is the preferred screening tool. “While those who attempt swimming upstream hold a special place in my heart, you are facing an awfully strong current,” declared Dr. Fabian, professor and deputy chairman of the department of surgery and director of trauma at the University of Tennessee, Memphis. As faster, more sensitive 32- and even 64channel CT angiography equipment replaces 16-channel machines such as the one used in the Virginia Commonwealth study, the entire controversy regarding CT versus conventional angiography will fade away in the face of CT’s indisputable superiority, Dr. Fabian predicted. He noted that nearly all of the false-negative CT angiograms in Dr. Malhotra’s study involved low-grade lesions without any apparent clinical impact. “Isn’t it possible that many of those false-negatives were in fact injection artifacts due to direct vessel injection, resulting in false-positive radiographic interpretation of conventional angiography?” he asked. Dr. Fabian also said the Virginia Commonwealth experience is at odds with a study at Parkland Memorial Hospital, Dallas, in which CT angiography had a 98% sensitivity and 99% negative predictive value and declared the imaging method ready for prime time (J. Trauma. 2006;60:925-9). And while blunt cerebrovascular injuries are typically associated with stroke rates of 20%-35%, there were no strokes at all in the Virginia Commonwealth series, he added. Dr. Malhotra replied that the probable explanation for the absence of strokes was that four of the five patients with grade 4 or 5 injuries received interventional vascular therapies. All papers presented at the 127th annual meeting of the ASA are subsequently submitted to the Annals of Surgery for consideration. ■ Surgical Wounds Pressure Ulcers Orthopedic Trauma Wounds Diabetic Wounds Skin Grafts Open Abdominal Wounds Partial-Thickness Burns FOR OUTCOMES YOU CAN TRUST, THERE’S ONLY ONE ■ ■ Helps promote wound healing Non-adherent layer of the V.A.C.® Abdominal Dressing System assists in protecting the abdominal contents May allow for delayed primary closure Minimizes suturing through fascia Assists in wound stabilization via dressing splinting effect Collects and quantifies fluid Open Abdominal Wound ■ ■ ■ ■ To learn more about V.A.C.® Therapy, visit us online at www.woundvac.com or call toll-free 1-800-275-4524. 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