Assessment of elastin deficit in a Marfan mouse aneurysm model using an elastin-specific magnetic resonance imaging contrast agent.

BACKGROUND: Ascending aortic dissection and rupture remain a life-threatening complication in patients with Marfan syndrome. The extracellular matrix provides strength and elastic recoil to the aortic wall, thereby preventing radial expansion. We have previously shown that ascending aortic aneurysm formation in Marfan mice (Fbn1(C1039G/+)) is associated with decreased aortic wall elastogenesis and increased elastin breakdown. In this study, we test the feasibility of quantifying aortic wall elastin content using MRI with a gadolinium-based elastin-specific magnetic resonance contrast agent in Fbn1(C1039G/+) mice. METHODS AND RESULTS: Ascending aorta elastin content was measured in 32-week-old Fbn1(C1039G/+) mice and wild-type (n=9 and n=10, respectively) using 7-T MRI with a T1 mapping sequence. Significantly lower enhancement (ie, lower R1 values, where R1=1/T1) was detected post-elastin-specific magnetic resonance contrast agent in Fbn1(C1039G/+) compared with wild-type ascending aortas (1.15±0.07 versus 1.36±0.05; P<0.05). Post-elastin-specific magnetic resonance contrast agent R1 values correlated with ascending aortic wall gadolinium content directly measured by inductively coupled mass spectroscopy (P=0.006). CONCLUSIONS: Herein, we demonstrate that MRI with elastin-specific magnetic resonance contrast agent accurately measures elastin bound gadolinium within the aortic wall and detects a decrease in aortic wall elastin in Marfan mice compared with wild-type controls. This approach has translational potential for noninvasively assessing aneurysm tissue changes and risk, as well as monitoring elastin content in response to therapeutic interventions.

Cost associated with D-Dimer screening for acute aortic dissection.

INTRODUCTION: D-Dimer (DD) has been described as a useful predictor of both morphologic changes in acute thoracic aortic dissection (TAD) and of TAD-associated mortality. This study analyzed the use of DD screening to screen patients with chest pain for acute (TAD) to determine if it improves diagnosis and cost effectiveness. This study also looked at the association of DD levels with diagnoses frequently seen in patients with dyspnea or chest pain. METHODS: At the Helios Hospital, Krefeld, the authors analyzed the data of all patients (n = 1053, age (mean, SD) 62 ± 19 years, 49% males) admitted for chest pain to the nonsurgical emergency department (ED) in February 2010. Chest pain was the second most frequent symptom causing 138 (13.1%) admissions, 102 of which had DD testing (Inniovance® D-Dimer Assay, Dade Behring/Siemens, Germany). To assess the diagnostic reliability of DD testing, the sensitivity, specificity, and odds ratio, including 95% confidence interval, were estimated. RESULTS: None of the patients admitted were found to have acute TAD. Had the authors used a computerized tomography (CT) scan to rule out TAD in every patient with chest pain, actual costs would have been euro 12,328. A restriction of CT scans to patients with elevated DD levels would have lowered costs to euro 5360. The actual costs were euro 670.30 for CT scans and euro 540.60 for DD tests. On analyzing the association with other diagnoses, both sensitivity and specificity were low, with the exception of pneumonia. CONCLUSION: Owing to the low incidence of TAD, DD screening increases diagnostic efforts and costs but it remains unclear whether it would actually speed up TAD diagnosis. In a clinical setting DD did not help to discriminate other relevant diagnoses. Despite the high sensitivity of DD for aortic dissection published in the literature, the physician's clinical judgment remains paramount.