Valley Heart & Vascular Institute - Sophisticated Imaging and Aneurysm Surveillance (TABAV Registry)
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Sophisticated Imaging and Aneurysm Surveillance
(TABAV Registry)

Sophisticated Imaging
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We have worked very closely with The Valley Hospital chest radiologists to develop the most advanced imaging package in the area. CT scans done outside of the Valley system may be limited either in their technical scope, or by more ‘general’ radiologic interpretation.

Often, CT scans done elsewhere come only with a simple comment of ‘the maximum diameter of the aorta is ‘x’…’. We use state-of-the-art CT scanners that enable our radiologists to capture each image at the same spot in the cardiac cycle using a technique called ‘ECG-gating’. This generally eliminates motion artifact, which is particularly important in portions of the aorta can that tend to change in size during different portions of the cardiac cycle (most noticeable in the aortic root), and yields the most accurate images possible.

Further, using advanced post-processing software, our radiologists use 3-dimensional volume rendering techniques to perform intensive measurements of different anatomic segments of the aortic aneurysm, both for research purposes, as well as to detect subtle changes in aneurysm characteristics that make it appear to be exhibiting aggressive behavior and favor earlier intervention. Many doctors do not know that not only do aneurysms grow radially (increasing diameter), but they also elongate (become longer). This is one of many variables whose clinical significance is not yet known. In general, a 10% increase over a stable baseline measurement is considered to be of some concern. With some novel clinical research here at Valley, we hope to shed some light on the relationship between radiographic findings, body dimensions and the real-life mechanical properties of aneurysmal aortas. We would hope to translate this information into better defining risk, and understanding why the IRAD data (click here for full article) shows so many aneurysms rupture or dissect at sizes smaller than 5 cm (40%).

In addition, we are in the process of defining some novel measurements of the aorta and aortic valve that may also prove clinically beneficial. One aspect deals with the ability to diagnose Bicuspid Aortic Valve (BAV) using a technique called retrospective gating. This appears particularly useful when standard echocardiography (cardiac ultrasound) fails to firmly characterize an aortic valve as normal or tri-leaflet. The difficulty lies in the fact that many BAVs are quite similar in appearance to tri-leaflet valves.

This is an important diagnosis to make, since it drastically affects the risk associated with aneurysm as well as with the expectation of adverse medical events over a BAV patient’s lifetime. We hope to publish on this novel technique over the next year or so. Another unique imaging technique is being applied to measurement of the aortic root. This is often reported as maximum diameter, but, anatomically, the aortic root is not circular, and therefore, this measurement is misleading.

The aortic root is comprised of three sinuses (‘of Valsalva’) that essentially represent three circular structures that overlap or meet in the center. The measurement that is usually reported as ‘maximum diameter’ is really the distance from a fibrous trigone (left ventricular outflow tract junction with the aortic valve) to a portion of a sinus of Valsalva furthest away from it. We think that a potentially more useful measurement might be that of something we have named ‘sinus radius’. Using 3-D volumetric techniques, we can measure the distance from the center of the closed aortic valve to each most distant point of each of the three sinuses of Valsalva.

We are finding that there can sometimes be substantial asymmetry in the sinus radii in some patients with aneurysm. It is yet unknown whether or not this somehow confers additional risk. Coupled with our aneurysm clinical research, it is possible that we may be able to show that sinus radius is a more accurate predictor of aortic mechanical properties than maximum diameter.

This is an important clinical area on which to focus, since the aortic root is one of the more common sites to find the ‘primary tear’ site during surgery for type A aortic dissection. We further plan to index these to body dimensions, in the style of relative aortic size systems already described elsewhere. We are in the process of defining control values of sinus radius in our non-aneurysmal CTA patients, and aim to define a new standard in the radiologic description of the aortic root.

Patients who are enrolled in the TABAV Registry will have these measurements made and compared over different time points. The purpose is to keep a close eye on aneurysm characteristics to be sure that the clinical situation continues to warrant surveillance, as opposed to intervention. The Registry assumes full responsibility for pre-certifying for radiologic studies, arranging and scheduling the imaging, contacting the patient at each surveillance interval to inquire about symptoms and compliance. This effort is meant to simplify the process for doctor and patient, and especially to ensure that the follow up is rigorous and accurate.

For more information, contact Leanne Scaglione, R.N., MSN, APN-BC, Coordinator for the Thoracic Aneurysm Surveillance Program, at 201-447-8398.

 
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