Acute Aortic Disease.. - Index of

Natural History of Thoracic Aortic Aneurysms 195
DISCUSSION AND COMMENTARY
Questions for the Authors
How often should the aorta be imaged in a patient in follow-up for a thoracic
aortic aneurysm?
We tend to image rather infrequently, as the aneurysmal thoracic aorta grows
slowly—at just over 1 mm (0.1 cm) per year. So, because of this indolent growth,
frequent scans will not show any changes—just like a parent does not notice the
growth of his children, whom he sees every day.
What is most important is to compare your current study, not with the last
prior study, but with the earliest study on record for your patient. This is how
growth can be appropriately noted and appreciated. This takes more work and
may mean digging deep into a computerized registry of CT scans or pulling old
hard copies of imaging studies. We recently published a plea to radiologists to do
this extra work of comparing with the earliest study on record, to prevent missing
substantive overall growth by comparing only with the most recent study (1).
When seeing a patient for the first time, we usually re-image in 6 to
12 months, so as to identify a quick second point on the size or growth curve for
that patient. Thereafter, it is rare for us to image more frequently than every one
to two years. We must be cognizant also of the radiation danger of CT scanning.
Does the aorta ever grow very rapidly?
With rare exceptions, sudden, rapid growth of the aorta is usually spurious, involving
measurement at noncorresponding segments of the aorta on different scans.
Another common source of error has to do with measuring across oblique segments
of the aorta (such as the aortic arch on an axial study); obliquity will give
an oblong cross-section, which overestimates true diameter.
A sudden true increase in caliber of the thoracic aorta can be caused by
intercurrent aortic dissection. If the aorta has truly grown, please be sure to
check for presence of a dissection flap, which may have developed in the interim
between studies.
What imaging study should I use in follow-up?
Our studies have shown a high concordance between dimensions on echocardiography,
CT scanning, and MRI imaging. For acutely ill patients, we usually prefer
ECHO and CT, which are immediately available. For chronic follow-up, we
usually prefer ECHO for young patients, especially women of childbearing age.
Of course, the (transthoracic) ECHO shows mainly the proximal ascending aorta,
so for older patients, we combine with either CT or MRI, which shows very well the
entirely of the aorta—ascending, arch, descending, and abdominal.
How about family members?
There is no longer any question that thoracic aortic aneurysm is a hereditary disease,
and abdominal aneurysm as well. We recommend imaging all first-order