| Determination of Entry Site for
Acute Type A Aortic Dissection by Initial Enhanced CT-Scan |
| Takenori Mase |
Chihiro Narumiya |
Takahiko Aoyama |
| Yoshihisa Nagata |
|
|
iThe Second Department of Surgery, School of Medicine,
Aichi Medical University, Aichi, Japan)
|
Acute type A aortic dissection presents
a surgical emergency because conservative therapy is not effective
in the majority of instances. Enhanced CT-scan of the chest is
commonly available and is considered to be an optimal diagnostic
method for this disease. The operative strategy is to resect
the primary tear to close the entry site of the aortic dissection
and replace it with a tubular Dacron graft. Therefore, the existence
of the entry site is important in determining the operative procedure.
Based on the numerical value of the enhanced CT-scan inspection,
the present study seeks to preoperatively identify the location
of the presumed entry site in aortic dissection. From May 1996
to June 1999, 21 consecutive patients (Marfan's syndrome excluded)
with acute type A aortic dissection underwent surgical treatment.
Nineteen patients were preoperatively examined by enhanced CT-scan:
11 men and 8 women, with a mean age of 61 years. CT-scan slices
used for early diagnosis were of the ascending aorta, aortic
arch, descending aorta, and thoracoabdominal aorta. The largest
diameters of the whole and true lumen were measured from cross-sectional
aortic images with a personal computer, and the areas of the
whole and true lumen were obtained by the manual tracing method.
The true ratio was calculated for the largest diameter and area
of the whole lumen. The nineteen patients were divided into two
groups according to the location of the entry site based on the
operating views. Seven patients with the entry site in the ascending
aorta were classified as group A, and twelve patients with the
entry site further in the aortic arch and descending aorta were
classified as group B. Comparisons were performed by non-parametric
analysis. Moreover, a discriminant analysis was applied to evaluate
the classification between the two groups. The ratio of the largest
diameter of the true lumen in group A at the level of the ascending
and descending aorta was significantly greater than that in group
B (75.0}11.3 vs. 59.7}14.0%, 82.7}8.6 vs. 70.1}11.4%). Linear
discriminant analysis resulted in the correct classification
rate of 68.2%, and 77.3%, respectively. The ratio of the area
of the true lumen in group A at the level of the aortic arch
was also significantly greater than in group B (65.4}17.3 vs.
45.7}15.8%) and linear discriminant analysis resulted in the
correct classification rate of 55.1%. When the entry site was
located in the aortic arch, the diameter of the true lumen was
seen to be smaller in the ascending and descending aorta, and
the dissecting lumen appeared enlarged. When the entry site is
located in the ascending aorta, the ratio of the area of the
true lumen in the aortic arch was significantly higher (55.1%).
Detailed examination of enhanced CT-scans is useful to
@Jpn. J. Cardiovasc. Surg. 31F12-17 (2002) |
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