부산대학교 도서관

Because improved understanding of the natural history of thoracic aneurysms would enhance our ability to determine in which cases the risk of surgical treatment is justified, the rate of enlargement of thoracic aneurysms and thoracoabdominal aneurysms was studied in 67 patients by means of serial computer-generated three-dimensional reconstructions of computed tomographic scans. Patients were followed for a mean of 1.5 ± 0.15 years (0.2 to 5.35 years) with an average interval between examinations of 0.9 ± 0.1 year (0.2 to 5.0 years). Thirty-nine patients continue to be followed; 7 were lost to follow-up; 14 died during follow-up (4 after aneurysm rupture), and 10 underwent an operation. Indications for operation included the presence of pain, an absolute aortic diameter larger than 8 cm, an increase in aortic diameter of more than 1 cm per year, or marked irregularity of aneurysm contour. Aortic diameter and volume data were generated from the aortic silhouette obtained by tracing each computed tomographic slice with a translucent digitizing tablet. Estimated change in aortic diameter after 1 year was 0.43 cm; estimated change in aortic volume was 88.1 ml. The impact of possible risk factors on the enlargement of aneurysms was examined by analysis of variance (p< 0.05). A significantly higher rate of aneurysm expansion was found in patients with a larger aortic diameter (>5 cm) at diagnosis (change in diameter = 0.17 cm versus 0.79 cm; change in volume = 40 ml versus 141.8 ml), and in smokers (change in diameter = 0.35 cm versus 0.70 cm; change in volume = 78.3 ml versus 120.8 ml). Changes in diameter and volume for aneurysms of different initial diameters and volumes was predicted by exponential regression by the equations: change in diameter = 0.0167 (initial aortic diameter)2.1; change in volume = 0.0356 (initial aortic volume)1.322. No correlation was noted between the rate of enlargement and age, sex, or the presence of dissection. A history of hypertension correlated with a greater aortic diameter at diagnosis but did not significantly affect the rate of enlargement. The rate of aneurysm enlargement for patients who underwent operation (change in diameter = 1.11 cm; change in volume = 178 ml) or had rupture of the aneurysm (change in diameter = 0.7 cm; change in volume = 124 ml) was compared with those without operation or rupture (change in diameter = 0.28 cm; change in volume = 57 ml) by one-way analysis of variance: all parameters were significantly greater (p< 0.05) in patients requiring operation and those in whom rupture occurred. By allowing more complete surveillance of aneurysm behavior, use of threedimensional reconstructions of computed tomographic scans enables recognition of potentially threatening patterns of aneurysm progression and thereby permits further refinement of operative indications for thoracic and thoracoabdominal aneurysms.