<Li> Pleural effusions, more commonly in descending aortic dissections, and typically left sided . </Li> <Li> Other: obliteration of the aortic knob, depression of the left mainstem bronchus, loss of the paratracheal stripe, and tracheal deviation . </Li> <P> Importantly, about 12 to 20% of aortic dissections are not detectable by chest radiograph; therefore, a "normal" chest radiograph does not rule out aortic dissection . If there is high clinical suspicion, a more sensitive imaging test (CT angiogram, MR angiography, or transesophageal echo) may be warranted . </P> <P> Computed tomography angiography is a fast, noninvasive test that gives an accurate three - dimensional view of the aorta . These images are produced by taking rapid, thin - cut slices of the chest and abdomen, and combining them in the computer to create cross-sectional slices . To delineate the aorta to the accuracy necessary to make the proper diagnosis, an iodinated contrast material is injected into a peripheral vein . Contrast is injected and the scan performed using a bolus tracking method . This type of scan is timed to an injection to capture the contrast as it enters the aorta . The scan then follows the contrast as it flows though the vessel . It has a sensitivity of 96 to 100% and a specificity of 96 to 100% . Disadvantages include the need for iodinated contrast material and the inability to diagnose the site of the intimal tear . </P>

Which sign or symptom is associated with acute dissection of the ascending aorta