Basics of cardiopulmonary bypass: normal and abnormal postoperative CT appearances

Cardiothoracic surgical procedures with and without cardiopulmonary bypass are becoming more commonly performed as surgical techniques improve and the population ages. Changes related to cardiopulmonary bypass are often depicted at routine postoperative computed tomographic (CT) studies performed for various reasons. The purpose of this article is to present knowledge critical to the accurate postoperative evaluation of the patient who has undergone cardiopulmonary bypass. This article will review the surgical technique for cardiopulmonary bypass, as well as the associated normal and abnormal postoperative imaging findings. Common cannulation sites used for cardiopulmonary bypass include the ascending aorta, axillary artery, right atrium, superior vena cava, and inferior vena cava. Normal postoperative findings related to cardiopulmonary bypass include (a) felt pledgets, which are used to reinforce cannulation sites; (b) oversewn side grafts; and (c) oversewn graft side branches. These normal postoperative findings can be mistaken for abnormalities. Abnormal postoperative findings related to cardiopulmonary bypass include pseudoaneurysm formation at cannulation sites, aortic dissection, and seroma formation. An awareness of normal and abnormal postoperative CT findings related to cardiopulmonary bypass is critical for all radiologists who interpret chest CT studies, to help prevent unnecessary further evaluation and to help direct prompt treatment when warranted.