Indirect-Oscillation Sign Suggesting Infective Endocarditis on the Routine Chest CT

Routine chest CT is not essential for the diagnostic workup for infective endocarditis (IE), but this type of study may be the initial imaging modality in the evaluation of patients ultimately proven to have IE who present to the emergency department with nonspecific clinical symptoms. Although routine chest CT cannot directly assess valvular oscillating motion due to the lack of cine images, we hypothesized that a combination of elongated nodular valve thickening and abnormal orientation to the normal valve with a blind end on routine CT (indirect-oscillation sign) might suggest movable vegetation indirectly. To evaluate this possibility, we studied 27 patients with IE and 35 controls who underwent both routine chest CT and echocardiography. CT scanning was initiated following a delay of 60-80 s after the administration of the contrast medium. Two cardiothoracic radiologists retrospectively analyzed the CT images to assess the indirect-oscillation sign with consensus. The sensitivity, specificity, positive predictive value, and negative predictive value of the indirect-oscillation sign on routine chest CT were 29.6% (8/27), 100% (35/35), 100% (8/8), and 64.8% (35/54), respectively. Although uncommon, the presence of the indirect-oscillation sign involving the aortic or mitral valve on routine chest CT is a suggestive finding for IE.