Thoracic radiographic findings for dogs with cardiac tamponade attributable to pericardial effusion

Objective—To determine the prevalence of various radiographic findings for dogs with cardiac tamponade (CT) attributable to pericardial effusion (PE) and to determine the sensitivity and specificity of such findings for identification of affected dogs. Design—Retrospective, randomized, blinded, controlled study. Animals—50 dogs with CT attributable to PE and 23 control dogs (10 healthy dogs and 13 dogs with cardiac diseases other than CT). Procedures—Thoracic radiographic images of dogs were evaluated by an observer who was unaware of the dogs' medical histories. For each dog, a vertebral heart score, globoid appearance of the cardiac silhouette, and convexity of the dorsocaudal aspect of the cardiac silhouette were determined. Results—The sensitivity and specificity of enlargement of the cardiac silhouette (vertebral heart score, ≥ 10.7) for identification of dogs with CT attributable to PE were 77.6% and 47.8%, respectively. The sensitivity and specificity of a globoid appearance of the cardiac silhouette for identification dogs with CT were 41.9% and 40.0%, respectively. The sensitivity and specificity of a convex appearance of the dorsocaudal aspect of the cardiac silhouette for identification of dogs with CT were 57.1% and 35.0%, respectively. Conclusions and Clinical Relevance—Results of this study indicated none of the evaluated radiographic variables was highly (> 90%) sensitive or specific for identification of dogs with CT attributable to PE. Thoracic radiographic findings should not be considered reliable for identification of dogs with CT attributable to PE. The characteristic radiographic sign of PE in dogs typically is defined as an enlarged cardiac silhouette with a globoid shape.1,2 This radiographic finding is attributed to stretching of the pericardium via accumulation of PE fluid. However, the prevalence of such a radiographic finding for dogs with CT attributable to PE and the sensitivity and specificity of such findings for identification of dogs with that problem have not been reported. Pericardial effusion may not be identified in dogs with CT when the characteristic radiographic signs are not detected. Dogs for which PE is not suspected via radiography may not receive appropriate treatments, even when hemodynamically important PE (ie, PE that causes CT) is present and urgent intervention is required. The objective of the study reported here was to determine the prevalence of various radiographic findings for dogs with CT attributable to PE and to determine the sensitivity and specificity of such findings for identification of affected dogs. The hypothesis was that > 90% of dogs with CT attributable to PE would have an enlarged cardiac silhouette with a globoid shape and convexity of the dorsocaudal aspect of the cardiac silhouette, as determined via evaluation of thoracic radiographic images.