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Can you detect pericardial effusion and cardiac tamponade on chest radiographs? | VETgirl Veterinary Continuing Education Podcasts

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In today’s VETgirl online veterinary continuing education podcast, we discuss whether you detect pericardial effusion and cardiac tamponade on chest radiographs in veterinary medicine.

How do you identify pericardial effusion and cardiac tamponade in your canine patients? Do you rely on physical exam findings? Radiographs? Ultrasound or echocardiogram? A combination of these?

While the classic radiographic findings associated with PCE include a globoid appearance to the heart and generalized cardiomegaly, the sensitivity and specificity of these findings has not been investigated in veterinary patients. So, Cote et al out of Angell Memorial Animal Hospital, Atlantic Veterinary College, and University of Pretoria wanted to evaluate this in a study called Thoracic radiographic findings for dogs with cardiac tamponade attributable to pericardial effusion. In this study, they retrospectively evaluated 50 cases of pericardial effusion and cardiac tamponade, and compared them to 23 control dogs that were healthy or had other cardiac disease (e.g., no pericardial effusion or cardiac tamponade).

So, what did they find?
When assessing vertebral heart score (VHS), 78% (39/50) of the dogs with pericardial effusion and cardiac tamponade had a VHS ≥ 10.7, while only 52% (12/23) of the controls had a VHS ≥ 10.7 (p = 0.03). 58% (25/43) of the dogs with pericardial effusion and cardiac tamponade had a globoid appearance to the cardiac silhouette, compared to 40% (8/20) of the control dogs. These results were not significantly different (p=0.18). Some dogs (e.g., 7 cases and 3 controls) were excluded from this part of the analysis because their results were equivocal. Convexity of the dorsocaudal aspect of the cardiac silhouette on lateral thoracic radiographic images was not significantly different between groups (p=0.55). Having a VHS ≥ 10.7 was the most sensitive and specific for cardiac tamponade and pericardial effusion (77.6% and 47.8% respectively), followed by the appearance of a globoid heart (41.9% and 40%) and convexity of the dorsocaudal aspect of the cardiac silhouette (57.1% and 35%). Even when all three variables were used in combination, sensitivity was only 66.7%.

So, what can we take away from this VETgirl podcast?
Unfortunately, none of the radiographic variables evaluated had a high sensitivity for identifying pericardial effusion and cardiac tamponade in dogs, even when they were used in combination. The specificity of the variables was also poor. The authors hypothesize that some of the reasons for the poor discerning ability of these variables might be due to the chronicity of pericardial effusion. Acute pericardial effusion might be less likely to cause stretching of the pericardium, and the capacity of the pericardium to stretch might be variable among dogs.

While radiographic findings such as generalized cardiomegaly and a globoid heart are classically described for dogs with cardiac tamponade and pericardial effusion, this study found that these characteristics are not very sensitive or specific. The classic radiographic findings that we associate with pericardial effusion and cardiac tamponade aren’t actually that sensitive or specific! That said, some limitations of this study are that it was retrospective and a rather small study, so further research (ideally prospective) would be ideal to confirm these results. One pro of this study is that all of the cases had confirmed pericardial effusion and cardiac tamponade, which has not been the case in some previous studies. Regardless, it looks like we shouldn’t rely on just chest radiographs to determine if our patient has pericardial effusion and cardiac tamponade. Ideally, add in a TFAST to help improve your diagnostic capability and detection of pericardial effusion. After all, it’s important to remember to combine the results of all of your diagnostic tests, including a thorough physical exam, in making a diagnosis of pericardial effusion and cardiac tamponade!

Abbreviations:
CT: cardiac tamponade
VHS: vertebral heart score
PCE: pericardial effusion

References:
1. Cote E, Schwarz LA, Sithole F. Thoracic radiographic findings for dogs with cardiac tamponade attributable to pericardial effusion. J Am Vet Med Assoc 2013;243:232-235.

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