Focused cardiac ultrasound and point-of-care NT-proBNP assay in the emergency room for differentiation of cardiac and non-cardiac causes of respiratory distress in cats

Objective –To assess the accuracy of focused cardiac ultrasound (FOCUS) and point-of-care NT-proBNP assay (POC-BNP) in the emergency setting for differentiation of cardiac from non-cardiac causes of respiratory distress in cats.

Design –Prospective diagnostic accuracy study between 2014-2016

Setting –Emergency room at urban university teaching hospital

Animals –Prospective cohort study of 41 cats presenting for evaluation to the Matthew J. Ryan veterinary hospital for respiratory distress

Interventions –Emergency clinicians made an initial diagnosis of non-cardiac or cardiac cause of respiratory distress based on PE findings and history. The diagnoses were updated after performing FOCUS and POC-BNP. Reference standard diagnosis was determined by agreement of a board-certified cardiologist and criticalist with access to subsequent radiographs and echocardiograms.

Measurements and Main Results –Forty-one cats were enrolled. Three cats with incomplete data and 1 cat with an uncertain reference standard diagnosis were excluded.  The remaining 37 cats were used for analysis: 21 cardiac and 16 non-cardiac cases. The ratio of left atrial to aortic root diameter (LA:Ao) measured by FOCUS was significantly correlated with LA:Ao measured by echocardiography (R=0.646, P<0.0001). Emergency clinicians correctly diagnosed 27/37 (73.0%) yielding a physical examination positive percent agreement =76.2% (95% CI, 52.8, 91.8), and negative percent agreement=68.8% (41.3, 89.0). Five non-cardiac and 5 cardiac cats were misdiagnosed. Post FOCUS, overall percent agreement improved to 34/37 (91.9%) with positive percent agreement =95.2% (76.2, 99.9), and negative percent agreement=87.5% (61.7, 98.5). The POC-BNP yielded an overall percent agreement =32/34 (94.1%), positive percent agreement =100% (82.4, 100.0), and negative percent agreement=86.7% (59.5, 98.3) in differentiating cardiac versus non-cardiac cases.

Conclusions –FOCUS evaluation of basic cardiac structure and LA:Ao by trained emergency clinicians improved accuracy of diagnosis compared to physical examination in cats with respiratory distress. FOCUS and POC-BNP are useful diagnostics in the emergent setting.