Radiographic reference limits for cardiac width in peregrine falcons (Falco peregrinus)

Abstract Journal of the American Veterinary Medical Association June 1, 2011, Vol. 238, No. 11, Pages 1459-1463 doi: 10.2460/javma.238.11.1459 Radiographic reference limits for cardiac width in peregrine falcons (Falco peregrinus) Johannes T. Lumeij, DVM, PhD; Muneer A. S. Shaik, BVSc, AH; Mohammed Ali, DVM, PhD Souq Waqif Falcon Hospital, Abdullah Bin Jassim St, Al-Jasra, Doha, Qatar. (Lumeij, Shaik, Ali); Division of Zoological Medicine, Department of Clinical Sciences of Companion Animals, Faculty of Veterinary Medicine, Utrecht University, 3584 CM Utrecht, The Netherlands. (Lumeij) Dr. Lumeij's present address is Division of Zoological Medicine, Department of Clinical Sciences of Companion Animals, Faculty of Veterinary Medicine, Utrecht University, 3584 CM Utrecht, The Netherlands. The authors thank His Excellency Shaikh Hamad bin Khalifa Al Atia for the facilities offered to perform clinical research in hunting falcons at the Souq Waqif Falcon Hospital, Doha, Qatar, and Ikdam M. Alkarkhi for permission to use his patient data. Address correspondence to Dr. Lumeij (j.t.lumeij@uu.nl). Objective—To determine radiographic reference limits for cardiac width (CW) in peregrine falcons. Design—Retrospective cross-sectional study. Animals—100 peregrine falcons. Procedures—CW, thoracic width (TW), and sternal width (SW) were measured at the level of maximum CW on ventrodorsal radiographs of 64 falcons. Ratios of CW:TW and CW:SW were compared between positive pressure insufflation (PPI) radiographs and standard radiographs in 6 falcons. A hypothesis for the most accurate predictor of CW was formulated and validated in a new set of 36 falcons. Results—PPI radiographs had a significantly lower CW:TW ratio than did standard radiographs. The CW:SW ratio was unaffected. The 95% confidence interval for a regression-based predicted CW was 19% larger for any given TW, compared with SW. The difference between predicted and measured CW was significantly smaller with SW, compared with TW. Validation of these findings in a new data set of 36 falcons confirmed that prediction of CW when SW was used as the independent variable in a regression equation was superior to use of the CW:SW ratio or the CW:TW ratio and was superior to prediction of CW when TW was used as the independent variable in a regression equation. Conclusions and Clinical Relevance—Of the variables examined, SW seemed to be the most precise and most accurate predictor for CW in peregrine falcons. Thoracic width seemed inferior as a predictor for CW because TW was influenced by respiratory movements. The following formula can be used to predict the 95% confidence interval for CW in peregrine falcons: CW = 0.83SW + 0.37 ± 0.16