Veterinary Cardiology Resident University of California Davis West Sacramento, California
Subjective assessment of heart size in kittens is challenging and there is a need for established reference ranges to prevent misdiagnoses of cardiomegaly in this patient population. The purpose of this study was to generate reference intervals for echocardiographic and radiographic quantification of cardiac size in apparently healthy kittens. Eighty-eight kittens aged 6-16 weeks were included in the study. Radiographic and echocardiographic evaluations were performed without sedation. Echocardiographic images and thoracic radiographs were measured to establish reference intervals for multiple echocardiographic variables, vertebral heart score (VHS) and cardiac thoracic ratio. N-terminal pro-brain type natriuretic peptide (NT-proBNP) was also measured. Statistical correlations between the echocardiographic parameters and age, body weight and sex were all evaluated and reference ranges were generated. Multiple moderate to strong correlations between body weight and age with various echocardiographic parameters were noted and allometric scaling was performed for body weight. Kittens had a VHS of 9.4 +/- 0.73 which is significantly larger (P < 0.0001) and exceeds the previously proposed cutoff of 7.8 in adult cats. Tricuspid regurgitation was a common finding and was present in 37.5% (33/88) of kittens. Measured NT-proBNP levels were comparable to healthy adult cats with a median of 31 pmol/L (Range 24-129 pmol/L). Specific reference ranges are reported in part as table 1 below and may be utilized when evaluating heart size in this population.