Measurement of pulmonary transit time in healthy cats by use of ultrasound contrast media “Sonovue®”: Feasibility, reproducibility, and values in 42 cats

To evaluate the feasibility of measuring pulmonary transit time (PTT) in healthy cats by transthoracic echocardiography using the ultrasound contrast agent Sonovue®. To determine normalized PTT (nPTT) values in 42 healthy cats and to estimate the interobserver variability and the within-day repeatability of nPTT measurements. Forty-two privately owned healthy cats of different breeds, gender and age presented for cardiac examination. A bolus injection of contrast agent (Sonovue®) was administered intravenously. The right parasternal short axis echocardiographic view was used to record the contrast agent's transit time from the pulmonary artery to the left atrium. Pulmonary transit time and nPTT were determined independently by three examiners with different levels of experience. Normalized PTT was 4.12 ± 1.0 (mean ± SD) in our population. The median interobserver variability across our population was 6.8%, the median within-day variability for the three observers were 13.1%, 12.7% and 13%. No effect of the observer's experience on nPTT measurement was identified. Age, sex and body weight did not significantly influence nPTT. This study demonstrates that nPTT measurement is feasible in cats using ultrasound and the blood pool contrast media Sonovue®. Measurements of nPTT can be performed in a clinical setting. Normalized PTT values in healthy cats are comparable with those reported in healthy dogs.