Measurement of Heart Size in the New Zealand White Rabbit by Cardiothoracic Ratio

Aim: Assessing the heart and other thoracic structures radiographically is very important, in small animal practice, when decisions must be made regarding staging a patient with suspected cardiac anomaly, deciding about therapy protocols, and monitoring disease progression or response to treatment. A number of methods and measurement techniques have been developed for objective estimation of cardiac size. The present work was carried out to generate a value for radiographic measurement of heart size in the New Zealand White (NZW) rabbit by the cardiothoracic ratio (CTR). The work evaluated the heart size using dorsoventral projections of the rabbits. Materials and Methods: Ten healthy NZW rabbits were used for the study. A dorsoventral (DV) thoracic radiograph was obtained in each of the animals. Cardiac and thoracic diameters of the ten rabbits were measured in the radiographs to determine a reference value of CTR in normal NZW rabbits. Results: Mean plus or minus standard error of mean (M±SEM) CTR was 0.54 ± 0.01. There was not a significant difference (p 0.05) between male (0.54 ± 0.01) and female (0.54 ± 0.01) CTR values. There was no correlation between sex and CTR. Conclusion: In clinical practice, the application of CTR in radiographic assessment of the heart is objective and very easy.