The Impact of Short-Term Formalin Fixation on Weight and Ventricular Dimensions in the Hearts of Cats and Small-to-Medium-Sized Dogs.

Organ weight and size are important data collected during post-mortem examination not only in neoplastic diseases but also in other conditions, like cardiomyopathies. As post-mortem cardiac examination is challenging, it should be performed by experienced specialists. Nonetheless, the low number of referral centres in veterinary medicine requires the shipment of formalin-fixed specimens to perform detailed post-mortem cardiac examinations. Data regarding other tissues suggest that even short-term formalin fixation can influence the organ's size and/or weight. Presently, no data are available on the impact of formalin fixation on heart weight and size in dogs and cats. The aim of this study was to evaluate the impact of short-term formalin fixation on cardiac weight and ventricular dimensions in cats and small-to-medium-sized dogs in the context of the usefulness and accuracy of referral examination. The study was conducted on 134 hearts (95 feline and 39 canine) obtained during necropsy. Each heart was dissected, cleaned, dried, and immersed in a 7% formalin solution for over 72 h. Weighing of the whole heart and measuring of the ventricular diameters was performed prior to fixation, after 24, 48, 72, and over 72 h of fixation. The study showed that in cats and small-to-medium-sized dogs, heart weight and ventricular dimensions are not significantly influenced by formalin fixation ( > 0.05). Nonetheless, the process of cleaning and drying the heart affects the organ weight significantly ( < 0.0001). The hearts of cats and small-to-medium-sized dogs can be shipped in formalin fixative for a referral opinion, as the fixation does not affect the obtained measurements.