Topography
The heart, wrapped in the pericardium, fills the middle mediastinum between the two lungs, mostly left of the median plane. The base, where the great vessels leave, faces dorsocranially; the apex points caudoventrally and to the left, close to the sternum. In older cats the cardiac axis often tilts so that the heart has more sternal contact, and the aortic arch may look undulating on radiographs; both are common findings without heart disease.
Parts
- Right atrium and ventricle: receive blood from the venae cavae and pump it into the pulmonary trunk.
- Left atrium and ventricle: the dorsocaudal left atrium receives the pulmonary veins; its auricle (auricula sinistra) is where thrombi form in the cardiomyopathies. The thick-walled left ventricle forms the apex and ejects blood into the aorta.
- Valves: tricuspid (right atrioventricular), mitral (left atrioventricular), pulmonary and aortic.
Clinical relevance
- Auscultation: the feline heart is small and fast (about 140–220 bpm in the clinic). Murmurs are best heard at the left or right sternal border; many are dynamic and do not always mean disease, whereas a gallop rhythm in a cat is always abnormal and suggests cardiomyopathy.
- Radiographic size: the normal feline vertebral heart score is about 7.5 ± 0.3 vertebrae on the lateral view, clearly lower than in the dog.
- Echocardiography: the diastolic thickness of the interventricular septum and the left ventricular free wall is normally below 6 mm; the left atrium to aorta ratio is usually below 1.5.
- Hypertrophic cardiomyopathy: the most common heart disease of the cat; it affects roughly one in seven apparently healthy cats and has known mutations in Maine Coons and Ragdolls. It can stay subclinical until it presents as heart failure, thromboembolism or sudden death.
- Congestive heart failure: in the cat it causes pulmonary oedema, pleural effusion or both.
- Hyperthyroidism: causes tachycardia and secondary ventricular hypertrophy, partly reversible with treatment.
- Dilated cardiomyopathy: rare today; it was linked to taurine deficiency before commercial diets were supplemented.
- Patent ductus arteriosus: less common than in the dog, with the same continuous murmur at the left heart base.
3D model
Schematic shape (illustrative fidelity), placed from landmarks on the skeleton and the scanned organs. It shows topography, not fine morphology.