Bigeminismo ventricular em um felino

Background: Cardiac arrhythmias are frequently associated with structural heart disease in dogs and cats. Bigeminy involves a sinus beat alternating with a ventricular ectopic beat. This rare arrhythmia in felines may be associated with cardiomyopathies, systemic diseases, poisoning, or idiopathic causes. Diagnosis involves clinical evaluation and complementary cardiological exams, while treatment depends on the severity of the condition. The prognosis is usually poor. This study reports a case of ventricular bigeminy in an asymptomatic domestic feline diagnosed during preoperative oncological evaluation of an ear neoplasm. Case: A 10-year-old male, mixed-breed feline patient was seen by a veterinary oncologist with a cytological diagnosis of mast cell tumor in the ear and subsequent indication for surgical removal. During the clinical examination, there were no reports of clinical signs related to arrhythmia. During the physical examination, the veterinarian observed an irregular rhythm, pulmonary auscultation, femoral pulse, and blood pressure readings within normal limits. The patient also presented normal-colored mucosa and hyporeactive lymph nodes. During preoperative examination, the electrocardiogram showed premature ventricular complexes alternating regularly with sinus beats, with morphology suggestive of right ventricular origin, suggesting ventricular bigeminy. The electrical axis was within physiological standards, and wave amplitude and duration were within the reference values ​​for the species. The echocardiogram demonstrated normal left ventricular systolic and diastolic function but revealed right ventricular diastolic dysfunction, as well as the presence of a structure with irregular contour, homogeneous echotexture, and hyperechoic intensity adjacent to the aorta and left atrium without flow on Doppler. This structure did not interfere with the hemodynamics of the region, suggesting a differential diagnosis of endocardial fibrosis or cardiac base neoformation. Other complementary tests were normal. The patient underwent the surgical procedure successfully and is maintained under cardiological follow-up. The patient remained stable, without developing clinical alterations. The histopathological report revealed a well-differentiated mastocytoma (mastocytic), and chemotherapy was not necessary. Discussion: The correlation between the electrocardiogram and echocardiogram findings allowed the arrhythmia to be characterized and significant structural alterations to be ruled out. The patient's absence of clinical signs suggests the electrical alteration is benign. This case highlights the importance of thorough cardiological monitoring, even in asymptomatic patients, especially in situations involving anesthesia and oncological diagnoses. The absence of electrocardiographic signs indicative of overload, electrolyte disturbances, or myocardial hypoxia suggests that the rhythm disturbance may be primary or associated with specific structural alterations still in their early stages. Therefore, the detection of arrhythmias, such as ventricular bigeminy, even in isolation, should be prioritized in felines, since electrocardiographic manifestations are less frequent and underdiagnosed in this species.