Clinical-Diagnostic and Therapeutic Advances in Feline Hypertrophic Cardiomyopathy

Abstract

A comprehensive literature review was conducted to summarise existing evidence and the latest therapeutic advancements in feline HCM. The disease phenotype is characterised by the development of concentric hypertrophy, which is variable but often asymmetric, primarily affecting the left ventricle. The HCM is marked by diastolic dysfunction, resulting in a reduced intracavitary internal diameter due to the disordered alignment of cardiomyocytes and excessive collagen deposition, which thickens the myocardial tissue and impairs relaxation. There is strong evidence supporting the role of genetic mutations in sarcomeric genes in the development of HCM. Clinical signs vary but are frequently associated with congestive heart failure (CHF) and ATE. Diagnosis is based on a combination of clinical evaluation, laboratory tests, and imaging studies, although certain aspects of the disease remain insufficiently understood and require further research. Therapeutic management focuses on controlling clinical signs, slowing disease progression, and improving both quality of life and life expectancy. However, ongoing studies are essential to refine diagnostic strategies and explore novel treatment options for better disease management.

Keywords: cardiovascular; cardiovascular pathophysiology; cats; heart failure; hypertrophy.

Figure 1

Schematic representation of the phenotype of feline HCM, including genetic, clinical, and pathophysiological factors associated with the development and progression of the disease. Consider: HCM—feline hypertrophic cardiomyopathy; A31P—A31P mutation; R820W—R820W mutation; LVOTO—left ventricular outflow tract obstruction; SAM—systolic anterior motion; ATE—arterial thromboembolism. BioRender 2025 (https://www.biorender.com/ (accessed on 10 January 2025)).

Figure 2

Macroscopic and histopathological changes in feline patients with hypertrophic cardiomyopathy. (A) The sectioned heart showing varying levels of hypertrophy of the left free ventricular wall and interventricular septum (yellow line); in the atrial region, it is possible to observe the presence of a thrombus (star). (B) Various levels of myocardial hypertrophy characteristic of heterogeneous hypertrophic conditions (blue lines) and septal hypertrophy at the level of the left ventricular outflow tract, which is a frequent finding in patients with outflow tract obstruction (star), were observed. (C) Cross-sectioned heart showing areas of cardiac fibrosis (arrows). (D) Histopathological evaluation of myocardial tissue showing muscle disarray and the presence of collagen fibre characteristic of a fibrotic process (dashed line). Images available in the Davis-Thompson Foundation database (Noah’s archive; (A). F64812, Heart: hypertrophic cardiomyopathy and thrombus of the left atrium, submitted by Sawang Kesdangsakonwut. Accessible at: https://davisthompsonfoundation.org/image-detail?image=F64812 (accessed on 10 January 2025). (B). F30288, Hypertrophic Cardiomyopathy, submitted by Williams. Accessible at: https://davisthompsonfoundation.org/image-detail?image=F30288 (accessed on 10 January 2025). (C). F32081, Hypertrophic Cardiomyopathy, submitted by Raquel Rech. Accessible at: https://davisthompsonfoundation.org/image-detail?image=F32081 (accessed on 10 January 2025). (D). F32760, Hypertrophic Cardiomyopathy (Histo), submitted by Raquel Rech. Accessible at: https://davisthompsonfoundation.org/image-detail?image=F32760 (accessed on 10 January 2025)).

Figure 3

Radiographic images of cats with hypertrophic cardiomyopathy obtained in the study by Kim et al. [93]. (A,B) Lateral projection images and (C,D) ventrodorsal projection images. (A,B) Note the atrial enlargement (dashed line) and the parallelism of the trachea (line), showing tracheal displacement (A). (C,D) Atrial and ventricular enlargement with changes in the normal cardiac structure.

Figure 4

An electrocardiographic examination of a 10-year-old female mixed-breed feline patient diagnosed with stage B2 hypertrophic cardiomyopathy was performed. Note the presence of premature ventricular complex and right bundle branch blocks in the DII derivation.

Figure 5

Echocardiographic examination showing right parasternal longitudinal 4 and 5 chambers in a feline patient diagnosed with hypertrophic cardiomyopathy. The images point to characteristics frequently observed in felines affected by the disease. There is evident left atrial dilation (dashed line), hypertrophy with a heterogeneous appearance in the region of the left ventricular free wall and interventricular septum (line), and a reduction in the size of the left ventricular cavity (dashed line). Consider: RA: right atrium; RV: right ventricle; LV: left ventricle; RV: right ventricle; AO: aorta; IVS: interventricular septum; LVFW: left ventricle free wall.