Assessment of left atrial function in feline hypertrophic cardiomyopathy by using two- dimensional speckle tracking echocardiography

Clinical-Diagnostic and Therapeutic Advances in Feline Hypertrophic Cardiomyopathy

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.

Left atrial fractional shortening in cats: a comparison between two echocardiographic views

INTRODUCTION/OBJECTIVES

Left atrial fractional shortening (LAFS%) is a widely used index of left atrial systolic function in cats that has been shown to predict development of hypertrophic cardiomyopathy (HCM) and cardiac mortality. It can be determined by two methods: from an M-mode right parasternal short-axis view (LAFS%RPSA-MM) or two-dimensional right parasternal long-axis four-chamber view (LAFS%RPLA-2D). We aimed to assess the agreement between LAFS%RPSA-MM and LAFS%RPLA-2D in cats and to evaluate the correlation between LAFS%RPSA-MM and LAFS%RPLA-2D and left ventricular systolic performance.

ANIMALS, MATERIALS, AND METHODS

One hundred and seventeen cats were enrolled in the study: 40 control, 41 HCM stage B (asymptomatic), and 36 HCM stage C (symptomatic) cats. This was a retrospective case-control study. Bland-Altman analysis was used to assess agreement between LAFS%RPSA-MM and LAFS%RPLA-2D across the whole cohort and in cats with asymptomatic and symptomatic HCM. Correlation analysis was used to assess associations between LAFS% methods and forward aortic flow, left ventricular fractional shortening, and aortic root motion.

RESULTS

The LAFS% determined by LAFS%RPSA-MM and LAFS%RPLA-2D was similar (P=0.8), but Bland-Altman analysis showed wide limits of agreement between methods. There was a good correlation between LAFS%RPSA-MM and LAFS%RPLA-2D and aortic root motion (r = 0.78 and r = 0.71, respectively) and a fair correlation with left ventricular fractional shortening (r = 0.31 and r = 0.29, respectively). None of the methods showed a correlation with indices of aortic flow.

CONCLUSIONS

Our study suggests a poor agreement between LAFS%RPSA-MM and LAFS%RPLA-2D, and thus, these methods should not be used interchangeably. Both echocardiographic methods showed good correlation with aortic root motion.

Assessment of left atrial myocardial deformation using two-dimensional speckle-tracking echocardiography in cats with cardiogenic and non-cardiogenic arterial thromboembolism

Arterial thromboembolism (ATE) in cats usually relates to cardiogenic causes that can be diagnosed by conventional echocardiography. Two-dimensional speckle-tracking echocardiography (2D-STE) is a new ultrasound modality with higher sensitivity. Our objective was to investigate left atrial myocardial deformation in cats with both cardiogenic and non-cardiogenic ATE and normal cats using 2D-STE. Twenty-three normal cats and 21 cats with ATE cats were recruited and performed conventional echocardiography and 2D-STE. From the results, left atrial (LA) strain and strain rate from 2D-STE were significantly decreased in cats with cardiogenic ATE (P < 0.001), but there was no significant difference in non-cardiogenic ATE compared with normal cats. From the correlation test, the use of left atrial strain during the reservoir phase (LASr) could represent the overall LA deformation. The intra- and inter-observer coefficient of variation of LASr was less than 15%. The logistic regression revealed that the LASr value of less than 11% was a significant factor for the occurrence of ATE (odd ratio = 189.0, P < 0.001). In conclusion, LASr derived by 2D-STE is a repeatable and non-invasive technique to assess LA myocardial deformation in cats with ATE. By 2D-STE, impaired LA function was detected in cats with cardiogenic ATE. LASr < 11% may use as a predictor of the risk of ATE occurrence in cats.

Case report: A novel occurrence of persistent left cranial vena cava coexisting with polycystic kidney disease in a cat

A 7-year-old castrated male Munchkin cat was presented with anorexia. This cat had been diagnosed with chronic kidney disease due to polycystic kidney disease. Tachycardia with a systolic murmur (grade III/VI) was auscultated and for further diagnosis, echocardiography was performed. Based on echocardiography, persistent left cranial vena cava (PLCVC) was suspected due to enlargement of the coronary sinus and confirmed by saline contrast echocardiography. The dilated coronary sinus compressed the left atrium, and left ventricular hypertrophy with the systolic anterior motion of the mitral valve, aortic regurgitation, and mitral regurgitation were identified. After medical management using atenolol, left atrial function and other hemodynamics of the heart were improved, including the disappearance of regurgitation and normalization of left ventricular wall thickness. This case report describes the echocardiographic characteristics, diagnostic procedures, and disease progression in a cat with PLCVC after medical management using atenolol. Additionally, this is the first report of a cat with PLCVC, coexisting with polycystic kidney disease.

The Feline Cardiomyopathies: 2. Hypertrophic cardiomyopathy

Practical relevance:

Hypertrophic cardiomyopathy (HCM) is the most common form of feline cardiomyopathy observed clinically and may affect up to approximately 15% of the domestic cat population, primarily as a subclinical disease. Fortunately, severe HCM, leading to heart failure or arterial thromboembolism (ATE), only occurs in a small proportion of these cats.

Patient group:

Domestic cats of any age from 3 months upward, of either sex and of any breed, can be affected. A higher prevalence in male and domestic shorthair cats has been reported.

Diagnostics:

Subclinical feline HCM may or may not produce a heart murmur or gallop sound. Substantial left atrial enlargement can often be identified radiographically in cats with severe HCM. Biomarkers should not be relied on solely to diagnose the disease. While severe feline HCM can usually be diagnosed via echocardiography alone, feline HCM with mild to moderate left ventricular (LV) wall thickening is a diagnosis of exclusion, which means there is no definitive test for HCM in these cats and so other disorders that can cause mild to moderate LV wall thickening (eg, hyperthyroidism, systemic hypertension, acromegaly, dehydration) need to be ruled out.

Key findings:

While a genetic cause of HCM has been identified in two breeds and is suspected in another, for most cats the cause is unknown. Systolic anterior motion of the mitral valve (SAM) is the most common cause of dynamic left ventricular outflow tract obstruction (DLVOTO) and, in turn, the most common cause of a heart murmur with feline HCM. While severe DLVOTO is probably clinically significant and so should be treated, lesser degrees probably are not. Furthermore, since SAM can likely be induced in most cats with HCM, the distinction between HCM without obstruction and HCM with obstruction (HOCM) is of limited importance in cats. Diastolic dysfunction, and its consequences of abnormally increased atrial pressure leading to signs of heart failure, and sluggish atrial blood flow leading to ATE, is the primary abnormality that causes clinical signs and death in affected cats. Treatment (eg, loop diuretics) is aimed at controlling heart failure. Preventive treatment (eg, antithrombotic drugs) is aimed at reducing the risk of complications (eg, ATE).

Conclusions:

Most cats with HCM show no overt clinical signs and live a normal or near-normal life despite this disease. However, a substantial minority of cats develop overt clinical signs referable to heart failure or ATE that require treatment. For most cats with clinical signs caused by HCM, the long-term prognosis is poor to grave despite therapy.

Areas of uncertainty:

Genetic mutations (variants) that cause HCM have been identified in a few breeds, but, despite valiant efforts, the cause of HCM in the vast majority of cats remains unknown. No treatment currently exists that reverses or even slows the cardiomyopathic process in HCM, again despite valiant efforts. The search goes on.