International collaborative study to assess cardiovascular risk and evaluate long-term health in cats with preclinical hypertrophic cardiomyopathy and apparently healthy cats: The REVEAL Study

Evolving FATE: A New Lens on the Pathogenesis and Management of Feline Cardiogenic Arterial Thromboembolism

Feline cardiogenic arterial thromboembolism (FATE) remains one of the most devastating complications of feline cardiomyopathies, with high mortality and recurrence rates. Despite its clinical importance, significant knowledge gaps persist in our understanding of FATE's pathogenesis and optimal management strategies. Our review aims to address these gaps by providing a comprehensive overview of the current understanding of FATE, including disease mechanisms, risk factors, emerging diagnostics, and preventative strategies. Importantly, we identify key areas such as immunothrombosis, procoagulant platelets, platelet heterogeneity, and altered fibrinolysis where future research may yield novel biomarkers and therapeutic targets to improve outcomes in affected feline patients.

Relationship Between Cardiac Troponin I Concentration and Myocardial Function in Hypertrophic Cardiomyopathy Cats With or Without Left Ventricular Outflow Tract Obstruction

Hypertrophic cardiomyopathy (HCM) is the most common cardiac disease in cats. HCM is classified into obstructive HCM (HOCM) and non-obstructive HCM (HNCM) forms based on the presence or absence of left ventricular outflow tract obstruction (LVOTO). In humans, LVOTO is a known poor prognostic factor and a target for therapeutic intervention. In contrast, LVOTO has been reported not to contribute to prognosis in cats. This study demonstrated significant correlations between cTnI levels and a maximal LV outflow tract velocity (LVOTV). This finding suggests that LVOTO is associated with myocardial cell injury.

Diagnostic Value of Echocardiography in Cats With and Without Ultrasonographic Evidence of Renal Infarction

BACKGROUND

Revisiting the association between heart disease and renal infarction (RI) in cats is relevant to determine whether those with RI should undergo echocardiographic screening.

OBJECTIVE

Compare the relative frequency of echocardiographically detectable heart disease and other comorbidities in cats with and without ultrasonographic evidence of RI.

ANIMALS

A total of 826 cats that underwent concurrent abdominal ultrasonography and transthoracic echocardiography and were assigned a cardiac diagnosis.

METHODS

Two-center cross-sectional study with a study population recruitment period from January 1, 2011 to June 15, 2021. Demographic, clinical, clinicopathologic, and ultrasonographic data were recorded. Available echocardiographic images were reviewed to assign a standardized cardiac diagnosis. Occult heart disease was defined as structural heart disease without clinical signs of congestive heart failure. Risk factors for RI were evaluated by univariable or multivariable logistic regression.

RESULTS

The relative frequency of structural heart disease in cats with and without RI was 63% (114/181) and 46% (297/645), respectively (adjusted odds ratio [OR] 95% confidence interval [CI], 1.6; 1.2-2.3). Older age (p = 0.03), higher maximum end-diastolic left ventricular wall thickness (p = 0.02), higher systolic blood pressure (p = 0.02), auscultable cardiac abnormalities other than murmur (p = 0.04), and diagnosis of acute kidney injury (p = 0.002), chronic kidney disease (p = 0.005), and occult heart disease (OR [95% CI], 2.4 [1.7-3.4]; p ≤ 0.001) were associated with increased risk of RI. Strength and statistical significance of associations varied by site.

CONCLUSIONS AND CLINICAL IMPORTANCE

Occult heart disease is more frequent in cats with RI, and echocardiographic screening of these cats should be considered.

Clinical and echocardiographic variables associated with the type of congestive heart failure manifestation in cats

INTRODUCTION/OBJECTIVES

The aim of this study was to determine clinical and echocardiographic findings associated with congestive heart failure (CHF) manifestation type in cats and to assess impact on the risk of CHF recurrence and survival.

ANIMALS, MATERIALS AND METHODS

A retrospective medical record review of 135 cats with CHF was conducted. Cats were grouped based on CHF manifestation type. Associations between CHF manifestation and clinical and echocardiographic variables were assessed using a Fisher's test and analysis of variance. Comparisons between CHF manifestations were performed using a pairwise Fisher's test with Bonferroni-Holm adjustment and Tukey's honestly significant difference method after analysis of variance.

RESULTS

Congestive heart failure manifestation was associated with sex (P=0.045), history of increased respiratory rate (P=0.006), effort (P=0.001), and signs of arterial thromboembolism (P=0.004). Significant differences between left atrium-to-aorta ratio (P=0.043), diastolic right ventricular internal dimension (P=0.001), systolic right ventricular internal dimension (P=0.015), tricuspid annular plane systolic excursion (P=0.044), and presence of non-specific cardiomyopathy phenotype (P=0.001) were identified among CHF groups. Cats with ascites as their CHF manifestation had significantly higher median diastolic right ventricular internal dimension (9.9 mm) and systolic right ventricular internal dimension (6.6 mm) on pairwise comparison than cats with other CHF manifestations. Congestive heart failure manifestation did not have a statistically significant association with survival but did with time to CHF recurrence (P=0.008).

STUDY LIMITATIONS

Retrospective design, small sample size, and potential misclassification of CHF manifestation type are limitations of this study.

CONCLUSIONS

Congestive heart failure manifestation type is associated with various clinical and echocardiographic findings in cats with heart disease.

Metabolic abnormalities and reprogramming in cats with naturally occurring hypertrophic cardiomyopathy

BACKGROUND AND AIMS

The heart is a metabolic organ rich in mitochondria. The failing heart reprograms to utilize different energy substrates, which increase its oxygen consumption. These adaptive changes contribute to increased oxidative stress. Hypertrophic cardiomyopathy (HCM) is a common heart condition, affecting approximately 15% of the general cat population. Feline HCM shares phenotypical and genotypical similarities with human HCM, but the disease mechanisms for both species are incompletely understood. Our goal was to characterize global changes in metabolome between healthy control cats and cats with different stages of HCM.

METHODS

Serum samples from 83 cats, the majority (70/83) of which were domestic shorthair and included 23 healthy control cats, 31 and 12 preclinical cats with American College of Veterinary Internal Medicine (ACVIM) stages B1 and B2, respectively, and 17 cats with history of clinical heart failure or arterial thromboembolism (ACVIM stage C), were collected for untargeted metabolomic analysis. Multiple linear regression adjusted for age, sex and body weight was applied to compare between control and across HCM groups.

RESULTS

Our study identified 1253 metabolites, of which 983 metabolites had known identities. Statistical analysis identified 167 metabolites that were significantly different among groups (adjusted P < 0.1). About half of the differentially identified metabolites were lipids, including glycerophospholipids, sphingolipids and cholesterol. Serum concentrations of free fatty acids, 3-hydroxy fatty acids and acylcarnitines were increased in HCM groups compared with control group. The levels of creatine phosphate and multiple Krebs cycle intermediates, including succinate, aconitate and α-ketoglutarate, also accumulated in the circulation of HCM cats. In addition, serum levels of nicotinamide and tryptophan, precursors for de novo NAD+ biosynthesis, were reduced in HCM groups versus control group. Glutathione metabolism was altered. Serum levels of cystine, the oxidized form of cysteine and cysteine-glutathione disulfide, were elevated in the HCM groups, indicative of heightened oxidative stress. Further, the level of ophthalmate, an endogenous glutathione analog and competitive inhibitor, was increased by more than twofold in HCM groups versus control group. Finally, several uremic toxins, including guanidino compounds and protein bound putrescine, accumulated in the circulation of HCM cats.

CONCLUSIONS

Our study provided evidence of deranged energy metabolism, altered glutathione homeostasis and impaired renal uremic toxin excretion. Altered lipid metabolism suggested perturbed structure and function of cardiac sarcolemma membrane and lipid signalling.

Post-carvedilol myocardial function in cats with obstructive hypertrophic cardiomyopathy

Introduction

Hypertrophic cardiomyopathy (HCM) is the most prevalent cardiac disease in cats, and one phenotype includes obstructive HCM with dynamic left ventricular outflow tract obstruction (DLVOTO). Myocardial function has been reported to be lower in cats with obstructive HCM than in non-obstructive HCM. Carvedilol, because of its pharmacological action, is expected to reduce the pressure gradient associated with DLVOTO, but no previous reports have studied its effects on myocardial function. This study aimed to evaluate myocardial function in cats with obstructive HCM with left ventricular outflow tract obstruction treated by carvedilol administration.

Methods

This retrospective observational study included 16 cats with obstructive HCM and subsequent treatment of DLVOTO with carvedilol. In addition to conventional echocardiography, strain and strain rates in the left ventricular longitudinal and circumferential directions were measured using layer-specific two-dimensional speckle tracking echocardiography. Each variable was then compared before and after carvedilol medication.

Results

Systolic anterior motion of the mitral valve disappeared in 14 cats and all cats showed resolved DLVOTO with maximal left ventricular outflow tract blood flow velocity of <2.5 m/s after carvedilol administration (P < 0.01). Circumferential strain in the epicardial layer and in the whole layer was significantly increased after carvedilol administration (P < 0.01, P = 0.04, respectively). In contrast, systolic longitudinal strain showed no significant difference between before and after carvedilol administration.

Conclusion

Treatment of obstructive HCM with carvedilol improved DLVOTO and myocardial function without a negative inotropic effect. Carvedilol may be effective in treating cats with obstructive HCM.

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.

Occurrence and distribution of left ventricular bands and normal anatomical features in 78 feline hearts

INTRODUCTION/OBJECTIVES

Left ventricular bands (LVBs) are common in feline hearts. Their importance and general features are incompletely described. This study aimed to characterize LVBs in feline hearts based on anatomical location, quantity, histological features, and attachment sites.

ANIMALS, MATERIALS AND METHODS

Hearts from 78 domestic cats with or without heart disease were included in this study. Cardiac weight and dimensions were measured, and LVBs were categorized as singular bands or nets, with further characterization by location, length, appearance, and histological examination of attachment sites.

RESULTS

Median cardiac weight was 4.34 g/kg (interquartile range: 2.1 g/kg). Left ventricular bands were present in all hearts, with 11% having only singular bands, 32% containing only nets, and 42% having nets covering the entire left ventricle (LV). The most common LVB attachment sites were the LV mid-region involving the posterior papillary muscle. Nets were most common in the mid-region including the papillary muscles (93%), followed by basilar (60%) and apical (59%) regions. All LVBs contained collagen, myocytes, adipose tissue, endothelial cells, and fibroblasts. No excess fibrosis, myocardial hypertrophy, or endocardial thickening at the attachment sites was identified.

STUDY LIMITATIONS

The study included mainly domestic stray cats aged 12 weeks to 15 years, with few purebred or diseased individuals. The hearts were examined by one person, which may introduce subjectivity.

CONCLUSIONS

Left ventricular bands are commonly found in the mid LV section of feline hearts, primarily involving the posterior papillary muscle, suggesting normal variation. Left ventricular bands contain myocytes, not Purkinje fibers, and are not fibrous tendons. Myocyte hypertrophy or excess fibrosis is absent at attachment sites.

Prevalence of cardiomyopathy and cardiac mortality in a colony of non-purebred cats in New Zealand

AIMS

To evaluate the prevalence of subclinical cardiomyopathy and cardiac mortality in a research colony of non-purebred cats, established as a model of the wider cat population in New Zealand.

METHODS

All apparently healthy, compliant, non-pregnant, non-neonatal cats in the colony at the Centre for Feline Nutrition (Massey University, Palmerston North, NZ) underwent physical examination and echocardiography using a 4.4-6.2-MHz probe by a board-certified veterinary cardiologist. Cardiac phenotype was classified following current guidelines. Hypertrophic cardiomyopathy (HCM) phenotype was defined as an end-diastolic left ventricular wall thickness ≥ 6 mm. Colony mortality data from February 2012 to February 2022 was reviewed to determine cardiac mortality.

RESULTS

Cats (n = 132; 65 females and 67 males) included in the study had a median age of 4.1 (IQR 3.0-8.0) years. Thirty-two (24%) cats had a heart murmur, and three (2%) cats had an arrhythmia. Echocardiography revealed heart disease in 24 (18.2%) cats, including 23 with an HCM phenotype and one with a restrictive cardiomyopathy phenotype. Of the cats with the HCM phenotype, 3/23 had systemic hypertension or hyperthyroidism or both, and these cats were excluded from the final diagnosis of HCM (20/132; 15.2 (95% CI = 9.5-22.4)%).Between 2012 and 2022, 168 colony cats died, with 132 undergoing post-mortem examination. Heart disease was considered the cause of death in 7/132 (5.3%; 95% CI = 2.2-10.6%) cats; five had HCM, one a congenital heart defect, and one myocarditis. The overall prevalence of death related to HCM in the colony during this period was 3.8% (95% CI = 1.2-8.6%). Three cats with HCM and the cat with a congenital heart defect died unexpectedly without prior clinical signs, while congestive heart failure was observed prior to death in two cats with HCM and the cat with myocarditis. Additionally, 30/132 (22.7%) cats had cardiac abnormalities but died for non-cardiac reasons.

CONCLUSIONS

Subclinical cardiomyopathy, specifically HCM, was common in cats in the colony. Given that the colony originated as a convenience selection of non-purebred cats in New Zealand, the true prevalence of HCM in the wider New Zealand population is likely to fall within the 95% CI (9.5-22%). The proportion of deaths of colony cats due to HCM was lower (3.8%) supporting the conclusion that subclinical cardiomyopathy may not progress to clinical disease causing death.

CLINICAL RELEVANCE

Veterinarians should be aware of the high prevalence of subclinical HCM when treating cats.

ABBREVIATIONS

CAM: Systolic anterior motion of the chordae tendineae; CFN: Centre for Feline Nutrition; HCM: Hypertrophic cardiomyopathy; LA/Ao: Left atrial to aortic ratio; LV FS: Left ventricular fractional shortening; LVIDd: Left ventricular internal diameters in end-diastole; LVIDs: Left ventricular internal diameter in end-systole; LVWT: Max Maximum left ventricular wall thickness; SAM: Systolic anterior motion of the mitral valve; 2D: Two-dimensional.

Frequency and progression of azotemia during acute and chronic treatment of congestive heart failure in cats

BACKGROUND

Azotemia is common in cats with congestive heart failure (CHF) and might be exacerbated by diuretic therapy.

HYPOTHESIS/OBJECTIVES

Determine frequency, risk factors, and survival impact of progressive azotemia in cats treated for CHF.

ANIMALS

One hundred and sixteen client-owned cats with kidney function testing performed at least twice during acute or chronic CHF treatment.

METHODS

Serum creatinine (sCr) and electrolyte concentrations were determined at multiple clinical timepoints to detect azotemia and kidney injury (KI; sCr increase ≥0.3 mg/dL). Furosemide dosage between timepoints was calculated. Multivariable modeling was performed to identify predictors of KI, change in serum biochemistry results, and survival.

RESULTS

Azotemia was common at all timepoints, including initial CHF diagnosis (44%). Kidney injury was documented in 66% of cats. Use of a furosemide continuous rate infusion was associated with increased risk of KI during hospitalization (odds ratio, 141.6; 95% confidence interval [CI], 12.1-6233; P = .01). Higher furosemide dosage was associated with increase in sCr during hospitalization (P = .03) and at first reevaluation (P = .01). Treatment with an angiotensin converting enzyme inhibitor was associated with fewer lifetime KI events (P = .02). Age in years was the only variable associated with shorter survival (hazard ratio, 1.1; 95% CI, 1.0-1.1; P = .03). Neither sCr nor KI were associated with long-term outcome.

CONCLUSIONS AND CLINICAL IMPORTANCE

Azotemia and KI were common in cats during CHF treatment but did not impact survival.

Transcriptomic and genetic profiling in a spontaneous non-human primate model of hypertrophic cardiomyopathy and sudden cardiac death

Hypertrophic cardiomyopathy (HCM) afflicts humans, cats, pigs, and rhesus macaques. Disease sequelae include congestive heart failure, thromboembolism, and sudden cardiac death (SCD). Sarcomeric mutations explain some human and cat cases, however, the molecular basis in rhesus macaques remains unknown. RNA-Seq of the LV tissues of five HCM-affected and seven healthy control rhesus macaques was employed for differential transcriptomic analyses. DNA from 15 severely HCM-affected and 21 healthy geriatric rhesus macaques were selected for whole-genome sequencing. A genome-wide association study (GWAS) of disease status and SCD outcome was performed. 614 down- and 1,065 upregulated differentially expressed genes (DEGs) were identified between groups. The top DEG (MAFF) was overexpressed in affected animals (log2FoldChange = 4.71; PAdjusted-value = 1.14E-133). Channelopathy-associated enriched terms were identified in ~ 57% of downregulated DEGs providing transcriptomic evidence of hypertrophic and arrhythmic disease processes. For GWAS, no putative variant withstood segregation. Polygenic modeling analysis resulted in poor prediction power and burden testing could not explain HCM by an association of multiple variants in any gene. Neither single nor compound genetic variant(s), or identified polygenic profile, suggest complex genotype-phenotype interactions in rhesus macaques. Brought forth is an established dataset of robustly phenotyped rhesus macaques as an open-access resource for future cardiovascular disease genetic studies.

Evaluation of potential novel biomarkers for feline hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is the most common cardiomyopathy in cats. The diagnosis can be difficult, requiring advanced echocardiographic skills. Additionally, circulating biomarkers (N-terminal pro-B type natriuretic peptide and cardiac troponin I) have several limitations when used for HCM screening. In previous work, we identified interleukin 18 (IL-18), insulin-like growth factor binding protein 2 (IGFBP-2), brain-type glycogen phosphorylase B (PYGB), and WNT Family Member 5 A (WNT5A) as myocardial genes that show significant differential expression between cats with HCM and healthy cats. The products of these genes are released into the circulation, and we hypothesized that IL-18, IGFBP-2, PYGB, and WNT5A serum RNA and protein concentrations differ between healthy cats, cats with subclinical HCM, and those with HCM and congestive heart failure (HCM + CHF). Reverse transcriptase quantitative polymerase chain reaction (RTqPCR) and enzyme-linked immunosorbent assay (ELISA) were applied to evaluate gene and protein expression, respectively, in the serum of eight healthy controls, eight cats with subclinical HCM, and six cats with HCM + CHF. Serum IGFBP-2 RNA concentrations were significantly different among groups and were highest in cats with subclinical HCM. Compared to healthy controls, serum IL-18 and WNT5A gene expression were significantly higher in cats with HCM + CHF, and WNT5A was higher in cats with subclinical HCM. No differences were observed for PYGB. These results indicate that further investigation via large scale clinical studies for IGFBP-2, WNT5A, and IL-18 may be valuable in diagnosing and staging feline HCM.

Longitudinal assessment of systolic anterior motion of the mitral valve in cats with hypertrophic cardiomyopathy

BACKGROUND

The proportion of cats with hypertrophic cardiomyopathy (HCM) that lose systolic anterior motion of the mitral valve (SAM) in the long term is unknown.

HYPOTHESIS/OBJECTIVES

Cats with HCM will lose SAM in the long term. Loss of SAM will be associated with greater age, longer scan-interval, and altered left ventricular (LV) dimensions.

ANIMALS

Sixty unsedated cats with HCM, not receiving beta blockers or pimobendan.

METHODS

A retrospective cohort study from 2 referral centers. Cats were eligible if they had been diagnosed with HCM and had a repeat echocardiogram ≥1 year later. Clinical and echocardiographic data of the left heart variables were collected.

RESULTS

Thirty-eight cats had SAM at the initial scan. After a median follow-up time of 2.1 years (range: 1.0-5.9), 7 cats had lost SAM (18%) and 5 cats (23%) gained SAM. On follow-up, cats with SAM at the initial scan had a larger left atrium (P = .037), lower left atrial fractional shortening (P = .014), greater LV internal diameter in end-systole (P = .002), and lower LV fractional shortening (P < .001). Four cats with SAM developed congestive heart failure. There were no new cases of congestive heart failure or change in left heart variables in cats without SAM at the initial scan. The gain or loss of SAM was not associated with age or time between scans.

CONCLUSIONS AND CLINICAL IMPORTANCE

Similar proportions of cats gained or lost SAM. Cats with SAM at baseline had more evidence of disease progression than cats without SAM.

The effect of concurrent clopidogrel and omeprazole administration on clopidogrel metabolism and platelet function in healthy cats

BACKGROUND

Some studies in humans show that the concurrent use of clopidogrel and omeprazole decreases plasma clopidogrel active metabolite (CAM) concentrations and clopidogrel antiplatelet effects. Whether this drug interaction occurs in cats is unknown.

HYPOTHESIS

We hypothesized that administration of clopidogrel with omeprazole would decrease plasma CAM concentrations and decrease clopidogrel antiplatelet effects in healthy cats.

ANIMALS

Ten domestic cats.

METHODS

In this 2-sequence, 2-period, 2-treatment randomized crossover study, healthy cats were randomly assigned to receive clopidogrel only (18.75 mg PO q24h) or clopidogrel with omeprazole (1 mg/kg PO q12h) for 10 days, followed by a 2-week washout period, and then the opposite treatment for another 10 days. Blood was collected by jugular venipuncture on days 0, 5, and 10. Plasma CAM concentrations were measured using high-performance liquid chromatography-tandem mass spectrometry. Platelet function was evaluated using Plateletworks, Multiplate Analyzer, and Platelet Function Analyzer-100 (PFA-100).

RESULTS

Multiplate Analyzer and PFA-100 detected no difference in platelet function between days or treatment groups. Plateletworks detected a significant difference (P < .001) in platelet function from day 0 to 5 and day 0 to 10 in both treatment groups but no difference between treatment groups. Plasma CAM concentrations were significantly lower on day 10 (P < .02) in cats receiving both medications versus clopidogrel only.

CONCLUSIONS AND CLINICAL IMPORTANCE

Concurrent omeprazole and clopidogrel administration was associated with altered pharmacokinetics on day 10, but no difference in pharmacodynamics between the 2 treatment groups. The short-term use of clopidogrel and omeprazole does not seem to alter platelet function significantly.

CRISPR/Cas9 gene editing in induced pluripotent stem cells to investigate the feline hypertrophic cardiomyopathy causing MYBPC3/R820W mutation

Hypertrophic cardiomyopathy (HCM) is the most common heart disease in domestic cats, often leading to congestive heart failure and death, with current treatment strategies unable to reverse or prevent progression of the disease. The underlying pathological processes driving HCM remain unclear, which hinders novel drug discovery. The aim of this study was to generate a cellular model of the feline HCM-causing MYBPC3 mutation R820W. Using CRISPR/Cas9 gene editing we introduced the R820W mutation into a human induced pluripotent stem cell (iPSC) line. We differentiated both homozygous mutant clones and isogenic control clones to cardiomyocytes (iPSC-CMs). Protein quantification indicated that haploinsufficiency is not the disease mechanism of the mutation. Homozygous mutant iPSC-CMs had a larger cell area than isogenic controls, with the sarcomere structure and incorporation of cMyBP-C appearing similar between mutant and control iPSC-CMs. Contraction kinetic analysis indicated that homozygous iPSC-CMs have impaired relaxation and are hypocontractile compared to isogenic control iPSC-CMs. In summary, we demonstrate successful generation of an iPSC model of a feline MYBPC3 mutation, with the cellular model recapitulating aspects of HCM including cellular hypertrophy and impaired relaxation kinetics. We anticipate that further study of this model will lead to improved understanding of the disease-causing molecular mechanism, ultimately leading to novel drug discovery.

Feline hypertrophic cardiomyopathy: Does the microRNA-mRNA regulatory network contribute to heart sarcomeric protein remodelling?

Feline primary hypertrophic cardiomyopathy (HCM) is an intrinsic myocardial disease characterized by concentric hypertrophy of the left ventricle. In the present study, we investigated the microRNA-mRNA regulatory network in feline myocardial tissue affected by primary (HCMI) and secondary HCM (HCMII). MRNA expression levels of sarcomeric genes, including, TNNT2, TNNI3, MYH7, MYBPC3, TPM1 and ACTC1 were assessed in the FFPE myocardial tissues. FFPE tissues from healthy cats were sequenced by the NGS, to explore, in the entire non-deposited miRNome, the expression level of microRNAs targeting the complementary sequences of selected sarcomeric mRNAs. The sarcomeric genes TNNT2, MYH7, MYBPC3 and TPM1 showed a statistically significant upregulation in HCMI compared to HCMII (p < .01), except ACTC1 which was downregulated (p < .01); TNNI3 showed no statistically significant difference. In HCMII miR-122-5p, miR-338-3p, miR-484, miR-370-3p, miR-92b-3p, miR-375 and miR-370-3p showed a significant upregulation (p < .01) compared to control. The exception was miR-30a-5p which showed downregulation. Worthy of note is the 4-fold higher expression of miR-370-3p, a key regulator of MYBPC3, in HMCI compared to HMCII. This research does not solve the aetiological mystery of HCM, but it may help to find a way to help diagnose and define the prognosis of HCM in cats.

Resolution of dynamic left ventricular outflow tract obstruction and reversible left ventricular hypertrophy in 4 cats

This case series describes spontaneous resolution of systolic anterior motion of the mitral valve, cessation of a dynamic left ventricular outflow tract obstruction, and reverse cardiac remodeling in 4 young cats. Following initial presentation with or without congestive heart failure, subsequent rechecks documented resolution of systolic anterior motion of the mitral valve and normalization of left heart dimensions. Those cats originally presented with congestive heart failure were successfully weaned off diuretic medications. Atenolol was prescribed to all 4 cats, and all remained on oral atenolol through the final recheck. There was no documented recurrence of progressive heart disease and heart failure in any of the cats. Consideration is given to transient myocardial thickening, spontaneous resolution of mitral valve dysplasia, and response to beta-1 adrenergic antagonism as possible underlying mechanisms. Key clinical message: When presented with young cats with hypertrophic obstructive cardiomyopathy, veterinarians should consider multiple differential diagnoses, as lifespan in these cases may be longer than typically expected for cats with primary hypertrophic cardiomyopathy, even with concurrent congestive heart failure.

Prevalence of Hypertrophic Cardiomyopathy and ALMS1 Variant in Sphynx Cats in New Zealand

Recently, hypertrophic cardiomyopathy (HCM) in Sphynx cats has been associated with a variant in the gene encoding Alström syndrome protein 1 (ALMS1). The primary aims of this study were to describe the prevalence of HCM in Sphynx cats in New Zealand, and to assess the association between HCM and the ALMS1 variant in this population. In this prospective study, 55 apparently healthy Sphynx cats from registered Sphynx breeders and pet owners in New Zealand were screened by a cardiologist. A total of 42 of these cats had a repeat cardiac examination after median 1.8 years (range: 1.6-2.2). The frequency of the ALMS1 variant was 70.9% (11 homozygous and 28 heterozygous). At the median age of 5.8 years (range: 2.4-13.1), the prevalence of HCM was 40% (20 out of 55 cats). Three cats with HCM died during the study with congestive heart failure. All three cats had focal but extensive myocardial ischemia or infarction at necropsy. The ALMS1 variant was not associated with the HCM diagnosis. In summary, HCM was common in the studied cohort, suggesting Sphynx cats are predisposed to this disease. While the ALMS1 variant was also frequently detected, it was not associated with HCM in this population.

Genetic Basis of Hypertrophic Cardiomyopathy in Cats

Hypertrophic cardiomyopathy (HCM) is a common cardiovascular condition in cats, affecting yth males and females of all ages. Some breeds, such as Ragdolls and Maine Coons, can develop HCM at a young age. The disease has a wide range of progression and severity, characterized by various pathological changes in the heart, including arteritis, fibrous tissue deposition, and myocardial cell hypertrophy. Left ventricular hypertrophy, which can restrict blood flow, is a common feature of HCM. The disease may persist into old age and eventually lead to heart failure and increased diastolic pressure. The basis of HCM in cats is thought to be genetic, although the exact mechanisms are not fully understood. Mutations in sarcomeric proteins, in particular myosin-binding protein C (MYBPC3), have been identified in cats with HCM. Two specific mutations, MYBPC3 [R818W] and MYBPC3 [A31P], have been classified as 'pathogenic'. Other variants in genes such as MYBPC3, TNNT2, ALMS1, and MYH7 are also associated with HCM. However, there are cases where cats without known genetic mutations still develop HCM, suggesting the presence of unknown genetic factors contributing to the disease. This work aims to summarise the new knowledge of HCM in cats and the alterations in cardiac tissue as a result of genetic variants.

Transient myocardial thickening after routine ovariohysterectomy in a 15-month-old Ragdoll cat

A 15-month-old female Ragdoll cat was evaluated for progressive lethargy, tachypnoea and increased respiratory effort for 1 week after routine ovariohysterectomy. Thoracic radiographs and an echocardiogram showed evidence of congestive heart failure and a hypertrophic cardiomyopathy phenotype, respectively. The maximum left ventricular wall thickness in end diastole was 6.2 mm. The serum cardiac troponin I concentration was 20.86 ng/mL. The cat was treated with furosemide and clopidogrel and discharged after 3 days. A repeat echocardiogram 2 weeks later showed complete resolution of the hypertrophic cardiomyopathy phenotype (maximum left ventricular wall thickness: 5.0 mm). A repeat cardiac troponin I concentration was 0.041 ng/mL. All cardiac medications were discontinued. A final recheck 4 weeks later revealed stable normal echocardiogram and further reduction in cardiac troponin I concentration to 0.004 ng/mL. This case report demonstrates that resolution of transient myocardial thickening can take 2 weeks after the echocardiographic diagnosis of left ventricular thickening.

Exploring the impact of age, and body condition score on erythrocytic B1-Dependent transketolase activity in cats: A comprehensive analysis of thiamine status

One of the key factors influencing aging and morbidity is the overall antioxidant status and regenerative capacity. In examining contributors to the antioxidant status, we analyzed the thiamine status in felines and the influence of age, gender, and body condition score. We measured erythrocytic B1-dependent specific transketolase (STKT) activity, an enzyme in the pentose phosphate pathway, in a group of 60 sexually intact, healthy, and specific pathogen-free felines (44 females, 16 males, aged 1-17 years) with thiamine diphosphate (TDP; 0.3 and 3 mM) and without it. Only two parameters (STKT activity with and without 0.3 mM TDP) decreased with age. After adjusting for age, statistical thresholds were established using these and other age-independent parameters, identifying 15 felines with subclinical thiamine deficiency. The red blood cell proteomics analysis revealed that the pentose phosphate shunt, glycolysis, and oxidative stress response were the most affected pathways in deficient felines, confirming the above diagnosis. Age emerged as the primary factor associated with thiamine deficiency, supported by the enrichment of neurodegenerative diseases with a proteotoxicity component; five young-adult felines showed marginal or acute B1 deficiency, and six were adult-mature with a more chronic deficiency, possibly linked to cognitive decline, all with an underweight to ideal body condition scores. Only three senior-adult felines were deficient and overweight-obese. Detecting thiamine deficiency emphasizes the need for more accurate reference values, the establishment of advanced preventive or therapeutic measures to enhance the well-being of aging companion animals, and potential extensions to human health, particularly concerning cognitive function.

The Unseen Side of Feline Hypertrophic Cardiomyopathy: Diagnostic and Prognostic Utility of Electrocardiography and Holter Monitoring

Hypertrophic cardiomyopathy (HCM) is a common heart disease in cats, characterized by regional or diffuse hypertrophy of the left ventricular walls, with an uncertain etiology and heterogenous natural history. Several types of rhythm disturbances are often associated with the disease. This study conducts a comprehensive review of the current literature, in order to evaluate the diagnostic and prognostic effectiveness of electrocardiography and Holter monitoring in the management of feline hypertrophic cardiomyopathy. The main subjects of discussion will include general information about HCM and its connection to arrhythmias. We will explore the rhythm disturbances documented in the current literature on Holter monitoring, as well as the techniques used for Holter monitoring. Additionally, the review will cover classical electrocardiography (ECG) and its diagnostic utility. Prognostic indicators and anti-arrhythmic therapy will also be discussed in detail. The findings highlight the importance of understanding arrhythmias in feline HCM for accurate diagnosis, risk assessment, and therapeutic intervention. ECG and Holter monitoring may offer valuable insights into managing feline HCM.

Cardiac myosin inhibitor, CK-586, minimally reduces systolic function and ameliorates obstruction in feline hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) remains the most common cardiomyopathy in humans and cats with few preclinical pharmacologic interventional studies. Small-molecule sarcomere inhibitors are promising novel therapeutics for the management of obstructive HCM (oHCM) patients and have shown efficacy in left ventricular outflow tract obstruction (LVOTO) relief. The objective of this study was to explore the 6-, 24-, and 48-hour (h) pharmacodynamic effects of the cardiac myosin inhibitor, CK-586, in six purpose-bred cats with naturally occurring oHCM. A blinded, randomized, five-treatment group, crossover preclinical trial was conducted to assess the pharmacodynamic effects of CK-586 in this oHCM model. Dose assessments and select echocardiographic variables were assessed five times over a 48-h period. Treatment with oral CK-586 safely ameliorated LVOTO in oHCM cats. CK-586 treatment dose-dependently eliminated obstruction (reduced LVOTOmaxPG), increased measures of systolic chamber size (LVIDs Sx), and decreased select measures of heart function (LV FS% and LV EF%) in the absence of impact on heart rate. At all tested doses, a single oral CK-586 dose resulted in improved or resolved LVOTO with well-tolerated, dose-dependent, reductions in LV systolic function. The results from this study pave the way for the potential use of CK-586 in both the veterinary and human clinical setting.

Influence of Clinical Aspects and Genetic Factors on Feline HCM Severity and Development

Hypertrophic cardiomyopathy (HCM), which is associated with thickening of the left ventricular wall, is one of the most common heart pathologies in cats. This disease has a hereditary etiology and is primarily related to mutations in the MYBPC3 and MYH7 genes. This study aims to determine the effect of the presence of heterozygosity or homozygosity for the p. A31P mutation (c.91G>C) in the MYBPC3 gene in cats (Maine Coon) of different ages referring to the HCM severity and development, and to compare echocardiographic data and various clinical aspects for the most objective detection of disease in cats of different breeds. The incidence of HCM was 59% of the 103 cases of heart disease in cats in this study. In 23 cats diagnosed with HCM, cats heterozygous for the mutation accounted for 34%, and homozygous cats accounted for 26%. Cats homozygous for this mutation had moderate to severe HCM, suggesting an association with high penetrance of HCM and a significant risk of cardiac death in this group. The penetrance of the heterozygous type was lower than that of the homozygous genotype. This study also indicates that HCM has some age-related penetrance. The disease did not occur in the study group of cats aged up to 1 year, whereas at the age of 7 and older, the percentage of animals diagnosed with HCM was the highest and amounted to 44.3% of the total number of studied cats with HCM.

Bicavitary effusion in cats: retrospective analysis of signalment, clinical investigations, diagnosis and outcome

OBJECTIVES

The aim of this study was to describe the clinical and diagnostic findings and outcome of cats with bicavitary effusion presenting to a referral centre.

METHODS

Medical records of cats presenting with bicavitary effusion were identified and their history, physical examination findings, clinicopathological data, diagnostic imaging findings, aetiology of bicavitary effusions (cardiac disease, neoplasia, infectious disease, sterile inflammatory disease, severe hypoalbuminaemia, trauma, coagulopathy or 'open' if no definitive diagnosis was reached) and outcome were recorded. Cox regression analysis was performed to identify independent predictors of death in cats with bicavitary effusion. Kaplan-Meier curves were generated for survival analysis.

RESULTS

In total, 103 cats with bicavitary effusion were included. Neoplasia and cardiac disease were the most common aetiologies of bicavitary effusion, in 21 (20.4%) and 20 (19.4%) cats, respectively, followed by infectious disease (n = 11, 10.7%), trauma (n = 13, 12.6%), hypoalbuminaemia (n = 6, 5.8%), sterile inflammatory disease (n = 4, 3.9%) and coagulopathy (n = 1, 1.0%). The median survival time for all cats with bicavitary effusion was 3 days. Cats with a neoplastic aetiology had a 2.03 times greater risk of death compared with cats in which no diagnosis was achieved. Neoplasia (P = 0.030) and pedigree breed status (P = 0.016) were independent predictors of death in the multivariable Cox regression model.

CONCLUSIONS AND RELEVANCE

This study highlights that bicavitary effusions in cats generally carry a guarded to poor prognosis, particularly if neoplasia is the underlying aetiology or if the cat is a pedigree breed. Cardiac disease appeared to be associated with a better prognosis, suggesting that assessment for congestive heart failure should be considered early when evaluating cats with bicavitary effusion. The prognosis for cats with feline infectious peritonitis is likely to be markedly improved by the advent of novel antiviral drugs, compared with the historical cohort of cats presented here.

Classification of feline hypertrophic cardiomyopathy-associated gene variants according to the American College of Medical Genetics and Genomics guidelines

Introduction

The correct labeling of a genetic variant as pathogenic is important as breeding decisions based on incorrect DNA tests can lead to the unwarranted exclusion of animals, potentially compromising the long-term health of a population. In human medicine, the American college of Medical Genetics (ACMG) guidelines provide a framework for variant classification. This study aims to apply these guidelines to six genetic variants associated with hypertrophic cardiomyopathy (HCM) in certain cat breeds and to propose a modified criterion for variant classification.

Methods

Genetic samples were sourced from five cat breeds: Maine Coon, Sphynx, Ragdoll, Devon Rex, and British Short- and Longhair. Allele frequencies were determined, and in the subset with phenotypes available, odds ratios to determine the association with HCM were calculated. In silico evaluation followed with joint evidence and data from other publications assisting in the classification of each variant.

Results

Two variants, MYBPC3:c.91G > C [A31P] and MYBPC3:c.2453C > T [R818W], were designated as pathogenic. One variant, MYH7:c.5647G > A [E1883K], was found likely pathogenic, while the remaining three were labeled as variants of unknown significance.

Discussion

Routine genetic testing is advised solely for the MYBPC3:c.91G > C [A31P] in the Maine Coon and MYBPC3:c.2453C > T [R818W] in the Ragdoll breed. The human ACMG guidelines serve as a suitable foundational tool to ascertain which variants to include; however, refining them for application in veterinary medicine might be beneficial.

Basic triage in dogs and cats: Part I

Background

Emergency cases can present at any time of the day or night. All small animal practitioners need to have the skills to triage and stabilize common emergency cases even if they ultimately aim to refer the patient to another facility.

Objectives and procedures

The first part of this 3-part review article series covers respiratory distress and seizures. A stepwise approach to categorize and stabilize these cases is outlined, along with helpful tips to optimize the referral experience, if indicated.

Results

Having a strong methodical approach to animals in respiratory distress optimizes treatment. Similarly, achieving cessation of seizures, along with having a good understanding of the causes of seizures, allows for patient stabilization.

Conclusion and clinical relevance

Do NOT refer emergent cases before completing basic stabilization. Many emergency cases do not require emergent referral and can be worked up by the primary veterinarian or sent to a referral clinic on an appointment basis after appropriate stabilization steps are completed.

Arterial thromboembolism in a cat with transient myocardial thickening

Feline arterial thromboembolism has been reported to be secondary to various feline cardiomyopathies; however, it has not been described in cats with transient myocardial thickening. A previously healthy, one-year-old, castrated male cat presented with acute paraparesis and congestive heart failure. Echocardiography revealed asymmetric left ventricular free wall thickening and left atrial enlargement. Antithrombotic treatment and cardiac medication resulted in reperfusion and mobility on day seven in one limb and on day 10 in the other. Different complications were managed successfully, including worsening acute kidney injury, inflammation, pleural effusion, and anemia. After three weeks, the cat was discharged and prescribed oral antithrombotic drugs (clopidogrel and rivaroxaban) and cardiac medication. Within five months, echocardiographic findings normalized, and medical treatment was gradually discontinued. To date, the cat remains healthy at 1735 days after the initial diagnosis and 1494 days after the last antithrombotic medication. To the best of our knowledge, this is the first case report on feline arterial thromboembolism combined with transient myocardial thickening, with favorable long-term survival.

Long-term safety of dietary salt: A 5-year ProspEctive rAndomized bliNded and controlled stUdy in healThy aged cats (PEANUT study)

BACKGROUND

High-salt diets promote urine dilution and decrease urolithiasis risk.

OBJECTIVE

Prospectively evaluate the safety of chronic high dietary salt intake (randomized controlled trial).

ANIMALS

Twenty research colony neutered, healthy aged cats (11.5 years [10.0-11.6], median [interquartile range]).

METHODS

Healthy cats were randomized to control or high-salt dry diets (sodium: 1.02 ± 0.16 [mean, SD] and 3.26 ± 0.30 g/Mcal metabolizable energy [ME], respectively; chloride: 2.26 ± 0.33 and 5.71 ± 0.28 g/Mcal ME, respectively), fed for up to 60 months. Assessments included CBC, plasma biochemistry, urinalysis, glomerular filtration rate (GFR), blood pressure, renal and cardiac (conventional Doppler and 2-dimensional color tissue Doppler) imaging, annually. Cats that died or were euthanized underwent necropsy. Diet effects over time were evaluated with linear mixed models.

RESULTS

Follow-up duration (median [Interquartile range]) was similar between the control (38.7 months [28.6-48.2]) and high-salt group (51.4 months [45.7-59.0]). Diet had no significant effect on changes in GFR, blood pressure, plasma creatinine concentration, end-diastolic left ventricular (LV) wall thicknesses, LV internal diameters, LV systolic function, left atrial size, or systolic and diastolic Doppler variables. One control cat developed hypertension. One high-salt group cat developed persistent azotemia. Serial plasma biochemistry and urine specific gravity suggested early chronic kidney disease in 4 nonazotemic cats (2 per group), consistent with necropsy findings.

CONCLUSIONS AND CLINICAL IMPORTANCE

In healthy aged cats, a commercial veterinary diet containing 3.26 ± 0.30 g/Mcal ME sodium was safe with regard to renal and cardiac function for up to 5 years.

Transient myocardial thickening: a retrospective analysis on etiological, clinical, laboratory, therapeutic, and outcome findings in 27 cats

INTRODUCTION/OBJECTIVE

Transient myocardial thickening (TMT) in cats is a poorly characterized clinical entity. Therefore, this study aimed to provide descriptions of additional cats diagnosed with this clinical phenomenon.

ANIMALS, MATERIALS, AND METHODS

For this multicenter observational retrospective study, cats diagnosed with TMT were searched in three medical databases. TMT was defined for cats with at least two echocardiograms showing an increased end-diastolic left ventricular wall thickness (LVWTd; i.e. ≥6 mm) at presentation and subsequent echocardiographic normalization (i.e. LVWTd <5.5 mm). Signalment, history, clinical, laboratory, therapeutic, and outcome data were retrieved.

RESULTS

Twenty seven cats were included. The median age was 3 years. In 9/27 cats, an antecedent event was documented. At admission, 27/27 cats had evidence of myocardial injury (median value of cardiac troponin I 5.5 ng/mL), 25/27 cats had congestive heart failure, 13/27 cats had hypothermia, 8/27 cats had systemic hypotension, 7/27 cats had bradycardia, and 7/27 cats had electrocardiographic evidence of an arrhythmia. The median LVWTd was 6.4 mm. A potential cause of myocardial injury was identified in 14/27 cats. The median time from diagnosis to a significant reduction in LVWTd was 43 days.

DISCUSSION

TMT can be diagnosed in a wide range of cats, including young subjects. An antecedent predisposing event and/or a possible causative trigger can be identified in some. The reduction in LVWTd that defines this phenomenon usually occurs over a variable time frame.

CONCLUSIONS

This study represents the largest investigation of TMT in cats and provides additional information on this uncommon clinical entity.

Single- and multiple-dose pharmacokinetics of sotalol hydrochloride in healthy cats

INTRODUCTION/OBJECTIVES

The objective of this study was to describe the single- and multiple-dose pharmacokinetics and urinary elimination of sotalol in healthy cats.

ANIMALS

Six adult purpose-bred cats MATERIALS AND METHODS: Cats were administered 2 mg sotalol/kg body weight as a single intravenous bolus and as a single oral dose in a randomized crossover study with a 2-week washout period. The same cats then received 3 mg sotalol/kg orally every 12 h for 2 weeks. Blood samples were collected at predetermined time points for 48 h postdose for quantification of sotalol using ultra-high-pressure liquid chromatography with mass spectrometry. Non-compartmental analysis was used to obtain pharmacokinetic parameters. Data are presented as median (min-max).

RESULTS

Following intravenous administration, plasma clearance and volume of distribution were 9.22 mL/min/kg (5.69-10.89) and 2175.56 (1961-2341.57) mL/kg, respectively. Bioavailability was 88.41% (62.75-130.29) following a single oral dose. Peak plasma concentration (Cmax) and time to Cmax were 0.94 μg/mL (0.45-1.17) and 1.5 h (0.5-4) after a single oral dose (2 mg/kg), and 2.29 μg/mL (1.91-2.48) and 1.0 h (0.5-1.5) with chronic oral dosing (3 mg/kg), respectively. Elimination half-life was 2.75 h (2.52-4.10) and 4.29 h (3.33-5.53) for single and chronic oral dosing, respectively. Accumulation index was 1.17 (1.09-1.29) after chronic dosing. Urinary sotalol recovery was 81-108% of the intravenous dose.

CONCLUSIONS

Oral sotalol administration resulted in plasma concentrations reportedly efficacious in other species, with good to excellent oral bioavailability. Urinary excretion appears to be a major route of elimination. Following repeated oral dosing, minimal drug accumulation was estimated. Additional studies in cats are recommended due to the possibility of nonlinear kinetics.

Hypertrophic Cardiomyopathy-Advances in Imaging and Diagnostic Strategies

Hypertrophic cardiomyopathy (HCM) is the most important and prevalent cardiac disease in cats. Due to the highly variable nature of HCM, a multimodal approach including physical examination, genetic evaluation, cardiac biomarkers, and imaging are all essential elements to appropriate and timely diagnosis. These foundational elements are advancing rapidly in veterinary medicine. Newer biomarkers such as galectin-3 are currently being researched and advances in tissue speckle-tracking and contrast-enhanced echocardiography are readily available. Advanced imaging techniques, such as cardiac MRI, are providing previously unavailable information about myocardial fibrosis and paving the way for enhanced diagnostic capabilities and risk-stratification in cats with HCM.

Preventing Cardiogenic Thromboembolism in Cats: Literature Gaps, Rational Recommendations, and Future Therapies

Cardiogenic arterial thromboembolism (CATE) is a devastating complication in cats with cardiomyopathies with significant morbidity and mortality. Despite recent advances in the diagnosis and treatment of CATE, its recurrence and mortality remain high. This highlights the urgent need for a greater understanding of CATE pathophysiology so that novel diagnostic tests and therapeutics can be developed. This comprehensive review aims to summarize existing literature on pathophysiology, clinical diagnosis, and current recommendations on the prevention and treatment of CATE. It also identifies and describes knowledge gaps and research priorities in the roles of immunothrombosis and procoagulant platelets in the pathogenesis of CATE.

Predicting Development of Hypertrophic Cardiomyopathy and Disease Outcomes in Cats

Echocardiography is the gold standard imaging modality to diagnose hypertrophic cardiomyopathy (HCM) in cats. Echocardiographic features can predict both cats at an increased risk of developing HCM and cats with HCM at an increased risk of developing cardiovascular events or experiencing cardiac death. Left atrial dysfunction seems to be an important feature of HCM, as it is an early phenotypic abnormality and is also associated with worse outcome.

Delayed-release rapamycin halts progression of left ventricular hypertrophy in subclinical feline hypertrophic cardiomyopathy: results of the RAPACAT trial

OBJECTIVE

Feline hypertrophic cardiomyopathy (HCM) remains a disease with little therapeutic advancement. Rapamycin modulates the mTOR pathway, preventing and reversing cardiac hypertrophy in rodent disease models. Its use in human renal allograft patients is associated with reduced cardiac wall thickness. We sought to evaluate the effects of once-weekly delayed-release (DR) rapamycin over 6 months on echocardiographic, biochemical, and biomarker responses in cats with subclinical, nonobstructive HCM.

ANIMALS

43 client-owned cats with subclinical HCM.

METHODS

Cats enrolled in this double-blinded, multicentered, randomized, and placebo-controlled clinical trial were allocated to low- or high-dose DR rapamycin or placebo. Cats underwent physical examination, quality-of-life assessment, blood pressure, hematology, biochemistry, total T4, urinalysis, N-terminal pro-B-type natriuretic peptide, and cardiac troponin I at baseline and days 60, 120, and 180. Fructosamine was analyzed at screening and day 180. Echocardiograms were performed at all time points excluding day 120. Outcome variables were compared using a repeated measures ANCOVA.

RESULTS

No demographic, echocardiographic, or clinicopathologic values were significantly different between study groups at baseline, confirming successful randomization. At day 180, the primary study outcome variable, maximum LV myocardial wall thickness at any location, was significantly lower in the low-dose DR rapamycin group compared to placebo (P = .01). Oral DR rapamycin was well tolerated with no significant differences in adverse events between groups.

CLINICAL RELEVANCE

Results demonstrate that DR rapamycin was well tolerated and may prevent or delay progressive LV hypertrophy in cats with subclinical HCM. Additional studies are warranted to confirm and further characterize these results.

Multi-Omic, Histopathologic, and Clinicopathologic Effects of Once-Weekly Oral Rapamycin in a Naturally Occurring Feline Model of Hypertrophic Cardiomyopathy: A Pilot Study

Hypertrophic cardiomyopathy (HCM) remains the single most common cardiomyopathy in cats, with a staggering prevalence as high as 15%. To date, little to no direct therapeutical intervention for HCM exists for veterinary patients. A previous study aimed to evaluate the effects of delayed-release (DR) rapamycin dosing in a client-owned population of subclinical, non-obstructive, HCM-affected cats and reported that the drug was well tolerated and resulted in beneficial LV remodeling. However, the precise effects of rapamycin in the hypertrophied myocardium remain unknown. Using a feline research colony with naturally occurring hereditary HCM (n = 9), we embarked on the first-ever pilot study to examine the tissue-, urine-, and plasma-level proteomic and tissue-level transcriptomic effects of an intermittent low dose (0.15 mg/kg) and high dose (0.30 mg/kg) of DR oral rapamycin once weekly. Rapamycin remained safe and well tolerated in cats receiving both doses for eight weeks. Following repeated weekly dosing, transcriptomic differences between the low- and high-dose groups support dose-responsive suppressive effects on myocardial hypertrophy and stimulatory effects on autophagy. Differences in the myocardial proteome between treated and control cats suggest potential anti-coagulant/-thrombotic, cellular remodeling, and metabolic effects of the drug. The results of this study closely recapitulate what is observed in the human literature, and the use of rapamycin in the clinical setting as the first therapeutic agent with disease-modifying effects on HCM remains promising. The results of this study establish the need for future validation efforts that investigate the fine-scale relationship between rapamycin treatment and the most compelling gene expression and protein abundance differences reported here.

Systolic third sound associated with systolic anterior motion of the mitral valve in cats with obstructive hypertrophic cardiomyopathy

BACKGROUND

Third heart sounds in cats frequently are associated with hypertrophic cardiomyopathy (HCM) but their exact characterization and timing within the cardiac cycle remains unknown.

OBJECTIVES

Characterize third heart sounds in cats by phonocardiography and test the ability of 3 observers with different levels of experience and training to recognize third systolic heart sounds in cats.

ANIMALS

Fifty client-owned cats of different breeds presented for heart screening.

METHODS

Cats were prospectively assessed using an electronic stethoscope (with digital recording) and then underwent full conventional echocardiographic examination. Audio recordings were blindly assessed in a random order by 3 observers: the cardiologist who collected clinical data, as well as a trained and an untrained junior veterinarian. Cohen's kappa coefficients were calculated to quantify agreement between the opinion of each observer and the echocardiography results (considered the gold standard).

RESULTS

Twenty cats had a third systolic sound on phonocardiography and an obstructive HCM phenotype with systolic anterior motion of the mitral valve (SAM) on echocardiography. Agreement with echocardiography was very good for the experienced cardiologist, substantial for the trained junior veterinarian, and poor for the untrained junior veterinarian (kappa of 0.92, 0,64, and 0.08, respectively).

CONCLUSIONS AND CLINICAL IMPORTANCE

We describe here a new auscultatory abnormality in cats with obstructive HCM. It could help a trained non-cardiologist veterinarian in suspecting obstructive HCM in cats based on auscultation only.

Prospective evaluation of a telmisartan suppression test as a diagnostic tool for primary hyperaldosteronism in cats

BACKGROUND

In a previous study, telmisartan suppressed aldosterone secretion in healthy cats but not in cats with primary hyperaldosteronism (PHA).

HYPOTHESES

Telmisartan suppresses aldosterone secretion in middle-aged healthy cat and cats with diseases that may result in secondary hyperaldosteronism, but not in those with PHA.

ANIMALS

Thirty-eight cats: 5 with PHA; 16 with chronic kidney disease (CKD), subclassified as hypertensive (CKD-H) or non-hypertensive (CKD-NH); 9 with hyperthyroidism (HTH); 2 with idiopathic systemic arterial hypertension (ISH); and 6 healthy middle-aged cats.

METHODS

Prospective, cross-sectional study. Serum aldosterone concentration, potassium concentration, and systolic blood pressure were measured before and 1 and 1.5 hours after PO administration of 2 mg/kg of telmisartan. The aldosterone variation rate (AVR) was calculated for each cat.

RESULTS

No significant difference in the minimum AVR was observed among groups (median [quartile 1 (Q1); quartile 3 (Q3)]: 25 [0; 30]; 5 [-27; -75]; 10 [-6; -95]; 53 [19; 86]; 29 [5; 78]) for PHA, CKD, HTH, ISH, and healthy cats, respectively (P = .05). Basal serum aldosterone concentration (pmol/L) was significantly higher in PHA cats (median [Q1; Q3]: 2914 [2789; 4600]) than in CKD-H cats (median [Q1; Q3]: 239 [189; 577], corrected P value = .003) and CKD-NH cats (median [Q1; Q3]: 353 [136; 1371], corrected P value = .004).

CONCLUSIONS AND CLINICAL IMPORTANCE

The oral telmisartan suppression test using a single dose of 2 mg/kg telmisartan did not discriminate cats with PHA from healthy middle-aged cats or cats with diseases that may result in secondary hyperaldosteronism.

Synergistic inhibitory effects of clopidogrel and rivaroxaban on platelet function and platelet-dependent thrombin generation in cats

BACKGROUND

Dual antithrombotic treatment (DAT) with clopidogrel and rivaroxaban sometimes is prescribed to cats with hypertrophic cardiomyopathy at risk of thromboembolism. To date, no studies have evaluated their combined effects on platelet function.

OBJECTIVES/HYPOTHESIS

Evaluate the safety of DAT in healthy cats and compare, ex vivo, platelet-dependent thrombin generation and agonist-induced platelet activation and aggregation in cats treated with clopidogrel, rivaroxaban, or DAT. We hypothesized that DAT would safely modulate agonist-induced platelet activation and aggregation more effectively than single agent treatment.

ANIMALS

Nine apparently healthy 1-year-old cats selected from a research colony.

METHODS

Unblinded, nonrandomized ex vivo cross-over study. All cats received 7 days of rivaroxaban (0.6 ± 0.1 mg/kg PO), clopidogrel (4.7 ± 0.8 mg/kg PO), or DAT with defined washout periods between treatments. Before and after each treatment, adenosine diphosphate (ADP)- and thrombin-induced platelet P-selectin expression was evaluated using flow cytometry to assess platelet activation. Platelet-dependent thrombin generation was measured by fluorescence assay. Platelet aggregation was assessed using whole blood impedance platelet aggregometry.

RESULTS

No cats exhibited adverse effects. Of the 3 treatments, only DAT significantly decreased the number of activated platelets (P = .002), modulated platelet activation in response to thrombin (P = .01), dampened thrombin generation potential (P = .01), and delayed maximum reaction velocity (P = .004) in thrombin generation. Like clopidogrel, DAT inhibited ADP-mediated platelet aggregation. However, rivaroxaban alone resulted in increased aggregation and activation in response to ADP.

CONCLUSION AND CLINICAL IMPORTANCE

Treatment combining clopidogrel and rivaroxaban (DAT) safely decreases platelet activation, platelet response to agonists, and thrombin generation in feline platelets more effectively than monotherapy with either clopidogrel or rivaroxaban.

Hypertrophic cardiomyopathy in purpose-bred cats with the A31P mutation in cardiac myosin binding protein-C

We sought to establish a large animal model of inherited hypertrophic cardiomyopathy (HCM) with sufficient disease severity and early penetrance for identification of novel therapeutic strategies. HCM is the most common inherited cardiac disorder affecting 1 in 250-500 people, yet few therapies for its treatment or prevention are available. A research colony of purpose-bred cats carrying the A31P mutation in MYBPC3 was founded using sperm from a single heterozygous male cat. Cardiac function in four generations was assessed by periodic echocardiography and measurement of blood biomarkers. Results showed that HCM penetrance was age-dependent, and that penetrance occurred earlier and was more severe in successive generations, especially in homozygotes. Homozygosity was also associated with progression from preclinical to clinical disease. A31P homozygous cats represent a heritable model of HCM with early disease penetrance and a severe phenotype necessary for interventional studies aimed at altering disease progression. The occurrence of a more severe phenotype in later generations of cats, and the occasional occurrence of HCM in wildtype cats suggests the presence of at least one gene modifier or a second causal variant in this research colony that exacerbates the HCM phenotype when inherited in combination with the A31P mutation.

Comparative study of myocardial function in cases of feline hypertrophic cardiomyopathy with and without dynamic left-ventricular outflow-tract obstruction

In recent years, hypertrophic cardiomyopathy (HCM) in cats has become much more common in clinical practice due to improvements in diagnostic techniques and equipment performance. One phenotype is obstructive HCM with left ventricular (LV) outflow tract obstruction (DLVOTO). It has been reported that the presence or absence of DLVOTO does not affect long-term prognosis in cats with HCM. In this study, we evaluated and compared myocardial function in HCM-affected cats with and without DLVOTO using the two-dimensional speckle-tracking echocardiography. LV longitudinal strain of the endocardial, epicardial, and whole layer and LV circumferential strain of the epicardium were significantly decreased in all HCM-affected cats compared to healthy cats. However, these values were not significantly different between those with and without DLVOTO. In contrast, the endocardial and whole layers of LV circumferential strain were only significantly decreased in HCM-affected cats with DLVOTO compared to healthy cats. This could be attributed to the fact that the LV pressure load associated with DLVOTO affected the endocardial myocardium more in the LV endocardial layer, and that lower values of LV endocardial strain lowered the values of LV strain in the whole layer. In conclusion, our results suggest that LV myocardial function may have been more compromised in the HCM-affected cats with DLVOTO.

Clinical findings using echocardiography and plasma cardiac troponin I and pathological findings in dogs with hypertrophic cardiomyopathy: A retrospective study

Background

Hypertrophic cardiomyopathy (HCM) is considered rare in dogs, and there is a lack of clinical data. Cardiac troponin I (cTnI) is a biomarker of cardiomyocyte damage and necrosis and can be used to diagnose cat and human HCM.

Aim

We investigated whether the presence of cTnI in clinical data can be used in conjunction with echocardiography to diagnose canine HCM.

Methods

This study comprised client-owned dogs with clinical evidence of concentric hypertrophy on echocardiographic images, serum total thyroxine levels of ≤5 µg/dl, systolic blood pressure of ≤180 mmHg, and absence of aortic stenosis. All cases were necropsied.

Results

Cardiomyocyte hypertrophy (mean diameter, 18.3 ± 1.8 µm), myocardial fiber disarray (70%), interstitial fibrosis (80%), and small vessel disease (100%) were assessed. In dogs with HCM, the left ventricles were concentric, almost symmetrical, and hypertrophied above the aortic diameter. The end-diastolic interventricular septum normalized to body weight [intraventricular septal thickness in diastole (IVSDN)] was 0.788 [interquartile range (IQR), 0.7-0.92], which exceeded the normal range (5%-95%, IQR: 0.33-0.52). In total, 70% of the dogs with HCM had syncope and dyspnea, and all dogs had high cTnI levels (median, 3.94 ng/ml), exceeding the upper limit of normal (0.11 ng/ml) and indicating cardiomyocyte damage. IVSDN and serum cTnI levels were correlated (ρ = 0.839, p = 0.01).

Conclusion

Ventricular wall thickening and high serum cTnI levels can provide a presumptive diagnosis of HCM and prompt the initiation of treatment or additional diagnostic investigations.

Thin and hypokinetic myocardial segments in cats with cardiomyopathy

INTRODUCTION/OBJECTIVES

Thin and hypokinetic myocardial segments (THyMS) represent adverse ventricular (LV) remodeling in human hypertrophic cardiomyopathy. We describe the echocardiographic features and outcome in cats with THyMS, and in a subpopulation, the echocardiographic phenotype before LV wall thinning was detected (pre-THyMS).

ANIMALS

Eighty client-owned cats.

MATERIALS AND METHODS

Retrospective multicenter study. Clinical records were searched for cats with THyMS, defined as LV segment(s) with end-diastolic wall thickness (LVWT) <3 mm and hypokinesis in the presence of ≥one LV segment(s) with LVWT >4 mm and normal wall motion. When available, echocardiograms pre-THyMS were assessed. Survival time was defined as time from first presentation with THyMS to death.

RESULTS

Mean thickest LV wall segment (MaxLVWT) was 6.1 mm (95% CI 5.8-6.4 mm) and thinnest (MinLVWT) was 1.7 mm (95% CI 1.6-1.9 mm). The LV free wall was affected in 74%, apex in 13% and septum in 5%. Most cats (85%) presented with heart failure and/or arterial thromboembolism. Median circulating troponin I concentration was 1.4 ng/mL ([range 0.07-180 ng/mL]). Prior echocardiography results were available for 13/80 cats, a mean of 2.5 years pre-THyMS. In segments subsequently undergoing thinning, initial MaxLVWT measured 6.7 mm (95% CI 5.8-7.7 mm) vs. 1.9 mm (95% CI 1.5-2.4 mm) at last echocardiogram (P<0.0001). Survival data were available for 56/80 cats, median survival time after diagnosing THyMS was 153 days (95% CI 83-223 days). Cardiac histopathology in one cat revealed that THyMS was associated with severe transmural scarring.

CONCLUSIONS

Cats with THyMS had advanced cardiomyopathy and a poor prognosis.

Longevity and mortality in cats: A single institution necropsy study of 3108 cases (1989-2019)

Client-owned cats who underwent a post-mortem examination (n = 3,108) at a veterinary medical teaching hospital between 1989 and 2019 were studied to determine longevity and factors affecting mortality. Demographic factors, environmental factors, age, and causes of death were assessed. Sexes included 5.66% intact females, 39.86% spayed females, 6.95% intact males and 47.49% neutered males. 84.2% were mixed breed cats. Age at death was known for 2,974 cases with a median of 9.07 years. Cancer was the most common pathophysiologic cause of death (35.81%) and was identified in 41.3% of cats. When categorized by organ system, mortality was most attributed to multiorgan/systemic (21.72%). Renal histologic abnormalities were noted in 62.84% of cats but was considered the primary cause of death in only 13.06% of cats. Intact female and male cats had significantly shorter lifespans than their spayed or neutered counterparts. FeLV positive status was associated with decreased longevity (P<0.0001) while FIV status was not. This study reports on risk factors associated with mortality and highlights areas of research that may contribute to improved lifespan in cats.

Effects of ivabradine and atenolol on heart rate and heart rate variability in healthy cats over a 24 h period: A pilot study

BACKGROUND

Ivabradine is used to treat tachycardia; unlike atenolol, it does not affect blood pressure or myocardial contractility. This study compared the impact of ivabradine and atenolol on heart rate (HR) and HR variability (HRV) during a 24 h period, feeding and sleeping times, via a Holter electrocardiogram in healthy cats. We hypothesised that ivabradine and atenolol would lower the HRs equally well, even at times of excitement and rest, such as during feeding and sleep; that ivabradine, unlike atenolol, would have an effect on HRV.

METHODS

Five clinically healthy cats were used in the prospective blinded crossover study receiving 3 days of ivabradine (0.30 mg/kg per os twice daily) followed by atenolol (6.25 mg/cat per os twice daily, range 1.3-2.0 mg/kg) or receiving atenolol followed by ivabradine. A placebo period was initiated before the start of the crossover test, data obtained during that period were used as a baseline (BL). Evaluation parameters included HR and HRV, for the whole 24 h period and for feeding and sleeping times, comparing the effect of ivabradine and atenolol with BL.

RESULTS

The HR for the whole 24 h, feeding and sleeping times, were significantly lower with ivabradine and atenolol, compared to BL (p < 0.05). The HRV for the whole 24 h and sleeping time were significantly higher after ivabradine compared with BL and after atenolol.

CONCLUSIONS

In healthy cats, ivabradine and atenolol significantly reduced the HR regardless of excitement and rest; their effects were comparable. Ivabradine significantly increased HRV in comparison to BL whereas atenolol did not.

A Questionnaire Survey on Long-Term Outcomes in Cats Breed-Screened for Feline Cardiomyopathy

Feline cardiomyopathy (FCM) is an important contributor to feline morbidity and mortality. This explorative follow-up questionnaire study was aimed at investigating the long-term outcome in cats breed-screened for FCM (BS-FCM) in three Nordic countries. Records of cats with ≥1 BS-FCM between 2004−2015 were included. Of the 1113 included cats, 104/1113 (9.3%) had developed FCM at some time-point. Fifty-nine of the 104 (56.7%) FCM cats were diagnosed within the screening program (ScreenFCM), and 33/59 (55.9%) of these were diagnosed at the first BS-FCM. ScreenFCM cats or with an owner-reported FCM diagnosis at a later time-point had a higher risk of cardiac-related death compared to cats that never developed FCM. A shorter lifespan was found in ScreenFCM cats compared to those with normal screen results (p < 0.001). Times to all-cause mortality were shorter (p < 0.001) in cats that developed FCM at any time-point compared to those that did not. Non-cardiac morbidities were similar in all screen classification groups. The large proportion of cats that developed FCM at a later time-point underscores the need for repeated screenings later in life. Cats that developed FCM at any time-point had a shorter lifespan, with a similar proportion and in line with the nature of non-cardiac morbidities, compared to those without FCM.

Reduced risk of arterial thromboembolism in cats with pleural effusion due to congestive heart failure

OBJECTIVES

The aim of the study was to determine whether cardiogenic pleural effusion in cats is associated with a lower risk of arterial thromboembolism (ATE) compared with cats with cardiac disease without evidence of pleural effusion.

METHODS

A cross-sectional study was conducted on owned cats with natural occurring cardiac diseases. Cats included were classified in three groups: those with cardiac disease but no evidence of congestive heart failure (CHF); those with evidence of cardiogenic pulmonary oedema; and those with evidence of cardiogenic pleural effusion. Prevalence of ATE was calculated and the variables analysed for an association with this outcome were the presence and type of CHF, sex and neuter status, age, breed, type of cardiac diseases and left atrial (LA) dimension. A multivariable logistic regression model was used to fit the association between ATE and these variables.

RESULTS

A total of 366 cats with cardiac disease met the inclusion criteria: 179 were included in the group with cardiac disease but no evidence of CHF, 66 in the group with evidence of cardiogenic pulmonary oedema and 121 in the group with evidence of cardiogenic pleural effusion. Prevalence of ATE (58/366 [15.8%]) was significantly different among groups (with no evidence of CHF, 28/179 [15.6%]; with evidence of cardiogenic pulmonary oedema, 22/66 [33.3%]; with evidence of cardiogenic pleural effusion, 8/121 [6.6%]; P <0.001). Cats with ATE had a significantly higher LA to aortic root ratio (2.30 ± 0.46) than those without ATE (2.04 ± 0.46; P <0.001). Multivariable logistic regression analysis indicated that the group with evidence of cardiogenic pleural effusion was associated with a lower risk of developing ATE compared with groups with cardiac disease but no evidence of CHF and with evidence of cardiogenic pulmonary oedema (P = 0.005 and P <0.001, respectively).

CONCLUSIONS AND RELEVANCE

Presence of cardiogenic pleural effusion is associated with a lower risk of developing ATE, while LA enlargement is a risk factor for ATE.

Should we be screening cats for cardiomyopathy? If so, how?

Occult feline hypertrophic cardiomyopathy (HCM) can result in unexpected sudden death or congestive heart failure (CHF) following routine interventions such as anesthesia, fluid administration, or, potentially, administration of corticosteroids. Consequently, clinicians would like to be able to screen at-risk cats to detect occult HCM and either avoid the risky intervention or attempt to reduce the risk of death or CHF. Currently, the feline N-terminal-proBrain natriuretic peptide test is the only potential screening test for detecting occult HCM. However, some cardiologists have pointed out the poor sensitivity of the test precludes its use as a screening test. This interpretation appears somewhat flawed. Using the current rapid test will allow clinicians to correctly identify half of the cats with moderate-to-severe occult HCM. A small number of cats without HCM will also test positive, necessitating an ultimately needless echocardiographic evaluation to demonstrate their disease-free status. However, the low prevalence of HCM in the general cat population and the apparently much lower rate of adverse events than would be predicted brings into question whether clinicians should bother screening. Therefore, until a more sensitive and accurate screening test becomes available, clinicians will have to decide for themselves whether identifying half of the at-risk cats of sudden death and CHF with this test is better than identifying none of them.

Cardiac gene activation varies between young and adult cats and in the presence of hypertrophic cardiomyopathy

Little is known about the difference of myocardial gene transcription in young and adult cats and how transcription is further modified in cats with hypertrophic cardiomyopathy (HCM) and with left atrial (LA) thrombus formation. We hypothesized that selected factors for coagulation, endothelial activation, inflammation, and remodelling are modified with age and are activated in the hearts of cats with HCM. Left atrial and ventricular (LV) samples from 12 cats with HCM (seven without (HCMwoAT] and five with LA thrombi [HCMwAT]), and six young (YC) and six adult (AC) control cats without cardiac disease were investigated for relative expression of the following genes using quantitative polymerase chain reaction: von Willebrand factor, a disintegrin and metalloproteinase with a thrombospondin type 1 motif member 13, platelet activating factor, E- and P-selectin, intercellular and vascular adhesion molecules-1, ß2-integrin, vascular endothelial growth factor, interleukin-6 (IL-6), monocyte chemoattractant protein-1 (MCP-1), heat shock protein-70, and myocyte-specific enhancer factor 2C. Significant differences in gene activation were found between YC and AC, and YC and cats with HCM. Compared to AC, MCP-1 and IL-6 were significantly higher in cats with HCM. The presence of an LA thrombus was associated with higher IL-6 expression. These results illustrate the relevance of age and/or lifestyle on gene expression in the feline heart. The gene transcription pattern found in AC hearts might predispose cats to their characteristic cardiac remodelling processes and thrombus formation if disease occurs. It further supports the involvement of inflammation, but not coagulation and endothelial activation, in HCM.