Asymptomatic Hypertrophic Cardiomyopathy

Comparison of two multimodal intramuscular anaesthetic protocols in uncooperative feline patients: effects on sedation and echocardiographic measurements

OBJECTIVES

The aims of this study were to compare the sedative effect, feasibility of venous angiocatheter placement and influence on heart rate (HR), systemic blood pressure (SBP) and echocardiographic variables of two multimodal anaesthetic protocols in uncooperative cats; and to compare their influence on HR, SBP and echocardiographic variables 20 mins after sedation and after elective ovariectomy.

METHODS

Eighteen stray female cats randomly received intramuscular (IM) ketamine (2 mg/kg) and methadone (0.3 mg/kg) plus dexmedetomidine (7 µg/kg; group D, n = 9) or alfaxalone (2 mg/kg; group A, n = 9). A sedation score (0-15 [from none to good sedation]) was assigned at 5 mins, 10 mins, 15 mins and 20 mins after IM injection. Venous angiocatheter placement and echocardiographic examination feasibility scores (both from 0 to 3 [from very difficult to very easy]) were recorded at 20 mins. Echocardiography, HR and blood pressure measurements (Doppler and oscillometric methods) were performed at 20 mins and at the end of surgery.

RESULTS

Sedation and angiocatheter feasibility scores did not differ significantly between groups (P >0.05); the feasibility score of echocardiographic examination was higher in cats in group D (P = 0.01). HR was higher in group A at 20 mins and after surgery (P <0.05). The systolic arterial pressure obtained with the Doppler method was statistically significantly higher in cats in group D than in group A at 20 mins (P = 0.01), while postoperatively there were no differences between groups. Cats in group D showed significantly higher atrial diameters (P <0.05) and slower atrial flows (P = 0.04) compared with group A; ventricular thickness and atrial function did not differ between groups (P >0.05). Most echocardiographic variables were not different at 20 mins vs postoperatively.

CONCLUSIONS AND RELEVANCE

Both protocols allowed for effective sedation; however, cats in group D presented alterations in some echocardiographic measurements; the use of alfaxalone, combined with ketamine and methadone, is recommended to obtain a reliable echocardiographic evaluation in uncooperative cats.

Effects of Aficamten on cardiac contractility in a feline translational model of hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is the most prevalent inherited cardiac disease in humans and cats and lacks efficacious pharmacologic interventions in the preclinical phase of disease. LV outflow tract obstruction (LVOTO) is commonly observed in HCM-affected patients and is a primary driver of heart failure symptoms and reduced quality of life. Novel small-molecule cardiac myosin inhibitors target actin-myosin interactions to alleviate overactive protein interactions. A prospective, randomized, controlled cross-over study was performed to evaluate pharmacodynamic effects of two doses (0.3 and 1 mg/kg) of a next-in-class cardiac myosin inhibitor, aficamten (CK-3773274, CK-274), on cardiac function in cats with the A31P MYBPC3 mutation and oHCM. Dose-dependent reductions in LV systolic function, LVOT pressure gradient, and isovolumetric relaxation times compared to baseline were observed. Promising beneficial effects of reduced systolic function warrant further studies of this next-in-class therapeutic to evaluate the benefit of long-term administration in this patient population.

Essential microelement (copper, selenium, zinc) status according to age and sex in healthy cats

Although domestic cats are one of the most popular companion animals, current knowledge on the fate of micronutrients in cats according to their age, sex, and health is very limited. In this study, 72 whole blood and 54 plasma samples from cats of different ages and sex were collected at three veterinary offices in the Czech Republic, and the copper (Cu), selenium (Se), and zinc (Zn) concentrations were determined using inductively coupled plasma mass spectrometry (ICP-MS). The results showed that Cu was significantly (P < 0.05) higher in both plasma and whole blood of males (980 and 958 μg L-1 in plasma and whole blood, respectively) than in females (741 and 766 μg L-1 in plasma and whole blood, respectively), whereas no significant differences between males and females were found for Se and Zn. Similarly, no significant differences were recorded for any of the three elements according to age, although animals older than 7 years tended to have lower plasma concentrations of all three elements. Hypertrophic cardiomyopathy (HCM) is one of the most prevalent diseases of domestic cats. The potential relationship between the essential microelement status in the blood of cats with HCM vs. cats with no clinical signs of HCM was taken into account, but the limited number of HCM-positive individuals did not allow any clear conclusion. Thus, the potential relationships between micronutrient status in cats and the incidence of HCM should be elucidated in further research.

Ambulatory electrocardiography, heart rate variability, and pharmacologic stress testing in cats with subclinical hypertrophic cardiomyopathy

The utility of ambulatory electrocardiography (AECG) to evaluate cats with subclinical hypertrophic cardiomyopathy (HCM) for arrhythmias and heart rate variability (HRV) is not well defined but may provide information regarding risk stratification. This prospective study used AECG to evaluate ectopy and HRV in subclinical HCM cats compared to healthy controls and is the first to implement a pharmacologic cardiac stress test. Twenty-three purpose-bred, Maine coon cross cats (16 HCM, 7 control) underwent 48-h of continuous AECG. Terbutaline (0.2-0.3 mg/kg) was administered orally at 24 and 36 h. Heart rate, ectopy frequency and complexity and HRV parameters, including standard deviation of normal R-R intervals (SDNN), were compared pre-terbutaline and post-terbutaline and across phenotype, genotype and sex. Genotype for an HCM-causative mutation was significantly associated with the frequency of supraventricular (P = 0.033) and ventricular (P = 0.026) ectopy across all cats. Seven HCM cats and zero healthy cats had a sinus arrhythmia. Mean heart rate was significantly higher post-terbutaline (p < 0.0001). HCM cats had significantly greater HRV compared to controls (SDNN: p = 0.0006). Male cats had significantly higher HRV (SDNN: p = 0.0001) and lower mean heart rates (p = 0.0001). HRV decreased post-terbutaline (SDNN: p = 0.0008) and changes in HRV observed between sexes were attenuated by terbutaline.

Feline hypertrophic cardiomyopathy: reduced microvascular density and involvement of CD34+ interstitial cells

The sequence of pathological events in feline hypertrophic cardiomyopathy (fHCM) is still largely unknown, although we know that fHCM is characterized by interstitial remodeling in a macrophage-driven pro-inflammatory environment and that myocardial ischemia might contribute to its progression. This study aimed to gain further insights into the structural changes associated with interstitial remodeling in fHCM with special focus on the myocardial microvasculature and the phenotype of the interstitial cells. Twenty-eight hearts (16 hearts with fHCM and 12 without cardiac disease) were evaluated in the current study, with immunohistochemistry, RNA-in situ hybridization, and transmission electron microscopy. Morphometrical evaluations revealed a statistically significant lower microvascular density in fHCM. This was associated with structural alterations in capillaries that go along with a widening of the interstitium due to the accumulation of edema fluid, collagen fibers, and mononuclear cells that also proliferated locally. The interstitial cells were mainly of fibroblastic or vascular phenotype, with a substantial contribution of predominantly resident macrophages. A large proportion expressed CD34 mRNA, which suggests a progenitor cell potential. Our results indicate that microvascular alterations are key events in the pathogenesis of fHCM and that myocardial interstitial cell populations with CD34+ phenotype play a role in the pathogenesis of the disease.

Correlation of Histopathological Changes in the Left Atrium and Left Atrial Appendage with the Degree of Dilation in Cats

Although atrial dilation is a common finding in feline cardiac disease, detailed investigations of atrial pathology are rare in cats. The aim of the study was to investigate the correlation between pathohistological findings, morphometric data and the degree of dilation of the left atrial appendage (LAA) in 53 cats. Based on the LAA volume, the samples were grouped into normal/control (group 0, ≤1 ml [n = 9]), mildly dilated (group 1, >1 to ≤2 ml [n = 16]), moderately dilated (group 2, >2 to ≤3 ml [n = 14]) and markedly dilated (group 3, >3 ml [n = 14]) groups, independent of the underlying disease. Samples from the LAA and the left atrium (LA) were histologically evaluated using haematoxylin and eosin- and Picrosirius red-stained sections, and morphometrically analysed using an image analysis system. The degree of endo-, myo- and epicardial fibrosis was directly correlated with increased LAA dilation. Due to cardiomyocyte hyperplasia and hypertrophy, the mean thickness of the atrial wall was significantly greater in groups 1 and 2 than in group 0. Conversely, group 3 had a lower mean atrial wall thickness than groups 1 and 2, which was attributed to increased transmural fibrosis and cardiomyocyte atrophy. These findings reflect intensive dynamic remodelling processes during LA and LAA dilation, indicating that reversibility appears to be limited in cases of severe left atrial dilation.

Topical Minoxidil Exposures and Toxicoses in Dogs and Cats: 211 Cases (2001-2019)

Topical minoxidil is a medication for hair loss, initially available in the United States by prescription only and available since 1996 as an over-the-counter product. To determine the epidemiology of minoxidil exposures and toxicoses in dogs and cats, 211 dog and cat cases with topical minoxidil exposure were identified from the American Society for the Prevention of Cruelty to Animals Animal Poison Control Center database. In 87 cases with clinical signs of toxicosis (62 cats, 25 dogs), case narratives were reviewed and coded for exposure-related circumstances. Unintentional delivery, especially while pet owners applied minoxidil for his/her own hair loss (e.g., pet licked owner's skin or pillowcase, pet was splashed during a medication spill), was the most common cat exposure circumstance. Exploratory behavior (e.g., searching through trash) was the most common dog exposure circumstance. Clinical signs occurred in dogs and cats even with low exposure amounts, such as drops or licks. In patients that developed clinical signs, most developed moderate or major illness (56.0% dogs, 59.7% cats). Death occurred in 8/62 (12.9%) cats that developed clinical signs after the pet owner's minoxidil use. Pet owners should be educated on the risk of dog and cat toxicosis from accidental minoxidil exposure.

Sudden cardiac death: A comparative review of humans, dogs and cats

Sudden death is one of the most common causes of death in humans in Western countries. Approximately 85% of these cases are of cardiac origin. In dogs and cats, sudden cardiac death (SCD) also commonly occurs, but fewer pathophysiological and prevalence data are available. Both structural, primarily 'electrical' and ischemic heart diseases are known to cause SCD, many of which share similar underlying arrhythmogenic mechanisms between humans and companion animals. As for underlying genetics, numerous mutations on multiple loci have been related to SCD in humans, but only a few mutations associated with dilated cardiomyopathy and SCD have been identified in dogs, e.g. in the phospholamban and titin genes. Information published from human medicine can therefore inform future veterinary studies, but also dogs and cats could act as spontaneous models of SCD in humans. Further research in both fields is therefore warranted to better understand the pathophysiology, genetics, and prevention of SCD.

Dual therapy with clopidogrel and rivaroxaban in cats with thromboembolic disease

OBJECTIVES

Feline arterial thromboembolism (ATE), an often devastating outcome, was recently shown to affect 11.3% of cats with hypertrophic cardiomyopathy over 10 years. Current American College of Veterinary Internal Medicine guidelines recommend the use of clopidogrel in cats at risk for ATE, with addition of a factor Xa inhibitor in very high risk or post-ATE cases. To date, no studies have examined the safety or efficacy of this combined antithrombotic therapy. This retrospective case series aimed to assess the frequency and type of adverse events that occurred in cats prescribed dual clopidogrel and rivaroxaban therapy. Secondary aims were to evaluate indications for dual therapy and clinical outcome.

METHODS

The study included 32 cats prescribed clopidogrel (18.75 mg PO q24h) and rivaroxaban (2.5 mg PO q24h) on an outpatient basis over a 5-year period.

RESULTS

Cats were prescribed dual therapy for at least one of the following: ATE event (n = 18), presence of an intracardiac thrombi (n = 17) or presence of spontaneous echocardiographic contrast (SEC) (n = 16). Five cats experienced adverse effects that could be attributed to medications, a median of 13 days from initiation (epistaxis, hematemesis, hematochezia or hematuria). No cat required hospitalization as a result of these events. Median survival time from onset of therapy was 257 days (interquartile range [IQR] = 38-497) for all cats, 502 days (IQR = 171-663) for ATE cats, 725 days (IQR = 133-856) for cats with an ATE to two or more limbs and 301 days (IQR = 221-431) for cats with only one limb affected. Recurrence rate of ATE while on dual therapy was 16.7%; no cat newly developed an ATE while on dual therapy.

CONCLUSIONS AND RELEVANCE

Dual antithrombotic therapy with clopidogrel and rivaroxaban resulted in a low reported incidence of adverse events. Cats placed on dual therapy for an ATE event experienced a low rate of recurrence and effective thromboprophylaxis was achieved in cats with intracardiac thrombi or SEC.

Intramuscular alfaxalone and methadone with or without ketamine in healthy cats: effects on sedation and echocardiographic measurements

OBJECTIVE

To evaluate the effect of alfaxalone and methadone administered intramuscularly (IM), with or without ketamine, on sedation and echocardiographic measurements in healthy cats.

STUDY DESIGN

A randomized, blinded, clinical study.

ANIMALS

A group of 24 client-owned cats.

METHODS

Baseline echocardiographic evaluation (bEchoCG) was performed. Cats were given IM alfaxalone (2 mg kg^-1) and methadone (0.3 mg kg^-1) with (AMK group) or without (AM group) ketamine (1 mg kg^-1). A sedation score (0-5, indicating none to good sedation) was assigned at 5 (T5), 10 (T10) and 15 (T15) minutes after IM injection. At T15, a second echocardiographic evaluation (sEchoCG) was performed. Data are shown as median (range). Significance was p < 0.05.

RESULTS

Finally, 21 cats were included. Sedation score was significantly higher in the AMK (11 cats) than in the AM group (10 cats): 4 (1-5) versus 0.5 (0-4) at T5 (p = 0.003); 4 (1-5) versus 1.5 (0-5) at T10 (p = 0.043); and 4 (1-5) versus 2 (0-5) at T15 (p = 0.024). All echocardiographic measurements obtained were within reference ranges. Between the groups, aortic root area (p = 0.009) and end-diastolic aortic dimension (p = 0.011) were significantly higher in the AM group at bEchoCG and sEchoCG, respectively. Within each group, values at bEchoCG and sEchoCG showed no significant differences, except for pulmonary peak velocity (0.85 m second^-1; p = 0.028) in the AMK group and ejection time (154 m second; p = 0.03) in the AM group; both variables decreased after sedation.

CONCLUSIONS AND CLINICAL RELEVANCE

In this population of healthy cats, neither protocol produced clinically meaningful effects on the echocardiographic variables evaluated. Alfaxalone with methadone produced mild sedation, whereas the addition of 1 mg kg^-1 ketamine induced adequate sedation for diagnostic procedures.

Genetics of feline hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is characterized by an abnormal increase in myocardial mass that affects cardiac structure and function. HCM is the most common inherited cardiovascular disease in humans (0.2%) and the most common cardiovascular disease in cats (14.7%). Feline HCM phenotype is very similar to the phenotype found in humans, but the time frame for the development of the disease is significantly shorter. Similar therapeutic agents are used in its treatment and it has the same complications, such as heart failure, thromboembolism and sudden cardiac death. In contrast to humans, in whom thousands of genetic variants have been identified, genetic studies in cats have been limited to fragment analysis of two sarcomeric genes identifying two variants in MYBPC3 and one in MYH7. Two of these variants have also been associated with human disease. The high prevalence of the reported variants in non-affected cats hinders the assumption of their pathogenicity in heterozygotes. An in-depth review of the literature about genetic studies on feline HCM in comparison with the same disease in humans is presented here. The close similarity in the phenotype and genotype between cats and humans makes the cat an excellent model for the pathophysiological study of the disease and future therapeutic agents.

Cats with thermal burn injuries from California wildfires show echocardiographic evidence of myocardial thickening and intracardiac thrombi

Recent increases in the prevalence and severity of wildfires in some regions have resulted in an increased frequency of veterinary burn patients. Few studies exist regarding diagnostics and management of burn wounds in veterinary patients and current knowledge is extrapolated from human literature and research models. Post-burn cardiac injury is a common finding and predictor of mortality in human patients and echocardiography is an important tool in monitoring response to therapy and predicting outcome. We describe the notable findings from cats naturally exposed to California wildfires in 2017 and 2018. Domestic cats (n = 51) sustaining burn injuries from the Tubbs (2017) and Camp (2018) wildfires were prospectively enrolled and serial echocardiograms and cardiac troponin I evaluations were performed. Echocardiograms of affected cats revealed a high prevalence of myocardial thickening (18/51) and spontaneous echocardiographic contrast and thrombi formation (16/51). Forty-two cats survived to discharge and 6 died or were euthanized due to a possible cardiac cause. For the first time, we describe cardiovascular and coagulation effects of thermal burn and smoke inhalation in cats. Further studies in veterinary burn victims are warranted and serve as a translational research opportunity for uncovering novel disease mechanisms and therapies.

Cats with thermal burn injuries from California wildfires show echocardiographic evidence of myocardial thickening and intracardiac thrombi

Recent increases in the prevalence and severity of wildfires in some regions have resulted in an increased frequency of veterinary burn patients. Few studies exist regarding diagnostics and management of burn wounds in veterinary patients and current knowledge is extrapolated from human literature and research models. Post-burn cardiac injury is a common finding and predictor of mortality in human patients and echocardiography is an important tool in monitoring response to therapy and predicting outcome. We describe the notable findings from cats naturally exposed to California wildfires in 2017 and 2018. Domestic cats (n = 51) sustaining burn injuries from the Tubbs (2017) and Camp (2018) wildfires were prospectively enrolled and serial echocardiograms and cardiac troponin I evaluations were performed. Echocardiograms of affected cats revealed a high prevalence of myocardial thickening (18/51) and spontaneous echocardiographic contrast and thrombi formation (16/51). Forty-two cats survived to discharge and 6 died or were euthanized due to a possible cardiac cause. For the first time, we describe cardiovascular and coagulation effects of thermal burn and smoke inhalation in cats. Further studies in veterinary burn victims are warranted and serve as a translational research opportunity for uncovering novel disease mechanisms and therapies.

Antioxidant defence and oxidative stress markers in cats with asymptomatic and symptomatic hypertrophic cardiomyopathy: a pilot study

Background

Hypertrophic cardiomyopathy is the most common cardiovascular cause of death in cats. Although the majority of cats remain asymptomatic, some may develop signs of chronic heart failure due to diastolic failure, arterial thromboembolism (ATE) or sudden cardiac death. Therefore, it is crucial to identify individuals that are in high risk of developing cardiac complications before the onset of life-threatening signs. Oxidative stress is the imbalance between the production and neutralisation of reactive oxygen species. Uncontrolled reactive oxygen species overproduction leads to protein and lipid peroxidation and damages the DNA strands, injuring the cells and leading to their death. The aim of the study was to evaluate the oxidative state in cats with hypertrophic cardiomyopathy and healthy controls.

Results

In total, 30 cats divided into three groups were assessed: animals with clinically evident hypertrophic cardiomyopathy (HCM; n = 8), subclinical hypertrophic cardiomyopathy (SUB-HCM; n = 11) and healthy controls (n = 11). The activity of superoxide dismutase was statistically significantly lower in animals with symptomatic and asymptomatic hypertrophic cardiomyopathy (HCM 0.99 ± 0.35 U/mL; SUB-HCM 1.39 ± 0.4 U/mL) compared to healthy cats (2.07 ± 0.76 U/mL, p < 0.01). The activity of catalase was significantly lower in the SUB-HCM group (19.4 ± 4.2 nmol/min/mL) compared to the HCM (23.6 ± 5.9 nmol/min/mL) and the control (30 ± 7.5 nmol/min/mL, p < 0.01) group. The activity of glutathione peroxidase was 4196 ± 353 nmol/min/mL in the HCM group, 4331 ± 451 nmol/min/mL in the SUB-HCM group and 4037 ± 341 nmol/min/mL in the control group and did not differ significantly between groups. The total antioxidant capacity of plasma was 602 ± 65.5 copper reducing equivalents (CRE) in the HCM group, 605.9 ± 39.9 CRE in the SUB-HCM group and 629 ± 77.5 CRE in the healthy cats and did not differ significantly between the groups.

Conclusions

Activities of superoxide dismutase and catalase differed in cats with hypertrophic cardiomyopathy, however the activity of the latter was only significantly lower in asymptomatic stage of the disease. The potentially beneficial effect of antioxidative substances on the disease progression in the asymptomatic and symptomatic stage of this disease should also be examined.

Pericardial Disease, Myocardial Disease, and Great Vessel Abnormalities in Horses

Pericardial, myocardial, and great vessel diseases are relatively rare in horses. The clinical signs are often nonspecific and vague, or related to the underlying cause. Physical examination usually reveals tachycardia, fever, venous distension or jugular pulsation, a weak or bounding arterial pulse, ventral edema, and abnormal cardiac auscultation such as arrhythmia, murmur, or muffled heart sounds. The prognosis depends on the underlying cause and the disease progression, and ranges from full recovery to poor prognosis for survival. This article focuses on the etiology, diagnosis, prognosis, and treatment of pericarditis, pericardial mass lesions, myocarditis, cardiomyopathy, and great vessel aneurysm or rupture.

Survival and prognostic factors in cats with restrictive cardiomyopathy: a review of 90 cases

OBJECTIVES

Large studies focusing on restrictive cardiomyopathy (RCM) in the cat are scarce. The aims of this retrospective study were to describe epidemiological characteristics and to analyse prognostic factors affecting survival in cats with RCM.

METHODS

The clinical archives of the Gran Sasso Veterinary Clinic (Milan, Italy) and of the cardiology unit of the Department of Veterinary Medicine (University of Milan, Italy) from 1997-2015 were reviewed for all cats diagnosed with RCM based on an echocardiographic examination (left atrial/biatrial enlargement, normal left ventricle wall thickness, normal or mildly decreased systolic function and restrictive left ventricle filling pattern with pulsed Doppler echocardiography).

RESULTS

The study population comprised 90 cats (53 male, 37 female) with an echocardiographic diagnosis of RCM. Most were domestic shorthairs (n = 60) with a mean ± SD age of 10.0 ± 4.3 years and a median weight of 3.8 kg (interquartile range 3.2-5 kg). Most cats were symptomatic (n = 87). The most common clinical sign was respiratory distress (n = 75). Follow-up was available for 60 cats and the median survival time (MST) was 69 days (95% confidence interval [CI] 0-175 days). Cardiac-related death occurred in 50 cats. In the multivariate Cox analysis only respiratory distress showed a statistically significant effect on survival. The cats without respiratory distress showed an MST of 466 days (95% CI 0-1208); cats with respiratory distress showing an MST of 64 days (95% CI 8-120; P = 0.011).

CONCLUSIONS AND RELEVANCE

RCM can be considered an end-stage condition associated with a poor prognosis, with few cats not showing clinical signs and surviving >1 year. Most cats died of cardiac disease within a very short time.