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Cardiac cachexia in cats with congestive heart failure | VETgirl Veterinary Continuing Education Podcasts

In this VETgirl online veterinary CE podcast, we review cardiac cachexia in cats with congestive heart failure (CHF) – does it affect their prognosis and outcome? Cachexia, or bodily wasting in the form of muscle and weight loss, is a common systemic effect of numerous chronic diseases, including CHF. Sarcopenia refers to muscle loss associated with aging in the absence of an overt disease state. Cachexia negatively impacts patient quality of life and survival. Uniformly accepted definitions to identify cachexia and sarcopenia are lacking, and many variations in definition exist. The limited data evaluating cardiac cachexia in dogs and cats suggests a prevalence of 48-69%. Weight loss is a generally accepted criterion for determination of the presence of cachexia, which may result in underdiagnosis of cachexia in the early stages because muscle loss may precede loss in actual body weight. In cardiac cachexia, this lag in loss of body weight may be even more likely due to fluid retention, which may offset detectable loss of tissue weight. In humans, the loss of muscle itself is correlated with the aforementioned reductions in vigor and quality of life, not weight loss.

Defining and recognizing cachexia in animals may carry particular importance in that it may play a role in owner decisions about euthanasia, representing one of a number of barometers for quality of life. So, Santiago et al out of Tufts Cummings School of Veterinary Medicine wanted to evaluate this in a study entitled Cardiac cachexia in cats with congestive heart failure: Prevalence and clinical, laboratory, and survival findings. The purpose of this retrospective study was to use a variety of available definitions for cachexia to compare prevalence of cachexia in cats with CHF, with the premise that using a focused muscle condition score (MCS) would be more accurate in detecting cachexia than other methods. Clinical and laboratory findings, as well as overall outcomes, were also evaluated.

Data on cats presenting to the Cardiology service at Tufts Vet between 2015-2018 was collected, corresponding with the time period at which routine recording of MCS was instituted for cardiology patients. Cats were determined to have CHF secondary to cardiomyopathy based on radiographs and/or thoracic ultrasound and echocardiogram. Exclusion criteria included age < 1 year, significant concurrent systemic disease, unregulated hyperthyroidism or systemic hypertension, and cats with cardiac diagnoses other than primary cardiomyopathy. Data recorded included signalment, type of cardiomyopathy, International Small Animal Cardiac Health Council (ISACHC) heart disease stage, complete blood count, serum chemistry, body weight, body condition score (BCS, out of 9), and MCS [A-D representing normal (A), mild, moderate, or severe muscle loss (D) – a pictorial representation of MCS is available in the manuscript]. Follow-up on survival status was attempted for all cats if not immediately evident in the medical record. Seven different definitions of cardiac cachexia from human and veterinary literature were compared, one of which included solely the aforementioned MCS scale (definition #7). For complete description of these definitions, please refer to the manuscript in full.

Provided courtesy of the World Small Animal Veterinary Association (WSAVA) Global Nutrition Committee. Copyright Tufts University, 2014.

In this study, a total of 125 cats met criteria for inclusion into the study. The median age at time of diagnosis of CHF was 10.3 years of age. Male cats (89) were noted more frequently than females (36). Domestic short hair or long hair represented the overwhelming majority (101). The vast majority of cats had hypertrophic cardiomyopathy (HCM, 107 cats) compared with other cardiomyopathies. The vast majority of cats also had ISACHC stage 3 disease (advanced CHF). 41.6% (52/125) of cats had cachexia present at time of diagnosis using definition number 7 (MCS only), which corresponds fairly well to the prevalence obtained in prior studies of dogs and cats referenced above. By comparison, only 12% of cats were considered cachectic using BCS alone (BCS < 4/9, definition #6). Muscle loss was noted across all BCS categories, but more commonly in normal to underweight versus overweight cats. Across the seven definitions, prevalence of cachexia varied widely from 0-66.6%. The lowest prevalence (0%) was noted with definition 1, which required weight loss of at least 5% in the 12 months prior to diagnosis of CHF plus at least three of the following: decreased muscle strength, fatigue, anorexia, low fat-free mass index, anemia or hypoalbuminemia. The highest prevalence occurred for definition 3 (greater than or equal to 5% weight loss after the diagnosis of CHF). Overall, median percentage body weight change in the 6-12 months prior to diagnosis of CHF (for cats where a weight in this time period was available) was -3.3%, compared with -11.1% median percentage body weight change after diagnosis. Since MCS alone (definition #7) was available for all cats at time of diagnosis (compared with some of the definitions of cachexia which required parameters not available or routinely measured in cats), and since MCS directly assesses visible muscle loss, this definition was used for the remaining analyses of cachexia with all other parameters. Cats with cachexia had higher age, presence of pleural effusion, and BUN. They also had lower body weight (at time of diagnosis as well as lowest recorded weight thereafter), hematocrit and hemoglobin.

Cats with cachexia had shorter all-cause survival time (95 days) versus those without (281 days), but there was no difference between these groups with regards to cardiac mortality. A similar difference in all-cause mortality was observed for underweight (BCS < 4/9) versus overweight cats (BCS > 5/9), but not for normal/ideal BCS versus underweight cats, or normal/ideal BCS versus overweight cats. Regarding type of cardiomyopathy, cats with dilated cardiomyopathy (DCM) had shorter survival times than those with HCM. No other variables evaluated displayed statistically significant differences among groups. One of the authors’ goals of this study was to begin a new conversation about cachexia in veterinary medicine based on what is currently known, and what is still debated, regarding definitions of cachexia. It appears relatively clear, however, that identification of muscle loss, specifically, is likely of greatest clinical importance in defining cachexia, which is why the authors used an isolated MCS (definition #7) parameter as a point of comparison to a variety of other definitions.

So, what can we take away from this VETgirl podcast? The study results supported this notion, as use of BCS alone identified a relatively small number of cats (12%) as cachectic compared with MCS, suggesting that BCS is not likely an accurate measure for detecting cachexia and will result in underdetection in earlier stages. Cachexia as defined by MCS alone was noted to occur across all stages of BCS, in support of the idea that the two are not always directly linked. Both MCS and BCS data was an available parameter across all cats’ medical records.

What are some of the limitations of this study? The wide variety of prevalence observed across the seven definitions further emphasized the lack of a well-defined method of identifying cachexia. Some of the definitions (with definition #1 described previously as an example) hold relatively limited utility in veterinary medicine due to potential lack of available data in a retrospective study, or parameters that are not routinely measured in animals. MCS holds an advantage in this regard in that it is an isolated parameter that can be obtained on a single visit, and does not require comparison with prior or future assessments (in contrast to change in body weight). The primary limitation of MCS is that it is subjective. Some of the associations identified in this study, such as the association of anemia with cachexia, support previously published data in dogs and humans. Others, such as the association of pleural effusion or elevated BUN concentrations, are not completely understood and may not necessarily be supported by prior studies or repeatable in future studies.

Do you have MCS on your medical record? We need to implement the WSAVA Muscle Condition Score more into our medical records and physical examination assessment! Let’s start prioritizing sarcopenia and cachexia in our geriatric patients.

Abbreviations:
CHF: Congestive heart failure
MCS: Muscle condition score

References:
Santiago SL, Freeman LM, Rush JE. Cardiac cachexia in cats with congestive heart failure: Prevalence and clinical, laboratory, and survival findings. J Vet Intern Med 2019; 1-10.

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