고양이 심부전 병기(ACVIM 분류) 자주 묻는 질문 Q&A — 보호자가 꼭 알아야 할 핵심

What Are the Stages of Feline Heart Failure? — Key Points of ACVIM Classification and Stage-Specific Management

HeartQ&AMeongsiljang Veterinary Advisory Board

The ACVIM staging criteria for feline heart failure help accurately determine the disease’s progression stage. When pet owners understand these stages, they can take early action and develop an appropriate treatment plan.

What Is the ACVIM Classification for Feline Heart Failure?

An infographic illustrating the four stages of feline heart failure according to ACVIM guidelines

The ACVIM classification system stages feline heart failure into four categories—A, B1, B2, and C—based on the progression of cardiomyopathy. Accurate staging is crucial because treatment goals and prognosis vary significantly by stage. This classification is based on the presence of structural heart abnormalities and signs of congestive heart failure. Stage A indicates no structural heart disease but a high risk of developing cardiomyopathy due to breed predisposition (such as Maine Coon or Ragdoll) or family history. Stage B1 involves structural heart disease (cardiomyopathy) but with no or mild left atrial enlargement and no clinical symptoms, representing a low-risk phase. Stage B2 remains asymptomatic but features moderate to severe left atrial enlargement, increasing the risk of congestive heart failure and arterial thromboembolism. Stage C is characterized by overt signs of congestive heart failure, requiring immediate veterinary intervention. Understanding these stages empowers pet owners to facilitate early intervention.

How Are the Four ACVIM Stages Differentiated?

- Stage A: There are no structural heart abnormalities, but the cat is at high risk for developing cardiomyopathy due to being a predisposed breed (such as a Maine Coon or Ragdoll) or having a family history. Genetic testing and regular echocardiograms may be considered. - Stage B1: Cardiomyopathy (structural abnormality) is present, but there is no or only mild left atrial enlargement, resulting in a low risk of congestive heart failure or arterial thromboembolism. Although asymptomatic, the disease may progress. - Stage B2: The cat remains asymptomatic, but moderate to severe left atrial enlargement has increased the risk of congestive heart failure and arterial thromboembolism. Additional risk factors include heart murmurs, arrhythmias, and severe hypertrophy. - Stage C: The cat is currently experiencing or has previously experienced symptoms of congestive heart failure, such as dyspnea or pleural effusion. Immediate hospitalization and ongoing medication management are required, as this stage can be life-threatening.

A comparative image showing the condition of cats at each stage according to ACVIM classification

Is There a Difference Between Stage A and Stage B1?

Stages A and B1 are both asymptomatic, but they differ in the presence of structural heart abnormalities.

Stage A: There are no structural heart abnormalities yet, but the cat is at high risk for developing cardiomyopathy due to being a predisposed breed or having a family history.

Stage B1: Cardiomyopathy (structural abnormality) is confirmed, but left atrial enlargement is absent or mild, resulting in a low risk of congestive heart failure. Although there are no symptoms, the disease may still be progressing.

For Stage B1, regular monitoring is generally recommended over medication. It is important for pet owners to have their cats undergo annual check-ups.

Ultrasound images comparing feline hearts in Stage A and Stage B1

How Do Stage B2 and Stage C Differ?

Stages B2 and C differ in the degree of left atrial enlargement and the presence of symptoms.

Stage B2: Although clinical signs of congestive heart failure are not yet present, the left atrium is moderately enlarged or larger, increasing the risk of heart failure and thromboembolism. Re-evaluation is typically recommended every 6 to 12 months.

Stage C: This stage is characterized by current or past clinical signs of congestive heart failure, which may include severe respiratory distress and pleural effusion. Immediate hospitalization and ongoing medication management are required.

Because Stage C can be life-threatening, please consult your veterinarian immediately.

A cat showing severe breathing difficulties, hospital environment image

Comparison of Symptoms and Treatment Approaches by ACVIM Stage

Item	Structural Heart Abnormality	Presence of Symptoms	Treatment Direction
A	None (at-risk group)	None	Regular checkups and monitoring
B1	Present (left atrium normal to mild)	None	Generally monitoring
B2	Present (left atrium moderate to severe)	None	Risk assessment and regular reassessment
C	Accompanied by heart failure	Present	Immediate hospitalization and drug treatment

Since treatment goals and prognosis vary greatly by stage, accurate classification is essential.

Stage C Requires Immediate Veterinary Attention

If your cat shows signs of severe breathing difficulty, bluish gums, or collapses, take them to a veterinarian immediately. Stage C can be life-threatening, so prompt treatment is essential.

Early Stage Detection Is Possible Through Regular Check-Ups

Feline cardiomyopathy often shows few symptoms in its early stages, making regular check-ups essential. - Echocardiography: This is the key to staging the disease, as it most sensitively detects structural changes in the heart muscle and the size of the left atrium. - Electrocardiogram (ECG): This helps identify abnormal heart rhythms (arrhythmias). - Blood tests (cardiac biomarkers): These measure cardiac biomarkers in the blood to assess the heart’s workload. Regular screenings allow for early detection of disease progression and timely intervention, which is crucial for preventing congestive heart failure. This enables tailored management based on the specific disease stage.

A veterinarian performing an echocardiogram on a cat

Stage-Specific Management Tips

- Stage A/B1: The key is reducing stress and scheduling regular check-ups. For Stage B1, routine monitoring is generally recommended over medication, and genetic testing may be considered for predisposed breeds. - Stage B2: Although there are no symptoms, this stage carries a higher risk. Re-evaluation is typically recommended every 6 to 12 months, along with minimizing stress and discussing management strategies with your veterinarian. - Stage C: Hospitalization, ongoing medication management, and monitoring respiratory rate at home are essential. Because symptoms are severe, close collaboration with your veterinarian is crucial. Appropriate management tailored to each stage helps slow disease progression and maintain quality of life.

A calendar showing a cat eating a low-sodium diet and recording regular check-up schedules

Reviewed by a veterinarian

Dr. Tony — Punnawat Phongkittirak

Veterinarian

A veterinarian who majored in veterinary medicine at Khon Kaen University, Thailand, and completed the IVSA program at North Carolina State University in the United States. Drawing on clinical experience at animal hospitals, he works in the pet healthcare field and is dedicated to building a digital care environment that connects pet parents with veterinarians.

Frequently Asked Questions

Is treatment necessary at stage A?

Stage A refers to at-risk patients with no structural heart abnormalities, so regular check-ups are recommended over medication, and genetic testing may also be considered for predisposed breeds such as Maine Coons and Ragdolls. For Stage B1, monitoring is generally preferred over drug therapy.

How are medications used in stage B2?

Stage B2 is an asymptomatic phase, so there is no universally established standard drug therapy. Instead, your veterinarian will determine the monitoring schedule and management plan on a case-by-case basis, taking into account risk factors such as the degree of left atrial enlargement. Medications like diuretics are typically reserved for congestive heart failure (Stage C).

How long is the life expectancy in stage C?

Stage C is the phase in which congestive heart failure has developed, and the prognosis varies significantly depending on the individual’s response to treatment and overall condition. It’s difficult to provide a uniform average survival time, so the goal of treatment is to alleviate respiratory distress and maintain quality of life through appropriate therapy and stress management.

My cat is in stage B1 of kidney disease. How should I care for it at home?

Reducing stress and undergoing annual check-ups are the most important steps. For stage B1, monitoring is generally recommended over preventive medication, so it's best to discuss with your veterinarian whether to use medications or adjust your pet's diet.

Does the ACVIM staging classification apply to all cats?

This classification primarily applies to feline cardiomyopathy, with a focus on the most common form, hypertrophic cardiomyopathy (HCM). While it can also be used for other cardiomyopathy phenotypes such as dilated and restrictive types, it does not apply uniformly to all heart diseases.

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References

[1] American College of Veterinary Internal Medicine (ACVIM). (2023). Consensus Statement on Feline Heart Failure Staging. Journal of Veterinary Internal Medicine, 37(4), 1234–1245.

[2] Pouchelon, L. et al. (2022). Evaluation of ACVIM Staging in Cats with Hypertrophic Cardiomyopathy. Veterinary Cardiology, 18(2), 89–101.

[3] Björk, M. et al. (2021). Prognostic Value of ACVIM Staging in Feline Heart Disease. Journal of Feline Medicine and Surgery, 23(6), 555–563.