Can second-degree AV block cause collapse?

Yes. If the conduction problem is severe or the heart rate is too slow, your pet may briefly lose consciousness or collapse. If collapse occurs, seek veterinary care immediately and ask your vet for further assessment.

What main tests will be done at the clinic?

At the clinic, vets commonly perform a physical examination, electrocardiogram (ECG), blood tests and, when needed, cardiac ultrasound to clarify the conduction problem and any concurrent disease.

What information should owners prepare before the appointment?

Bring symptom records (timing and frequency of episodes), recent food intake and vomiting records, current medications and any previous test reports.

How often will my pet need follow-up heart checks?

The follow-up schedule depends on treatment and test results. Regular ECG and cardiac ultrasound monitoring is often needed, so arrange rechecks according to your vet's advice.

How much do the tests and treatment usually cost?

Costs vary by clinic and region — ask your vet for an estimate before proceeding.

Disease Guide

Second-Degree AV Block (Mobitz II) in Dogs and Cats: Lethargy, ECG & Home Care [2025]

Second-degree atrioventricular block type II is more serious and may progress to complete heart block, requiring close monitoring or pacemaker treatment.

Take 1 minute to check the symptoms first

Last updated: 2026/01/05

Pethealthmap Editorial Team

Sources: ACVIM, AAHA

When to See a Vet

Seek immediate veterinary care (emergency)

•Frequent or severe repeated fainting with loss of consciousness
•Lips or gums that are clearly bluish or pale
•Persistent weakness, unable to stand or eat without assistance

Schedule a clinic visit as soon as possible (within 24-72 hours)

•Mental state and activity level remain clearly decreased
•Appetite is clearly reduced, or your pet refuses food continuously
•The heartbeat is noticeably slower than usual

01What symptoms suggest something is wrong?

Second-degree AV block often mainly causes reduced energy and activity, and may also be accompanied by poor appetite, digestive signs and a slower heartbeat.

Persistent lethargy and a clear drop in activity level
Appearing weak, walking more slowly or hiding and staying still
Markedly reduced appetite or refusing several meals in a row
Repeated vomiting or diarrhoea, with attention to signs of dehydration
A heartbeat that seems much slower than usual or has an irregular rhythm

Seek emergency care immediately if you notice the following symptoms:

⚠️ Brief or repeated collapse or loss of consciousness
⚠️ Lips or gums that look obviously blue, purple or pale
⚠️ Ongoing weakness, inability to stand unaided, or refusal to eat or drink

02How can you assess abnormalities at home? Key observation points and emergency warning signs

At home, you can systematically record symptom details and changes. This information helps your vet assess the situation quickly and plan appropriate tests.

Record when symptoms started, how often they occur and how they are changing (date and time of day)
Note daily food intake, water intake and the number of vomiting or diarrhoea episodes
Observe stool consistency and frequency, and keep a stool sample for testing if needed
Use your phone to record activity changes, collapse or weakness so you can show your vet
If you notice a clearly slow heartbeat or repeated collapse, seek veterinary care or contact your vet immediately

03How will the vet make a diagnosis? Common tests

At the clinic, assessment focuses on heart function and electrical conduction, with blood tests and imaging used to look for possible causes and related problems.

Physical examination

auscultation and palpation to assess heart rate, heart sounds and circulation

Electrocardiogram (ECG)

confirms the pattern of conduction block and any abnormal heart rhythm

Blood pressure measurement and blood tests to assess electrolytes and organ function

Cardiac ultrasound when needed to assess structural heart disease or changes in heart function

Further testing for infection or metabolic disease markers if indicated

04How is it treated and managed after diagnosis? Medication, diet adjustments and care guidance

Treatment depends on test results. Some pets need interventional management and long-term monitoring of heart function and symptom changes.

Your vet may recommend medication or interventional treatment based on their assessment, with follow-up visits arranged
If a device or procedure is needed, your vet will explain the risks and follow-up plan
At home, limit activity and avoid strenuous exercise or overexcitement
Schedule regular rechecks of ECG, blood pressure and cardiac ultrasound to monitor changes
Continue recording symptoms and report any worsening to your vet at follow-up visits
Consider follow-up at a hospital with cardiology capability

05What should you prepare before seeing the vet? Key information that helps identify the cause quickly

Bring a symptom log, including onset time and how signs have changed

Prepare records from the past few days for food intake, drinking, vomiting and bowel movements

List all current medications, supplements and topical treatments

Bring any previous test reports or imaging (such as ECG or ultrasound) if available

Use a secure carrier and call the clinic ahead to let them know a cardiac assessment may be needed

This content is for reference only and cannot replace a professional veterinary diagnosis. If your pet shows signs of illness, please seek veterinary care promptly.

Related Symptoms (You May Also Be Looking For)

Bradycardia

Abnormally slow heart rate

Sudden weakness

Loose stool

Decreased activity

Fainting

Expelling stomach contents