What are the common causes of sinus bradycardia?

A slow heart rate in pets can be related to abnormal cardiac conduction, medication effects, metabolic or electrolyte imbalances, or age-related changes. Your vet will need to perform further tests to determine the cause and establish a monitoring plan.

How will the vet diagnose sinus bradycardia?

Common tests include an electrocardiogram (ECG) to confirm heart rate and rhythm, blood work to rule out metabolic or electrolyte issues, and chest imaging or an echocardiogram to evaluate heart structure. A specialist referral may be arranged if needed.

How should I care for a pet with a slow heart rate at home?

Keep a record of episodes, their timing and frequency. Avoid strenuous activity and provide a calm, quiet environment. Follow your vet's instructions for recheck visits and monitoring. Seek emergency care immediately if an acute episode occurs.

When should I consider referral to a veterinary cardiologist?

If your pet continues to collapse, symptoms keep recurring, or there is no clear improvement with standard treatment, your vet may recommend referral to a veterinary cardiologist for advanced imaging and specialist evaluation. Discuss this with your primary vet.

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

Sinus Bradycardia in Dogs & Cats: Symptoms, ECG & Care Guide [2025]

Abnormally slow heart rate — finding the underlying cause is key

Take 1 minute to check the symptoms first

Last updated: 2026/01/06

Pethealthmap Editorial Team

Sources: ACVIM, AVMA, National Taiwan University Veterinary Hospital

When to See a Vet

Seek Emergency Care Immediately

•Sudden fainting or prolonged loss of consciousness
•Difficulty breathing or noticeably blue/purple lips and gums
•Extreme weakness, inability to stand, or persistent unresponsiveness

Schedule a Clinic Visit Soon (within 24–72 hours)

•Noticeably decreased alertness and reduced activity
•Brief fainting episodes or suspected dizzy spells
•Slowed gait or recurring lethargy and sluggish movement

01What symptoms indicate something is wrong?

Sinus bradycardia often causes noticeable lethargy or reduced activity in pets. Some pets may show a drop in body temperature, slower responses, or brief episodes of collapse. The following outlines common signs and emergency warning signals to watch for.

Lethargy, noticeably reduced activity, or reluctance to move
Weakness when standing or walking, slowed or unsteady gait
Low body temperature, dull responses, or increased sleepiness
Brief collapse, sudden loss of consciousness, or apparent dizziness
If any of the above occur, seek veterinary assessment as soon as possible

Seek emergency care immediately if you notice the following symptoms:

⚠️ Sudden collapse or prolonged loss of consciousness
⚠️ Difficulty breathing or obviously blue or purple gums and lips
⚠️ Extreme weakness — unable to stand or persistently unresponsive

02How can I tell if something is wrong at home? Key observation points and when to go to the emergency vet

Recording key observations at home helps your vet assess the severity of the condition and identify episode patterns.

Note when symptoms first appeared, how often they occur, and how long each episode lasts
Observe changes in alertness, ability to stand, and overall activity level
Track appetite, water intake, and bathroom habits daily
Record video of any collapse, unsteady gait, or episode on your phone
Measure and record body temperature if safe to do so (not required)
If symptoms worsen or emergency warning signs appear, seek immediate veterinary care

03How will the vet diagnose this? Common diagnostic tests

At the clinic, your vet will use a systematic approach to identify possible causes. Common tests include heart rhythm assessment, blood work, and imaging.

Physical examination

auscultation, palpation, and vital signs (heart rate, respiration, temperature)

Electrocardiogram (ECG)

assesses heart rhythm and rate for abnormalities

Complete blood count and electrolytes

rules out metabolic or electrolyte imbalances

Blood biochemistry panel

evaluates liver and kidney function and systemic diseases that may affect heart rhythm

Chest X-ray or cardiac ultrasound (echocardiogram)

assesses heart size and structure; specialist referral for advanced imaging if needed

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

Treatment and follow-up are tailored to the underlying cause and clinical signs, and may include supportive care, medication adjustments, and regular monitoring.

Your vet will assess whether medication or supportive treatment is needed
IV fluids or electrolyte supplementation to address low blood pressure or dehydration
For severe or recurring symptoms, specialist options such as a pacemaker may be discussed
Regular recheck appointments to monitor ECG findings and clinical signs
At home, keep a log of any episodes and follow your vet's instructions for activity restrictions and diet
If symptoms persist or recur, referral to a veterinary cardiologist is recommended for further evaluation

05What should I prepare before the vet visit? Key information to help your vet identify the cause quickly

Note when symptoms first appeared, how often they occur, and any possible triggers

Bring a list of current medications, supplements, and a summary of medical history

Prepare a recent log of appetite, water intake, and bathroom habits

Bring any video or photos of episodes or abnormal gait

Bring previous test results if available (ECG, X-ray, ultrasound)

Use a secure carrier and arrange a clinic or emergency appointment as soon as possible

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.