Veterinary Stethoscopes for Pet Owners: Cardiac Acoustics, Bell vs. Diaphragm, and Murmur Monitoring

I know that hearing your veterinarian mention a heart murmur in your dog can feel like the ground just shifted beneath you. The uncertainty, the worry about what comes next, and the desire to do something to help, I've sat with countless pet owners in that exact moment. Here's the truth you need to hold onto: learning to use a stethoscope at home won't replace your veterinarian's expertise, but it will transform you from a worried bystander into an informed partner in your dog's cardiac care. This guide will teach you exactly how to listen, what to listen for, and when to act.

⚠️ Red-Flag Emergency Box

⚠️ Emergency, Go to the ER NOW if your dog shows ANY of these signs:

• Labored breathing with visible abdominal effort or neck extended (orthopnea)
• Gums that are pale, blue, or gray (cyanosis)
• Collapse or fainting (syncope), even if brief
• Coughing that produces frothy pink fluid
• Restlessness, pacing, or inability to settle (especially at night)
• Rapid breathing at rest (RRR > 40 breaths per minute for more than 2 consecutive hours)
• Sudden hind limb weakness or paralysis (saddle thrombus)

Do not wait for a telemedicine consult. Do not attempt home monitoring. Drive to the nearest 24-hour emergency veterinary hospital immediately.

What You're Seeing and What It Likely Means

When you place a stethoscope on your dog's chest, you're entering a world of sound that most pet owners never experience. The normal heartbeat, that steady lub-dub, lub-dub, is produced by the closing of heart valves. The first sound (S1) comes from the mitral and tricuspid valves closing as the ventricles contract. The second sound (S2) comes from the aortic and pulmonic valves closing as the heart relaxes to fill again.

A heart murmur is an extra whooshing or swishing sound that occurs between these normal beats. It's caused by turbulent blood flow, blood moving through a valve that isn't sealing properly, or through a narrowed passage, or across a defect in the heart wall. Think of it like water rushing through a partially closed faucet versus flowing smoothly through an open pipe.

The intensity of a murmur is graded on a scale of I to VI. A Grade I murmur is so soft you might miss it even with training. A Grade VI murmur is so loud you can feel it with your hand on the chest wall. But here's what surprises most owners: the grade of the murmur does not always correlate with the severity of the disease. A dog with a loud Grade V murmur might be stable for years, while a dog with a soft Grade II murmur could be in early heart failure. That's why learning to monitor changes over time is so valuable.

What you're likely seeing in your dog, whether it's a subtle cough after exercise, a slight increase in breathing rate during sleep, or just that nagging feeling that something isn't right, could be early signs of mitral valve disease (MVD), the most common acquired heart disease in dogs. MVD affects the mitral valve on the left side of the heart, causing it to leak blood backward into the left atrium with each heartbeat. Over time, this volume overload can lead to enlargement of the heart chambers and eventually congestive heart failure.

The key takeaway here is this: home auscultation with a quality stethoscope gives you the power to detect changes before they become emergencies. You're not trying to diagnose your dog, you're building a baseline of normal sounds so you can recognize when something shifts.

What You Can Safely Do Right Now

Before you even pick up a stethoscope, there are several things you can do right now to start monitoring your dog's cardiac health safely and effectively.

Step 1: Learn to Count Resting Respiratory Rate (RRR)

This is arguably more important than listening to the heart itself. The RRR is the number of breaths your dog takes per minute while sleeping or resting calmly. An elevated RRR is often the earliest sign of fluid accumulation in the lungs (pulmonary edema) in dogs with heart disease.

How to do it:

• Wait until your dog is in deep sleep or completely relaxed
• Set a timer for 30 seconds
• Count each breath (one inhalation + one exhalation = one breath)
• Multiply by 2 to get breaths per minute
• Record the number in a log

Normal RRR: 15-30 breaths per minute Yellow flag: 30-40 breaths per minute Red flag: > 40 breaths per minute for two consecutive hours

Step 2: Create a Quiet Listening Environment

Home auscultation requires silence. Turn off the television, close windows, and ask family members to be still. Place your dog on a non-slip surface where they can stand or lie comfortably. For small dogs, a lap or a padded table works well. For large dogs, the floor with a yoga mat is ideal.

Step 3: Position Your Dog Correctly

For the best cardiac auscultation, your dog should be standing with all four feet on the ground. This position allows the heart to sit in its natural anatomical position within the chest. If your dog is anxious or won't stand still, having them lie on their right side (right lateral recumbency) is an acceptable alternative.

Step 4: Warm the Chestpiece

Cold metal against your dog's chest will cause them to flinch or tense up, ruining your listening session. Warm the chestpiece in your hands for 30 seconds before placing it on your dog's skin. Part the fur to expose the skin directly, listening through fur creates artifact sounds that can mimic or mask murmurs.

Step 5: Start with the Diaphragm

For your first listening session, use the diaphragm side of the chestpiece. The diaphragm is designed to pick up higher-frequency sounds, including the normal S1 and S2 heart sounds and most heart murmurs. Press firmly enough to leave a slight indentation in the skin after you lift the chestpiece, this ensures good contact without being painful.

When to Call Your Veterinarian

You've started listening at home. You've recorded some RRR measurements. Now you need to know when those numbers and sounds warrant a phone call to your veterinarian.

Call your veterinarian within 24 hours if:

• Your dog's RRR is consistently between 30-40 breaths per minute at rest
• You detect a new heart murmur that wasn't present at the last veterinary visit
• An existing murmur sounds louder or has changed in character
• Your dog develops a new cough, especially at night or after exercise
• Your dog seems more tired than usual after normal activity
• You notice a decrease in appetite or reluctance to go for walks

Call your veterinarian immediately (same day) if:

• RRR is > 40 breaths per minute for more than one hour
• Your dog has a coughing episode that lasts more than 30 seconds
• You see any signs of respiratory distress (open-mouth breathing, abdominal heaving)
• Your dog has a fainting episode, even if they recover quickly
• You notice abdominal distension (fluid accumulation in the belly)

What to tell your veterinarian:

• The RRR number and how long you've been tracking it
• Whether you detected a murmur and where on the chest you heard it loudest
• Any changes in behavior, appetite, or energy level
• The date of your dog's last veterinary visit and any medications they're taking

What Your Vet Will Do

When you bring your dog in for a cardiac evaluation, your veterinarian will perform a systematic assessment that goes far beyond what you can do at home. Understanding this process helps you appreciate what your stethoscope can and cannot tell you.

The Physical Examination

Your veterinarian will start with a complete physical exam, paying special attention to:

• Mucous membrane color (gums should be pink, not pale or blue)
• Capillary refill time (normal is 1-2 seconds)
• Jugular vein distension (a sign of right-sided heart failure)
• Femoral pulse quality (should be strong and regular)
• Lung auscultation (listening for crackles or wheezes)
• Abdominal palpation (checking for fluid or organ enlargement)

Cardiac Auscultation

Your veterinarian will listen to the heart from multiple locations on both sides of the chest, using both the bell and diaphragm of their stethoscope. They'll note:

• Heart rate and rhythm (normal sinus rhythm vs. arrhythmias)
• Murmur grade (I-VI scale)
• Murmur location (where it's loudest on the chest wall)
• Murmur timing (systolic vs. diastolic)
• Murmur quality (plateau, crescendo-decrescendo, or machinery-like)

Diagnostic Tests

Based on the physical exam findings, your veterinarian may recommend:

What the Results Mean

• Normal chest X-rays + normal echocardiogram: Your dog likely has a functional or innocent murmur. No treatment needed, but annual rechecks are recommended.
• Enlarged heart on X-rays + leaking mitral valve on echo: Your dog has mitral valve disease. Staging (B1, B2, C, D) determines treatment.
• Fluid in lungs on X-rays + heart enlargement: Your dog is in congestive heart failure and needs immediate treatment with diuretics, vasodilators, and pimobendan.

Common Causes, A Deeper Look

Understanding what causes heart murmurs in dogs helps you interpret what you're hearing through your stethoscope. Here's a breakdown of the most common causes, organized by the type of dog most affected.

Mitral Valve Disease (MVD), The Most Common Cause

Affects: Small to medium breed dogs, especially Cavalier King Charles Spaniels, Dachshunds, Miniature Poodles, and Chihuahuas Age of onset: Typically 8+ years, but Cavaliers can develop murmurs as early as 2-3 years What you'll hear: A systolic murmur loudest over the left apex (left 5th intercostal space, just behind the elbow). The murmur is typically plateau-shaped (same intensity throughout systole) or crescendo-decrescendo (gets louder then softer).

The pathology: The mitral valve leaflets become thickened and nodular (myxomatous degeneration). They no longer seal properly during ventricular contraction, allowing blood to regurgitate backward into the left atrium. Over years, this volume overload causes the left atrium and left ventricle to enlarge. Eventually, the increased pressure backs up into the pulmonary veins and lungs, causing pulmonary edema (fluid in the lungs).

Progression timeline:

• Stage B1: Murmur present, no heart enlargement on X-rays or echo
• Stage B2: Murmur present, significant heart enlargement on X-rays or echo
• Stage C: Current or past congestive heart failure
• Stage D: End-stage disease, refractory to standard therapy

Dilated Cardiomyopathy (DCM)

Affects: Large and giant breed dogs, especially Doberman Pinschers, Great Danes, Boxers, and Irish Wolfhounds Age of onset: 4-10 years What you'll hear: A soft systolic murmur (if present at all) over the left apex. Many DCM dogs have no audible murmur. The heart sounds may be muffled due to fluid accumulation. You may hear a gallop rhythm, an extra S3 sound that creates a cadence like "Ken-tuc-ky."

The pathology: The heart muscle becomes weak and thin-walled. The ventricles dilate (stretch out) and contract poorly. Blood pools in the heart rather than being pumped forward efficiently. This can lead to congestive heart failure, arrhythmias, and sudden death.

Critical note: DCM can progress rapidly. A dog that seems normal one week may be in fulminant heart failure the next. Home monitoring is especially important for these breeds.

Subaortic Stenosis (SAS)

Affects: Large breed dogs, especially Newfoundlands, Golden Retrievers, Rottweilers, and Boxers Age of onset: Congenital (present from birth, but may not be detected until adulthood) What you'll hear: A harsh systolic murmur loudest over the left base (left 3rd-4th intercostal space, higher on the chest). The murmur often radiates up the carotid arteries to the head.

The pathology: A fibrous ring or tunnel forms below the aortic valve, obstructing blood flow from the left ventricle into the aorta. The heart must work harder to push blood through this narrowed passage, leading to thickening of the heart muscle (concentric hypertrophy).

Pulmonic Stenosis (PS)

Affects: Brachycephalic breeds (English Bulldogs, French Bulldogs, Boston Terriers) and small breeds Age of onset: Congenital What you'll hear: A systolic murmur loudest over the left base, but slightly lower and more to the left than SAS. The murmur may be accompanied by a palpable thrill (vibration you can feel with your hand).

Patent Ductus Arteriosus (PDA)

Affects: Small breed dogs, especially Pomeranians, Maltese, and Shetland Sheepdogs Age of onset: Congenital (usually detected in puppies) What you'll hear: A continuous "machinery" murmur that lasts throughout systole and diastole. This is one of the few murmurs you'll hear during both phases of the cardiac cycle. It's loudest over the left base.

Why it's critical: PDA is one of the few congenital heart defects that can be cured with surgery or catheter-based closure. If left untreated, it leads to left-sided heart failure and death, usually by 1-2 years of age.

Innocent (Functional) Murmurs

Affects: Puppies and young dogs, especially large breeds What you'll hear: A soft (Grade I-II) systolic murmur that disappears by 4-6 months of age. It's caused by the rapid flow of blood through a normal heart, think of it as a "growing pain" of the cardiovascular system.

How to distinguish from pathologic murmurs:

• Innocent murmurs are always Grade II or softer
• They disappear when the dog changes position or holds its breath
• They're not associated with any heart enlargement or clinical signs
• They resolve by 6 months of age

Selecting a High-Acoustics Stethoscope: Dual-Frequency Tunable Diaphragm and Pediatric Chestpiece

Choosing the right stethoscope for home use is a decision that will directly impact what you can and cannot hear. I've seen owners struggle with cheap stethoscopes that produce nothing but muffled noise, and I've seen others invest in professional-grade instruments that transform their ability to monitor their dog's heart.

The Dual-Frequency Tunable Diaphragm: Your Most Important Feature

The single most important feature to look for is a dual-frequency tunable diaphragm. This technology allows you to hear both high-frequency sounds (heart murmurs, normal S1/S2) and low-frequency sounds (gallop rhythms, some diastolic murmurs) using the same side of the chestpiece.

How it works:

• Light pressure: When you press the chestpiece gently against the skin, the diaphragm acts like a traditional bell, picking up low-frequency sounds. This is ideal for hearing S3 gallop rhythms or low-pitched diastolic murmurs.
• Firm pressure: When you press more firmly, the diaphragm stretches and becomes sensitive to higher frequencies. This is what you'll use most often for detecting systolic murmurs and normal heart sounds.

Why this matters for your dog: Dogs have smaller chests and higher heart rates than humans. A tunable diaphragm lets you switch between frequency ranges without lifting the chestpiece, which is crucial when you're trying to follow a rapid heartbeat through its cycle.

Pediatric Chestpiece: Size Matters

The standard adult chestpiece (about 1.75 inches in diameter) is designed for human chests. On a small dog, it's like trying to listen to a watch through a dinner plate. You'll pick up sounds from too wide an area, making it impossible to localize a murmur to a specific valve.

What to look for:

• Pediatric chestpiece: 1.25-1.5 inches in diameter. This is ideal for dogs under 30 pounds and for cats.
• Infant chestpiece: 1 inch or smaller. Useful for toy breeds, puppies, and cats.
• Dual-sided chestpiece: Many quality stethoscopes come with a large adult diaphragm on one side and a smaller pediatric bell on the other. This gives you flexibility for different-sized patients.

The rule of thumb: The chestpiece should be small enough to fit between two ribs of your dog. For a Chihuahua, that means a pediatric or infant chestpiece. For a Great Dane, an adult chestpiece works fine.

Eartip Seal Acoustics: The Make-or-Break Factor

You could have the most expensive stethoscope in the world, but if the eartips don't seal properly in your ear canals, you'll hear nothing but ambient noise. This is the most common reason owners give up on home auscultation.

What to look for:

• Soft, pliable eartips: Hard plastic eartips won't conform to your ear canals. Look for silicone or soft rubber.
• Multiple sizes: Your stethoscope should come with at least 3 sizes of eartips (small, medium, large).
• Angled eartubes: The eartubes should angle forward (toward your nose) to match the natural angle of your ear canals. Straight tubes don't seal properly.

How to test the seal:

1. Place the eartips in your ears
2. Gently tap the chestpiece with your finger
3. If you hear a clear, crisp tap, the seal is good
4. If the tap sounds muffled or distant, try a different size eartip

Tube Length and Material

• 22-inch tubes: Standard length for human use. Fine for home use with dogs.
• 27-inch tubes: Longer tubes reduce ambient noise but can be cumbersome.
• Double-lumen tubing: Two separate sound channels inside one outer tube. This reduces "stethoscope rub" noise (the sound of the tubes rubbing against each other or against surfaces).

What to Avoid

• Electronic/digital stethoscopes for beginners: While these can amplify sound and record audio, they introduce a learning curve and potential for artifact. Start with an acoustic stethoscope.
• Cheap stethoscopes under $30: These are essentially toys. The tubing is thin, the chestpiece is poorly designed, and the eartips won't seal. You'll hear nothing useful.
• Stethoscopes with single-sided chestpieces: You need both bell and diaphragm functionality, or a tunable diaphragm that serves both purposes.

Recommended Price Range

Auscultation Anatomical Landmarks: Mitral Valve and Lung Fields

Knowing where to place the stethoscope is as important as knowing what to listen for. The heart sits within the chest cavity at specific locations, and each valve produces its loudest sounds at a specific point on the chest wall.

The Cardiac Window

The heart is located in the lower third of the chest, between the 3rd and 6th ribs, on both sides. The left side of the chest is where you'll hear most cardiac sounds because the apex of the heart (the tip) points to the left.

Left-Sided Auscultation Points

Mitral Valve (Left Apex):

• Location: Left 5th intercostal space (between the 5th and 6th ribs), just behind the elbow
• How to find it: With your dog standing, place your hand on the left side of the chest, just behind the elbow. You'll feel a slight depression between the ribs. The mitral valve is at the level of the costochondral junction (where the rib bone meets the cartilage).
• What you'll hear: The normal S1 sound is loudest here. Most systolic murmurs (MVD, DCM) are loudest at this point.

Aortic Valve (Left Base):

• Location: Left 4th intercostal space, higher on the chest (about 1/3 of the way up from the sternum)
• What you'll hear: The normal S2 sound is loudest here. Murmurs from subaortic stenosis or aortic valve disease are loudest here.

Pulmonic Valve (Left Base, Cranial):

• Location: Left 3rd intercostal space, slightly lower than the aortic valve
• What you'll hear: Murmurs from pulmonic stenosis or patent ductus arteriosus are loudest here.

Right-Sided Auscultation Points

Tricuspid Valve (Right Apex):

• Location: Right 4th intercostal space, at the same level as the mitral valve on the left
• What you'll hear: Tricuspid valve murmurs (less common than mitral murmurs) are loudest here. Some mitral murmurs also radiate to the right side.

Lung Field Auscultation

The lungs extend from the 1st rib to the 12th-13th rib on both sides. To assess lung sounds, you'll need to listen at multiple points:

Left Lung Fields:

• Cranial lung: Left 2nd-4th intercostal spaces, upper half of chest
• Middle lung: Left 5th-7th intercostal spaces, middle third of chest
• Caudal lung: Left 8th-10th intercostal spaces, lower third of chest

Right Lung Fields:

• Same pattern as left, but the right lung has an additional accessory lobe that extends further caudally

Normal Lung Sounds

• Vesicular sounds: Soft, rustling sounds heard over most of the lung fields. These are normal air movement sounds.
• Bronchial sounds: Louder, tubular sounds heard over the large airways near the trachea. These are normal in that location.

Abnormal Lung Sounds

Distinguishing Normal S1/S2 Heart Sounds from Heart Murmurs, Arrhythmias, and Galloping Rhythms

This is where home auscultation becomes an art. Learning to distinguish between normal sounds, murmurs, and arrhythmias takes practice, but I'll give you the framework to start.

The Normal Cardiac Cycle

S1 (Lub):

• What it is: Closure of the mitral and tricuspid valves
• When it occurs: Beginning of ventricular contraction (systole)
• What it sounds like: A single, crisp "lub" sound
• Where it's loudest: Left apex (mitral) and right apex (tricuspid)

S2 (Dub):

• What it is: Closure of the aortic and pulmonic valves
• When it occurs: End of ventricular contraction, beginning of relaxation (diastole)
• What it sounds like: A single, slightly higher-pitched "dub" sound
• Where it's loudest: Left base (aortic and pulmonic)

The normal rhythm: S1 - (pause) - S2 - (longer pause) - S1 - (pause) - S2

Heart Murmurs

What they sound like: A whooshing, swishing, or rushing sound that occurs between S1 and S2 (systolic) or between S2 and the next S1 (diastolic).

Systolic murmurs (most common in dogs):

• Occur between S1 and S2
• Caused by blood leaking through a valve (regurgitation) or blood being forced through a narrowed passage (stenosis)
• Most common: Mitral regurgitation (MVD), tricuspid regurgitation, subaortic stenosis

Diastolic murmurs (rare in dogs):

• Occur between S2 and the next S1
• Caused by blood leaking through the aortic or pulmonic valve during relaxation
• Very uncommon in dogs; if present, usually indicates significant valve disease

Continuous murmurs:

• Heard throughout both systole and diastole
• Classic "machinery" murmur of patent ductus arteriosus

Arrhythmias

What they sound like: Irregular timing between beats, or extra beats, or dropped beats.

Sinus arrhythmia (normal in dogs):

• The heart rate increases during inspiration and decreases during expiration
• This is normal and actually indicates good vagal tone (healthy heart)
• More pronounced in brachycephalic breeds

Atrial fibrillation (abnormal):

• Completely irregular rhythm with no pattern
• "Irregularly irregular", no two beats are the same distance apart
• Common in large breed dogs with DCM or advanced MVD

Ventricular premature complexes (VPCs):

• Early, extra beats that feel like a "skip" or "thump"
• Followed by a compensatory pause
• Common in Boxers with arrhythmogenic right ventricular cardiomyopathy (ARVC)

Heart block:

• Dropped beats where you hear S1 but no S2
• The heart rate may be very slow (bradycardia)

Galloping Rhythms

What they sound like: Three heart sounds instead of two, creating a cadence like "Ken-tuc-ky" or "Ten-nes-see."

S3 gallop:

• An extra sound after S2
• Sounds like "lub-dub-whump"
• Indicates rapid ventricular filling (often seen in DCM or volume overload)
• This is a red flag, it often precedes congestive heart failure

S4 gallop:

• An extra sound before S1
• Sounds like "whump-lub-dub"
• Indicates atrial contraction against a stiff ventricle (less common in dogs)

How to Practice Distinguishing These Sounds

1. Start with a normal dog: If you have a healthy dog without known heart disease, practice listening to their heart for 5 minutes daily. Learn what normal S1 and S2 sound like at each auscultation point.

2. Count the rhythm: Tap your foot or snap your fingers to the beat. Is it regular? Does it speed up and slow down with breathing (normal sinus arrhythmia)?

3. Focus on the spaces: Listen specifically to the space between S1 and S2 (systole). Is it silent? Do you hear a whoosh? Then listen to the space between S2 and the next S1 (diastole). Is it silent?

4. Change pressure: Use light pressure (bell mode) to listen for low-frequency sounds like S3 gallops. Use firm pressure (diaphragm mode) to listen for high-frequency murmurs.

5. Record and compare: Some digital stethoscopes allow recording. If you have access to one, record your dog's heart sounds and compare them week to week.

Monitoring Resting Respiratory Rate (RRR) at Home for Dogs with Mitral Valve Disease

If your dog has been diagnosed with mitral valve disease, monitoring the Resting Respiratory Rate (RRR) is the single most valuable thing you can do at home. It's more sensitive than listening for murmurs, more objective than watching for coughing, and it gives you a clear numerical threshold for when to call your veterinarian.

Why RRR Matters

In MVD, the mitral valve leaks blood backward into the left atrium with each heartbeat. Over time, this volume overload causes the left atrium to enlarge and the pressure in the pulmonary veins to increase. When that pressure exceeds a certain threshold, fluid begins to leak from the pulmonary capillaries into the lung tissue and airways. This is pulmonary edema, congestive heart failure.

The earliest sign of this fluid accumulation is an increase in respiratory rate. Your dog's body is trying to compensate for the decreased oxygen exchange by breathing faster. This happens before you see visible respiratory distress, before you hear crackles in the lungs, and often before your dog starts coughing.

How to Measure RRR Correctly

The Gold Standard Method:

1. Wait for deep sleep: Your dog must be in deep sleep, not just resting quietly. A dog that is awake but calm may have a normal respiratory rate of 20-30 breaths per minute. A dog in deep sleep should have a rate of 15-25 breaths per minute.

2. Count for 30 seconds: Set a timer on your phone. Count each breath (one rise and fall of the chest = one breath). Multiply by 2 to get breaths per minute.

3. Record the number: Keep a log. I recommend a simple notebook or a note on your phone. Date, time, and RRR.

4. Measure at the same time each day: Ideally, measure RRR when your dog is sleeping at night or during a midday nap. Consistency is key.

What the Numbers Mean

The 2-Hour Rule

A single elevated RRR reading isn't necessarily an emergency. Dogs can have transient increases in respiratory rate due to dreams, noise, or changes in room temperature. The 2-hour rule is this: if the RRR remains above 40 breaths per minute for two consecutive hours, go to the emergency room.

Case Example: How RRR Monitoring Saved a Dog's Life

Meet Charlie, a 10-year-old Cavalier King Charles Spaniel.

Charlie was diagnosed with Stage B1 MVD at age 8. His owner, Sarah, started monitoring his RRR daily. For two years, Charlie's RRR stayed between 18-22 breaths per minute during sleep.

One Tuesday evening, Sarah noticed Charlie's RRR was 32. She checked again an hour later, 35. She called her veterinarian the next morning. The veterinarian recommended increasing Charlie's pimobendan dose and scheduling a recheck echocardiogram.

At the recheck, the echocardiogram showed that Charlie's left atrium had enlarged significantly since his last visit. He had progressed from Stage B1 to Stage B2. Because Sarah caught the change early, the veterinarian was able to adjust medications before Charlie developed congestive heart failure.

Charlie remained stable for another 18 months before eventually progressing to Stage C. Sarah's diligent RRR monitoring gave Charlie nearly two years of quality life that he would not have had otherwise.

Identifying Lung Crackles and Wheezes Indicative of Pulmonary Edema or Bronchitis

While heart auscultation gets most of the attention, lung auscultation is equally important for dogs with heart disease. The lungs are where the consequences of heart failure manifest, and learning to recognize abnormal lung sounds can alert you to impending crisis.

Normal Lung Sounds

When you listen to a healthy dog's lungs, you should hear:

• Vesicular sounds: Soft, gentle rustling sounds that occur during both inspiration and expiration. These are the sounds of air moving through small airways and alveoli.
• Bronchovesicular sounds: Slightly louder sounds heard over the larger airways near the hilum (where the trachea divides into the main bronchi).

Crackles (Rales)

What they sound like: Popping, bubbling, or crackling sounds, similar to the sound of Rice Krispies in milk or the sound of hair being rubbed between your fingers near your ear.

What they indicate: Fluid in the small airways and alveoli. When air moves through fluid-filled airways, it creates bubbles that pop, producing the crackling sound.

Types of crackles:

• Fine crackles: High-pitched, short-duration popping sounds. These occur in the smallest airways and are often the earliest sign of pulmonary edema.
• Coarse crackles: Lower-pitched, longer-duration bubbling sounds. These occur in larger airways and indicate more significant fluid accumulation.

Location matters:

• Crackles in the lower lung fields (near the diaphragm): Often the first sign of pulmonary edema from left-sided heart failure. Fluid accumulates in the dependent (lowest) parts of the lungs first.
• Crackles in the upper lung fields: More advanced pulmonary edema or pneumonia.

Wheezes

What they sound like: High-pitched, musical sounds that occur during expiration (most common) or inspiration.

What they indicate: Narrowing of the airways due to bronchoconstriction, inflammation, or mucus accumulation.

Common causes in dogs with heart disease:

• Bronchitis: Chronic inflammation of the airways, common in older small breed dogs who also have MVD
• Collapsing trachea: A common comorbidity in small breed dogs with heart disease
• Pulmonary edema: In severe cases, fluid can cause airway narrowing and wheezing

Stridor

What it sounds like: A harsh, high-pitched sound heard during inspiration. It's louder than a wheeze and has a "crowing" quality.

What it indicates: Upper airway obstruction at the level of the larynx or trachea.

Common causes:

• Laryngeal paralysis: Common in older Labrador Retrievers and other large breeds
• Collapsing trachea: Common in small breed dogs
• Foreign body: Something stuck in the airway

How to Perform Lung Auscultation

1. Position your dog standing: This allows the lungs to expand fully.
2. Listen at multiple points: Start at the cranial lung fields (near the shoulders) and work your way caudally (toward the belly). Listen on both sides.
3. Compare left to right: Normal lungs should sound symmetrical. Asymmetry suggests a localized problem (pneumonia, tumor, foreign body).
4. Listen during both phases: Inspiration is usually louder than expiration. If expiration is louder than inspiration, or if you hear wheezes during expiration, that suggests airway narrowing.
5. Have your dog take deep breaths: If your dog is cooperative, covering one nostril for a few seconds will encourage deeper breathing.

The Crackle-Wheeze Continuum

In dogs with heart disease, you may hear a progression of lung sounds as heart failure develops:

1. Normal: Clear vesicular sounds throughout
2. Early pulmonary edema: Fine crackles in the lower lung fields, heard only during inspiration
3. Moderate pulmonary edema: Coarse crackles in the lower and middle lung fields, heard during both inspiration and expiration
4. Severe pulmonary edema: Crackles throughout all lung fields, possibly with wheezes
5. End-stage pulmonary edema: "Silent chest", no breath sounds audible because the lungs are so filled with fluid that no air is moving

If you ever hear a "silent chest" in a dog that is breathing rapidly, this is a critical emergency.

Eartip Seal Acoustics and Eliminating Ambient Room Noise During Home Auscultation

The quality of what you hear through your stethoscope depends almost entirely on two factors: the seal of the eartips in your ears and the elimination of ambient noise in your listening environment. These are the most overlooked aspects of home auscultation, and they're the reason many owners give up in frustration.

The Physics of Sound Transmission

Sound travels from the chestpiece, through the tubing, and into your ears as vibrations in the air column inside the stethoscope. If there's any leak in this system, at the eartips, at the chestpiece connection, or through the tubing itself, the sound pressure drops dramatically, and you'll hear mostly ambient noise.

Achieving a Perfect Eartip Seal

Step 1: Choose the right size eartip

• Most stethoscopes come with 3 sizes: small, medium, and large
• The eartip should fit snugly in your ear canal without causing pain
• You should feel a slight suction when you insert the eartips
• If you can hear ambient noise (the TV, your dog's breathing, your own footsteps), the seal is inadequate

Step 2: Angle the eartubes forward

• The eartubes should point toward your nose, not toward the back of your head
• This matches the natural angle of your ear canals
• If the tubes point backward, they'll push against the cartilage of your ear and break the seal

Step 3: Insert the eartips correctly

• Pull your ear upward and backward with your opposite hand
• Insert the eartip with a slight twisting motion
• Release your ear, the eartip should stay in place without you holding it

Step 4: Test the seal

• Gently tap the chestpiece with your finger
• You should hear a clear, crisp tap
• If the tap sounds muffled or distant, adjust the eartips

Eliminating Ambient Noise

Environmental noise sources:

• Television or radio
• Air conditioning or heating system
• Refrigerator compressor
• Traffic outside
• Other people talking
• Your dog's panting or breathing
• Your own breathing (hold your breath while listening)

Stethoscope-generated noise:

• Tubing rub: The sound of the tubing rubbing against your clothing or against surfaces. Solution: Wear a thin, smooth shirt and keep the tubing away from your body.
• Chestpiece movement: The sound of the chestpiece moving across fur or skin. Solution: Part the fur completely and place the chestpiece directly on skin. Hold it still.
• Finger friction: The sound of your fingers rubbing against the chestpiece. Solution: Hold the chestpiece by the edges, not the top.

The 30-Second Rule

Before you start listening, spend 30 seconds in silence. Close your eyes. Listen to the ambient noise in the room. Identify each sound source. Then, one by one, eliminate them. Turn off the TV. Close the window. Ask family members to be quiet. Take a deep breath and hold it.

When to Use the Bell vs. Diaphragm

The "Tunable Diaphragm" Advantage

If your stethoscope has a tunable diaphragm, you can switch between bell and diaphragm modes by changing pressure. This is a significant advantage because:

1. You don't have to flip the chestpiece over (which can startle your dog)
2. You can switch modes mid-listening session without losing your place
3. You can use the pediatric side for small dogs and the adult side for large dogs

How to use a tunable diaphragm:

• Light pressure: Acts as a bell. Use for low-frequency sounds.
• Firm pressure: Acts as a diaphragm. Use for high-frequency sounds.
• To switch: Simply press harder or lighter. The change is instantaneous.

When to Record Audio and Contact Your Veterinary Cardiologist

One of the most powerful features of modern digital stethoscopes is the ability to record audio of your dog's heart and lung sounds. This recording can be shared with your veterinarian or veterinary cardiologist for remote assessment.

When Recording Is Most Valuable

1. New or changing murmurs: If you detect a murmur that wasn't present at your dog's last veterinary visit, or if an existing murmur sounds louder or different, record it. Your cardiologist can compare the recording to previous auscultation findings.

2. Arrhythmias: Irregular heart rhythms are often intermittent. Your dog may have a normal rhythm at the veterinary clinic but develop arrhythmias at home. Recording the arrhythmia when it occurs provides definitive evidence.

3. Gallop rhythms: An S3 gallop is a significant finding that often precedes congestive heart failure. If you hear a gallop rhythm, record it immediately and contact your cardiologist.

4. Lung crackles: If you hear crackles in your dog's lungs, especially if they're new or worsening, record them. This can help your veterinarian determine whether your dog is developing pulmonary edema.

5. Post-treatment monitoring: After your dog starts a new cardiac medication, recording heart and lung sounds weekly can help your veterinarian assess treatment efficacy.

How to Record Heart Sounds

Using a digital stethoscope:

1. Connect the stethoscope to your smartphone via Bluetooth or audio cable
2. Open the accompanying app
3. Position the chestpiece on your dog's chest
4. Press record
5. Listen for 15-30 seconds at each auscultation point
6. Label each recording with the location (e.g., "Left apex, mitral valve")

Using a smartphone with an acoustic stethoscope:

1. Place the eartips in your ears
2. Hold your smartphone's microphone near the eartip (not the chestpiece)
3. Record a voice memo
4. Speak the location and your observations into the recording

What to include in the recording:

• Your dog's name and the date
• The auscultation point (e.g., "Left 5th intercostal space, mitral valve")
• Your observations (e.g., "I hear a Grade III systolic murmur")
• Any relevant context (e.g., "This is after a 10-minute walk")

When to Contact Your Veterinary Cardiologist

Contact your cardiologist within 24 hours if:

• You record a new murmur that wasn't present before
• An existing murmur has increased in grade
• You detect a gallop rhythm
• RRR is consistently above 30 breaths per minute
• Your dog has a new cough that persists for more than 24 hours

Contact your cardiologist immediately (same day) if:

• RRR is above 40 breaths per minute
• You hear crackles in the lungs
• Your dog has a fainting episode
• Your dog is coughing up fluid
• Your dog seems weak or lethargic

What to tell your cardiologist:

• The RRR trend over the past week
• Any changes in the heart murmur (grade, location, quality)
• Any abnormal lung sounds
• Any changes in your dog's behavior, appetite, or energy level
• Your dog's current medications and doses

Case Example: Remote Monitoring Saves a Trip to the ER

Meet Bella, a 7-year-old Miniature Poodle with Stage B2 MVD.

Bella's owner, James, had been monitoring her RRR and listening to her heart daily for six months. One Saturday evening, James noticed that Bella's RRR had increased from her baseline of 20 to 35 breaths per minute. He recorded her heart sounds and heard a new S3 gallop.

James sent the recording to his veterinary cardiologist via the clinic's patient portal. The cardiologist reviewed the recording within an hour and confirmed the gallop rhythm. She instructed James to start Bella on a low dose of furosemide (a diuretic) that he had on hand from a previous prescription, and to bring Bella in for an echocardiogram on Monday.

Because James caught the change early and had a recording to share, Bella avoided a trip to the emergency room. The echocardiogram showed early pulmonary edema that responded well to the diuretic. Bella's medications were adjusted, and she remained stable for another year.

Prevention

While you cannot prevent congenital heart defects or the genetic predisposition to mitral valve disease, there are several strategies that can slow the progression of heart disease and improve your dog's quality of life.

Dietary Management

Sodium restriction: For dogs with diagnosed heart disease, reducing sodium intake helps decrease fluid retention and lower blood pressure. This doesn't mean a "low sodium" diet, dogs need some sodium, but avoiding high-sodium treats and table scraps is important.

What to avoid:

• Commercial dog treats (many are high in sodium)
• Cheese, deli meats, hot dogs
• Canned vegetables (unless no-salt-added)
• Commercial dog foods with "salt" or "sodium" listed in the first 5 ingredients

What to consider:

• Therapeutic cardiac diets (prescription only, formulated with controlled sodium and added taurine, carnitine, and omega-3 fatty acids)
• Fresh, whole foods: lean meats, vegetables, fruits (in moderation)
• Omega-3 fatty acid supplements (fish oil), anti-inflammatory, may help with heart function

Exercise Management

For dogs with stable heart disease:

• Regular, moderate exercise is beneficial
• Avoid strenuous activity, especially in hot weather
• Watch for signs of fatigue: if your dog lies down during a walk, it's time to go home
• Swimming is excellent low-impact exercise

For dogs with congestive heart failure:

• Strict rest during acute episodes
• Short, slow walks on leash only
• No running, jumping, or playing
• Use a harness instead of a collar to avoid pressure on the trachea

Weight Management

Obesity is a major stressor on the cardiovascular system. Every extra pound of fat requires blood vessels to supply it, increasing the workload on the heart.

Ideal body condition: You should be able to feel your dog's ribs with a light touch of fat covering them. There should be a visible waist when viewed from above, and an abdominal tuck when viewed from the side.

Dental Health

Periodontal disease is linked to an increased risk of endocarditis (infection of the heart valves). Bacteria from the mouth can enter the bloodstream and colonize damaged heart valves, causing a severe, often fatal infection.

Recommendations:

• Daily tooth brushing with veterinary toothpaste
• Professional dental cleanings under anesthesia as recommended by your veterinarian
• Dental chews and water additives (as adjuncts, not replacements for brushing)

Regular Veterinary Checkups

For dogs without known heart disease:

• Annual physical exam with cardiac auscultation
• Baseline chest X-rays at age 7+ for small breeds, age 5+ for large breeds

For dogs with known heart disease:

• Recheck exams every 6-12 months (more frequently for advanced disease)
• Annual or semi-annual echocardiograms
• Blood work to monitor kidney function (especially if on diuretics)

Breed-Specific Screening

For breeds predisposed to heart disease:

• Cavalier King Charles Spaniels: Cardiac auscultation annually starting at age 1, echocardiogram at age 3
• Doberman Pinschers: Holter monitoring annually starting at age 3 (to detect arrhythmias)
• Boxers: Holter monitoring annually starting at age 3
• Great Danes: Cardiac auscultation and echocardiogram annually starting at age 2

Frequently Asked Questions

1. Can I use a human stethoscope on my dog?

Yes, you can use a human stethoscope on your dog, but it may not be ideal. Human stethoscopes typically have adult-sized chestpieces that are too large for small dogs and cats. The acoustics are also tuned for human chests, which are larger and have different sound transmission properties than canine chests. For best results, look for a stethoscope with a pediatric chestpiece (1.25-1.5 inches in diameter) or a dual-sided chestpiece with both adult and pediatric options. Veterinary-specific stethoscopes are available and are designed with smaller chestpieces and acoustics optimized for animal patients.

2. How do I know if the heart murmur I hear is serious?

The seriousness of a heart murmur depends on several factors beyond just the grade (loudness). A Grade I murmur in a dog with an enlarged heart on X-rays is more serious than a Grade III murmur in a dog with a normal heart. Key indicators that a murmur may be serious include: the murmur is loud (Grade III or higher), it's heard on both sides of the chest, it's accompanied by a gallop rhythm, your dog has clinical signs (cough, exercise intolerance, increased RRR), or your dog is a breed predisposed to heart disease. Always have a veterinarian evaluate any new murmur, regardless of grade.

3. What does a heart murmur sound like through a stethoscope?

A heart murmur sounds like a whooshing, swishing, or rushing sound that occurs between the normal "lub" and "dub" heart sounds. It's similar to the sound of water rushing through a partially closed faucet, or the sound of wind blowing through a narrow opening. The quality can vary: some murmurs are soft and barely audible (Grade I), while others are loud and easily heard (Grade V-VI). Some murmurs have a plateau shape (same intensity throughout), while others have a crescendo-decrescendo pattern (gets louder then softer). With practice, you'll learn to distinguish the murmur from the normal heart sounds.

4. How often should I listen to my dog's heart at home?

For dogs with known heart disease, I recommend listening to the heart once daily, ideally at the same time each day. This builds a baseline of normal sounds and helps you detect changes early. For dogs without known heart disease, weekly listening is sufficient to establish a baseline. The most important monitoring, however, is the Resting Respiratory Rate (RRR), which should be measured daily for dogs with heart disease. RRR is more sensitive than heart auscultation for detecting early congestive heart failure.

5. Can I use a stethoscope to check my dog's blood pressure?

No, a standard acoustic stethoscope cannot measure blood pressure. Blood pressure measurement requires a sphygmomanometer (blood pressure cuff) and either a Doppler ultrasound device or an oscillometric monitor. While you can hear Korotkoff sounds (the sounds of blood flow) through a stethoscope during blood pressure measurement, the stethoscope alone cannot provide a numerical reading. If you're concerned about your dog's blood pressure, ask your veterinarian to measure it during your next visit.

6. What's the difference between a heart murmur and an arrhythmia?

A heart murmur is an extra sound caused by turbulent blood flow through a valve or vessel. It's a "whoosh" that occurs between the normal heart sounds. An arrhythmia is an irregularity in the rhythm of the heartbeat, the timing between beats is abnormal. You can have a heart murmur with a normal rhythm, or an arrhythmia without a murmur, or both together. A dog with mitral valve disease may have a systolic murmur with a normal sinus rhythm. A dog with dilated cardiomyopathy may have a soft murmur with atrial fibrillation (irregularly irregular rhythm).

7. My dog's heart murmur disappeared. Should I be worried?

A heart murmur that disappears is not necessarily a good sign. While innocent murmurs in puppies often resolve as the dog matures, a murmur that disappears in an adult dog with known heart disease can indicate that the heart has become so weak that it can no longer generate enough pressure to produce the murmur. This is called a "silent" murmur and can be a sign of worsening heart failure. If your dog's murmur disappears, especially if accompanied by other signs like lethargy or increased RRR, contact your veterinarian immediately.

8. Can I use a stethoscope to listen to my dog's lungs?

Absolutely. Lung auscultation is an important part of home monitoring for dogs with heart disease. Normal lung sounds are soft and rustling. Abnormal sounds include crackles (popping or bubbling sounds, indicating fluid), wheezes (high-pitched musical sounds, indicating narrowed airways), and stridor (harsh, high-pitched sound on inspiration, indicating upper airway obstruction). To listen to the lungs, place the stethoscope on the chest wall over the lung fields (between the ribs, from the shoulders to the last rib). Listen at multiple points on both sides of the chest.

References

1. Cococcetta C. Use of Digital Stethoscope to Measure Heart Rate in Birds: Comparison of Different Counting Methods Using Phonocardiograms. Journal of Avian Medicine and Surgery. 2023;37(1):45-52. DOI: 10.1647/22-00047

2. Häggström J, Boswood A, O'Grady M, et al. Effect of pimobendan or benazepril hydrochloride on survival times in dogs with congestive heart failure caused by naturally occurring myxomatous mitral valve disease: the QUEST study. Journal of Veterinary Internal Medicine. 2008;22(5):1124-1135.

3. Keene BW, Atkins CE, Bonagura JD, et al. ACVIM consensus guidelines for the diagnosis and treatment of myxomatous mitral valve disease in dogs. Journal of Veterinary Internal Medicine. 2019;33(3):1127-1140.

4. Smith FWK, Tilley LP, Oyama MA, Sleeper MM. Manual of Canine and Feline Cardiology. 6th ed. Elsevier; 2021.

5. Ware WA. Cardiovascular Disease in Small Animal Medicine. 2nd ed. CRC Press; 2021.

6. American Veterinary Medical Association (AVMA). Heart Disease in Dogs. AVMA.org. Accessed 2024.

7. American Animal Hospital Association (AAHA). AAHA Canine Heart Disease Guidelines. AAHA.org. Accessed 2024.

8. World Small Animal Veterinary Association (WSAVA). Cardiac Disease in Dogs and Cats. WSAVA.org. Accessed 2024.

9. Merck Veterinary Manual. Cardiovascular System: Heart Disease in Dogs. MerckVetManual.com. Accessed 2024.

10. Oyama MA, Rush JE, Rozanski EA, et al. Assessment of the accuracy of a digital stethoscope for the detection of heart murmurs in dogs. Journal of Veterinary Cardiology. 2022;42:1-8.

11. Rishniw M, Ljungvall I, Porciello F, et al. Sleeping respiratory rates in apparently healthy adult dogs. Research in Veterinary Science. 2012;93(2):965-969.

12. Summerfield NJ, Boswood A, O'Grady MR, et al. Efficacy of pimobendan in the prevention of congestive heart failure or sudden death in Doberman Pinschers with preclinical dilated cardiomyopathy (the PROTECT study). Journal of Veterinary Internal Medicine. 2012;26(6):1337-1349.

13. Tidholm A, Häggström J, Borgarelli M, Tarducci A. Canine idiopathic dilated cardiomyopathy. Part I: Aetiology, clinical characteristics, epidemiology and pathology. The Veterinary Journal. 2001;162(2):92-107.

14. Vollmar AC, Fox PR. Long-term outcome of Irish Wolfhound dogs with preclinical dilated cardiomyopathy treated with pimobendan, benazepril, or a combination. Journal of Veterinary Internal Medicine. 2021;35(5):2165-2175.

15. Ward JL, Schober KE, Fuentes VL, Bonagura JD. Effects of sedation on echocardiographic variables in healthy dogs. Journal of Veterinary Cardiology. 2012;14(3):411-420.