Chihuahuas are prone to heart problems, and heart disease is one of the leading causes of death in the breed. A UK study of over 5,000 Chihuahuas found that heart disease accounted for nearly 19% of deaths, and about 2% of all Chihuahuas in the study had a documented heart murmur. The two main categories are congenital defects (present from birth) and degenerative valve disease that develops in middle age or later.
The Most Common Heart Condition
The heart problem Chihuahuas are most likely to develop is myxomatous mitral valve disease, or MMVD. This is the most common acquired heart disease in dogs overall, and small breeds are especially susceptible. The mitral valve sits between the two left chambers of the heart, controlling blood flow in one direction. In MMVD, scar-like tissue gradually builds up inside this valve, causing it to thicken and lose its seal. When the valve no longer closes properly, blood leaks backward with each heartbeat instead of flowing entirely out to the body.
This process is slow. Many Chihuahuas live for years with a leaky valve before it causes any noticeable symptoms. A veterinarian will typically detect a heart murmur during a routine exam well before your dog shows signs of trouble. The murmur is simply the sound of blood flowing abnormally through the damaged valve.
Congenital Heart Defects in Puppies
Some Chihuahuas are born with structural heart problems. The breed has a recognized predisposition to patent ductus arteriosus (PDA) and pulmonic stenosis. PDA occurs when a small blood vessel that normally closes shortly after birth stays open, allowing blood to bypass the lungs. It produces a distinctive continuous murmur that a vet can detect as early as six to eight weeks of age. Early detection matters because surgical repair becomes riskier if the condition leads to severe lung pressure changes over time.
Pulmonic stenosis involves a narrowed valve on the right side of the heart, forcing it to work harder to push blood to the lungs. Both conditions can sometimes be corrected with minimally invasive procedures, and outcomes are generally good when caught early.
Signs That Something Is Wrong
The earliest stages of heart disease produce no visible symptoms at all. Your Chihuahua may have a murmur for years while feeling perfectly fine. As the disease progresses and the heart struggles to compensate, fluid begins to build up in the lungs. This is congestive heart failure, and it produces symptoms you can recognize at home.
The most common sign is a persistent cough, especially when your dog is resting or sleeping. You may also notice:
- Reduced energy or stamina, with less interest in walks or play
- Faster or harder breathing, even at rest
- Loss of appetite that doesn’t resolve
- A swollen belly from fluid accumulation
- Pale or bluish gums, indicating poor oxygen circulation
- Fainting episodes, particularly during excitement or exertion
Because Chihuahuas are small and often carried around, reduced exercise tolerance can be easy to miss. Pay attention to whether your dog tires faster on walks or pants more than usual after mild activity.
How Heart Disease Is Diagnosed
A heart murmur found during a physical exam is usually the first clue. From there, an echocardiogram (an ultrasound of the heart) is the gold standard for diagnosis. It allows a veterinarian or cardiologist to see the valve’s structure, measure chamber sizes, and determine how much blood is leaking. These measurements help stage the disease and predict how quickly it may progress.
Chest X-rays are also used, though Chihuahuas present a quirk here: their hearts naturally appear larger on X-rays than the standard reference values for most dogs. A veterinarian familiar with the breed will account for this higher baseline heart size score to avoid misdiagnosis. Listening carefully with a stethoscope remains a simple but effective screening tool, especially for congenital defects in puppies.
Treatment and What to Expect
Heart disease in Chihuahuas is managed rather than cured. In the early stages, when a murmur is present but your dog has no symptoms, treatment may not be necessary beyond regular monitoring. Once the disease progresses to congestive heart failure, medication becomes essential.
The typical treatment plan involves a combination of drugs. One strengthens the heart’s contractions and opens up blood vessels, reducing the workload on the heart. Another type, a diuretic, helps the body shed excess fluid that has built up in the lungs or abdomen. Some dogs also receive medication to lower blood pressure and slow further heart enlargement. In clinical trials, Chihuahuas were among the most common breeds enrolled in studies of these heart failure medications, so the treatment approach is well established for the breed.
With appropriate medication, the median survival time after a diagnosis of advanced heart failure is about 9 months, though the range is wide. Some dogs live less than a month, while others survive over two years. Dogs whose fluid retention is aggressively managed with diuretics tend to do significantly better, with a median survival around 13 months compared to roughly 4 months for those on lower doses.
Monitoring at Home
One of the most useful things you can do for a Chihuahua with heart disease is count their resting respiratory rate. While your dog is relaxed or sleeping, count the number of breaths in 60 seconds. A healthy rate, and the target for a dog with well-controlled heart failure, is under 30 breaths per minute. A sustained rate above 36 breaths per minute at rest is a red flag that fluid may be building up in the lungs, and your dog needs veterinary attention.
Getting in the habit of checking this number regularly gives you an early warning system. Many owners track it daily in a notebook or phone app so they can spot upward trends before a crisis develops.
Diet and Lifestyle Adjustments
Sodium is the main dietary concern for dogs with heart failure. Salt causes the body to retain water, which worsens the fluid buildup that heart failure already causes. Sodium hides in places you might not expect: dental chews, rawhides, table scraps, and even some senior dog foods that are marketed as heart-healthy but are actually high in salt. Not all senior diets are low-sodium, so check with your vet about specific brands.
Fish oil and taurine supplements are sometimes recommended for dogs with heart disease, but both can interact with medications or cause side effects, so they shouldn’t be added without veterinary guidance. Keeping your Chihuahua at a healthy weight is also important. Excess body weight forces the heart to work harder, while significant weight loss and muscle wasting, which can happen in advanced heart failure, signals that nutrition needs to be reassessed. Raw meat diets are specifically discouraged for dogs with heart disease.
Screening and Early Detection
Veterinary cardiology guidelines recommend that small breeds predisposed to MMVD receive yearly heart auscultation (stethoscope exam) as part of routine care. For Chihuahuas, this means your vet should be listening carefully to the heart at every annual visit, starting when your dog is young. Congenital defects can be detected as early as six to eight weeks, while degenerative valve disease typically appears in middle-aged to older dogs.
If a murmur is detected, your vet may recommend an echocardiogram to establish a baseline. From there, periodic follow-up imaging helps track whether the heart chambers are enlarging, which is the key indicator that the disease is progressing toward heart failure. Catching that transition early means treatment can start before your dog is in distress, which generally leads to better outcomes.