Heart disease in dogs and cats can develop slowly over months or years, or in some cases show up more suddenly. Because pets can't tell us they're feeling short of breath or that their chest feels tight, owners often only notice something's wrong once the changes have become fairly obvious. Knowing the earlier, subtler warning signs — and understanding that dogs and cats tend to show heart disease somewhat differently — can help you get your pet in front of a vet sooner rather than later.
Signs Worth Watching For
In Dogs
- A persistent cough, especially one that's worse at night, after lying down, or during or after exercise
- Tiring more easily on walks than they used to, or needing to stop and rest partway through activities they used to handle easily
- Rapid or labored breathing, particularly while resting or sleeping — this is one of the more important signs to watch for and time if you notice it
- A swollen abdomen, which can indicate fluid buildup in more advanced cases
- Fainting or brief collapse episodes, sometimes after excitement or exercise
In Cats
Cats are notoriously good at hiding heart disease, and coughing — a hallmark sign in dogs — is actually uncommon in cats with heart disease. Instead, watch for reduced activity or hiding more than usual, rapid or open-mouthed breathing, a noticeably faster resting breathing rate, or sudden weakness or difficulty using the back legs, which can indicate a blood clot related to heart disease and needs emergency care right away. Because cats mask illness so well, heart disease in cats is sometimes only discovered when a vet hears a heart murmur or abnormal rhythm during a routine exam — another good reason not to skip annual checkups.
Why Prompt Attention Matters
Some heart disease signs — particularly labored breathing at rest, a blue or pale tinge to the gums, or sudden collapse — are true emergencies and warrant immediate veterinary attention rather than a "wait and see" approach. Other signs, like an occasional cough or slightly reduced stamina, are worth a scheduled vet visit rather than a panic, but shouldn't be ignored either, since earlier diagnosis generally means more effective long-term management.
How Vets Diagnose and Manage Heart Disease
A vet will typically start with a physical exam, listening carefully to the heart and lungs, and may recommend chest X-rays, an ultrasound of the heart, or other imaging depending on what they hear and see. Blood tests can also help rule out or identify other contributing conditions.
Management is highly individualized and depends heavily on the specific type and stage of heart disease. Vets typically build a plan that may include medications to support heart function and manage fluid buildup, activity adjustments, dietary changes, and a schedule of regular monitoring to track how the condition is progressing and adjust treatment as needed. Many pets with heart disease live comfortably for a good stretch of time with the right ongoing management — this is also a good moment to think about pacing activity appropriately, an idea we build on in our guide to managing chronic pain and comfort in pets more broadly.
Breed and Age Patterns Worth Knowing
Certain dog breeds are more prone to specific types of heart disease — some smaller breeds are more likely to develop a particular valve condition as they age, while some larger breeds are more prone to a condition affecting the heart muscle itself. In cats, a thickening of the heart muscle is the most common form of heart disease, and it can occur in cats of almost any age, including younger cats, though it becomes more common with age. Knowing your pet's breed-related risk isn't something to be anxious about, but it is useful context your vet may factor into how closely they monitor your pet's heart at routine visits.
A simple home habit some vets recommend for at-risk pets is periodically counting resting breaths per minute while your pet is calmly asleep, since a rising resting respiratory rate over time can be one of the earlier, more measurable warning signs available to owners between vet visits.
The Bottom Line
Heart disease can be subtle at first, particularly in cats, which makes routine vet checkups and attentiveness to small changes in energy and breathing especially valuable. If your pet is coughing persistently, breathing rapidly at rest, or tiring more easily than usual, don't wait for it to get worse — an exam now can catch things while there are still more options on the table.