Heart murmurs in a puppy should not be dismissed

SINGAPORE – Imagine taking your new puppy to the clinic for a routine check, with its tail wagging, eyes bright and paws just a little too big for its body.

To you, everything seems perfect. But as the veterinarian listens carefully to your puppy’s chest, he pauses and mentions a heart murmur.

Hearing the word “murmur” can feel alarming, but it is not always bad news.

What is a heart murmur?

A heart murmur is an extra sound, often described as a “whoosh” or “swish”, heard when a veterinarian listens to the heart with a stethoscope. It occurs when blood flow becomes turbulent.

This turbulence can arise for several reasons, ranging from normal transitional changes in circulation in young puppies to structural abnormalities, such as narrowed or leaky valves, or abnormal blood flow between vessels or chambers.

The good news is that not every murmur is significant. Some puppy murmurs are harmless and temporary. These are usually soft, “innocent” murmurs that disappear on their own, often by about six months of age.

However, some murmurs can indicate congenital heart conditions and these are the ones that matter most because early detection can significantly impact outcomes.

Not every murmur requires the same level of investigation. The sound itself, along with the puppy’s overall condition, helps determine how concerned a veterinarian should be.

A murmur is more worrisome when it is loud and continuous, rather than limited to part of the heartbeat, or found in certain breeds with additional risk factors. For example, French bulldogs are predisposed to a condition called pulmonic stenosis.

When should you be worried about your pup’s health?

Further evaluation becomes important if the puppy is not thriving as expected. Signs such as poor growth, tiredness or difficulty keeping up with normal activity suggest that the murmur may reflect a meaningful heart defect rather than an innocent finding.

Even if a puppy appears outwardly well, a murmur that is present early in life and persists on recheck deserves attention, especially when the veterinarian feels it is more than a trivial sound.

If your veterinarian is concerned about a murmur, the next step is usually diagnostic imaging.

The most important test is echocardiography, an ultrasound of the heart that allows clinicians to see cardiac structures, evaluate blood flow patterns and assess pressure changes that cannot be determined with a stethoscope alone.

In most cases, this test provides a definitive diagnosis and distinguishes between an innocent and a pathological murmur.

In young puppies, this distinction is critical, as some conditions are best treated before prolonged strain causes irreversible damage to the heart or lungs.

Common conditions and treatments

One of the most common congenital defects is patent ductus arteriosus (PDA).

Before birth, all puppies have a temporary vessel that allows blood to bypass the lungs. Usually, it closes shortly after birth. If it remains open, blood flows abnormally, placing strain on the heart and lungs.

A puppy with PDA may initially appear healthy, but the condition can cause progressive damage and, if left untreated, most affected dogs will not survive beyond the first year.

Fortunately, PDA is often highly treatable. In many cases, the vessel can be closed using a minimally invasive catheter-based procedure, greatly improving long-term prognosis. In fact, most dogs that undergo successful occlusion of their PDA have a normal life expectancy.

Another common condition that may present with a murmur is pulmonic stenosis, in which the valve between the right side of the heart and the lungs is narrowed. This causes the heart to work harder to pump blood through the restricted opening.

Depending on severity, treatment may involve balloon valvuloplasty, a procedure in which a balloon attached to a catheter is guided to the valve and inflated to widen it. While not curative in every case, it can significantly reduce the obstruction and lessen the strain on the heart.

There are, of course, many other congenital heart conditions that can cause a murmur, but they are beyond the scope of this article.

Nonetheless, the take-home message is simple: A murmur in a puppy is not automatically a crisis, but it should never be dismissed.

Some murmurs are temporary and harmless, while others can be early signs of a condition that is best treated as soon as it is found.

A loud, continuous or persistent murmur, or one associated with clinical signs, should prompt further investigation as soon as possible. An echocardiography can also provide reassurance for puppy owners, even when the murmur is soft, by turning uncertainty into a clear and informed plan.