If your new puppy's first veterinary examination revealed a heart murmur, keep in mind that murmurs are not uncommon findings in puppies, and many of them resolve on their own without devastating consequences. Find out what physiological heart murmurs are and how they are addressed.
"Lub-dub" is the sound of a normal heartbeat. However, if your veterinarian hears a whooshing sound after the "lub" and before the "dub," this is the characteristic sound of a murmur. Heart murmurs can be caused by an abnormal flow of blood through the heart when one of the valves doesn't function properly. Mitral valve leakage is one common example of such a defect. However, not all heart murmurs are the result of a physical defect or cardiac disease. Heart murmurs can be caused by turbulent blood flow through normal heart valves. In fact, these benign murmurs can be detected in an excited dog that is panting heavily while being examined. This type of murmur, known as a physiological or innocent murmur, is also a common finding in puppies. The reason your veterinarian listened so intently to your puppy's heart was so that he could assign a grade to the murmur.
The intensity of a heart murmur is graded on a scale from one, which is the lowest intensity grade, to six, which is the highest intensity grade. In a dog with a lower grade heart murmur, the whooshing sound may only occur intermittently, and the murmur cannot be felt from the outside of the dog's chest. A murmur of a higher grade is more pronounced, louder, and a veterinarian might be able to feel it from the outside of the dog's chest. Most physiological murmurs are graded as a one, two or three.
It is perfectly understandable to be concerned if your veterinarian has just informed you that your happy, active and playful puppy has a heart murmur. Here are some key points to remember for your peace of mind:
- Physiological murmurs are often heard in puppies, especially in those who are less than six months old.
- Physiological murmurs are more common in large breeds.
- Physiological murmurs first present when a puppy in between six and eight weeks old.
- Physiological murmurs often disappear when the puppy is between four and five months old.
You read that last point correctly. In most puppies who are diagnosed with physiological heart murmurs, the murmurs resolve on their own without any need for treatment and without consequence. The reason that these murmurs occur in the first place is that your puppy is growing rapidly, and his heart has to adjust to an increase in blood flow to accommodate his increase in size. Your puppy will be visiting the pet hospital frequently over the next couple of months for vaccine boosters. The doctor will listen closely to your puppy's heart during each visit to monitor the murmur.
Since your puppy will likely complete his or her vaccination series around four months of age, it is possible that the murmur may still be heard during that visit. If this is the case, your veterinarian will want to conduct an additional examination before your puppy is scheduled for the spay or neuter procedure, which typically occurs around six months of age. By that time, a physiological murmur will most likely have disappeared and that will be the end of it. If the veterinarian still hears the murmur, however, then further evaluation will be needed to determine if there is a physical defect or underlying heart disease that is causing it. An echocardiogram, which is a noninvasive ultrasound of the heart, will provide the answers. No anesthesia is required for this diagnostic imaging test.
The good news is that physiological heart murmurs usually disappear, these dogs do not develop heart disease, don't require treatment and have excellent prognoses for living full, happy and normal lives.