Written by Jennifer West, VMD
Heart murmurs are abnormal heart sounds heard with a medical stethoscope. A stethoscope is an acoustic device used to amplify to the sounds of the heart and lungs. Heart murmurs are indicative of heart disease; however, a heart murmur alone does not clarify the significance of a heart issue. An echocardiogram (heart ultrasound) performed by a board certified cardiologist (heart doctor) is necessary to diagnose the cause of a heart murmur and develop the most effective treatment plan.
Zhuang, Xiahai. (2010). Automatic whole heart segmentation based on image registration.
There are 2 phases of heart pumping. The first is called systole, which is contraction for the heart muscle to pump blood into the arteries. The second is called diastole, which is relaxation of the heart muscle to allow blood to fill the heart after circulating through the body.
Normal heart sounds are described as “lub dub.” The “lub” is the sound of closure of the mitral and tricuspid heart valves at the beginning of heart contraction. These valves separate the atria (upper heart chambers) from the ventricles (lower heart chambers). The “dub” is the sound of closure of the aortic and pulmonic heart valves at the end of heart contraction. These valves separate the ventricles from the vessels going to the lungs (where red blood cells collect oxygen) and the vessels going to the body (where red blood cells deliver oxygen).
A leaky valve has a less crisp, whooshing sound. This sound occurs because the flow of some blood is slowed or even traveling against the normal movement, like turbulence of rocks in a fast moving water. Heart murmurs are graded on a scale of 1-6 with a 1 being very quiet and a 6 being so loud that it can be felt on the side of the chest with your hand.
Some causes of a heart murmur may be innocent and benign. These cases typically do not require heart medications and include young large breed puppies with developing hearts, anemia (low blood volume), or cats with hyperthyroidism.
Heart murmurs can come and go, so it is important to note if it is a new sound or if it is worsening at each veterinary visit.
Symptoms of heart disease include:
- Exercise intolerance.
- Fast breathing rate or increased breathing effort. When your pet is sleeping or calmly resting, count breaths in 15 seconds and multiply by 4 to get breaths per minute. One chest rise and fall is 1 breath. This number should be less than 40 for the average cat or dog at rest.
- Blue or grey gums. Normally, the tongue and gums should be a nice pink color due to good blood flow to these areas. If they are having breathing difficulty and the color is becoming less pink, the heart may not be pumping through the body well.
- Collapse. Syncope (fainting episode) can occur if blood flow to the brain is insufficient. This is very different from a seizure in that the pet will collapse without paddling the limbs or chewing at the air and they will usually regain consciousness rapidly.
Some of the most common heart medications:
(1) Furosemide/ Lasix
Use: This is a diuretic used to help reduce the buildup of fluid within the body when the heart is not
pumping efficiently.
Side effects: Increased thirst, increased urination including accidents in the house, dehydration, progression of kidney disease
(2) Pimobendan/ Vetmedin
Use: This is an inodilator used to increase heart muscle contractility by sensitizing heart muscle and increasing binding of calcium ions. It also decreases blood flow resistance through vasodilation (dilation of blood vessels).
Side effects: Usually well tolerated but may result in decreased appetite, vomiting, diarrhea, or lethargy.
(3) Enalapril
Use: This is an ACE (angiotensin-converting enzyme) inhibitor used to decrease blood pressure by preventing production of angiotensin II, which narrows blood vessels.
Side effects: Decreased appetite, vomiting, diarrhea, or weakness.
