Wed, October 5, 2011
Premature Ventricular Contractions (PVC’s)
A premature ventricular contraction (PVC) is caused by an early electrical impulse coming from somewhere in the ventricles. Fortunately most premature ventricular contractions in children are benign.
Normal Electrical Conduction
Every time the heart squeezes it requires an electrical impulse. With normal electrical conduction, impulses originate from an area in the top right corner of the heart known as the sinus node. Electricity initially spreads across the upper two chambers of the heart, and is then transmitted to the lower two chambers through the AV node. Every piece of tissue in the heart is electrically active. All heart tissue can conduct electricity. However, in addition, all heart tissue can generate electricity as well. Normally the heart tissue is simply conducting electricity generated by the sinus node. However, occasionally it will generate it as well; when this happens a premature contraction results.
Premature ventricular contractions (PVC's)
A premature ventricular contraction is a premature contraction coming from a piece of tissue in the ventricle. This is in contrast to a premature atrial contraction, where the early beat comes from somewhere in the atria. A PVC results in an electrical impulse coming earlier than expected, and in most cases causes an extra contraction of the heart. This in and of itself is not dangerous. In fact, almost everyone has at least a few PVC's every day! In this sense, PVC's can be considered a normal variant. Most children don't feel PVC's, although some kids do seem to feel them. Occasionally a situation will arise when a child is having PVC's fairly frequently. They may be happening so frequently that the doctor can appreciate them on a routine checkup. Usually when this occurs the child is referred for further evaluation.
When PVC's are happening frequently, the question arises as to whether they are still a normal variant or not. Occasionally frequent PVC's may be a marker of some type of disease process in the heart. For example, PVC's may occur if the heart muscle is inflamed or irritated. They may also occur if there is some type of problem with the electrical conduction system. The job of the pediatric cardiologist is to determine whether a child with frequent premature ventricular contractions has any type of disease process that is causing them, or whether the PVC's are still normal but simply more frequent than most other children have.
Typically the evaluation of a child or infant with frequent PVC's involves an electrocardiogram (ECG), an echocardiogram to evaluate the appearance and function of the heart muscle, and a 24-hour recording of the heart rhythm (Holter monitor). The Holter monitor allows the doctor to assess the frequency and pattern of PVC's over a prolonged period of time. Provided the studies do not show any abnormalities other than isolated PVC's, usually it can be assumed that the PVC's are benign in nature, and simply more frequent than what is seen in most children. The prognosis for an infant, child or teenager with benign premature ventricular contractions is generally excellent. No special medication treatment is needed; no special activity restrictions or precautions are needed either. It is often the case that the PVC's spontaneously decrease in frequency over time. Occasionally they may completely disappear. However, provided the PVC's are determined to be benign, there is no danger to the heart one way or the other.
In summary, premature ventricular contractions in children are fairly common. Fortunately, they are usually benign.