Pulmonic Stenosis and Balloon Valvuloplasty
Alan D. Tong, M.D., FACC
Pediatric Cardiologist
Cedars-Sinai Medical Center
Los Angeles, CA |
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Posted: May 9, 1997
Updated: May 3, 2001
Edited by: Mona Barmash
What is pulmonic stenosis?
Pulmonic stenosis (or PS) is a general term indicating that there is obstruction to normal blood flow in the pulmonary arterial system, which conducts less oxygenated or "blue" blood to the lungs so it can become oxygenated or "pink". This can be at the level of the pulmonic valve, located between the right ventricle and the main pulmonary artery, or in the pulmonary arterial system itself . For the purposes of this discussion, we will discuss the most common type of
PS, which is at the level of the valve (figure 1).
The pulmonic valve is normally quite thin (no more than a few millmeters in an adult), and composed of three portions arranged in a circle like a three-slice pie. Normally, the leaflets open in the direction of blood flow with each contraction of the right ventricle, then close to keep blood from traveling backward from the pulmonary arteries.
In valvar PS, the leaflets may be abnormally thick; there may be only one or two functioning leaflets; or there may be a lack of normal separation of the edges of the valve leaflets (called fusion of the valve commissures). Because the valve leaflets cannot open to their full extent, the right ventricle must pump with greater force to overcome this blockage and ensure adequate blood flow to the lungs.
Valvar pulmonic stenosis can range from very mild to very severe, and characteristically a heart murmur can be heard at the left upper chest, near the breastbone. It may become apparent in a child in many ways, ranging from cyanosis (skin blueness) in the newborn, to a heart murmur detected at physical examination in an older child without symptoms of any kind, or with such findings as fatigue or heart rhythm abnormalities. Often, the degree of PS detected is mild, and routine checkups are indicated but no intervention is necessary. In most cases, an echocardiogram (heart ultrasound test) is done to determine the location and estimate the severity of PS; in general, an estimated pressure difference between the right ventricle and pulmonary artery of 50 millmeters of mercury (mm Hg) at rest due to isolated PS is sufficient to consider treatment.
How is pulmonic stenosis treated?
Prior to the mid-1980s, the only treatment for PS was an open surgical procedure. The valve commissures could be separated; one or more valve leaflets could be removed; or in certain instances the entire valve could be removed and replaced with a biologic (usually porcine) or mechanical valve. In the early 1980s, the first case reports of non-surgical treatment of valvar PS were first reported. Non-surgical opening of the pulmonic valve (balloon pulmonary valvuloplasty, or BPV) is now the procedure of choice for relief of nearly all cases of valvar PS.
How is a balloon pulmonary valvuloplasty performed?
Balloon pulmonary valvuloplasty is performed as part of a procedure called a cardiac catheterization. In children, this procedure should generally be performed by pediatric cardiologists in medical centers which are equipped and qualified to care for children with congenital heart disease. For a BPV, the catheterization is generally performed using a combination of local and general anesthesia. Flexible, sterile tubes are introduced into blood vessels, usually in the groin area, and are sufficiently long to reach the inside of the heart as well as the major blood vessels. Movement of the catheters in the heart and vessels is monitored by fluoroscopy, which uses radiation energy to produce a picture on a TV monitor located in the catheterization lab.
Pressures in the right ventricle (before the pulmonic valve, and therefore at higher pressure) and the pulmonary artery (after the valve, at lower pressure) are directly measured by placing the catheter tip in each area. The catheter is connected to a transducer, an instrument that senses blood pressures which are displayed on a second monitor in the lab. The difference between the two pressures is called the valve gradient, and will usually approximate the estimated pressure difference obtained by echocardiography fairly closely.
Next, the diameter of the pulmonic valve annulus (the ring of tissue which supports the valve leaflets) is measured by a procedure called an angiogram. A special substance called contrast is injected into the right ventricle through a catheter under high pressure, while being filmed with a high-speed movie camera. The contrast (a thick, clear fluid) appears dark under fluoroscopy, and fills the internal cavities of the right ventricle and pulmonary arteries as the heart pumps it through these structures. A measurement of the annulus diameter can be obtained as the contrast passes across it by careful review of still frames of the movie.
The first catheter is then withdrawn, and a second catheter which has an inner channel throughout its entire length is then placed with its tip in one of the branch pulmonary arteries. A long, tightly woven metal string called a guidewire is then advanced through the inner channel of the catheter; the tip of the wire is positioned as far into one pulmonary artery branch (either the left or right) as possible, and the wire-positioning catheter is then withdrawn from the body. The purpose of the wire is to steady the catheter used for the valve dilation.
The balloon valvuloplasty catheter is then threaded over the wire, and the balloon is positioned such that its center is in the annulus. The dilation is performed by inflating the balloon with dilute contrast under fluoroscopy, and observing that the balloon remains centered and for inflation of the balloon to its full diameter (figure 2).
Usually, this is repeated two to three times to ensure that maximal effect has been achieved. In older children and adults, two guidewires and balloons may be used for a BPV due to the size of the valve annulus.
After the dilation of the valve is completed, pressures are remeasured as described above. Balloons of different lengths and diameters may be substituted if the previous dilations did not optimally dilate the valve. Finally, a repeat angiogram is performed in the right ventricle to document improved valve mobility and filling of the pulmonary arteries with contrast. The tubes are then withdrawn from the vessels, and pressure is applied to the entrance sites with sterile gauze using arm pressure or with weights placed over the sites. Patients are monitored for several hours after the procedure to ensure a normal recovery from anesthesia, and to observe the catheter entry sites for bleeding. Usually, a repeat echocardiogram is performed soon after the procedure to further document relief of the obstruction and to look for valve leakage. In general, patients are discharged within 24 hours after completion of the procedure.
What are the complications of a balloon pulmonary valvuloplasty?
There are many potential complications of both cardiac catheterizations and BPV; fortunately, all are rare. As with all procedures that are done inside the body, there are risks of bleeding or introduction of an infection. Blood for transfusion is always ready to be given during the catheterization but is seldom needed, and the procedure is performed under completely sterile conditions similar to an operating room. Blood clots may form in the vessels in which the catheters are placed; these generally dissolve by themselves, but may rarely require clot-breaking medications. The risk of vessel blockage is greatest in infants, where even the smallest available catheters are large compared to the vessels involved. Movement of the catheters inside the heart can cause either fast or slow heart rhythms, which are usually brief in duration and resolve without treatment. Very rarely, there is a body reaction to the contrast fluid given for angiography which is usually treatable. The risk of a catastrophic event during a cardiac catheterization (including death) is estimated at about 1 in 50,000 procedures.
The most common side effect of BPV is that the pulmonic valve tends to develop some degree of leakage, also known as valve insufficiency or regurgitation. The BPV is intended to reduce the degree of valve obstruction to the fullest extent possible, while accepting a small to moderate degree of valve leakage, which is felt to be better tolerated in the long term than residual valve obstruction. In older children and adults with longstanding PS, the right ventricle is usually quite muscular, and occasionally this muscle buildup can itself cause an obstruction of blood flow to the lungs after a BPV. Medications to help prevent this condition can be given before or after the procedure if it is suspected, but rarely open-heart surgery to remove the buildup of muscle is necessary.
What happens after a balloon pulmonary valvuloplasty?
Depending upon several factors, the follow-up results after BPV for isolated PS are very encouraging. Valves which are severely malformed (dysplastic) tend to respond poorly to dilation, and the presence of associated problems such as a very small valve annulus are also indicators that the valve may not open adequately after a BPV. In general, however, the procedure has been proven to be both effective and safe, and in 80-90% or more of patients in the follow-up studies available thus far (covering 5-10 years of experience) there has been good relief of PS, no significant valve leakage, and a very low incidence of complications.
Follow-up visits with a pediatric cardiologist are still necessary, as the valve may rarely renarrow over time, and the degree of valve leakage (if any) needs to be monitored. Children who have PS require antibiotics at the time of certain procedures, such as dental cleanings, even after a successful BPV. In general, however, a child with isolated PS who has mild or no residual valve obstruction nor leakage after a BPV should, as best as we can tell, lead a perfectly normal life in both duration and quality.
Note: This article is intended as a general overview of the topic of pulmonic stenosis and balloon pulmonary valvuloplasty. It should not be regarded as a definitive description of either PS or BPV, and your (or your child's) pediatric cardiologist should be consulted if you have questions about these topics.
- This article was reviewed prior to publication by:
- Benjamin Zeevi, M.D.
- Director, Pediatric Cardiac Catheterization Unit
- Schneider Children's Medical Center of Israel
- Petach-Tikva , Israel
- Parent Reviewer:
- Rita Scoggins
- Harlingen, TX
Your feedback is very important! Please e-mail us with any questions or comments about this article.
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