What is Pulmonary Stenosis?
Pulmonary stenosis is a fairly common heart defect that often appears along with other heart problems present from birth, such as the “tetralogy of Fallot”. This condition is typically caused by some form of blockage within the heart’s right ventricle (RV), the passages leading to the lungs, or around the heart’s pulmonary valve-sized rings (annulus) or leaflets. While pulmonary stenosis can occur on its own in about 7%-12% of patients, it’s more often seen in conjunction with other heart defects – happening in 25%-30% of patients with such conditions. Generally, people with moderate or severe pulmonary stenosis may feel short of breath or tired after exertion, depending on the blockage’s severity and how well their heart can compensate. In rare cases, individuals can experience chest pain (angina) or even sudden cardiac arrest. Large aneurysms in the pulmonary artery (the blood vessels leading to the lungs) can also cause chest pain by putting pressure on the heart’s main blood carrying tube (the left main coronary artery).
To diagnose pulmonary stenosis, doctors often use echocardiography, a test that uses sound waves to create images of the heart. However, they might also use a cardiac computed tomography (CCT) or a cardiac magnetic resonance (CMR) scan. These methods are especially helpful for patients who might need an intervention to relieve the blockage in their RV. Recently, doctors are increasingly using less invasive methods, known as transcatheter approaches, to treat this condition. However, if these methods aren’t suitable due to a patient’s specific heart structure, surgery might be required. The choice of treatment will depend on how severely the pulmonary valve restricts blood flow and the valve’s structure. The American Heart Association and American College of Cardiology provide guidelines to help doctors determine the most suitable management plan.
What Causes Pulmonary Stenosis?
Pulmonary stenosis is a condition where the opening of the heart’s pulmonary valve is abnormally narrow. This situation can happen on its own, or it can be linked to birth defects of the heart such as tetralogy of Fallot, tricuspid atresia, complete and corrected transposition of the great arteries, and double outlet right ventricle. It can also be tied to genetic disorders like Noonan syndrome. The most common cause of Noonan syndrome is a mutation in the PTPN11 gene, but mutations in the KRAS, SOS1, and RAF1 genes can also cause it.
Peripheral pulmonary stenosis, a specific kind of pulmonary stenosis, may be linked to certain conditions such as Alagille syndrome and Williams-Beuren syndrome. Alagille syndrome usually comes from a mutation in the JAG1 gene on chromosome 12q24, or less often, NOTCH2 mutations. Williams-Beuren syndrome arises from a mutation in the ELN gene on chromosome 7q11.23.
Another known cause of pulmonary stenosis is Maternal rubella syndrome. In this case, the condition isn’t tied to any genetic defects, but rather due to an infection during pregnancy.
Rarely, pulmonary stenosis can appear during pregnancy in people who had previously not been diagnosed with it, or in patients who have an underlying condition known as carcinoid syndrome, a rare type of cancer. Furthermore, patients with rheumatic heart disease, those who’ve undergone heart surgeries, or those who have certain types of heart tumors such as pericardial sarcoma, teratoma thymoma, or Hodgkin disease may develop what is referred to as an acquired form of pulmonary stenosis.
Risk Factors and Frequency for Pulmonary Stenosis
Isolated valvar pulmonary stenosis is a condition that makes up 7% to 12% of all birth heart defects. Around 56% of those with pulmonary stenosis also suffer from other health issues outside the heart and mental development difficulties. These patients usually receive a molecular diagnosis. For example, a mutation in the PTPN11 gene is found in 50% of pulmonary stenosis patients who also have Noonan syndrome – a disorder that affects many areas of the body. A certain type of pulmonary stenosis, thought to be connected with mutations in the GATA4 gene, occurs within families. However, it’s important to note that pulmonary stenosis does not prefer one gender over another.
- Isolated valvar pulmonary stenosis is a type of congenital heart disease, making up 7% to 12% of such cases.
- About 56% of patients with pulmonary stenosis also have conditions that affect other parts of the body and their mental development.
- A molecular diagnosis is more commonly found in such cases. An example is a PTPN11 gene mutation found in 50% of pulmonary stenosis patients who also have Noonan syndrome.
- A familial form of nonsyndromic pulmonary stenosis, potentially linked to GATA4 gene mutations, has been observed.
- Pulmonary stenosis doesn’t show a preference for either gender.
Signs and Symptoms of Pulmonary Stenosis
Mild pulmonary stenosis, a heart condition, often does not show any symptoms. Those who do show symptoms usually have a more severe case. They may feel short of breath during physical activities or generally fatigued. Other rare symptoms include chest pain or sudden cardiac arrest. Enlarged pulmonary artery aneurysms can also lead to chest pain.
Doctors usually listen to the patient’s heart to evaluate the severity of the condition. Here are some things they might hear:
- Mild pulmonary stenosis: A normal first heart sound is usually followed by an ejection click. The pulmonic part of the second heart sound typically sounds normal or is more intensified.
- Moderate pulmonary stenosis: The first heart sound is present, but the ejection click is closer to it. The second heart sound is split with a soft pulmonic component that varies depending on the severity of the obstruction
- Severe pulmonary stenosis: An absent click or a click that is too close to first heart sound to identify. This is joined with a louder murmur. The second heart sound is widely split with an extremely soft or inaudible pulmonic component due to decreased flow across the pulmonic valve.
Infants with a critical condition may show blue or purple skin color after birth due to low oxygen levels in the blood. They may also show signs of a disorder in the right ventricle from the heart obstruction. If the right ventricle of the heart becomes larger, it suggests an atrial septal defect which is a hole in the wall between the two upper chambers of the heart. This can also lead to low oxygen levels in the blood.
If the right ventricle stops working due to the severe condition, systemic venous congestion can occur, which is a kind of blood congestion. Additional noticeable signs in a child or an adult with severe pulmonary stenosis might show a left parasternal heave due to right ventricle enlargement. The systolic ejection murmur, a specific type of heart sound, can radiate to the back. There might also be an associated fourth heart sound in severe pulmonary stenosis due to reduced ventricular compliance, which is a decrease in the flexibility of the heart wall.
Testing for Pulmonary Stenosis
To assess a potential condition called pulmonary stenosis, medical professionals often use an imaging technique called echocardiography. This method, which uses sound waves to create detailed pictures of your heart, provides a better look at the pulmonary valve and nearby structures compared to other imaging methods. Usually, a type of echocardiography that involves placing the ultrasound probe on the chest, called a transthoracic echocardiogram, is sufficient. A more specialized type, called transesophageal echocardiography, which places the probe in the esophagus, may be used when the views are not clear or when there’s a need to check for heart infection, also known as endocarditis.
An electrocardiogram, a test that checks how your heart’s electrical signals are working, can also provide clues about how severe the pulmonary stenosis is. In mild cases, it may show a shift in the heart’s electrical axis to the right, while severe cases may show large, prominent electrical waves in certain lead placements.
Doppler studies, a part of echocardiography that uses sound waves to measure the speed and direction of blood flow, are used to grade the severity of the pulmonary stenosis. According to guidelines from various heart associations:
- Mild stenosis: Peak speed of blood flow across the valve less than 36 mm Hg or less than 3m/second.
- Moderate stenosis: Peak speed of blood flow across the valve 36 to 64 mm Hg, or from 3 to 4m/second.
- Severe stenosis: Peak speed of blood flow across the valve more than 64 mm Hg, or faster than 4m/second.
Heart catheterization, a procedure that involves threading a thin tube through a blood vessel to your heart, and pulmonary angiography, an x-ray imaging that shows the blood flow in your lungs, are typically not needed to diagnose pulmonary stenosis as echocardiography is usually effective and safe. However, in cases where echocardiography pictures aren’t clear or the anatomy is complicated, doctors might use CMR imaging. This advanced scanning technology uses strong magnets and radio waves to create detailed pictures of your heart. It can measure the size and function of the right side of your heart and the blood flow in the pulmonary artery. It can also be used during pregnancy to get a better view of the baby’s heart structures. If you can’t undergo a CMR, a CCT might be used instead. Plain x-rays aren’t typically used to diagnose pulmonary stenosis, as its sensitivity is not sufficient. However, x-rays can indirectly support the diagnosis if they show clear pulmonary arteries or the border of the right side of the heart.
Treatment Options for Pulmonary Stenosis
Treatment for Pulmonary Stenosis, a condition that restricts blood flow to your lungs, will depend on the severity of this restriction and the shape of the valve causing the problem. The American Heart Association and American College of Cardiology have laid out some guidelines for managing this condition in 2018.
If you have this condition but aren’t experiencing any symptoms and your valve is causing less than a certain level of restriction (as indicated by a tool called a peak Doppler gradient), you might just be monitored every 2-5 years with an electrocardiogram (a test that measures the electrical activity of your heart) and Doppler echocardiography (an ultrasound method that examines your heart and blood vessels).
A procedure called a balloon valvuloplasty could be recommended for some patients. In this procedure, a balloon is used to widen the valve and improve blood flow. This might be especially useful for patients who aren’t showing symptoms but whose valves are causing a high level of restriction. On the other hand, if the valves are abnormally formed (dysplastic), then surgery could be a better option. However, for some patients with dysplastic valves, a balloon valvuloplasty might still be reasonable.
Though this procedure to widen the valve can often be successful, you might need additional procedures if the valve tightens up (restenosis) after treatment. Also, patients who are young, lightweight, have a small valve opening to the lungs (pulmonary annulus), and severe pulmonary stenosis are more likely to experience moderate leakage of blood backwards (regurgitation) after the procedure.
In some circumstances, balloon valvuloplasty isn’t recommended. For instance, if you’re not experiencing any symptoms, you have normal blood flow and your Doppler peak instantaneous gradient (a measurement of blood flow) is less than 50 mm Hg. It’s also not recommended for patients with severe backflow of blood into the heart (pulmonary regurgitation) or those whose Doppler PIG is less than 30 mm Hg.
Surgical intervention could be needed for those with severe blockage and backflow of blood into the heart or when the heart structure is not as it should be. Some signs are a small opening to the lungs (pulmonary annulus), obstruction below the valve (subvalvular stenosis), obstruction above the valve (supravalvular stenosis), and abnormal valves.
Furthermore, antibiotics might be used to protect against infection in certain cases, such as before dental procedures, childbirth, or in patients with certain heart conditions.
Newborns with a very severe form of pulmonary stenosis can sometimes need emergency treatment to keep blood flowing to the lungs (prostaglandin E1 infusion) and to relieve the pressure in the smaller chamber of the heart (Rashkind procedure).
If the right side of the heart is very small (hypoplastic) and not able to do its job, then more complex surgical procedures might be undertaken. These procedures aim to stabilize circulation and sometimes create a path for blood flow around the heart (single ventricle palliation). In some cases, doctors might also attempt a procedure to open and widen the tiny valve (fetal pulmonary valvuloplasty) in unborn babies predicted to need these complex surgical procedures.
What else can Pulmonary Stenosis be?
In babies, doctors consider several other conditions that are similar to the medical issue they’re trying to diagnose:
- Heart defects that are present from birth and cause a narrow pulmonary artery such as double-chambered right ventricle, double outlet right ventricle, absence of the pulmonary valve, tetralogy of Fallot, atrioventricular septal defect, atrial septal defect, and ventricular septal defect
- Blockage of the pulmonary artery with the heart’s ventricles remaining intact
- Ventricular septal defect, a hole in the wall separating the lower chambers of the heart
For adults, the following conditions may be considered in the diagnosis by the doctors:
- Rheumatic valvular heart disease, caused by rheumatic fever
- Carcinoid heart disease, a condition caused by the growth of carcinoid tumors
- Pulmonary embolism, a blockage of an artery in the lungs
- Right heart failure, when the right side of the heart can’t pump blood efficiently
- Heart tumors
- Cardiac sarcoma, a rare type of cancer originating from the heart
What to expect with Pulmonary Stenosis
The course that pulmonary stenosis, a lung valve condition, takes largely depends on its severity and the structure of the impacted lung valve or blood vessel. Typically, the majority of patients live normal lives without any symptoms and excellent chances of recovery. This excludes cases of critical stenosis identified in newborns. Yet, there are some instances where patients develop serious pulmonary stenosis and need treatment.
Patients who get a balloon valvuloplasty, a treatment procedure, generally fare better if their valves are dome-shaped as opposed to dysplastic, or malformed. The complications that might arise during this procedure are usually minor. Some potential complications include a vagal response (an involuntary nervous system reaction), unusual heart rhythms triggered by the catheter, a blockage of the electrical signals in the right side of the heart, and a temporary or permanent severe block in the heart’s electrical system.
A rather rare but severe side effect is the “suicidal right ventricle.” This happens when the output passage of the right ventricle suddenly blocks, leading to a significant drop in the pressure across the lung valve. This is a serious, potentially life-threatening event after the procedure. One way to prevent it is by using beta-blockers, a type of medication that can reduce the chance of excessive contraction of the right ventricular output passage after the valve treatment.
Patients who undergo surgical corrections generally experience improved exercise capacity, with a minority (15% to 20%) requiring repeat procedures. Most repeat procedures are due to significant backflow in the lung valve. In these patients, a fast and irregular heart rate, if present, usually subsides after the repeat procedure.
During pregnancy, those with mild pulmonary stenosis may experience a symptomless heart murmur. That said, they might also have trouble tolerating exercise. Pregnancy is generally well tolerated unless the lung valve condition is severe. Valve treatment can still be performed during pregnancy, although it’s rarely needed.
Possible Complications When Diagnosed with Pulmonary Stenosis
Infective endocarditis, an infection in the heart’s inner lining, doesn’t commonly happen with isolated pulmonary stenosis, a heart valve disorder. In kids, it usually occurs due to a birth defect affecting the pulmonary valve, like in Noonan syndrome patients. For adults, the leading cause is often intravenous drug abuse. People having moderate and severe pulmonary stenosis can have complications. These may consist of heart rhythm disorders, typically recognized as premature beats in the upper or lower chambers of your heart.
Common Causes and Complications in Infective Endocarditis and Pulmonary Stenosis:
- Anomalous pulmonary valve in children (For example, Noonan syndrome)
- Drug abuse via injection in adults
- In moderate and severe cases of pulmonary stenosis, complications may occur
- Premature beats in upper or lower chambers of heart (arrhythmias)
Preventing Pulmonary Stenosis
Parents need to be informed about the possible complications and available treatments for children with pulmonary stenosis, which is a condition that narrows the passageway from the heart to the lungs. It’s also important for adults with pulmonary stenosis to understand the risks and outcomes, particularly if they’re planning on having a baby. Pregnancy can worsen pulmonary stenosis, so it’s crucial for these individuals to be fully aware of the potential challenges associated with their condition.
