Pulmonary Hypertension

High blood pressure, or hypertension, in the circulation of the lungs can be a scary condition. As blood is pumped from the right side of the heart into the pulmonary artery, any challenges to the movement of this blood can stress the right side of the heart and eventually lead to right heart failure. Unfortunately, there are many reasons to have high blood pressure in the lung circulation and it’s not always the easiest to identify a cause or even diagnose the condition.

In our bodies, we have two circulations. One for the body and one for the lungs. The blood in the body returns to the right side of the heart where it is sent out to the lung circulation (pulmonary arteries, capillaries and pulmonary veins), receives oxygen and returns to the left side of the heart. The left heart then pumps blood with oxygen on to the body and the tissues that require this oxygenated blood.

The lung circulation is very different than the body’s circulation. There are many very small blood vessels connected to the main pulmonary arteries and at any given time we’re only sending blood to a fraction of these vessels. When the heart or lungs are stressed, such as with exercise or in disease states (lung disease, heart disease or diseases of the blood vessels themselves), we send blood to more of these vessels in order to help bring more oxygen to the body. If there is an obstruction to the flow of blood, this can lead to increased pressures in the pulmonary arteries and the right side of the heart has to work harder to push blood through the lungs.

There are many causes of high pulmonary artery pressures. This review will focus on a select few but there are many others.

If we break down the circulation in the lungs one can identify sites that can lead to trouble.

Problems with the pulmonary arteries themselves (pulmonary arterial hypertension) can occur for various reasons that include genetic or inflammatory causes. People with this condition develop a narrowing or remodeling of the pulmonary arteries which adds more resistance to the flow of blood. Resistance makes it harder for the heart to pump blood through the arteries. This can be a challenging form of pulmonary hypertension to diagnose and treat, but there are many new therapies now available that can be helpful.

Pulmonary arterial hypertension associated with congenital heart disease is a common form of pulmonary hypertension in children and often manifests when there is a hole in the heart that leads a shunting of blood from the left side to the right side of the heart, increasing the flow of blood to the pulmonary arteries. Many children with congenital heart disease tolerate some increased flow of blood, but with time, this can lead to narrowing or remodeling of the pulmonary arteries. High flows can stress the lining of these vessels stimulating the remodeling associated with this condition. Often, a surgical correction of the heart defect, can lead to a resolution of the high pressures.

Diseases of the lungs or conditions that lead to low oxygenation can also cause pulmonary hypertension. Oxygen is a very potent dilator of the blood vessels in our lungs. If regions of our lungs are not receiving oxygen (such as with obstructive sleep apnea or during an acute pneumonia), or if there are reasons for vessel compression (e.g. hyperinflation), impacted vessels then constrict leading to an increase in resistance and subsequent pulmonary hypertension. The treatment of pulmonary hypertension caused by lung disease is vastly different than disorders of the blood vessels themselves and requires addressing of the underlying challenge to the lungs, before starting medications specific to pulmonary arterial hypertension.

Frequent or chronic blood clots in the pulmonary blood vessels can also reduce the number of vessels available to send blood through causing a condition called chronic thromboembolic pulmonary hypertension (CTEPH). This is a rare condition in children, but is a major contributor to the development of pulmonary hypertension in adults. Blood clots block vessels and increase resistance, again increasing the pressures of the pulmonary arteries and subsequently put stress on the right side of the heart. Treatment of this condition requires anti-coagulation (blood thinners) and can sometimes require vascular surgery.

Failure or damage to the left side of the heart can also cause an increase in pulmonary artery pressures. If the pump (the heart) is functioning well on the right side, but not on the left side, a backup of blood within the pulmonary circulation can develop. This can also occur in situations where the pulmonary veins are narrow or stenotic. As more and more blood can’t pass the lungs back into the heart, vessels become engorged and distended, eventually increasing the pressures within them and stressing the right side of the heart. This type of pulmonary hypertension requires addressing the problematic pulmonary veins or the left sided heart disease.

There are many groups of people with an increased risk for developing pulmonary hypertension including people with Down syndrome or trisomy 21, sickle cell disease, thyroid conditions, metabolic conditions and many others.

Symptoms

• Symptoms can be very nonspecific and include:

  • Exercise intolerance or fatigue with activity

  • Fainting or passing out (syncope)

  • Rapid heart rate or palpitations (tachycardia)

  • Swelling of lower extremities (edema)

Diagnosis

Diagnosis can be very challenging and may require multiple tests to understand the reason behind the condition. These may include blood tests, imaging (Xray, CT scan or MRI) and invasive tests such as a flexible bronchoscopy or tissue biopsy.

Echocardiograms are ultrasounds of the heart that can give the clinician strong evidence of elevated blood pressures in the lungs. It isn’t perfect, but it is helpful in monitoring changes in the disease and can be a useful initial screening tool. If pulmonary arterial hypertension (meaning high blood pressure due to a problem with the pulmonary arteries themselves) is the cause, a cardiac catheterization may be necessary.

Cardiac catheterization includes the placement of a catheter into a large vein of the neck or extremities and passing the catheter up to the right side of the heart and into the pulmonary arteries themselves. Important data can be obtained including a measurement of the actual pressures of the lung circulation. This is the gold standard for diagnosing pulmonary hypertension.

Treatments

Treatment requires an understanding of why the high blood pressures exist and addressing the underlying problem. If the problem is a condition innate to the pulmonary arteries themselves, there are some oral, intravenous or subcutaneous options that can be discussed with your pulmonary hypertension specialist.

If your child has pulmonary hypertension, it is important that they are followed at a center with expertise in pediatric pulmonary hypertension. Pulmonary hypertension centers often have a multidisciplinary group of providers in pulmonology, cardiology, interventional cardiology and cardiothoracic surgery. A collaborative approach to the care of children with pulmonary hypertension is important.

For help identifying a pulmonary hypertension center, please contact us at webreathenyc@gmail.com and we’d be happy to help connect you with one.