Pulmonic stenosis

New treatments mean new hope for patients with this devastating disease. Here's what you need to know.

AWARENESS OF pulmonary arterial hypertension (PAH) increased dramatically after it was linked to the weightreduction medications fenfluramine and dexfenfluramine. However, this rare and potentially fatal disorder has numerous causes, so the removal of fenfluramine and dexfenfluramine from the U.S. market in 1997 didn't mean an end to PAH.

The good news is that new therapies are making PAH easier to manage, although its still incurable. Here, I'll discuss available treatments and how they affect nursing care for your patient. But first, let's review what PAH is and how it develops.

Under pressure

Pulmonary arterial hypertension is simply elevated blood pressure (BP) in the pulmonary arteries. Although variable, this pressure normally ranges from 15 to 25 mm Hg systolic and 8 to 15 mm Hg diastolic, with mean pressure between 10 and 20 mm Hg. (Pulmonary BP is much lower than systemic BP because the pulmonary arteries transport blood only from the heart to the lungs, not throughout the body.) When the mean pulmonary artery pressure is 25 mm Hg or greater, with a pulmonary capillary wedge pressure of 15 mm Hg or less (both measured at rest with a right-sided heart catheterization), the patient has PAH.

In July 2004, the American College of Chest Physicians (ACCP) released revised classifications for PAH. Primary PAH is now classified as idiopathic PAH (cause unknown) or familial PAH (when the cause is supported by genetic investigation). Other classifications of PAH relate to specific etiologies, such as collagen vascular disease.

Idiopathic PAH, a rare condition, is most prevalent in young adults who are probably genetically predisposed to the disorder. Pulmonary arterial hypertension related to an underlying disease (such as collagen vascular disease or human immunodeficiency virus [HlV] infection) or a toxic insult is far more common. (See What Can Cause Pulmonary Arterial Hypertension?)

Regardless of the cause, PAH leads to enlargement of the right ventricle as the heart tries to overcome abnormal pressure in the pulmonary arteries. If the right ventricle can't overcome the resistance, pressure also will increase in the right atrium and in the systemic venous system, leading to signs and symptoms of right-sided heart failure. Right-sided heart failure caused by pulmonary disorders, including PAH, is called cor pulmonale.

If the right ventricle can't pump enough blood into the lungs, blood won't pick up enough oxygen to meet metabolic demands. Sensing trouble, the bone marrow steps up production of red blood cells to carry more oxygen. Unfortunately, this causes polycythemia, which complicates matters by making the blood thicker, so it's harder to pump and more likely to clot.

Symptoms mimic heart failure

A patient with PAH has signs and symptoms associated with reduced oxygenation, decreased cardiac output, and inability to increase cardiac output, especially during activity. These signs and symptoms, which mimic those of heart failure, include shortness of breath, fatigue, and syncope. During exertion, symptoms may increase and be accompanied by angina-like chest pain.

Signs of right ventricular failure include peripheral edema, hepatomegaly, tricuspid regurgitation, an S^sub 3^ heart sound, prominent right ventricular impulse, and jugular vein distension. You'll also hear an accentuated P^sub 2^ (the pulmonic component of the second heart sound) at the apex. This reflects the increased force of pulmonary valve closure as a result of increased pulmonary artery pressure.

Typically, a patient with PAH first visits his primary care provider or emergency department complaining of shortness of breath. (Exertional dyspnea is the most frequent presenting symptom, and was found in 60% of patients in the National Institutes of Healths prospective cohort study of patients with PAH.) The patient's medical history holds the key to determining the cause of his symptoms. For example, a history of congenital heart disease or use of a now-banned weight-reduction medication should make you suspect PAH. Be aware that although fenfluramine and dexfenfluramine anorectic agents are off the U.S. market, they're still available illegally.

During your physical assessment, pay special attention to the patient's respiratory and cardiovascular systems, as follows:

* Assess his breathing for rhythm, use of accessory muscles, nasal flaring, increased anterior-posterior diameter of the chest ("barrel chest"), and pursed-lip breathing.

* Auscultate his lungs; breath sounds should be normal despite PAH, unless he also has underlying cardiopulmonary disease.

* Note whether he can speak in complete sentences or if respiratory distress is limiting his speech to a few words at a time.

* Palpate and percuss the anterior and posterior thorax, looking for areas of consolidation that may point toward other causes of shortness of breath, such as pneumonia.

* Auscultate the heart for gallops, splits, and murmurs, which may occur from right ventricular hypertrophy and failure. You may hear a split-second heart sound, pulmonic regurgitation murmur, or tricuspid regurgitation murmur.

* Look for peripheral edema and jugular vein distension. Assess the extent of peripheral edema and test capillary refill time.

* Palpate for an enlarged liver from venous engorgement.

What tests can tell

To diagnose PAH and rule out other disorders, the health care provider will order a 12-lead electrocardiogram, which may show signs of right ventricular hypertrophy (such as tall right precordial R waves and right axis deviation). A two-dimensional echocardiogram with Doppler flow studies can allow the health care provider to identify tricuspid regurgitation and right ventricular dilation and hypertrophy, and help him estimate systolic pulmonary pressure.

A chest X-ray may show an enlarged heart, prominent pulmonary arteries, and evidence of underlying lung disease. The health care provider may order a computed tomography scan of the chest or a ventilationperfusion scan to rule out other causes of shortness of breath, such as cancer or pulmonary embolism.

Right-sided heart catheterization should be done for all patients with suspected PAH, according to the ACCP. The most definitive test to diagnose and quantify PAH, catheterization can measure pressure in the pulmonary circulation and reveal occult shunts, congenital heart disease, and pulmonary artery stenosis. This procedure lets the health care provider evaluate pressure in the right atrium and right ventricle and assess valve function. Determining the severity of PAH with this test also helps guide therapy.

Pulmonary function tests can help the health care provider identify or rule out other pulmonary diseases that can cause shortness of breath, including asthma and chronic obstructive pulmonary disease. Arterial blood gas analysis can rule out hypoxia and acidosis as contributing factors to PAH. The new guidelines recommend these tests for all patients with PAH, to evaluate for lung disease.

Obtain a complete blood cell count to check for polycythemia or anemia and a comprehensive metabolic profile to check renal and liver function and identify electrolyte imbalances. Because thyroid dysfunction is common in patients with PAH, the patient should also be tested for thyroid function.

If the health care provider suspects an autoimmune disorder, or if the cause of PAH is unexplained, he'll order an antinuclear antibody test. He may also want to test the patient for HIV infection because HIV is a known cause of PAH.

Genetic testing and professional genetic counseling should be offered to relatives of patients with familial PAH, according to the new guidelines. Patients with idiopathic PAH should be told that testing and counseling are available for their families. Researchers have found mutations in the bone morphogenetic protein receptor II gene in 50% of patients with familial PAH and 25% of patients with idiopathic PAH.

Once the health care provider diagnoses PAH, he'll use the World Health Organization grading criteria to stage the disease according to the patient's ability to function. (The guidelines recommend a 6-minute walk test to assess the patient's functional class and exercise capacity.) Functional levels are classified as follows:

* Class I-no limitation of physical activity. Ordinary physical activity doesn't cause undue dyspnea, fatigue, chest pain, or near syncope.

* Class II-slight limitation of physical activity. Patients are comfortable at rest, but ordinary physical activity causes undue dyspnea, fatigue, chest pain, or near syncope.

* Class III-marked limitation of physical activity. Patients are comfortable at rest, but less-than-ordinary physical activity causes undue dyspnea, fatigue, chest pain, or near syncope.

* Class IV-unable to carry out any physical activity without symptoms. Patients may have dyspnea and fatigue at rest, and discomfort is increased with any physical activity. Patients have signs of right-sided heart failure.

Treatment options

Treating PAH starts with eliminating the cause of the problem if it's known; for example, stopping use of anorectic drugs. Pulmonary arterial hypertension isn't curable, so treatment is aimed at reducing pressure, removing excess fluid, and reducing the risk of clotting. The usual regimen consists of vasodilators, anticoagulants, and judicious use of diuretics. If the patient is hypoxic, provide supplemental oxygen to maintain his oxygen saturation above 90% at all times. Patients with obstructive sleep apnea and PAH should have positive airway pressure treatment for their sleep apnea; this treatment decreases pulmonary artery pressure.

Prepare the patient for therapeutic phlebotomy if his hematocrit level reaches 60% or higher, to reduce the risk of polycythemia. To reduce fluid overload, which would increase pressure on the right side of the heart, teach him to adhere to a low-sodium diet and fluid restrictions, as prescribed.

Taking off the pressure with medications

Calcium channel blockers, the first vasodilators used to treat PAH, help only about 20% of patients with idiopathic PAH and don't seem to help patients with other types of PAH at all. In fact, calcium channel blockers are contraindicated for patients with cor pulmonale because they decrease myocardial contractility and may worsen heart failure.

Because high doses of calcium channel blockers are required to effectively dilate the pulmonary arteries, these drugs generally are initially administered in the critical care unit so the patient can be closely monitored for response and adverse reactions, such as arrhythmias, systemic hypotension, and worsening right ventricular failure.

The new guidelines recommend that patients with idiopathic PAH and those with PAH associated with an underlying disease undergo a vasodilator challenge to determine if they'll benefit from calcium channel blocker therapy. This testing, also called acute vasoreactivity testing, uses a known short-acting vasodilator, such as intravenous (I.V) adenosine or epoprostenol, or inhaled nitric oxide. About 25% of patients with PAH have a positive response to the vasodilator challenge (defined as a fall in pulmonary arterial pressure of 10 to 40 mm Hg, with an increased or unchanged cardiac output); those who don't usually have a worse overall prognosis.

Calcium channel blocker therapy should be considered for patients who have a positive response to the vasodilator test and who have idiopathic PAH without right-sided heart failure, or PAH associated with an underlying disease without right-sided heart failure.

Newer treatments

Before the advent of vasodilators such as prostacyclin and endothelin receptor antagonists, only about 30% of patients with PAH lived 3 years after diagnosis. These newer medications dilate the pulmonary arteries and reduce pressure, and may increase life expectancy.

Epoprostenol (Flolan), approved in 1995, is a prostacyclin administered via continuous I.V. infusion through a long-term central venous access device by a portable, battery-operated pump. This drug is recommended, under the new guidelines, for patients with PAH who are in Class III and who aren't candidates for calcium channel blocker therapy or aren't helped by it. Intravenous epoprostenol is the drug of choice for patients in Class IV who need long-term therapy, but aren't candidates for calcium channel blocker therapy, or aren't helped by it.

An analogue of prostacyclin, treprostinil (Remodulin) was approved in 2002. Given as a continuous subcutaneous infusion, treprostinil has boosted 5-year survival rates to over 65% in some patients. The guidelines recommend this drug for patients in Class IV and patients in Class III who aren't candidates for or aren't helped by calcium channel blockers.

Iloprost, a newer drug similar to prostacyclin, is approved in Europe, but is awaiting Food and Drug Administration (FDA) approval in the United States. Because iloprost is inhaled, it's easier for patients to take, avoids the risks associated with injectable and I.V. medications, and causes fewer systemic adverse reactions, such as hypotension. The guidelines recommend this drug for patients in Class IV and for patients in Class III who aren't candidates for or aren't helped by calcium channel blockers.

In 2001, bosentan (Tracker), an endothelin receptor blocker, became the first oral drug for PAH approved by the FDA. Used in patients in Class III or Class IV, bosentan may halt progression of PAH and may even reverse it. Bosentan is available only through the Tracleer Access Program.

Researchers continue to look for better pulmonary vasodilators-drugs that are easy to take and don't cause systemic hypotension. Medications such as prostacyclin analogues, endothelin receptor antagonists, phosphodiesterase inhibitors such as sildenafil (Viagra), and thromboxane inhibitors dilate the pulmonary artery, are anticoagulant in nature, and may stop the progression of PAH by maintaining endothelium integrity. The new guidelines suggest sildenafil therapy for patients with PAH who aren't candidates for other therapies, or aren't helped by them.

Researchers also are investigating L-arginine, an amino acid that's a precursor to nitric oxide, as a possible treatment for PAH.

Turning to surgery

The new guidelines also recommend various surgical procedures for adults whose PAH is refractory to medical therapy. Atrial septostomy may be an option for some patients. Pulmonary thromboendarterectomy is the treatment of choice for patients with chronic thromboembolic PAH.

Patients with PAH in Class III or Class IV should be referred for evaluation and listing for lung or heart-lung transplant. Bilateral lung transplant is preferred. Adults with PAH and simple congenital heart lesions may have bilateral lung transplant and repair of the heart defect; for patients with complex congenital heart defects, a heart-lung transplant is the procedure of choice.

Supporting your patient

Be sure to address your patient's emotional and psychological needs as he and his family come to terms with this devastating illness. Teach him and his family about the illness and treatments and talk with them about end-of-life issues. Refer him to a local or national PAH support group and other support services as appropriate.

By learning how to recognize PAH, you can make sure your patient benefits from available treatments that can slow disease progression and extend his life.

SELECTED WEB SITES

What You Need to Know about Living with Pulmonary Hypertension http://www.clevelandclinic.org/health/health-info/docs/0600/0622. asp?index=6530

Pulmonary Hypertension Association

http://www.phassociation.org

Last accessed August 2, 2004.

SELECTED REFERENCES

American College of Chest Physicians: "Diagnosis and Management of Pulmonary Arterial Hypertension: ACCP Evidence-Based Clinical Practice Guidelines," Chest. 126(1, Suppl.):1S-92S, July 2004, http://www. chestjournal.org.

Nause, T., and Stites, S.: "Diagnosis and Treatment of Pulmonary Hypertension," American Family Physician. 63(9):1789-1802, May 1, 2001.

Steinbis, S.: "What You Should Know about Pulmonary Hypertension," Nurse Practitioner 29(4):8-20, April 2004.

BY SUSAN SIMMONS HOLCOMB, RN,BC, ARNP,BC, MN, PHD

Susan Simmons Holcomb is a nurse practitioner at the Walk-In Health Care of Olathe, Kan., and a consultant in continuing nursing education at Kansas City (Kan.) Community College.

Copyright Springhouse Corporation Sep 2004
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