June 19, 2007 — The American College of Chest Physicians provides an update of the evidence-based treatment recommendations for patients with pulmonary arterial hypertension. The new guidelines are published in the June issue of Chest.
"Pulmonary arterial hypertension (PAH), defined as a mean pulmonary artery pressure (PAPm) ≥ 25 mm Hg with a pulmonary capillary wedge pressure ≤ 15 mm Hg measured by cardiac catheterization, is a disorder that may occur either in the setting of a variety of underlying medical conditions or as a disease that uniquely affects the pulmonary circulation," write David B. Badesch, MD, FCCP, from the University of Colorado Health Sciences Center in Denver, and colleagues. "Irrespective of its etiology, PAH is a serious and often progressive disorder that results in right ventricular dysfunction and impairment in activity tolerance, and may lead to right-heart failure and death. The pathogenesis of PAH is complex and incompletely understood, but includes both genetic and environmental factors that alter vascular structure and function."
Since a consensus panel convened by the American College of Chest Physicians developed guidelines for PAH treatment that were published in 2004, several important clinical trials have been published and new treatments have received regulatory approval. Add-on and combination therapy are being explored as potential new therapeutic options.
These updated guidelines, taking into consideration studies published before September 1, 2006, provide a summary of the original guidelines, a discussion of new studies, and a revised treatment algorithm taking into account recent developments in therapy.
"Due to the complexity of the diagnostic evaluation required and the treatment options available, referral of patients with PAH to a specialized center continues to be strongly recommended," the authors write. "The pace of developments in the treatment for PAH has quickened, with several important clinical trials having been published over the past 2 years that have led to regulatory approval of newer drugs and experience with combinations of existing drugs. These advances are likely to impact on the way physicians should now approach the treatment of PAH."
The treatment algorithm provided summarizes the current approach to therapy for PAH, based on functional class. However, the authors note that functional class is difficult to quantify, may vary among patients and care providers, and may not always correlate with other indexes of disease severity, although it does correlate with outcome (in patients with IPAH [idiopathic PAH]).
When making decisions regarding treatment, one should therefore consider not only functional class but also cardiopulmonary hemodynamics, 6-minute walk distance, signs and symptoms of right-sided heart failure, adverse effect profile, and drug-drug interactions, as well as cost.
Functional class II: The only treatments currently approved for patients with PAH in functional class II are sildenafil and subcutaneous and intravenous treprostinil. Because of the ease of administration and relative efficacy, sildenafil may be the first choice for most of these patients. Clinical trials with sitaxsentan and ambrisentan have included patients with PAH in functional class II, and a trial with bosentan is ongoing. Patients should be encouraged to enroll in clinical trials.
Functional class III: For the treatment of patients with PAH in functional class III, there are now 5 drugs approved by the US Food and Drug Administration, in 3 therapeutic classes, allowing rational therapeutic decisions based on available evidence, knowledge of an individual patient's specific situation, clinical judgment, and patient preferences.
For patients with "early" PAH in functional class III, most experts now consider 1 of the 2 approved oral therapies (bosentan or sildenafil, listed in no specific order). When choosing between these agents, one should take into account relative toxicities (eg, patients with hepatic abnormalities may do better with sildenafil, whereas patients with ocular disease or recurrent epistaxis may do better with bosentan). Sildenafil is generally less expensive.
Patients with more advanced class III disease may need a prostanoid, such as intravenous epoprostenol or treprostinil, inhaled iloprost, or subcutaneous treprostinil. While awaiting additional evidence regarding the use of add-on and combination therapy, one might consider these in the context of enrollment into clinical trials.
Functional class IV: All currently labeled therapies are approved for patients with PAH in functional class IV. However, based on the quality of the evidence and the net risk-benefit profile, the guidelines strongly recommend intravenous epoprostenol as the treatment of choice. Most experts are familiar with how to titrate intravenous epoprostenol in the acute setting, and it has a rapid and predictable onset of action.
As experience with intravenous treprostinil is accumulating, this may be a suitable alternative to intravenous epoprostenol in some cases. Except for patients who refuse intravenous therapy or who are not capable of managing the complex delivery system, oral, subcutaneous, and inhaled agents should generally not be used as first-line therapy for patients with PAH in functional class IV.
"Recommendations regarding therapy obviously need to be applied in light of the individual patient's specific situation," the authors conclude. "The importance of a thorough diagnostic evaluation, looking for underlying causes and contributing factors, cannot be overemphasized. Educational efforts have contributed to improved recognition of PAH, facilitating earlier initiation of therapy [which] should contribute to better clinical outcomes."
Some of the authors have disclosed various financial relationships with pharmaceutical companies and organizations, including the National Institutes of Health, GlaxoSmithKline, United Therapeutics/LungRx, and Actelion. A complete listing of financial relationships is available in the original article.
PAH is defined by a mean pulmonary artery pressure of at least 25 mm Hg along with a pulmonary capillary wedge pressure of 15 mm Hg or less. PAH may be an intrinsic process within the pulmonary vasculature, or it may be secondary to other disease states such as connective tissue disease or congenital heart conditions.
The American College of Chest Physicians last published guidelines for the management of PAH in 2004. Since then, new research has mandated a rethinking of treatment of PAH. The current clinical practice guidelines highlight this research.
An expert panel reviewed pertinent literature published prior to September 1, 2006, to shape the current guidelines. Only studies published in English were included, and the authors focused on trials of prostanoids, endothelin receptor antagonists, and phosphodiesterase inhibitors. The etiology of PAH was not considered in the decision whether to include a study in the literature review.
Patients with PAH and a favorable response to short-term vasodilator testing during cardiac catheterization, defined as a decrease in mean pulmonary artery pressure of at least 10 mm Hg to a level of 40 mm Hg or below, may be amenable to therapy with calcium channel blockers.
The authors recommend long-acting nifedipine or diltiazem along with amlodipine for this small subgroup of patients, but verapamil should be avoided. If the patient does not improve to functional class I or II following 3 months of treatment with calcium channel blockers, other therapy should be considered.
Treprostinil and sildenafil are indicated for the treatment of patients with PAH in functional class II. Because sildenafil is delivered orally and treprostinil via either the subcutaneous or intravenous route, sildenafil might be preferred by most patients. Trials of sitaxsentan, ambrisentan, and bosentan for patients with PAH in functional class II are underway.
Sildenafil or bosentan may be considered for patients with PAH in functional class III whose symptoms are not too severe. The authors recommend consideration of the toxicities of these agents in choosing treatment. Patients with headache, epistaxis, and ocular disease should avoid therapy with sildenafil if possible. Also, patients with liver disease should preferably not receive bosentan. Sildenafil is somewhat more affordable than bosentan.
Patients with more advanced PAH in functional class III should receive epoprostenol, treprostinil, or iloprost. There is little evidence regarding the benefits for combination therapy with different treatments if monotherapy is insufficient, and this management strategy may be considered in the context of enrollment into clinical trials.
The authors strongly recommend intravenous epoprostenol for the treatment of patients with PAH in functional class IV. Intravenous epoprostenol has a rapid and predictable onset of action, and many clinicians have good experiences with this medication. Evidence of the efficacy of intravenous treprostinil is increasing, and this medication may be considered as an alternative to epoprostenol. The use of oral, subcutaneous, or inhaled agents among patients with PAH in functional class IV is discouraged.
Pearls for Practice
Treprostinil and sildenafil are indicated for the treatment for patients with PAH in functional class II, and sildenafil may be the preferred agent because of ease of administration and cost.
Intravenous epoprostenol as the first-line treatment for patients with PAH in functional class IV is strongly recommended.