MARINA DEL REY, CALIF. — Right ventricle catheterization is essential to confirm a diagnosis of pulmonary artery hypertension in patients with systemic sclerosis, according to Dr. Philip Clements, professor of medicine at the University of California, Los Angeles.
Doppler echocardiogram, which is the method used most often to diagnose pulmonary artery hypertension (PAH), is accurate to within 10 mm Hg only half the time, compared with catheterization.
More than a quarter of the time, it overestimates pulmonary artery pressure by at least 10-30 mm Hg, he said at a rheumatology seminar sponsored by the school. As a result, echocardiogram can lead to misdiagnosis and overtreatment, he said.
On top of that, it cannot distinguish between the causes of elevated pulmonary artery pressure.
In patients with systemic sclerosis, the cause of PAH is narrowed precapillary pulmonary arterioles.
In interstitial lung diseases, the cause is destruction of the pulmonary capillary bed, which elevates pressure.
And in left heart failure, a backup of blood in the pulmonary circulation elevates pressure, causing PAH, Dr. Clements said.
The different causes are treated differently.
“Can echo tell the difference?” Dr. Clements asked. “No. And before you put someone on $100,000 of medications [for PAH], it would be nice to know that the patient actually has what you're about to treat,” he said.
Right heart catheterization is moderately invasive, but in the hands of skilled cardiologists and pulmonologists, the morbidity and mortality are low.
PAH is defined on catheterization as a mean pulmonary artery pressure greater than 25 mm Hg at rest, or 30 mm Hg during exercise.
The prevalence of PAH in scleroderma patients is about 16%-20%; women and older patients are those most affected.
PAH on exercise as well as a reduction in diffusion capacity of carbon monoxide are both early indicators that PAH at rest will eventually develop.
“Left alone, it is likely to progress,” Dr. Clements said.
Whether PAH treatment makes a difference in the survival of scleroderma patients, however, is uncertain.
“The story so far is that the randomized controlled trials are short (3-4 months in duration) and done in small groups of patients. We want our patients to live for years. Unfortunately, we don't have years' worth of data,” he said.
Despite those limits, Dr. Clements said the trial findings suggest that treatment can help, especially if it comes early and involves more than one agent.
In a randomized, placebo-controlled trial that included patients with connective tissue disease, 256 subjects with PAH on long-term background intravenous epoprostenol were randomized to receive either sildenafil (20 mg t.i.d.) or placebo.
At the end of 16 weeks, the sildenafil group had a 28.8-m improvement in their 6-minute walk test distances, compared with the placebo group.
Sildenafil subjects also had greater drops in mean pulmonary arterial pressure, improvements in cardiac output, and longer time to clinical worsening. Quality of life improved as well (Ann. Intern. Med. 2008;149:521-30).
Subgroup analyses of patients who were enrolled in randomized, controlled trials with bosentan, sitaxentan (not yet approved in the United States), and treprostinil have also shown favorable effects in scleroderma PAH patients, although with lower responses than in idiopathic PAH (Eur. Respir. J. 2009;34:1219-63).
Dr. Clements believes that combination therapy is likely to evolve for scleroderma PAH, just as it has for rheumatoid arthritis, hypertension, and a host of other medical problems.
Disclosures: Dr. Clements disclosed that he is a member of Gilead Sciences Inc.'s pulmonary hypertension advisory board.
Scleroderma can affect the upper lobes of the lungs, as seen above.
Source © Bates, M.D./Custom Medical Stock Photo, Inc.