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HONOLULU -- Are the updated European guidelines on pulmonary arterial hypertension (PAH) applicable to American practice?

The European Society of Cardiology and European Respiratory Society guidelines changed the treatment algorithm for PAH to account for certain cardiopulmonary comorbidities, expanded the definition of pulmonary hypertension (PH), and lowered the cutoff for pulmonary vascular resistance (PVR) from three Wood units to two.

While the guidelines have been endorsed by various cardiac societies throughout the world, U.S. organizations have yet to sign on. Whether U.S. clinicians should use them was the topic of a debate at the CHEST annual meeting hosted by the American College of Chest Physicians.

"We base all our guidelines, European [and] U.S., essentially from the same information -- the same clinical trials and registries across the world. And so to try to pick and choose when we're going to use this, I don't think it's the sound argument," said Lana Melendres-Groves, MD, of the University of New Mexico School of Medicine in Albuquerque.

For example, even if the data upon which the guidelines have been based don't exactly reflect her patient population in New Mexico, "I have to take what we have," she said.

Fellow debater Christopher Mullin, MD, MHS, of the Warren Alpert Medical School at Brown University in Providence, Rhode Island, acknowledged some merit to the updated guidelines, citing the potential to treat patients who are considered to be "borderline" PH but are also in at-risk cohorts.

On the other hand, he argued that, despite having access to the same studies and information, treating patients who are considered to be borderline based on their PVR and mean pulmonary arterial pressure with pulmonary vasodilators is "not necessarily going to make anybody better, and it has the potential to really [have] detrimental effects on the PH community at large."

He noted that it's easy to fall into the trap of overestimating one's ability to identify the borderline patients who will benefit from treatment even when knowing that the larger majority may not.

"We already prescribe too many pulmonary vasodilators for areas where there's no good data for efficacy," Mullin said, citing a that showed that group 1 PAH-specific therapies were often prescribed for patients categorized as group 2 or 3 PH.

"This also can hurt our patients because ... that's cost, that's time, that's energy that takes away from the patients, from us, or from other doctors for managing your other comorbidities," he said.

Harrison Farber, MD, of Tufts Medical Center and Tufts School of Medicine in Boston, agreed, stating that the European guidelines did not adequately factor in the patient's pulmonary capillary wedge pressure (PCWP) for treatment.

"The key number is a wedge [PCWP], because your PVR basically changes or not depending on what your wedge is," said Farber. "What is a normal wedge? It's fascinating to me... this was never discussed."

He explained that what is considered to be a "normal" PCWP has changed over the years, moving from 8 to the current 15. PCWP can also decrease over time due to factors like diastolic dysfunction or increase with higher BMI.

He also cited several areas in which he felt American patients were not particularly comparable to European patients, including rates of obesity and hypertension as well as exercise.

Another key difference between the U.S. and its European counterparts addressed in the debate was how their respective healthcare systems work.

Franck Rahaghi, MD, MHS, of the Cleveland Clinic Florida's Weston Hospital, suggested that the support of European governments, as well as a more centralized healthcare system, have led to more frequently updated guidelines in comparison to the U.S. He suggested that this subsidization "pushes patients to the center, and they have this wealth of data."

He also challenged the notion that American and European patients are too different to compare, as both have a range of demographics.

"Underneath it all, we're the same humans in the end: some fat people, some skinny people, some exercise, some don't. But the United States is diverse enough that we can fit Europe in the U.S. somewhere in there," he said. "The more fundamental and important aspects of guidelines are probably above regional sensitivities."

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