Pulmonary arterial hypertension: a rare disease

Dr. Sébastien Renart, cardiologist at the CHU de la Timone, is an expert in pulmonary arterial hypertension (PAH), a rare disease that more often affects women! He explains what this disease is, what the warning symptoms are, and how to treat it. Above all, it's important not to confuse pulmonary hypertension with classic arterial hypertension, a well-known cardiovascular risk factor.

The pulmonary arteries play an essential role in transporting oxygen-poor blood from the heart to the lungs, where it is loaded with oxygen. PAH is characterized by abnormally high pressure in the blood vessels (arteries) in the lungs, which carry blood from the heart to the lungs.

Among the cardiovascular diseases that preferentially affect women, pulmonary arterial hypertension (PAH) is a rare condition that should be systematically evoked in the event of the progressive onset of symptoms such as shortness of breath on exertion, syncope on exertion, fatigue, chest pain, or even the appearance of generalized edema.

Much less well known than pulmonary embolism (an acute and frequent pathology characterized by the migration of a clot into the large pulmonary arteries from a vein, and preferentially affecting the elderly), PAH, which also affects the pulmonary arteries (but younger subjects), proceeds from a progressive and diffuse rigidification of the small pulmonary arteries (called arterioles) and most often irreversibly..

These "structural" anomalies progressively lead to poor circulation of blood through the lung, resulting in pathologically increased pressures in the arteries (hence the term pulmonary arterial hypertension), with the clinical consequence of poor exercise tolerance and the risk of progression to heart failure.

Its rarity and diagnostic difficulty (at least initially) make it a matter for specialists (usually pulmonologists or hospital cardiologists); this chronic pathology is still mostly unknown to the non-specialist medical population at large.

There is not always an obvious cause identified for this disease; we then speak of idiopathic HTAP(classic "isolated" form most often affecting young women). A genetic abnormality is, however, frequently identified in this patient population.
PAH can be caused or promoted by exposure to certain molecules such as anorectics, also known as "appetite suppressants"(widely prescribed in the 1980s-1990s-2000s, but now unavailable in Europe). Nevertheless, more often than not, PAH is associated withother chronic diseases including autoimmune pathologies, liver disease, congenital heart defects or chronic infections.

This rare disease was considered orphan until the mid-1990s, since there was no treatment; fortunately, since then many drugs have been developed to stabilize or even partially regress PAH. Unfortunately there is still no curative treatment; treatments are therefore prescribed on a long-term basis.
The drugs available are pulmonary antihypertensive treatments (to be differentiated from "classic" antihypertensives); they take the form of tablets or sometimes injectable products (delivered by a 24-hour pump) for the most advanced cases. As these treatments are expensive and highly specific, they are only available in France from hospital pharmacies.
For the most severely affected patients, lung transplantation is sometimes an option.

Management of this chronic disease in France is based on a "rare disease" plan with a regional competence center led by a national reference center that is very active in therapeutic innovation and research (Hôpital Kremlin Bicêtre, AP-HP). Under the aegis of the HAS (Haute Autorité de Santé), this organization has made it possible to establish a single care protocol for all patients in France and the French overseas territories (Plan National de Soins : PNDS : HTAP drafted in 2020).

Finally, a dynamic patient association also enables patients to find a different kind of listening ear to that offered by the medical profession. In addition to providing practical advice and encouraging the sharing of experience, this association organizes forums and regional patient-doctor meetings, and publishes a quarterly magazine that is highly instructive and much-needed for relaying patients' views www.htapfrance.com 

Dr Sébastien RENARD Cardiologist PAH Competence Center. Hôpital La Timone CHU de Marseille.