The outlook for patients with pulmonary arterial hypertension (PAH) in the Republic is about to take a turn for the better with the licensing of the first oral treatment for the disease and the provision of a specialist treatment centre, writes Dr Muiris Houston
Unlike generalised hypertension, PAH is a rare condition resulting in abnormally high blood pressure in the blood vessels which supply the lungs. A progressive disease, PAH often lies undetected until it reaches the most severe stages. The outlook for untreated patients is bleak, with between 45 and 60 per cent dying within two years of diagnosis.
Endothelin, a hormone manufactured in the lining of the blood vessels, has been implicated in the development of the condition. It causes constriction of the smooth muscle of arteries as well as thickening the wall of the vessel (fibrosis) and enlarging the cells that make up this wall.
As a result, it becomes more and more difficult for blood to flow from the heart to the lungs. The main chamber (ventricle) on the right side of the heart has to work harder to try and force the blood through. Eventually the right ventricle is damaged and the patient develops heart failure.
The first symptom of PAH is breathlessness, especially on exertion. Patients will also experience fatigue, dizziness and fainting. But because these symptoms are non-specific and are usually due to other causes, they are unlikely to be attributed to PAH at an initial consultation. In fact, the diagnosis is often delayed until symptoms have progressed quite considerably. Research shows that, on average, three different physicians are seen prior to a final diagnosis, with an average time from first reporting symptoms to diagnosis of one-and-a-half years.
All of which makes the Mater Hospital's decision to develop a specialist centre for the treatment of the condition a welcome one. Dr Seán Gaine, a consultant in respiratory medicine at the hospital, carried out extensive research into PAH during his time at Johns Hopkins Hospital in Baltimore.
"The Mater Hospital has seen this as an important opportunity to provide a countrywide service for this serious and life-threatening disease. It is an opportunity to provide treatment in the Republic and reduces the need for patients to travel to Britain for treatment," he says.
The current principal treatment for PAH, intravenous prostacyclin (epopro-stenol), involves a highly complex regime whereby the treatment must be infused continuously. Because it is temperature sensitive, a permanent central catheter is implanted in the patient and a portable infusion pump is used to deliver the drug. Close follow-up care by fully trained nurses is necessary because of the potential side-effects and problems with continuous infusion.
Up to now, when specialists saw a patient with late-stage PAH requiring this treatment, they had little option but to refer them to specialist centres in Newcastle and London. For the 50 or so patients requiring treatment, the appointment by the Mater of a clinical nurse specialist will give them the choice of having their therapy carried out nearer home. In addition to offering prostacyclin treatment, the nurse specialist will be available for 24-hour patient contact advice.
The availability of the new oral drug, bosentan, means that the 250-plus people with PAH in the Republic now have a promising new treatment available to them. Bosentan is an endothelial receptor antagonist (ERA). It works by binding to the endothelial receptors in the blood vessel walls and blocking the hormone's harmful effects. Blood-flow to the lungs improves and the pressure on the heart lessens. The new treatment means doctors can slow the progression of the disease as well as treating the patients symptoms. Bosentan is suitable for all stages of PAH; it even offers those receiving complex intravenous treatment the chance to switch, thus freeing up their lives.
Another measure of its potential value is that it is expected to allow up to 70 per cent of those waiting for lung/heart transplant - the last-ditch option for those with end-stage PAH - to come off the transplant waiting list. This is a similar success rate to prostacyclin.
While bosentan has been available in some European countries since May, in the last year 3,500 patients have been treated with it in the United States. A small number of patients have developed reversible liver problems with the drug; otherwise it has been a remarkable success.
Interestingly, Dr Gaine was involved in the initial trials of bosentan in the US and now finds himself back in the Republic just as the drug becomes available here. "The new drug is an exciting development in pulmonary arterial hypertension allowing treatment with oral medication for the first time. It will reduce the need for the more complicated and dangerous intravenous therapies used in the past. It is one of a whole new class of medications never used before which will hopefully develop over the years," he says.
E-mail Dr Muiris Houston, Medical Correspondent, at mhouston@irish-times.ie or leave a message at 01-6707711 ext 8511. He regrets he cannot reply to individual medical problems