Viagra (sildenafil) may substantially improve exercise capacity in patients with severe pulmonary hypertension, according to a study reported at the 12th Annual Meeting of the European Respiratory Society (ERS).

The eight-patient investigation was led by Dr. Timothy Higenbottam, a consultant in respiratory diseases at the University of Sheffield in Sheffielf, England.

The patients had varying forms of pulmonary hypertension, but all were defined as falling with Class III of the New York Heart Association (NYHA) classification system, and were already being treated with other pulmonary vasodilators including a stable prostacyclin analogue or nitric oxide. They received sildenafil, either 25 mg/day (n=7) or 50 mg/day (n=1). After a mean period of five months, they were required to perform an incremental walking test and a shuttle-walking test, as well as to undergo cardiac catheterisation.

The patients showed significant improvements in shuttle walking distance and incremental walking distances over baseline on each measure: 274 versus 189 metres for the shuttle walking test and 201 versus 116 for the incremental walking test (p= 0.45)

Unfortunately, no improvements in haemodynamics were seen in terms of pulmonary vascular resistance (PVR), mean pulmonary arterial pressure (mPAP), right atrial pressure (RAP) or cardiac output (CO). There was a slight improvement in pulmonary cardiac wedge pressure (pCWP).

Two of the eight patients discontinued therapy because their health continued to decline, but the remaining six remained on sildenafil therapy for a mean duration of six months.

Dr. Higenbottam said that although sildenafil was well-tolerated and helped patients improve their exercise capacity, further examination must be undertaken to evaluate whether it is truly effective as a long-term treatment for severe pulmonary hypertension.

Other investigations, it was noted, have shown conflicting results. One study involving more than 200 subjects reported that sildenafil, when used in combination with iloprost had a strong synergistic effect and was a potent vasodilator -- something that was not seen in the pilot study.

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