ABSTRACT
The underlying processes that lead to the development of PAH are complex and the disease remains clinically silent until the right side of the heart begins to fail, initially only on exertion, but in later stages of the disease, at rest. Definitive diagnosis requires specialist skills. Invasive diagnostic procedures are necessary to determine the underlying aetiology and associated disease states. Due to the non-specific nature of the early symptom manifestations, diagnosis is commonly not confirmed until up to 3 years from the initial symptom presentation, when disease pathophysiology is well developed.1-3
In recent years there has been increasing interest in the causes, consequences and treatment of PAH. Pulmonary hypertension is defined haemo-dynamically, as a mean pulmonary arterial pressure of >25 mmHg at rest or 30 mmHg with exercise.1,2 Pulmonary arterial hypertension is diagnosed by excluding other causes of PH, particularly left heart disease. Much attention has focussed on two specific forms of PAH that typify the clinical quandaries that surround this condition, and which have benefited from the introduction of effective treatment strategies. The first of these is idiopathic (formerly referred to as primary) PAH,1-3 and the related familial PAH.4 The other is PAH related to collagen vascular disease (predominantly systemic sclerosis, otherwise known as scleroderma).5,6
Without treatment, the prognosis for patients with significant PAH is poor. The reported median life expectancy of idiopathic PAH is 2.8 years from diagnosis.7 Similarly, 2-year survival rates in PAH associated with collagen vascular disease are reported to be as low as 40-55%.8 As such, PAH is a leading cause of death in individuals with PAH complicating systemic sclerosis.5,6
Idiopathic PAH is reported to generate 1-2 incident cases per million per annum in the USA.9 Reports of incidence rates for PAH related to congenital heart disease,10 collagen vascular disease5,6,8 and other miscellaneous conditions, including HIV infection11 and portal hypertension,12 are slightly higher.1,2 However, it is important to note that these figures emanate from specialist centres most interested in monitoring the disease, and there are few data to describe the incidence and prognostic impact of PAH within whole populations.
