Introduction

Pulmonary hypertension was first recognized as a distinct illness in the nineteenth century (Romberg, 1891). It required the detailed clinical descriptions of primary pulmonary hypertension (PPH) from Dresdale et al. (1951) and Wood (1952) to facilitate the modern diagnosis. In 1973, as a result of the widespread use of cardiac catheterization and detailed histopathology, a World Health Organization (WHO)-sponsored meeting was held to classify the many different forms of pulmonary hypertension. The meeting classified pulmonary hypertension into primary or unexplained pulmonary hypertension and those forms that are secondary to other disease (Hantano and Strasser, 1975). Also, the concept of pulmonary vasodilatation was introduced to encourage specific therapies for the illness. The establishment of the National Institute of Health (NIH)-sponsored register of PPH patients in the 1980s led to further changes in clinical practice, as well as basic understanding of the disease. The place of right heart catheterization was established as the essential step in diagnosis and quantification of the severity of the disease (Rich et al., 1987). Evidence of right heart failure proved valuable in predicting survival (D'Alonzo et al., 1991). In only a relatively small proportion of patients is it possible to vasodilate the pulmonary circulation.

Interest in pulmonary hypertension was increased by successful heart–lung and lung transplant surgery (Reitz et al., 1982). Limited numbers of suitable donors, however, preclude this form of treatment for the majority of patients.