5.Classification

Current classification
In 2003, the 3rd World Symposium on Pulmonary Arterial Hypertension was convened in Venice to modify the classification based on the new understanding of disease mechanisms. The revised system developed by this group provides the current framework for understanding pulmonary hypertension.
The system includes several improvements over the former 1998 Evian Classification system. Risk factor descriptions were updated, and the classification of congenital systemic-to pulmonary shunts was revised. A new classification of genetic factors in PH was recommended, but not implemented because available data were judged to be inadequate.
The Venice 2003 Revised Classification system can be summarized as follows:[9]
WHO Group I - Pulmonary arterial hypertension (PAH)
WHO Group II - Pulmonary hypertension associated with left heart disease
WHO Group III - Pulmonary hypertension associated with lung diseases and/or hypoxemia
WHO Group IV - Pulmonary hypertension due to chronic thrombotic and/or embolic disease
WHO Group V - Miscellaneous

[edit] Previous terminology
The terms primary and secondary pulmonary hypertension (PPH and SPH) were formerly used to classify the disease. This led to the assumption that only the primary disease should be treated, and the secondary variety should be ignored in favor of treating only the underlying illness. In fact all forms of pulmonary arterial hypertension are treatable. Unfortunately, this classification system still persists in the minds of many physicians, and probably leads to many patients with being denied treatment. This approach to pulmonary arterial hypertension may also contribute to underdiagnosis. It is estimated that there are about 100,000 patients with PAH in the US, but only 15-20,000 have been diagnosed. Many others have been misdiagnosed as COPD, asthma, or congestive heart failure.
The term primary pulmonary hypertension (PPH) has now been replaced with idiopathic pulmonary arterial hypertension (IPAH) in much of the medical literature. However, some physicians continue to use the older classification inappropriately.
Familial pulmonary arterial hypertension (FPAH) and pulmonary arterial hypertension associated with anorexigens such as Fen-Phen also used to be called PPH, and now are a subcategory of PAH.