Introduction

Pulmonary hypertension (PHT) can be associated with a variety of both pulmonary and extrapulmonary diseases. Acute PHT in critical care may often be secondary to conditions such as acute respiratory failure, left heart failure and pulmonary embolism, or due to decompensation of chronic PHT by concurrent pulmonary or cardiovascular disease. Patients with chronic PHT can also be admitted to critical care for the treatment of other conditions, or as part of their perioperative management. Some are admitted because they have benefited from a specific operation to treat the underlying pulmonary condition (lung transplantation, pulmonary endarterectomy).

Definition

Pulmonary arterial hypertension (PAH) is a term used to classify a variety of conditions that share in common an injury to the pulmonary vasculature that produces elevations in pulmonary arterial pressure. It is noteworthy that the definition of PHT has been the subject of heated debates for many years, and various numbers or indices have been proposed to define it.

It is now accepted that PHT can be defined as a sustained elevation of pulmonary arterial mean pressure to more than 25 mmHg at rest or 30 mmHg with exercise. It is defined as PAH if in addition the mean capillary wedge pressure and left ventricular end-diastolic pressure are less than 15 mmHg.

Clinically, PHTis a condition in which an increase in the right ventricular (RV) afterload leads to organ damage, either as a consequence of hypoxia or decreased blood flow. Treating PHT is ultimately taking care of the RV because it is the integrity of RV function, rather than the degree of vascular injury, that is the major determinant of symptoms and survival in PHT.