Pulmonary vascular pathology

Introduction Pulmonary hypertension is defined as a sustained mean pulmonary arterial pressure at rest of ≥ 25 mmHg, i.e., elevated significantly above the upper limit of normal (20 mmHg). Typically, pulmonary arterial pressure increases during exercise. In pulmonary hypertension, this increase is disproportionately high. The pressure is measured by right heart catheterization or can be estimated by echocardiography. Pulmonary hypertension is a consequence of right ventricular adaptation to increased vascular resistance, increased pulmonary blood flow, or a combination of both. Initially, the symptoms of pulmonary hypertension are nonspecific and usually limited to dyspnea, particularly on exertion, or patients may be asymptomatic. As the pulmonary hypertension progresses, signs and symptoms of right-sided heart failure develop; namely peripheral edema, fatigue, abdominal fullness, angina pectoris and syncope. Depending on its cause, severity and possible treatment options, pulmonary hypertension may lead to death. Pulmonary hypertension is a feature of a heterogeneous group of disorders which differ in risk factor profile, initiating factors, response to treatment and prognosis (Table 1).4,5 Among the causal factors, left ventricular failure and mitral valve insufficiency are the commonest, followed by chronic thromboembolic disease.6 Globally, there are marked variations in prevalence of some important causes and risk factors, especially sickle cell disease, chronic schistosomiasis and HIV-AIDS.