Pregnancy and pulmonary hypertension

Abstract

Pulmonary hypertension, irrespective of the etiology, carries a high mortality when associated with a pregnancy. Causes of pulmonary hypertension include primary pulmonary hypertension (PPH), and pulmonary vascular disease secondary to other causes such as thromboembolic disease, connective tissue disorders, and side effects from certain drugs. The most common cause of pulmonary hypertension in young women of childbearing age however is due to the late consequences of a large cardiac shunt at any level (Eisenmenger syndrome). This review will focus on the latter, in which the risk of maternal death is approximately 30–50% [1–4]. 1. Hemodynamic perturbations Several of the hemodynamic changes that occur during a normal pregnancy contribute to the high maternal mortality in patients with pulmonary vascular disease. The progressive increase in plasma volume, which peaks at about 50% above baseline early in the third trimester, adds to the burden of a compromised right ventricle and may precipitate right heart failure. The pre-existing pulmonary vascular disease restricts this increased flow of blood to the lungs and increases right ventricular work. Systemic vasodilatation is a physiological adaptation of normal pregnancy and it is associated with an increase in the cardiac output and renal blood flow. As the peripheral vascular resistance falls, the patient with Eisenmenger syndrome may augment the right to left shunting that exacerbates the pre-existing hypoxia, which, in turn, may cause more pulmonary vasoconstriction. At the time of labor and delivery, severe hemodynamic compromise may occur. Acidosis and hypercarbia may further increase pulmonary vascular resistance. Any hypovolemia resulting from blood loss or hypotension from a vasovagal response to pain may result in sudden death. In addition, death may also occur from pulmonary thromboembolism or in situ pulmonary infarction.