The pregnant cardiac patient and anaesthesia

Abstract

Cardiac disease is the leading cause of morbidity and mortality in pregnant women. There is a wide range of diagnoses ranging from congenital heart disease (CHD) to valvular heart disease. Obstetricians and anaesthesiologists need great understanding of physiology and pharmacological therapy of these parturients.

Physiological changes in pregnancy occur in the first trimester and peak at term. Parturients respond differently to physiological changes. Cardiovascular system changes include a fall in systemic vascular resistance (SVR), increased cardiac output (CO) and plasma volume. Oxygen consumption, metabolic rate, oxygen demand, minute ventilation and tidal volume are increased in pregnancy. Anaemia of pregnancy, fall in platelet count and hypercoagulability also occur. Serum creatinine and urea are decreased.

General principles and management of pregnant cardiac patients include optimising the mother, managing complications, analgesia and haemodynamic monitoring. Vaginal delivery and regional analgesia is generally recommended. Caesarean section (CS) can be safely done with segmental epidural anaesthesia.

Rheumatic heart disease (RHD) is the most common cause of valvular disease in pregnancy and mitral stenosis is the dominant (90%) lesion. Symptoms include orthopnoea, exertional dyspnoea or pulmonary oedema. The anaesthetic goals for mitral and aortic stenosis are to avoid tachycardia and decrease in SVR, maintain sinus rhythm and optimise preload. Labour, vaginal and CS delivery anaesthesia may be accomplished with segmental epidural. Regurgitant lesions are well-tolerated in pregnancy, and anaesthetic goals are to avoid increase in SVR and bradycardia, and prevention of myocardial depression.

CHD is becoming a common disease in pregnancy, with acyanotic lesions well-tolerated in pregnancy compared to cyanotic lesions. Acyanotic lesions' anaesthetic goals for labour, delivery and CS are to avoid intravenous injection of air, hypoxia, hypercarbia and decrease in SVR. Regional anaesthesia must be used with caution in Tetralogy of Fallot (TOF) patients, however it is deemed safe in Eisenmenger syndrome.

Pulmonary hypertension (PHT) in pregnancy carries a very high risk of mortality (5–25%) and pregnancy should be discouraged, however epidural anaesthesia is recommended in these patients. Segmental epidural is also recommended for patients with postpartum cardiomyopathy. Pregnant women presenting for emergency cardiac surgery should not be postponed due to pregnancy.