Periods of special concern are between 28 and 34 wk, during labor, and immediately postpartum, when the physiologic load on the heart is maximal. The fetus shares the increased risk from maternal heart disease. The fetus may die during an episode of maternal heart failure or may be born prematurely. Labor and delivery are threatening to a cardiac patient because the work of labor, the straining during the 2nd stage, and the increased amount of venous blood returning to the heart from the contracting uterus markedly alter cardiac hemodynamics. An anesthesiologist familiar with cardiac physiology and disease in pregnancy should attend the labor.
Conduction anesthesia is preferred for patients with mitral valve disease.
Because patients with aortic valve disease cannot tolerate the transient circulatory stasis and occasional drops in BP that occur with conduction anesthesia, they should be given a local anesthetic or, if necessary, a general anesthetic. No straining should be allowed in the 2nd stage of labor because this effort halts all oxygenation, and the patient can become anoxic within seconds. In the postpartum period, the patient should be closely monitored because mobilization of fluid produces wide swings in cardiac function. Cardiac patients are not out of danger for several weeks and should be monitored by a cardiologist. Patients in class III may need digitalis as well as bed rest beginning in the 20th wk of pregnancy.