EXPLANATION


Cardiovascular disease has become increasingly common during pregnancy and is one of the leading causes of maternal mortality in developed countries. This is due to both improved survival of children with congenital heart disease reaching childbearing age, as well as increased prevalence of acquired heart disease. The presence of cardiovascular disease during pregnancy increases the risk of maternal and fetal mortality and morbidity. The physiologic changes of pregnancy, including decreased systemic and pulmonary vascular resistance and increased cardiac output due to an elevation in heart rate and total blood volume, impose additional stress on the cardiovascular system. Ultimately, these physiologic changes may lead to clinical decompensation. Although most pregnant patients’ cardiac disease can be managed medically, some require percutaneous intervention or surgery. Mitral and aortic valvular disease, cardiac tumors, and thromboembolic disease often require intervention during pregnancy. Historically, maternal morbidity and mortality after cardiac surgery were estimated to be 24% and 6%, respectively. Fortunately, more recent data seems to indicate perioperative maternal mortality is similar to that of non-pregnant patients undergoing non-urgent cardiac surgery, at roughly 1-5%. However, fetuses remain at high risk of mortality and morbidity. Schmitz et al. recently reported the Mayo Clinic experience on 29 pregnant patients undergoing cardiac surgery spanning from 1978 to 2023. Primary outcomes were maternal and fetal survival. The average gestational age at the time of surgery was 25 weeks. Fifty-five percent underwent surgery in the second trimester and 35% in the third trimester. More than half of the patients (55%) underwent aortic or mitral valve surgery. Only one woman died in the perioperative period (3%) in the context of emergent thrombectomy for thrombosis of a mechanical aortic valve. About one quarter of the patients underwent a cesarian section before cardiopulmonary bypass (CPB). Preterm delivery was the most common fetal outcome (68%), and fetal mortality remained high at 17%. Not surprisingly, fetal death was more common if delivery occurred after CPB.


The Modified World Health Organization classification is the most used risk-stratification tool in pregnant women with heart disease. The American Heart Association recommends that expecting mothers with class III or IV disease (significantly or extremely elevated risk of mortality or morbidity) receive care from a multidisciplinary team in an experienced center to determine the location, timing, and mode of fetal delivery. In general, the goal is to reach 39 weeks of gestation before delivery, but maternal or fetal well-being may dictate otherwise. Maternal mortality and morbidity tend to correlate with functional status. Predictors of worse outcomes include a history of stroke, transient ischemic attack or arrhythmia, severe fixed or dynamic left-sided obstruction, or an LV ejection fraction <40%.


Parturients with severe symptomatic mitral stenosis are at high risk of developing pulmonary edema, heart failure, arrhythmias, cerebrovascular events, pulmonary hypertension, and death. Medical management includes beta-blockers and diuretics. These patients may be treated with percutaneous balloon valvuloplasty with successful relief of valvular stenosis, with known favorable maternal and fetal outcomes. However, if the valvular stenosis is not amenable to balloon valvuloplasty, surgical replacement may be necessary. The preferable timing for cardiac surgery during pregnancy is thought to be the second trimester, as third-trimester surgery increases the risk of maternal complications. If the fetus has reached viability, pre-operative delivery or cesarian section may be indicated to increase the chances of fetal survival.


Cardiac surgery with cardiopulmonary bypass (CPB) in pregnant patients is uncommon. Management relies on physiological principles, experience, and expert opinion. General obstetric principles still apply, including maternal steroid administration to promote lung maturity if gestational age is less than 34 weeks and left uterine displacement to avoid aortocaval compression. Fetal heart rate and monitoring for uterine contractions, if possible, should be strongly considered. During CPB, maintenance of maternal homeostasis is essential, including acid-base status, oxygenation, and glucose levels. A mean arterial pressure greater than 70 mmHg should be targeted, which may be achieved with high CPB flow rates to sustain uteroplacental perfusion. Placental hypoperfusion is associated with fetal bradycardia, especially at the onset of CPB. Both fetal bradycardia and uterine contractions are strongly associated with fetal death. Normothermia is associated with improved fetal outcomes despite the potential challenges to myocardial and cerebral protection. A report by Jahangiri et al. on four women undergoing CPB during pregnancy seems to suggest that pulsatile flow may be better for the fetus, although good results have been achieved with non-pulsatile flows. Cardioplegia administration must be limited to avoid hyperkalemic arrest of the fetal heart. It is important to note that, following CPB, the fetus may experience significant metabolic acidosis from a rise in placental and fetal systemic vascular resistance, leading to low cardiac output, which may contribute to fetal demise. Some centers perform a cesarian section just before the sternotomy, pack the abdominal wound during CPB, and then close the abdomen after the reversal of heparin.


The correct answer is thus A. The risk of maternal mortality in pregnant patients after cardiac surgery is 1-8%.


REFERENCES


Schmitz KT, Stephens EH, Dearani JA, et al. Is Cardiac Surgery Safe During Pregnancy? A 40-Year Single-Institution Experience. Ann Thorac Surg. 2024;S0003-4975. doi:10.1016/j.athoracsur.2024.07.026


Meng ML, Arendt KW, Banayan JM, et al. Anesthetic Care of the Pregnant Patient with Cardiovascular Disease: A Scientific Statement From the American Heart Association. Circulation. 2023;147(11):e657-e673. doi:10.1161/CIR.0000000000001121


Mehta LS, Warnes CA, Bradley E, et al. Cardiovascular Considerations in Caring for Pregnant Patients: A Scientific Statement from the American Heart Association [published correction appears in Circulation. 2020;141(23):e904. doi: 10.1161/CIR.0000000000000845


Kapoor MC. Cardiopulmonary bypass in pregnancy. Ann Card Anaesth. 2014;17(1):33-39. doi:10.4103/0971-9784.124133


Chandrasekhar S, Cook CR, Collard CD. Cardiac surgery in the parturient. Anesth Analg. 2009;108(3):777-785. doi:10.1213/ane.0b013e31819367aa


Jahangiri M, Clarke J, Prefumo F, Pumphrey C, Ward D. Cardiac surgery during pregnancy: pulsatile or nonpulsatile perfusion? [published correction appears in J Thorac Cardiovasc Surg. 2003 Nov;126(5):1680. Clark James [corrected to Clarke James]; Prefumo Frederico [corrected to Federico Prefumo]]. J Thorac Cardiovasc Surg. 2003;126(3):894-895. doi:10.1016/s0022-5223(03)00607-x