Cardiovascular Disease in Pregnancy
Case 3: Valvular Stenosis, Mitral Stenosis
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(class C), and ibutilide (class C) [13]. They have not demonstrated any adverse fetal effects, but experience with these medications in pregnancy is limited. Amiodarone is usually recommended against in pregnancy. It is a pregnancy class D medication and its use in pregnancy should be restricted to arrhythmias that are resistant to other drugs or are life threatening [15]. Bypass tract or atrioventricular nodal ablation is possible during pregnancy if necessary and is best performed during the second tri- mester when the fetus has undergone initial development and the mother and fetus can still be adequately shielded from radiation exposure.
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IV daily with improvement in her symptoms. She is started on therapeutic low molecular weight heparin twice daily and metoprolol 25 mg orally twice daily and spontaneously converts to sinus rhythm on hospital day two. She is discharged from the hospital on day four on furosemide 20 mg oral daily, metoprolol succinate 25 mg once daily, and therapeutic low molecular weight heparin. At 37-week gesta- tion, she undergoes a planned induction of labor with an interdisciplinary team.
Low molecular weight heparin is discontinued 12 h prior to induction and anesthe- sia. An epidural is placed, and she receives an assisted second stage of labor with low forceps extraction and delivers a healthy baby girl. In the immediate postpartum period, she is restarted on therapeutic low molecular weight heparin 12 h after deliv- ery. She notes increased shortness of breath at 18 h after delivery, and a chest radio- graph reveals mild pulmonary vascular congestion. An EKG shows atrial fibrillation at 108 bpm. She is restarted on furosemide 20 mg IV daily with resolution of her symptoms.
Rheumatic heart disease is the most common etiology of mitral stenosis in reproductive- aged women. It remains a major problem in developing countries and is still seen in developed countries, especially in immigrant populations. In general, stenotic valves confer a higher risk to the pregnant patient than regurgitant valves, and left-sided valve diseases involving the mitral and aortic valves have a higher complication rate than right-sided valve lesions of the tricuspid and pulmonic valves [1–3, 16]. Physiologic changes during pregnancy can cause previously asymptom- atic patients to become symptomatic, as the heart rate may increase by 25 % and blood volume can expand by 40–50 % during pregnancy, leading to a marked increase in stroke volume and cardiac output. In stenotic valve disease, these hemo- dynamic changes increase the transvalvular gradient and decrease the filling time of the left ventricle and, thus, increase left atrial pressures, resulting in pulmonary venous congestion, pulmonary edema, and congestive heart failure. The presence of atrial fibrillation with a rapid ventricular rate often causes further clinical deteriora- tion. Additionally, the rapid increase in venous return during labor and delivery, partially related to autotransfusion of maternal blood into the circulation from uter- ine contractions and from relief of inferior vena cava compression from the gravid uterus, may cause a further surge in preload to the left atrium, which can stress the heart further.
Management of MS is related to the severity of stenosis, the presence of symp- toms, and timing of diagnosis. Moderate or severe MS is typically poorly tolerated during pregnancy [16], even when the patient is previously asymptomatic. Two main predictors of adverse outcomes during pregnancy include mitral valve area < 1.5 cm2 and abnormal functional class prior to pregnancy. If diagnosed prior to pregnancy, patients with severe MS regardless of symptoms (valve area < 1 cm2) or moderate symptomatic stenosis (valve area 1–1.5 cm2) should be considered for percutaneous mitral balloon valvuloplasty (PMBV) or mitral valve replacement if PMBV is not appropriate. If a patient is pregnant and congestive heart failure cannot be managed with medical therapy, valvuloplasty can be performed resulting in a significant hemodynamic benefit and usually favorable pregnancy outcome [16, 17].
However, valvuloplasty-related complications including cardiac tamponade,
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systemic embolization, maternal arrhythmias, initiation of uterine contractions, fetal distress, and fetal loss have been reported, in addition to radiation exposure to the fetus [16]. Optimal management of the pregnant patient with MS is focused on reducing left atrial pressures with careful diuresis and improving left ventricular filling with heart rate control, typically using beta-blockers. Judicious diuresis is crucial to avoid hypotension and volume depletion which may result in decreased uteroplacental perfusion and intrauterine growth restriction.
With pressure and volume overload, mitral stenosis can lead to left atrial stretch and dilatation and place the patient at increased risk of atrial arrhythmias, the most common of which is atrial fibrillation. Patients with valvular atrial fibrillation or atrial flutter require systemic anticoagulation as they are more prone to thromboem- bolic events than the general population with atrial fibrillation. With any episode of atrial fibrillation, continuous anticoagulation is recommended throughout preg- nancy and up to 12 weeks postpartum, when the hypercoagulable state of pregnancy resolves. It is important to screen patients with mitral stenosis for symptoms of atrial arrhythmias, which includes sensations of palpitations, skipped beats, or rapid heart rates. This patient is presenting in the second trimester when intravascular volume is highest with congestive heart failure and atrial fibrillation. Mitral stenosis represents at least a WHO class III risk classification, with significant increased risk of maternal mortality and severe morbidity. She requires immediate treatment with intravenous diuretics, medications for heart rate control, and admission for monitor- ing. She should be started on unfractionated heparin (UFH) continuously for thera- peutic anticoagulation of valvular atrial fibrillation, due to her risk of intracardiac thrombus and systemic embolism. UFH does not cross the placenta and does not expose the fetus to anticoagulation, as does warfarin. Unlike warfarin, heparin does not confer teratogenic effects and is, therefore, considered safer for the fetus. Low molecular weight heparin (LMWH) may also be utilized, using a twice daily weight- based dosing schedule. During pregnancy the volume of distribution for LMWH is variable, and it is essential to monitor anti-factor Xa levels drawn four hours after administration to establish an appropriate dose. Appropriate levels of anti-Xa should range between 0.7 and 1.2 U/mL.
Most patients with MS with NYHA class I/II symptoms can safely undergo vagi- nal delivery. Patients with class III/IV symptoms or with pulmonary hypertension who do not undergo valvuloplasty should be considered for cesarean delivery [1]. In patients with symptomatic moderate-to-severe mitral stenosis, anesthesia with regional epidural is recommended with an assisted second stage of delivery to decrease pain, abrupt hemodynamic changes, and the adverse cardiovascular effects of repeated, prolonged Valsalva maneuver. Additionally, patients need close moni- toring during the immediate postpartum period (12–24 h) when uterocaval venous obstruction is relieved, and sudden increased venous flow to the heart can result in pulmonary edema. Patients with rheumatic valvular disease who traditionally require antibiotic prophylaxis for dental procedures do not routinely require antibiotic prophylaxis for vaginal or cesarean delivery, as long as infection is not suspected and aseptic measures are followed [6, 18].
J.B. Whelan and L.S. Feinberg
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