Cardiac disease in pregnancy overview

Overview
Approximately 1-4% of pregnancies in the United States occur in women with maternal cardiovascular disease. In fact, pregnancy can "unmask" underlying cardiovascular disease, due to the hemodynamic changes associated with pregnancy. With a careful pre-pregnancy evaluation, most women with cardiovascular disease can carry a pregnancy to term with proper care.

Epidemiology and Demographics
Increasing numbers of women with congenital heart disease are now reaching childbearing age, making congenital heart disease the most common form of heart disease complicating pregnancy in the United States. Rheumatic heart disease is still prevalent in the developing world and in immigrant populations. Overall, maternal death during pregnancy in women with heart disease is rare, but certain conditions are associated with an increased mortality.

Disorders Associated with Cardiovascular Disease in Pregnancy
Maternal cardiovascular disease includes (most commonly) congenital heart disease. Other cardiovascular disorders encountered during pregnancy include cardiomyopathies, both dilated and hypertrophic, and valvular heart disease, such as bicuspid aortic valve and mitral valve prolapse. Less common cardiovascular disorders include pulmonary hypertension and, rarely, coronary artery disease. The above cardiovascular disorders require a strategy regarding the frequency of follow-up by the cardiologist and a plan for labor and delivery.

Risk Factors
The following clinical characteristics are independent predictors of adverse outcomes in a risk score for maternal cardiac complications :
 * Prior cardiac events or arrhythmia
 * Poor functional class or cyanosis
 * Left ventricular outflow tract obstruction
 * Left ventricular systolic dysfunction

Pulmonary hypertension is a well recognized risk factor during maternal pregnancy. In particular the presence of Eisenmenger syndrome places the mother particularly high risk.

History and Symptoms
Common symptoms present during pregnancy include: fatigue, decreased exercise capacity, hyperventilation, dyspnea, tachycardia and palpitations.

Secondary to inferior vena caval compression by the gravid uterus resulting in reduced venous return from the lower extremities, patients may even experience orthostatic lightheadedness and syncope.

Pedal edema is often observed during the last trimester and may lead to an erroneous diagnosis of heart failure.

Physical Examination
Significant similarities exist between the normal signs of pregnancy and the presence of an underlying cardiac disease; hence poses a clinical challenge to differentiate between the two. However, common signs include: jugular venous distension, pulmonary rales, increased intensity of heart sounds and pedal edema.

ECG
The common electrocardiographic findings that occur secondary to physiological changes during pregnancy include: tachycardia, short PR interval and left axis deviation.

Echocardiography
Echocardiograhy does not carry the risk of fetal irradiation; hence, is a safe and preferred screening method to assess cardiac function and valvular lesions.

Chest X Ray
Routine chest x-ray is avoided, especially in the first trimester.

Chest x-ray in normal pregnancy may reveal physiologic changes such as increased left ventricular dimension and cardiomegaly, which in the absence of dyspnea is secondary to the elevation of diaphragm and should be interpreted with caution.

Among patients with dyspnea, chest x-ray in done to identify the presence of heart failure, which may show cardiomegaly, Kerley B lines, pleural effusion and cephalization of blood vessels.

MRI
No known safety hazards are observed with MRI, especially after first trimester. However, the experience with this technique is limited and is indicated only when other imaging modalities such chest x-ray and echocardiography are inconclusive or to identify aortic diseases in pregnancy. Currently, the FDA recommends prudent use of MRI during pregnancy.

Contrast MRI using gadolinium is contraindicated as gadolinium crosses the trans-placental membrane and exposes the fetus to teratogenicity.

CT
The preferable estimated fetal exposure from ionizing radiation should be below 50 mGy and with CT, the exposed radiation is 0.3 mGy and therefore contra-indicated during pregnancy.

The only exception for the use of CT during pregnancy include to diagnosis pulmonary embolism, for which a low-radiation CT is recommended.