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.

# Physiology of Pregnancy
There are significant hemodynamic changes associated with pregnancy that begin early, reach their peak during the second trimester, and persist through delivery.  These changes include a 40% increase in blood volume expansion, reductions in both the systemic vascular resistance and pulmonary vascular resistance, a 30% rise in cardiac output and little change in the blood pressure.  These changes can have a significant impact on both the mother and the fetus, particularly when there are maternal cardiac disorders.

# 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.

# Diagnosis

## History
A history should be taken to assure that the patient does not have a condition that would place them at high risk during the pregnancy such as Marfan's syndrome, Eisenmenger's syndrome, congestive heart failure, a prior history of peripartum cardiomyopathy or pulmonary arterial hypertension.

## 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
Normal physical exam signs of pregnancy include an "innocent" systolic flow murmur in 96% of patients due to the hyperdaynamic circulation, a diastolic murmur in 18% of patients, jugular venous distension and a displaced cardiac apex due to volume expansion, an S3 in 84% of patients, an occasional S4, varicose veins 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 and is a safe and a preferred screening method to assess cardiac function and valvular lesions.

## Chest X Ray
Performance of routine chest x-rays should be avoided, especially in the first trimester of pregnancy.  A chest x ray may be indicated in the pregnant patient with dyspnea  or cough .  Among patients with dyspnea, a chest x-ray may be obtained to eavluate the patient for the presence of heart failure due to peripartum cardiomyopathy.  In this scenario, the chest x ray may show cardiomegaly, Kerley B lines, pleural effusion and cephalization of blood vessels.

## MRI
There are no known safety hazards associated with the performance of an MRI, especially after the first trimester. However, data evaluating the safety of MRI during pregnancy is limited and an MRI is indicated only when other imaging modalities such chest x-ray and echocardiography are inconclusive. Currently, the FDA recommends prudent use of MRI during pregnancy.

## 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.

# Treatment

## Labor and Delivery
The preferred route of delivery is vaginal, but indications for a C-section include:
- Traditional obstetric indications
- Warfarin anticoagulation
- Severe pulmonary hypertension
- In the presence of fixed obstructive congenital lesions sudden BP changes may be dangerous
- Unstable aorta

# Radiation and Pregnancy
If a pregnant patient is radiated with less than five rads, then they can be reassured that there is a very low likelihood of risk. If a pregnant patient is exposed to more than 15 rads, termination of the pregnancy is recommended.  A routine chest x-ray is associated with radiation of 20 millirads to the chest.  Standard fluoroscopy delivers 1-2 rads per minute.  Cineangiography delivers 5-10 rads per minute. Only 5% of the radiation delivered is absorbed by the fetus.  A lead apron should be used over the mother's pelvis to minimize the risk of radiation exposure.  With the use of nuclear medicine procedures the radiopharmaceuticals collect in the bladder which is in close proximity to the placenta and is directly across from the fetus.  The expected radiation with thallium-201 or Tc imaging is less than one rad per examination.

# Absolute and Relative Contraindications to Pregnancy
Absolute and relative contraindications to pregnancy include severe pulmonary arterial hypertension; severe fixed valve stenoses (AS,MS,PS,HOCM, coarctation; Class III or IV congestive heart failure with a left ventricular ejection fraction of 40-45 mm; and severe cyanosis.