Heart Conditions and Pregnancy

Introduction

At the present time, approximately 75% of patients seen in obstetric practice with pre-existing heart disease have congenital anomalies as their basis and approximately 25% are from sequelae of rheumatic fever.
Most of the maternal deaths occur in patients with cyanotic heart disease and right to left shunts . These include such problems as obstructive lesions on the right side of the circulation. For example, tricuspid stenosis or atresia , pulmonary valvular or infundibular stenosis , and/or elevated pulmonary vascular resistance .
These patients may also involve those who have a mixing of systemic venous and arterialised blood such as those seen with total anomalous venous return , a single atrium or ventricle , or persistent truncus arteriosus .
The third group of patients are those who have an obligatory recirculation of systemic venous blood such as those patients with transposition of the great vessels. The maternal risk with pre-existing heart disease involve basically five areas of concern.

Congestive heart failure is more likely to occur in those patients who cannot increase their cardiac output to meet the normal physiologic demands of pregnancy . The risk of congestive heart failure in such patients is greatly increased if the peripheral vascular resistance also increases during pregnancy such as occurs with pregnancy-induced hypertension .
Pulmonary oedema occurs with greater frequency during pregnancy due to the fact that a lower pulmonary-capillary wedge pressure is required to produce the oedema due to the lower plasma oncotic pressure and increased pulmonary-capillary permeability seen as a normal consequence of pregnancy. The pulmonary oedema that such patients suffer is the greatest threat to maternal well-being.
The third area of risk involves that of a cardiac ischemia . This ischemia may develop due to the presence of an increased afterload seen in patients with either chronic hypertension or pregnancy-induced hypertension and it may develop in response to the increased demands on cardiac work required during normal pregnancy.
Arrhythmias are more common during pregnancy due to the enlarged heart and the disturbance in the conduction pathways. These arrhythmias may precipitate congestive heart failure for the first time or may manifest themselves with the onset of ischemia.
The final area of maternal risk is that of pulmonary emboli . This is particularly true if there is an underlying arrhythmia such as atrial fibrillation or in patients with damaged heart valves with vegetations.

Treatment During Pregnancy

The maternal surveillance of such patients should begin prior to conception. Consultation with cardiologists who are well versed with the normal physiologic changes of pregnancy should be obtained. Patients are usually advised to follow a prescribed program of bedrest in the lateral recumbent position involving two hours in the first trimester, three hours in the second trimester, and 4 hours in the third trimester, in addition to time they would normally spend off of their feet. Additional strains on the heart such as anaemia should be screened for and corrected. If patients have required sodium restriction prior to pregnancy, that should be continued and a modified low sodium diet should be advised to all patients. Medication use during pregnancy should be adjusted with an eye toward possible adverse foetal effects. It is well known that the cardiac glycosides such as digitalis are perfectly safe during pregnancy. The use of anticoagulants should involve heparin as the drug of choice since it does not cross the placenta.
There is no place for the use of orally active anticoagulants such as coumadin during pregnancy due to the possible foetal embryopathy as well as intracranial bleeding in the foetus. The use of diuretics should probably be reserved for those patients who are at high risk or have developed pulmonary oedema Finally, it should be remembered that these patients frequently require antibiotic prophylaxis around the time of their delivery and other instrumentation.

Foetal Risks

The foetal risks of patients with pre-existing heart disease are primarily related to the poor oxygen availability. Therefore, they are at high risk for intrauterine growth retardation (IUGR). This growth retardation is usually manifested after the 28th to 30th week of gestation and places the foetus at risk for intrauterine foetal death. These foetuses may not tolerate labour . This would be manifested in a higher rate of foetal distress. They are also at increased risk for premature labour. This is felt to be due to the poor oxygen delivery to the uterus.

The surveillance of the foetus involves early ultrasound to accurately determine dates as well as frequent ultrasounds to assess foetal growth. Biophysical assessment of the foetus, either with the non-stress test and/or biophysical profile, should commence at 30 weeks gestation and be performed on a regular basis until delivery. Any evidence of foetal compromise, either by poor growth or poor performance on the biophysical tests, may prompt an amniocentesis to assess pulmonary maturity and/or the decision to deliver the patient.

Delivery

Managing the delivery involves the expert care of the obstetrician, cardiologist, and anaesthesiologist. The use of conduction anaesthesia such as epidural and spinal anaesthesia has to be approached with caution. The risk of sudden hypotension in such patients may further compromise an already marginal uterine blood flow and therefore, place at foetus at risk. It may also interfere with the venous return to the mother and further compromise her cardiovascular condition. The use of conduction anaesthesia should only be undertaken with experienced personnel.

A prolonged second stage of labour is inadvisable in patients with compromised cardiovascular conditions. The valsalva manoeuvre increases the cardiac afterload as well as decreases the venous return and can further compromise their cardiac function. In such instances, assisted operative vaginal delivery with either forceps or vacuum extraction are usually indicated. Severely compromised patients will benefit from the use of Swan-Ganz catheters throughout labour and immediately postpartum.

It is most important to avoid fluid overload in such patients and very careful intake and output should be recorded. If pitocin is used to induce labour, its mild antidiuretic effect must be kept in mind. Of particular importance is the fact that the most critical time for the woman at risk is immediately after delivery. The reason for this is that as the placenta is delivered and the uterus contracts down, an extra bolus of blood (approximately 500 ccs) is squeezed into the central circulation. This sudden bolus of fluid may be enough to tip the patient into congestive failure and poses the time of greatest risk of pulmonary oedema. The management of the third state of labour is, therefore, critically important in patients with underlying cardiac disease.

The mode of delivery should still be based on standard obstetric indications. The mere presence of pre-existing heart disease does not mandate a caesarean section . The risk of this major abdominal surgery and greater blood loss may actually be a detriment to the patient's health.

Peripartal Cardiomyopathy

Description

A condition unique to that of the pregnant patient is that of peripartal cardiomyopathy. It is a condition of unknown cause which occurs with a frequency of between 1 in 10,000 and 1 in 15,000 deliveries.
A variety of statistical methods have been used to identify patients at greater risk for peripartal cardiomyopathy and they would indicate that both black patients as well as patients over the age of 30 are at greater risk. Patients who have a history of malnutrition or who have hypertensive disorders during pregnancy are at greater risk. As a matter of fact, it has been suggested that the overwhelming majority of patients who ultimately develop peripartal cardiomyopathy have a history of mild chronic hypertension . It is also more common in patients with multiple gestations .

Symptoms and Signs

The signs and symptoms begin in the last month of pregnancy or within the first 5 months postpartum and show evidence of biventricular involvement. There may be a proto-diastolic gallop as well as frequent PVCs. Cardiomegaly is uniformly present. These signs and symptoms are the same as those seen in any patient with idiopathic cardiomyopathy.

Diagnosis and Treatment

The treatment of the condition is strictly supportive, involving bedrest and sodium restriction. If arrhythmias are present, they are treated and anticoagulants are usually recommended in the form of heparin to prevent the increased risk of thromboemboli originating in the enlarged heart.
The delivery of the infant apparently does not influence the course of the disease. However, from a practical point, since these symptoms usually being in the last month of pregnancy and the congestive heart failure may certainly adversely affect the foetus, the baby is usually delivered once the diagnosis is made.

From a prognostic standpoint, approximately 20% of patients with peripartal cardiomyopathy suffer irreversible progressive deterioration in heart function. There are reports where patients have undergone heart transplants due to the irreversible nature of this disease in those 20% of patients. When these patients are followed serially, if the episode resolves and the heart size is normal 6 months after the episode, it has been said that the risk of recurrence is very low. Again, there are few patients who have survived such a serious medical complication of pregnancy and subsequently become pregnant to say this with confidence.

The information in this page is presented in summarised form and has been taken from the following source(s):
1. Robert J. Blaskiewicz, M.D. Clinical Professor, Department of Obstetrics, Gynecology and Women's Health, Saint Louis University, U.S.A.: http://obgyn.slu.edu/