|Birth||Postnatal||Childhood Illness||Glossary A-Z|
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
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
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.
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.
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.
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.
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.
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):
|http://www.hon.ch/Dossier/MotherChild/preexisting_conditions/heart.html||Last modified: Jun 25 2002|