The incidence of heart disease varies in different parts of the world. In Western countries, rheumatic heart disease is now on the decline and there is a relative increase in congenital heart disease. The advances in investigative procedures, medical and surgical management has made it possible for women with congenital heart disease to have successful pregnancies. In India, rheumatic heart disease still contributes to majority of the heart diseases encountered in pregnancy as compared to congenital heart disease.
CARDIOVASCULAR CHANGES
During Pregnancy
In pregnancy, the following changes occur in the cardiovascular system.
Cardiac output: During pregnancy the cardiac output is increased by as much as 30-50%. It increases from about 4.5 l/min before pregnancy to about 6-6.5 l/min. This increase is significant beginning in early pregnancy, reaches a peak at 28-32 weeks of gestation and remains elevated during the remainder of the pregnancy.
Heart rate: The heart rate increases by 10-15 beats per minute between 14 and 20 weeks, and this increase is maintained till term.
Blood pressure: The systolic blood pressure is unchanged or slightly lowered until the 20th week of pregnancy and then rises to prepregnancy levels. The diastolic pressure is slightly reduced.
Venous pressure: In the supine position, the femoral venous pressure rises steadily from early in pregnancy to term. The brachial venous] pressure remains unchanged during pregnancy.
Plasma volume: This increases by 40-45% between 12 and 32 weeks of gestation
Red cell volume: The red cell volume increases by 15-20%
During Labour and Delivery
It is important to understand the changes during labour and delivery since the maternal mortality is increases if proper care is not taken.
1.During labour and delivery, the heart rate increases in response to physical stress and returns to normal between contractions.
2.During the first stage of labour, cardiac output increases moderately, and during the second stage, with vigorous expulsive efforts, it is appreciably greater.
3. Oxygen consumption increases with uterine contractions, approaching that of moderate to intense exercise. With more severe pains, it may reach levels seen in intense exercise.
During Puerperium
In the immediate puerperium, the cardiac output is augmented and then loses most of the pregnancy induced increase.
HEART DISEASES
TYPES
1) Rheumatic heart disease:
This is the most common type of heart disease encountered during pregnancy in India contributing to 90-95% of cases. The commonest lesion seen is mitral stenosis. Other lesions include mitral incompetence, aortic stenosis and aortic incompetence.
2) Congenital heart disease:
These include atrial or ventricular septal defects, pulmonary stenosis and cyanotic lesions such as Fallot tetralogy and Eisenmenger syndrome.
3) Other cardiac lesions: These include mitral valve prolapse, peripartum cardiomyopathy, arrhythmias, myocardial infarction etc.
DIAGNOSIS
Diagnosis of heart disease during pregnancy is difficult since there is a similarity between the physiological changes in normal pregnancy and the symptoms and signs of heart disease. In 60% of normal pregnancies, dyspnea may occur on exertion. Functional systolic murmurs of the heart are quite common. In the second half of pregnancy, edema of the lower extremities may be observed. It is important not to diagnose heart disease during pregnancy when it does not exist. On the other hand, failure to detect and appropriately treat it would result in increased maternal morbidity. The following symptoms and signs may indicate an associated heart disease and require further investigations. These are: Symptoms of progressive dyspnea, nocturnal dyspnea, hemoptysis and chest pain
1)Systolic murmur of marked intensity or a diastolic murmur
2)Presence of persistent arrhythmia
3)Features of heart failure such as increased jugular venous pressure
4)Presence of clubbing, cyanosis indicating congenital heart disease
CLASSIFICATION
Heart diseases can be classified in terms of etiology, anatomical lesions and functional capacity. Such a description assumes increasing importance in the light of the present progress in medical and surgical therapy. For the obstetrician it is essential to know the functional classification. The classification that is generally in vogue to indicate functional capacity (New York Heart Association).
ASSESSMENT OF RISK AND PROGNOSIS
Many factors influence the prognosis. Some of the important factors are:
1) Age of the patient: The older the patient (over 35), the less satisfactory will be the prognosis.
2) History of previous pregnancies: If the patient has had no complications in her previous pregnancies and deliveries, the prognosis is satisfactory though she can develop problems in a subsequent pregnancy.
3) Functional grading of heart: This is the most important factor. With rare exceptions women in grade 1 and most in grade 2 go through pregnancy without morbidity. Grades 3 and 4 need intensive care and have a higher morbidity.
4) Socioeconomic status: This is specially important in India. Often even if it is known that a woman has heart disease, this is not disclosed to the husband and hence she reports to the hospital with complications. Unless efficient antenatal care and social services are available, often patients have to be kept in hospital.
5) The nature of the lesion: Of the various lesions, mitral stenosis has a better prognosis provided it is not close to total constriction. Eisenmenger syndrome has the worst prognosis and a high maternal mortality.
MANAGEMENT OF PREGNANCY
The whole aim in the management is prevention, early diagnosis and prompt and efficient treatment of heart failure during pregnancy.
ANTENATAL CARE
Whenever heart disease is diagnosed during pregnancy, the patient should preferably be referred to a tertiary care centre or a centre where an experienced obstetrician and a cardiologist are available.
1)Grades 1 and 2 are treated as outpatients. Grades 3 and 4 need to be hospitalised.
2)The patients should be seen atleast fortnightly until 30 weeks of gestation and then weekly until term. Ideally, if the patient stays in a remote area, even grade 1 and 2 may be hospitalised near term for safe confinement.
3)At each antenatal visit, the patient should be asked whether there is an increase in breathlessness or limitation of activity.
4)Increasing dyspnea, orthophea, signs of basal congestion in lungs are indicative of onset of cardiac failure and patients may require hospitalisation.
5)Iron and folic acid are administered routinely to all pregnant women. In women with heart disease, it is important to ensure that they are not anemic since this would add to the morbidity. Infection has proved to be an important factor in precipitating cardiac failure. Each patient must receive instructions to avoid contact with persons who have respiratory infections, including common cold.
Management of Labour and Delivery
There is general agreement that vaginal delivery is the safest for this group and that a cesarean section should be avoided if possible. Spontaneous onset of labour is awaited and induction of labour is avoided as far as possible. Principles of management in a patient with cardiac disease in labour include:
1) In the first stage of labour, the patient should be at rest in bed in a semi-recumbent position.
2) Infective endocarditis prophylaxis should be given. Intravenous or intramuscular ampicillin (after test dose) 2 g and gentamycin in the dose of 1.5 mg/ kg body weight is given initially and repeated after 6 hours.
3) Intravenous fluids are to be avoided; if given, a strict control needs to be kept.
4) Grade 3 and 4 patients require oxygen inhalation and for other patients oxygen should be readily available.
5) Adequate analgesia should be given since relief from pain and apprehension is especially important.
6) Vital signs such as pulse and blood pressure should be recorded every 30 minutes. Increase in pulse rate above 100 or a respiratory rate_of more than 24, if associated with dyspnea, may indicate impending heart failure.
7) Second stage of labour should be cut short with the use of outlet forceps. At the time of delivery, it is better to avoid giving ergometrine and give a bolus dose of oxytocin if required.
Management of Puerperium
Women who have shown little or no evidence of cardiac distress during pregnancy, labour or delivery may still decompensate after delivery. Therefore, it is important that meticulous care be continued into the puerperium.
Postpartum hemorrhage, anemia, infection and thromboembolism are much more serious complications with heart disease.
If tubal sterilisation is to be performed after vaginal delivery, it may be best to delay the procedure until it is obvious that the mother is afebrile, not anemic and has no evidence of distress.
Contraception
In India, most heart diseases are diagnosed for the first time during pregnancy. Even if this pregnancy may have been uneventful, it is necessary to advise the patient and her family that a detailed investigation needs to be done and corrective surgery if required, should be performed before another pregnancy. Hence it is essential to advise contraception. Barrier methods or progestogen only may be given.
Indications for Medical Termination of Pregnancy
In modern practice, the indications for therapeutic abortion are strictly limited. Patients in grade 3 or 4 should first get their treatment for heart disease before planning a pregnancy. If they do not and are seen in first trimester, it is better to treat the failure and then consider termination of pregnancy. If, however, the women are seen in second trimester, it would seem advisable to continue treating the failure without interfering with the pregnancy.
Eisenmenger syndrome is associated with a high maternal mortality and hence medical termination of pregnancy is advised if she is seen in the first trimester of pregnancy.
Prognosis
Maternal prognosis depends upon the functional cardiac capacity, complications that increase the cardiac load, and quality of medical care provided. Higher mortalities are associated in those who are brought in as emergencies complicated by anemia. Most such patients come and are unbooked cases with no prenatal care from lower socioeconomic status.
Congenital Heart Disease in the Offspring
Some women with congenital heart disease would give birth to similarly affected infants since these lesions appear to be inherited.
Cardiac Surgery during Pregnancy
If mitral stenosis is the predominant lesion causing symptoms, mitral valvotomy can be done. Balloon mitral valvotomy has largely replaced surgical valvuloplasty during pregnancy.