Cardiac disease in pregnancy

Published on 09/03/2015 by admin

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Last modified 09/03/2015

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Chapter 48 Cardiac disease in pregnancy

Incidence. Fewer than 1% of all pregnancies are affected by maternal cardiac disease.

Pathophysiology of cardiovascular changes in pregnancy

Intravascular volume

This is increased by 50% by early mid-trimester and peaks at 32–34 weeks gestation. In a woman with limited cardiac output secondary to cardiovascular disease, volume overload is poorly tolerated and congestive cardiac failure a risk.

Decreased peripheral resistance in pregnancy

This is important in the woman with potential right-to-left shunts, as the shunts tend to increase with lowered vascular resistance.

Cardiac output

• Cardiac output rises early in pregnancy, and is unrelated to rise in plasma volume.

• In labour, the cardiac output rises progressively from the first stage to an additional 50% in the late second stage, with an increase of over 7 L/minute. This great change, plus the dramatic shifts of fluid that occur at delivery, is poorly tolerated in women whose cardiac output depends on adequate preload (pulmonary hypertension) or those with fixed cardiac output (mitral stenosis).

• Epidural anaesthesia and general anaesthesia produce dramatic changes in cardiac output.

Maternal mortality risks in cardiovascular disease

Mortality is most likely in conditions where pulmonary blood flow cannot be raised secondary to obstruction. Maternal mortality risk may be classified into the following three groups.

Low risk (mortality <1 %)

• uncomplicated atrial septal defect, ventricular septal defect or patent ductus arteriosus

• mitral stenosis

• tricuspid incompetence

• corrected tetralogy of Fallot

• bioprosthetic valve

Medium risk (mortality <15%)

• mitral stenosis with atrial fibrillation

• artificial valve

• previous myocardial infarction

• aortic stenosis

• uncorrected tetralogy

• uncomplicated coarctation of aorta or Marfan’s syndrome

High risk (mortality <50%)

• pulmonary hypertension

• Eisenmenger’s syndrome

• complicated coarctation

• Marfan’s syndrome with aortic dilatation

• peripartum cardiomyopathy

Fetal risks in maternal cardiovascular disease

Family history

• The presence of a congenital cardiac anomaly in either parent or sibling increases the risk of cardiac anomaly in the offspring to about 2%–4%, or twice that of the normal population. The risk rises to 10%–12% in mothers with defects, including atrial septal defect, ventricular septal defect, patent ductus arteriosus and tetralogy of Fallot. These have multivariant inheritance.

• Idiopathic hypertrophic subaortic stenosis is an autosomal dominant condition.

• Environmental risk factors include rubella virus and alcohol.

In women with cyanotic heart disease

The maternal haematocrit appears to correlate with perinatal outcome; a haematocrit of >65% is associated with poor outcome.

Management of cardiovascular disease in pregnancy

History

• The commonest symptom of heart disease is breathlessness on exertion, although this is unreliable in pregnancy.

• Syncope can occur with normal pregnancy, aortic stenosis, hypertrophic obstructive cardiomyopathy, tetralogy of Fallot and dysrhythmias.

• A history of rheumatic fever or previous investigation for a murmur are important.

Physical examination

• In normal pregnancy it is common for premature atrial and ventricular ectopics, oedema, loud first heart sound and third heart sounds to be present.

• An ejection systolic murmur may be present in up to 90% of women.

Investigations

• Chest X-ray in normal pregnancy shows slight cardiomegaly and increased pulmonary vascular markings.

• Electrocardiograph in normal pregnancy shows inversion in T waves, Q wave in lead III.

• Echocardiography is required to identify structural abnormalities.

Counselling

• Ideally, cardiovascular disease is identified and investigated before pregnancy, with the maternal risks evaluated and appropriate contraception advised.

• If termination of pregnancy is indicated, prostaglandin termination should be used with caution. Possible indications for termination include Eisenmenger’s syndrome, primary pulmonary hypertension and pulmonary veno-occlusive disease.

• Risk factors for congestive cardiac failure need to be monitored and managed appropriately. Risks include infections, hypertension, obesity, multiple pregnancy, anaemia, arrhythmia and hyperthyroidism.

Endocarditis and pregnancy

• The efficacy of antibiotic prophylaxis against infective endocarditis in pregnancy has not been proven, although it is accepted that benefits override the possible risks.

• Women at risk include those with prosthetic heart valves, most congenital malformations, rheumatic mitral stenosis, hypertrophic cardiomyopathy, mitral valve prolapse with regurgitation, or past history of subacute bacterial endocarditis.

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