Describe the functional classification, effects, and management of heart Disease in Pregnancy.

The first 24 hours postpartum carry the greatest risk of failure.

Definition

Heart disease complicates about 1% of pregnancies and is an important cause of indirect maternal death. Rheumatic heart disease (chiefly mitral stenosis) remains the commonest type in developing countries, while congenital heart disease predominates in the West. Severity is graded by the New York Heart Association (NYHA) functional classification.

Nyha Grading & Management Timeline

Nyha Functional Classification

• Class I — no limitation of physical activity; ordinary activity causes no symptoms.
• Class II — slight limitation; comfortable at rest, but ordinary activity causes fatigue, palpitation or dyspnoea.
• Class III — marked limitation; symptoms on less-than-ordinary activity.
• Class IV — symptoms at rest; any activity causes discomfort.

Classes I–II generally tolerate pregnancy well; Classes III–IV carry a high risk of maternal mortality.

Effects of Pregnancy on the Heart

The physiological changes of pregnancy stress a diseased heart: blood volume and cardiac output rise by 30–50% (output peaks at 28–32 weeks), heart rate rises, and there are sudden additional loads during labour (each contraction shifts 300–500 mL into the circulation) and especially immediately after delivery, when relief of caval compression and uterine retraction abruptly increase venous return. The critical periods for cardiac failure are therefore 28–32 weeks, during labour, and the immediate puerperium.

Effects of Heart Disease on Pregnancy

Cardiac failure and pulmonary oedema, arrhythmias, infective endocarditis, thromboembolism, increased abortion/preterm labour, intra-uterine growth restriction, fetal hypoxia and increased perinatal loss.

Diagnosis

History of rheumatic fever or known cardiac lesion; symptoms of dyspnoea, orthopnoea or haemoptysis; signs including a diastolic murmur, loud or persistently split heart sounds, or cardiomegaly. Echocardiography confirms the lesion and assesses severity; ECG and chest radiograph (with shielding) assist.

Management

Pre-pregnancy counselling

Assess the lesion and functional class, optimise/correct it before conception (e.g. Valvotomy), and advise on the risks. Class III–IV disease may warrant advice against pregnancy or its termination.

Antenatal

• Shared (obstetrician–cardiologist) care with frequent visits; adequate rest, treatment of anaemia and infection, and avoidance of excess weight gain and salt.
• Prevent and promptly treat heart failure — recognise early signs (basal crepitations, persistent tachycardia, worsening dyspnoea); treat with rest, diuretics, digoxin and oxygen.
• Continue anticoagulation where indicated (e.g. Prosthetic valves), and give thromboprophylaxis.
• Hospitalise around the critical 28–32-week period and well before term in significant disease.

Intrapartum (labour)

• Aim for vaginal delivery in most cases; caesarean section is reserved for obstetric indications.
• Nurse in the propped-up left-lateral position; give oxygen and effective epidural analgesia to minimise the cardiovascular stress of pain.
• Shorten and assist the second stage (forceps/ventouse) to avoid prolonged bearing-down.
• Antibiotic prophylaxis against infective endocarditis for high-risk lesions.
• In the third stage, avoid ergometrine (sudden venous return and rise in pressure); manage with oxytocin, and avoid rapid IV fluids.

Postpartum

The first hour and first few days are the most dangerous — observe closely for pulmonary oedema and failure. Continue antibiotics if indicated, allow graded ambulation with thromboprophylaxis, advise effective contraception (sterilisation may be appropriate after a completed family), and support breastfeeding in stable women.

WHY the Three Critical Periods Determine Management

Understanding why cardiac disease in pregnancy is dangerous at three specific moments converts a list of complications into a plan. Pregnancy imposes a haemodynamic load: blood volume and cardiac output rise by 40–50%, and a diseased heart with limited reserve fails where that load peaks. The first peak is at 28–32 weeks, when plasma volume and cardiac output reach their maximum — the commonest time for heart failure to appear. The second is labour, especially the second stage, when each contraction squeezes 300–500 mL of blood into the circulation and bearing down (Valsalva) causes wide swings in venous return — which is why the second stage is cut short by forceps or ventouse and the mother told not to push. The third, and most dangerous, is the immediate puerperium: as the uterus contracts after delivery of the placenta it autotransfuses some 500 mL into the circulation, while caval compression is relieved — a sudden preload surge that can precipitate acute pulmonary oedema in the first hours after birth. Recognising these three peaks explains why such women are admitted early, delivered under epidural with an assisted second stage, and monitored intensively for 24–48 hours afterwards.

WHY Vaginal Delivery Is Usually Preferred

A point that often surprises students is why a woman with serious heart disease is usually delivered vaginally rather than by elective caesarean. Intuitively, a planned operation seems safer. In fact, caesarean imposes the greater cardiovascular stress: major surgery, greater blood loss, larger fluid shifts, the haemodynamic effects of anaesthesia, and higher risks of infection and thromboembolism — and it does not avoid the autotransfusion of the puerperium. A well-conducted vaginal delivery, by contrast, can be made remarkably gentle: epidural analgesia abolishes the pain-driven surges of catecholamines and cardiac output; the mother is nursed propped up in the left lateral position with oxygen and careful fluid balance; and the second stage is shortened by forceps or ventouse so that she never bears down. Caesarean is therefore reserved for obstetric indications or specific severe lesions. Ergometrine is avoided (it causes an abrupt rise in venous return and blood pressure), and oxytocin is given cautiously by slow infusion. Understanding that the aim is to avoid surges in cardiac output — which surgery causes and a well-managed labour avoids — explains this counter-intuitive preference.

• Pregnancy raises blood volume and cardiac output by 40–50%; a diseased heart may fail at the three critical periods.
• Critical periods: 28–32 weeks (peak cardiac output), labour (second stage) and the immediate puerperium (autotransfusion).
• Rheumatic mitral stenosis is the commonest lesion in India; NYHA class predicts outcome (III/IV = high risk).
• Vaginal delivery under epidural with a shortened second stage (forceps/ventouse) is usually preferred; avoid ergometrine.
• Nurse propped up, restrict fluids, give oxygen and antibiotic prophylaxis where indicated; monitor closely for 24–48 h after delivery.