Ebstein’s Anomaly

-A rare congenital cardiac abnormality.

-The septal and posterior cusps of the tricuspid valve are displaced downwards and are elongated, such that a varying amount of the right ventricle effectively forms part of the atrium. Its wall is thin and it contracts poorly. The remaining functional part of the right ventricle is therefore small.

-The foramen ovale is patent, or defective, in 80% of cases.

-The degree of abnormality of right ventricular function, and the size of the ASD, are probably the main determinants of the severity of the condition, which varies considerably.

-The right ventricular systolic pressure is low, and the RVEDP is elevated. Tricuspid incompetence can occur.

-There may be a right to left shunt, with cyanosis, on effort, and pulmonary hypertension, and right heart failure may supervene.

-The natural history of the disease is very variable. Fifty percent of cases present in infancy with cyanosis, and 42% die in the first 6 weeks of life.

-In those who survive to adulthood, symptoms may be precipitated by the onset of arrhythmias, or by pregnancy. A few patients remain asymptomatic, even as adults, although once symptoms develop, the disability can increase rapidly.

-A cardiothoracic ratio of ≥ 0.65 is a better predictor of sudden death than the symptomatic state, and those who developed atrial fibrillation died within 5 years. It has therefore been suggested that tricuspid surgery should be undertaken before the cardiothoracic ratio reaches 0.65.

Preoperative Abnormalities:

1. There may be a right to left shunt, with dyspnea and cyanosis at rest, or on moderate exertion. Alternatively, the patient may be asymptomatic.

2. Episodes of tachyarrhythmias occur in 25% of patients. Some provoke syncopal attacks.

3. The ECG may show varying abnormalities, including large peaked P waves, a long P–R interval, Wolff–Parkinson–White syndrome, RBBB, and right heart strain. Paroxysmal supraventricular tachycardia occurs in 15%, usually because of the presence of WPW syndrome.

4. Chest X-ray may show cardiomegaly, with a prominent right heart border, and poorly perfused lung fields.

5. Paradoxical systemic embolism and bacterial endocarditis may occur.

6. Many other lesions of the tricuspid valve or right ventricle may mimic Ebstein’s anomaly, therefore the discriminating clinical and echocardiographic features for correct diagnosis have been enumerated.

Anesthetic Problems:

These will depend upon the anatomical abnormality, the degree of right to left shunt, and the presence or absence of right heart failure.

1. Induction time is prolonged, because of the pooling of drugs in the large atrial chamber.

2. Intracardiac catheter insertion may be hazardous because it can provoke serious cardiac arrhythmias.

3. Air entering peripheral venous lines or any open veins at subatmospheric pressure may cause paradoxical air emboli.

4. Tachycardia is poorly tolerated because of impaired filling of the functionally small right ventricle.

5. Hypotension may increase the right to left shunt if present.

6. Hypoxia causes pulmonary vasoconstriction, which also increases a right to left shunt.

7. There is a risk of bacterial endocarditis, especially if a CVP line is in place.

8. Deterioration may occur in pregnancy because of a decrease in right ventricular function, and an increase in blood volume and cardiac output, or with the onset of arrhythmias.

Management:

1. The severity of the lesion must be assessed. In the presence of maternal cyanosis or arrhythmias during pregnancy, there should be close monitoring of both mother and fetus. Deterioration may occur, despite previous successful pregnancies.

2. Treatment of heart failure and arrhythmias.

3. Antibiotic prophylaxis against bacterial endocarditis.

4. If a CVP is used for monitoring, its tip should be kept within the superior vena cava. The use of intracardiac catheters should probably be avoided.

5. Techniques should aim to minimize tachycardia and hypotension.

6. Oxygen therapy increases pulmonary vasodilatation. Long-term maternal therapy is required during pregnancy from 14 weeks, to treat fetal hypoxia that is demonstrated by umbilical venous blood gases.

7. Several anesthetic techniques have been described. A two-catheter epidural technique can be used for vaginal delivery to minimize hypotension. Bupivacaine doses must be fractionated and saline rather than air used to site the epidural, to avoid paradoxical air emboli. Cesarean section under general anesthesia, preceded by fentanyl, and a neurolept analgesic technique for hysterectomy, have been described.

Categories: Congenital cardiovascular diseases