What is Ebstein’s anomaly ?
It was in 1866 that Ebstein first described the heart defect that bears his name. The defect includes the following components:
- Displacement of the tricuspid valve (that lies between the right atrium and right ventricle) leaflets downwards from it’s normal position.
- Abnormalities of the right ventricle
- “Atrialization” of a portion of the right ventricle
- An inter-atrial septal defect (ASD)
What happens in Ebstein’s anomaly ?
The primary problem is displacement of the tricuspid valve down from the normal position, which in turn results in the abnormal valve becoming leaky. This valve leak, combined with right ventricle muscle abnormalities, causes heart enlargement with heart failure, along with a “shunt” of blood from the right atrium, across the ASD, into the left side of the heart and circulation.
The result of these problems is that a patient with Ebstein’s anomaly has cyanosis (a bluish discoloration of the body, caused by mixing of impure blood from the right side of the heart with oxygenated pure blood in the left side). If the tricuspid valve leak is severe, the patient develops heart failure early in life, with swelling of the legs and belly, enlargement of the liver and breathlessness.
What other problems may occur in Ebstein’s anomaly ?
Due to the abnormal flow of blood from the right atrium, across the ASD, into the left atrium, there is a small risk of tiny blood clots that form inside the veins being washed in the blood stream into the left side of the heart. These clots might then enter the blood stream, and lodge in other parts of the body, like the brain or heart itself. This is called Paradoxic Embolism.
In 5 % of patients with Ebstein’s anomaly, there is an abnormality in rhythm of the heart beat. This is because there is an abnormal pathway for electric impulse conduction within the heart, and this may account for some serious arrhythmias like the Wolff-Parkinson-White (WPW) syndrome.
Why should Ebstein’s anomaly be corrected ?
Basically, Ebstein’s anomaly requires operative repair to avoid any of the complications mentioned above. In very small babies, with severe leak of the valves, heart failure may set in very early in life, and operation is then needed as a life-saving measure.
What is done during operation for Ebstein’s anomaly ?
The correction for Ebstein’s anomaly is by an open heart operation. The principles of repair are:
- Repair or replacement of the abnormal tricuspid valve
- Plication or exclusion of the “atrialized” portion of the right ventricle
- Closure of any inter-atrial communication
- Reduction in the atrial size, if it is very large
Valve repair is the preferred approach. At surgery, the tricuspid valve is first evaluated for suitability for repair. Usually, the septal and posterior leaflets of the tricuspid valve are displaced, while the anterior leaflet is large and “sail-like”, tethered and immobile.
A valve repair procedure includes releasing the anterior leaflet until it is freely mobile and is capable of maintaining competence. The tricuspid valve ring itself may be rather large, and an “anuloplasty” procedure – which involves sewing a rigid ring, or using a “purse-string” stitch to the anulus – helps to narrow the valve ring and keeps it from leaking.
In rare cases, the valve may be too badly deformed to be repaired, and in these cases, it is replaced using a mechanical artificial heart valve.
The displaced tricuspid valve causes a part of the right ventricle to be included in the atrium – “Atrialization” of the right ventricle. This reduces the effectiveness of the right ventricle in pumping of blood. At operation, this atrialized portion is excluded from the circulation by “plication” – two common methods used for this are the Danielson repair and the Quagebeur repair.
Finally, any inter-atrial communication is closed using a patch of synthetic material or pericardium. If the atrium is too large, a portion of it’s wall is also removed to increase the heart’s efficacy as a pump.
What are the other operations used for Ebstein’s anomaly ?
In very mild cases, all that may be required is simple closure of the atrial septal defect, with no repair of the tricuspid valve. In very small infants with heart failure due to Ebstein’s anomaly, a special type of operation – the Starnes procedure – is required.
In this operation, the atrial septal defect is made very wide, the tricuspid valve is closed using a patch of fabric or pericardium, and a connection made between the aorta and pulmonary artery – a systemic-to-pulmonary shunt. In the course of time, a Fontan type operation will be completed.
What to do for the rhythm disturbances in Ebstein’s anomaly ?
Heart failure and sudden fast heart rates – paroxysmal tachycardia – are the major killers in cases of Ebstein’s anomaly. The rhythm disturbances are caused by abnormal muscle bands that conduct electric impulses within the heart.
At the time of operation, these bands can be located and divided. The rhythm problems are usually corrected after this.
How good are the results of operations for Ebstein’s anomaly ?
The outcome of surgical correction depends on three factors – the age at first presentation, the severity of the tricuspid valve leak, and the seriousness of right heart muscle weakness.
While children who develop symptoms after 1 year of age have a good long term outcome, those who are in heart failure in the first few days of life have a poorer outcome directly related to the more serious nature of their illness.
When the valve is not very leaky, and the right ventricle muscle not too badly damaged, good long term survival is seen.
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