Right Atrial Reduction for Tachyarrhythmias in Ebstein's Anomaly in Infancy

Abstract

A 20-month-old girl with Ebstein's anomaly developed supraventricular paroxysmal tachycardia, which seemed to be a result of the wall tension of the giant right atrium. Right atrial resection reduced the wall tension and overall dimensions of the right atrium and finally resolved the tachycardia and ectopic electrical conduction. Six-year follow-up electrocardiograms confirmed continuing normal sinus rhythm without occurrence of supraventricular paroxysmal tachycardia or other ectopic electrical activity. The follow-up echocardiograms showed the size of the right atrium to be unchanged from the time of operation. There are few data in the available literature about performing right atriotomy to resolve a tachyarrhythmia associated with Ebstein's anomaly and none, to the best of our knowledge, about performing right atrial resection for this purpose. (Tex Heart Inst J 2001;28:297–300)

Ebstein's anomaly is an uncommon congenital cardiac anomaly involving the position and structure of the tricuspid valve. ¹ It consists of downward displacement of abnormal tricuspid valve leaflets into the right ventricle, where they are tethered. ² The severity of symptoms and the degree of cyanosis depend on the degree of displacement (and consequent malfunction) of the tricuspid valve and on the functional severity of the right ventricular outflow tract obstruction. Cardiac arrhythmias are frequent; the most common are numerous extrasystoles and paroxysmal tachycardia, usually supraventricular. ²

Case Report

In May of 1993, a 20-month-old girl was admitted for further management of a previously recognized congenital cardiac defect—Ebstein's anomaly—to the Cardiac Wing of the Great Ormond Street Hospital for Sick Children in London. The initial diagnostic procedures had been undertaken at Children's Hospital “Kantrida,” Rijeka (Croatia), where the diagnosis of Ebstein's anomaly was established.

The patient was the 2nd child of an otherwise healthy family. She was born at term with a birth weight of 2,800 g. She had been cyanotic at birth, but the diagnosis of Ebstein's anomaly was not established until the 6th month of age, when she came in February of 1992 as a refugee to Children's Hospital “Kantrida,” during the war in Croatia. There was a pansystolic murmur audible over the whole precordium. Chest radiography showed gross cardiomegaly but no lung disease (Fig. 1). The 2-dimensional transthoracic echocardiogram revealed enormous aneurysmal dilatation of the right atrium, notable tricuspid regurgitation, and displacement of the anterior and septal leaflets of the tricuspid valve into the right ventricle without the associated secundum atrial septal defect that is typical of Ebstein's anomaly. The size and rotation of the right atrium were such that it occupied most of the back of the cardiac silhouette (Fig. 2). The right ventricle itself was mildly dilated and contracted reasonably well, and there was no right ventricular outflow tract obstruction. There was good left ventricular function.

Fig. 1 Chest radiograph (anterior-posterior view) shows gross enlargement of the heart.

Fig. 2 Preoperative 2-dimensional transthoracic echocardiograms taken at 6 months of age: A) subcostal 4-chamber view shows marked enlargement of right atrium, downward displacement of tricuspid valve, and hypoplastic right ventricle, and B) parasternal long-axis and apical 4-chamber views show the same findings.

IVS = interventricular septum; LA = left atrium; LV = left ventricle; RA = right atrium

The electrocardiogram showed basic sinus rhythm, a normal axis, and incomplete right bundle-branch block. There was no evidence of pre-excitation on the resting electrocardiogram. Cardiac catheterization and angiocardiography confirmed Ebstein's malformation.

The child lived satisfactorily with little effort restriction and no progressive cyanosis until she was 17 months of age. At that time, there began a prolonged episode of supraventricular tachycardia (SVT) (Fig. 3), which was treated with digoxin as the 1st drug of choice and finally resolved with amiodarone as the 2nd drug of choice. Subsequently, every febrile illness provoked a new episode of SVT.

Fig. 3 Preoperative electrocardiogram displays pattern typical of paroxysmal supraventricular tachycardia.

Physical examination on admission to Great Ormond Street revealed a healthy girl of normal stature who was minimally cyanotic at rest but did not show any digital clubbing. She had an irregular pulse rate but normal pulse character in the upper and lower limbs. Her venous pressure was not elevated, and her cardiac impulse was somewhat diffuse. There was a loud pansystolic murmur audible over the whole precordium. The pulmonary component of the 2nd sound was widely split, and there was a soft mid-diastolic murmur. The liver was not enlarged, nor were there other abnormal clinical findings. The electrocardiogram showed frequent supraventricular extrasystoles, a normal QRS axis, and a right bundle-branch block. A 2-dimensional transthoracic color-flow Doppler echocardiogram confirmed the previous findings. Cardiac catheterization and angiocardiography were repeated entirely without event and confirmed the diagnosis of Ebstein's anomaly. The aortic saturation was 93%. The right and left mean atrial pressures were similar to one another, but had distinct waveforms. The right ventricular systolic pressure was 21 mmHg, and the pulmonary artery systolic pressure was 18 mmHg. Again, frequent single unifocal extrasystoles were noted. There was only 1 short, self-terminating run of supraventricular tachycardia. The preoperative cardiothoracic ratio was 0.75.

The major hemodynamic problem was considered to arise from the capacitance of this giant right atrium and its wall tension. It was postulated that the frequent ectopic electrical conduction, marked by a tendency towards SVT, was associated with the enlarged atrium. The right ventricular function was adequate, and the degree of tricuspid regurgitation was probably not, by itself, very consequential. If the wall tension and overall dimensions of the right atrium could be reduced, this might diminish the frequency of the episodes of SVT. Therefore, a partial resection of the right atrium was performed. Minimal procedures on the tricuspid valve were undertaken, and the atrial septum was left intact.

Postoperative recovery presented no particular problems. Fifteen days after surgery, transthoracic color-flow Doppler echocardiography showed a smaller right atrium (38 × 40 mm) and a moderate degree of tricuspid regurgitation. However, biventricular function remained extremely good, and the patient, at last follow-up in May of 1999, remained free of cyanosis and displayed good effort tolerance.

Antiarrhythmic agents were never resumed after surgery, and no symptoms suggesting paroxysmal tachycardia have recurred. During 24-hour Holter monitoring 1 month after the operation and again in May of 1999, there were no paroxysmal features or supraventricular ectopic activity. A follow-up echocardiogram performed in May of 1999 showed that the right atrium was the same size as it was immediately after the operation, 6 years earlier. The other chambers grew as the child grew.

Discussion

The most common initial symptoms of Ebstein's anomaly as it presents in infancy are severe cyanosis associated with poor effort tolerance and arrhythmia. Massive cardiomegaly and systolic murmur are characteristic features. The arrhythmia may be paroxysmal supraventricular tachycardia or, upon occasion, chronic atrial fibrillation or flutter. ^2,3 Ebstein's anomaly is also the most common congenital heart disease associated with Wolff-Parkinson-White syndrome. In selected patients, tachyarrhythmias unresponsive to medical therapy (digoxin, amiodarone, or propafe-none) may be treated by radiofrequency catheter ablation. ⁴ Various surgical techniques have been used to overcome the hemodynamic consequences of Ebstein's anomaly. These include repair or replacement of the abnormal tricuspid valve, plication of the atrial floor, or merely closing an atrial communication. ^2,5 Operation for Ebstein's anomaly has been suggested when any of the following conditions is present: profound cyanosis with poor effort tolerance, paradoxical emboli, polycythemia, a cardiothoracic ratio of 0.65 or greater, or refractory arrhythmias. ^6,7 Risk of sudden death remains an important problem in patients with Ebstein's anomaly, regardless of the severity of the disease or the mode of the treatment. ⁶

Transthoracic color-flow Doppler echocardiography has an important role in the diagnosis of Ebstein's anomaly and in the evaluation of tricuspid valve function. It is also particularly useful for intra- and postoperative monitoring and functional evaluation. ⁸ The prognosis in Ebstein's anomaly is extremely variable and depends chiefly on tricuspid valve function, which influences the atrial shunt (if one is present) and the degree of cyanosis. The incidence of arrhythmia is an independent factor. However, a cardiothoracic ratio equal to or greater than 0.65 is a better predictor of sudden death than is functional status. ⁹

Conclusion

The frequent ectopic electrical activity marked by the tendency towards SVT, in association with our patient's Ebstein's anomaly, may have been a consequence of the wall tension of the giant right atrium. Right atrial resection reduced overall the dimensions of the chamber and possibly the wall tension. The occurrence of ectopic electrical conduction was greatly reduced, and there has been no further episode of SVT during the 6 years of follow-up. We believe that this case is unusual, for there are few data in the literature about performing right atriotomy ¹⁰ to resolve tachyarrhythmias associated with Ebstein's anomaly and none, to the best of our knowledge, about performing right atrial resection for this purpose.