Indian Pediatrics 2003; 40:426-429 

Tachycardiac storm in infant with WPW syndrome: "Rescue" Radiofrequency Ablation

From the Department of Cardiology, P.D. Hinduja Hospital and Medical Research Centre and *Glenmark Cardiac Centre, Mumbai 400 016, India.

Correspondence to: Dr. Yashkhandwala, P.D. Hinduja Hospital and Medical Research Center, Veer Savarkar Marg, Mahim, Mumbai 400 016, India.
E-mail: yashlokhandwala@hotmail.com

Manuscript received: February 1, 2002; Initial review completed: February 25, 2002; Revision accepted: January 1, 2003.

A two-month-old child having WPW syndrome and orthodromic tachycardia was on treatment with digoxin, flecainide and amiodarone. Despite this, he continued to have severe, very frequent episodes of tachycardia. The left-sided accessory pathway was hence ablated via a patent foramen ovale.

Key words: Arrhythmia storm, pre-excitation, WPW syndrome.

Radiofrequency ablation (RF) is the standard treatment for symptomatic WPW syndrome. Usually this procedure is not performed in very small children due to technical limitations. The case reported herein was undertaken as a last resort.

Case Report

A one-month-old child born as a full term normal baby was referred to us with a diagnosis of WPW syndrome. The child first had an episode of paroxysmal tachycardia at the age of 15 days. Since then the child had experienced 2 more episodes. During the episodes, the child would appear limp. The ECG revealed narrow QRS tachycardia at 250 beats/min. The ECG in sinus rhythm suggested a left sided accessory pathway. The tachycardia could be terminated by intra-venous adenosine. The child had been started on digoxin and amiodarone. These medica-tions were continued and a weekly follow-up was advised. The echocardiographic exam-ination was normal; a patent foramen ovale was seen. Since the child continued to have episodes of tachycardia, flecainide 1 mg/kg twice a day was added. Despite this, episodes of tachycardia continued. At the age of 2 months the child, weighing 3.2 kg was admitted in the intensive pediatric care unit with tachycardia storm. In a period of 24 hours he had six episodes of orthodromic tachycardia, every time requiring 1.5 mg/kg adenosine. In view of his precarious state, a "rescue" ablation was considered.

The procedure was performed under general anesthesia. Both femoral veins were accessed percutaneously. A 4-F quadripolar electrode catheter (Bard) was introduced via the left femoral vein into right ventricle. A 5F (Medtronic) ablation catheter with a 4 mm tip was introduced via the right femoral vein into the right atrium. Orthodromic tachycardia was easily inducible and could be terminated by ventricular extra stimuli. The ablation catheter was passed into the left atrium through the patent foramen ovale. An early activation site was found in the left lateral region (Fig. 1). Transient "bumping" of the pathway was noted by catheter contact. Radiofrequency energy at this site led to immediate abolition of pre-excitation (Fig. 2). The peak temperature setting was kept at 60ºC and the maximum temperature achieved was 53ºC. The ECG next day showed that the preexcitation had returned. In view of this, flecainide was continued while amiodarone was stopped. Over the next 5 months the child has not had a single episode of tachycardia. Digoxin was stopped at 7 months of age. Serial ECGs have revealed intermittent pre-excitation. He is growing well with normal milestones. His echocardiogram revealed mild mitral regurgitation but no structural abnormality of the mitral valve apparatus was seen. At the last follow up the weight was 9 kg at 11 months of age.

Fig. 1. Fluoroscopy of successful RF ablation site. (a) 20º RAO, 10º cranial angulation. The ablation catheter is on mitral annulus across the patent foramen ovale. The diagnostic catheter is in the right ventricle. (b) 40º LAO view. The ablation catheter tip is seen in the left lateral region.

 

Fig. 2. RF energy delivery. Preexcitation is abolished from 10th QRS complex onwards. The initial 9 QRS complexes show a negative delta wave in lead aVF and a positive delta wave in lead V1, which disappear later.

Discussion

RF ablation is rarely performed in infancy. The small diameter of femoral vessels imposes severe limitations on catheter choices. Apart from vascular complications, there are concerns of damage to the fragile intracardiac structures at such a tender age. We undertook RF ablation after all other measures had failed. The return of pre-excitation in our patient was unusual, because adenosine had demonstrated transient AV block after RF ablation. The intermittent nature of pre-excitation at follow-up is indicative of a long antegrade refractory period of the accessory pathway. The absence of tachycardia recurrence suggests that retrograde conduction over the pathway has been markedly diminished, if not eliminated by the RF ablation.

There are apprehensions regarding increase in RF lesion size with growth based on studies in lambs(1). Hence RF ablation in infancy is undertaken only when severe tachycardia persists despite adequate trial of drug therapy. There are several reported series of RF ablation in children(2,3,4), but the proportion of infants in these studies have been very small. Our patient is the youngest reported hitherto from India. A previous report from India(5) highlighted a similar problem in a thirteen month old child. The mild mitral regurgitation noted in our patient has been well tolerated. It is possible that the RF lesion in some way has led to this regurgitation. However the absence of any visible damage to the leaflets or chordae is reassuring. The satisfactory clinical progress that we observed indicate a good prognosis in this regard.

Contributors: BD conducted initial clinical and echocardiographic evaluation, CKP assisted in the RF ablation procedure, KC assisted in the management and help in writing the manuscript, YL helped in patient care and preparation of the manuscript and will act as guarantor of the paper.

Funding: None.

Competing Interests: None stated.

 References