Indian Pediatrics 2003; 40:158-162 

Radiofrequency Ablation of Incessant Atrial Tachycardia in an Infant

Hetan C. Shah
Anoop K. Gupta
Yash Y. Lokhandwala

Correspondence to: Anoop K. Gupta, Consultant Cardiologist and Electrophysiologist, Krishna Heart Institute, 319, Green City, Ghuma, Ahmedabad 380 058, Gujarat, India. E-mail: [email protected]

Manuscript received: April 4, 2002; Initial review completed: June 20, 2002; Revision accepted: September 27, 2002.

Ectopic automatic atrial tachycardia, an uncommon type of supraventricular tachycardia in children and adults, has been reported to be resistant to medical therapy unlike reentrant supraventricular tachycardia. We report a case of incessant atrial tachycardia in an nfant, which was successfully treated with radiofrequency catheter ablation.

Keywords: Atrial tachycardia, electro-physiological study, supraventricular tachycardia.

Ectopic automatic atrial tachycardia (EAAT) is an uncommon type of supraventricular tachycardia (SVT) in the pediatric age group(1). Incessant atrial tachycardia can lead to left ventricular dysfunction (tachycardiomyopathy), which has adverse outcome if adequate measures are not taken in time(2). We report a case of incessant atrial tachycardia in 8-month old infant, which was successfully cured with radiofrequency ablation. However, pro-cedural issues and family education remain a big challenge.

Case Report

An 8-month-old male child was diagnosed to have SVT in a tertiary pediatric institute, when his mother noticed increased precordial pulsation and shortness of breath. The child was subsequently referred to us for further management. The 12-lead EKG at the time of presentation (Fig. 1) showed narrow QRS complex tachycardia with cycle length of 320 ms. The P wave preceded the QRS and was upright in the inferior leads, suggestive of atrial tachycardia. The diagnosis of atrial tachycardia was confirmed after giving intravenous adenosine (0.3 mg/kg), which demonstrated a 2 : 1 AV conduction with-out affecting the atrial rate. The 2 D-echo-cardiography revealed left ventricular dys-function (LVEF 30%); there was no structural heart disease. The chest X-ray showed cardiomegaly with cardiothoracic ratio of 65%.

Fig. 1. A 12-lead ECG showing narrow QRS tachycardia with cycle length of 360 milli second. P waves are upright in the inferior leads suggestive of atrial tachycardia.

In view of age and significant left ventricular dysfunction, calcium channel blockers were not administered. DC cardio-version (up to 4 Joule/kg) was attempted under general anesthesia without success. Intravenous metoprolol was also ineffective. Intravenous amiodarone (5 mg/kg) was given in an infusion for 24 hours followed by oral dose of 5 mg/kg thrice daily for a week. DC cardioversion was reattempted on amiodarone therapy without any success. However, the atrial rate came down to 130 beats/minutes with continued 1:1 AV conduction on amiodarone with a week’s therapy. He was discharged on a maintenance dose of 5 mg/kg/day amiodarone with an intention to follow after a month.

The child presented after 20 days with exacerbation of atrial tachycardia (rate 280/min) and congestive heart failure, which was triggered by a respiratory tract infection. The infection was controlled over the next 10 days, but atrial tachycardia persisted despite anti-arrhythmic therapy. Subsequently the child was subjected to electrophysiological studies (EPS) and radiofrequency ablation (RFA). The procedure was performed under general anesthesia after obtaining written informed consent from the parents. The femoral vein was cannulated (4F and 5F) and a quadripolar diagnostic electrode catheter was placed in the right atrium. The ablation catheter was used for mapping the right and left atrium (through patent foramen ovale) including the pulmonary veins.

The child was in incessant atrial tachycardia during the study. The earliest activation (–23 ms) was obtained in the region of crista terminalis (Fig. 2); the adjacent area was extensively mapped before radio-frequency (RF) energy application. The tachycardia was terminated within 2 second after starting RF energy and the energy was given for 60 seconds duration. The maximum temperature was 65º C with impedance of 110 ohms. No tachycardia could be induced after RF ablation despite vigorous stimulation protocol, which includes continous atrial pacing up to 220 ms cycle length and up to three programmed extra atrial stimuli with minimum duration of 200 ms with and without isoproterenol. There was no procedure related complications. The child remained in sinus rhythm and left ventricular function improved significantly (LVEF 55%) prior to discharge. At 3-month follow up the child was in sinus rhythm with normal LV function (LVEF 70%) and cardiothoracic ratio of 45%.

Fig. 2. Left panel shows intracardiac tracing during radiofrequency ablation. A vertical line is drawn to show the earliest activation (–23 ms from onset of P wave) in the RF distal electrode (arrow). RAP = right atrium proximal; RFD = radiofrequency distal; RFP = radiofrequency proximal. Paper speed is 100 mm/sec. The right panel shows catheter position during RF ablation. LAO = left anterior oblique; AP = antero-posterior; HRA = high right atrium; RFA = radiofreuqency ablation.

Discussion

Supraventricular tachycardia (SVT) is the most common sustained arrhythmia to present in the neonatal age and infancy. The mechanisms underlying SVT are atrial tachycardia (15%), atrioventricular nodal re-entrant tachycardia (5%), and atrioventricular reciprocating tachycardia (80%). Resultants tachycardiomyopathy may be quite difficult to control with conventional therapy(13). A conservative approach may be more prudent in view of the natural history of arrhythmias in infant and children and the unknown long-term effect of catheter ablation on growing hearts(4). In a recent study, Juneja et al.(5) have shown very high success rate of medical therapy in patients with cardio-myopathy secondary to incessant SVT in infants and children. The limitations of conservative approach may be related to (i) low success rate with drugs; (ii) the need for complete control of the tachyarrhythmia that may be more difficult with drugs; and (iii) lack of knowledge regarding the proarrhythmic risk of more effective class Ic drugs such as flecainide and propafenone(6).

Amiodarone is the most potent anti-arrhythmic drug, though it is mostly on a matter of principle that one should not use this as the first medication in children’s rhythm disturbances for long-term usage, even though amiodarone has been considered to be relatively safe in the pediatric population(7). In our patient, amiodarone was selected as the first line of therapy due to its potency and underlying left ventricular dysfunction.

Radiofrequency ablation (RFA) has been recommended as an alternative to medical or surgical treatment in-patients with incessant atrial tachycardia with left ventricular dysfunction(8-9). The limited studies have shown high success rate of RFA(1). However, complications such as perforation of the heart and thromboembolism during the procedure still remain a remote possibility.

In our case medical therapy was given first despite LV dysfunction in view of age of the child and secondly, with a possibility of spontaneous regression in 1-2 years time. However, the medical therapy was ineffective and the child was subjected to ablative therapy because of worsening of symptoms and ventricular dysfunction to which the child responded very well and recovered fully prior to discharge.

Contributors: HCS, AKG and YYL managed the patient, wrote and approved the article. AKG shall act as guarantor.

Funding: None.

Competing interests: None stated.

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