Pediatric Cardiology

, Volume 29, Issue 2, pp 457–462 | Cite as

Accelerated Idioventricular Rhythm in Newborns: A Worrisome But Benign Entity with or without Congenital Heart Disease

Case Report


Broad QRS rhythms (fast and slow) are worrisome findings in newborns. We present five cases with varied clinical presentations found to have broad QRS tachycardias, consistent with idioventricular rhythms. Each patient had an excellent prognosis because the tachycardias resolved, and eventually the patients were in sinus rhythm. None were symptomatic from their arrhythmia. It is important to establish the diagnosis when it occurs to differentiate this benign phenomenon from dangerous ventricular tachycardia.


Accelerated ventricular rhythm Ventricular tachycardia 

Broad QRS tachycardia/rhythm is a worrisome occurrence in early infancy. The differential diagnosis is between supraventricular tachycardia (SVT) with aberrancy and ventricular tachycardia (VT), which is rare early in life. Accelerated idioventricular rhythm (AIVR) is a benign variant of VT with a rate slightly faster than the prevailing sinus rate (SR). Usually, the cardiac morphology is normal, but in some cases ventricular septal defect (VSD) has been reported. We present five cases of AIVR in newborns, pointing out that this rhythm is commonly an innocent and benign variant, and also present management strategies. Of note, two patients had a history of fetal arrhythmia.


Diagnosis criteria of the five cases consisted of the following: three or more consecutive beats with broad QRS and rate faster than the SR, warm-up, isorhythmic dissociation with fusion beats, 1:1 ventriculoatrial (VA) capture, and gradual termination with SR acceleration and/or AIVR deceleration [6]. Congenital heart disease was established by echocardiogram (ECG) in two cases. ECGs were reviewed. Follow-up information was obtained from referring physicians.

Case Reports

Case 1

This term infant presented with a murmur (found to be an uncomplicated VSD on echo) and an arrhythmia. ECG revealed wide QRS tachycardia, an average heart rate (HR) of 160 beats per minute (bpm), 1:1 capture and VA disassociation, left axis, and left bundle branch block (LBBB) pattern with a positive deflection in aVF (Fig. 1A). Holter monitor showed AIVR with frequent runs up to 216 bpm.
Fig. 1

(A) A 12-lead ECG showing broad QRS tachycardia with apparent ventriculoatrial (VA) conduction intermittently in the lead II of the rhythm strip, left bundle branch pattern, and leftward QRS axis. (B) Rhythm strip recorded during administration of an adenosine bolus. Note that in the middle of the second panel VA conduction disappears, manifested by change in P vector, and sinus rhythm appears. (C) Following adenosine, sinus rhythm gives way to accelerated idioventricular rhythm with VA conduction, 1:1

Adenosine bolus led to abrupt VA dissociation, with continuing broad QRS at no rate change (Figs. 2B and 2C). The patient was started on amiodarone, rather than a beta blocker, because the VSD was of significant size and the potential for negative inotropy was a concern, not knowing the stage of pulmonary vascular resistance, which could lead to increased left to right shunt and congestive heart failure.
Fig. 2

A 12-lead ECG showing broad QRS tachycardia and left bundle branch pattern, without recognizable P waves

On amiodarone, the arrhythmia was controlled; however, after discontinuation at 4 months of age, the arrhythmia recurred and the medication was restarted. After 11 months, amiodarone was discontinued and AIVR remained quiescent.

Case 2

At a few hours of age, this full-term infant fell from a caregiver’s arms, striking the floor. Head injury was a concern, and she was transferred to the neonatal intensive care unit, where ECG monitor showed an arrhythmia. Twelve lead ECG showed singleton broad QRS extra systoles with LBBB pattern. Her echo was normal. Computed tomography scan of the brain was negative. At 2.5 weeks of age, she was asymptomatic but ECG showed broad QRS rhythm, HR of 150 bpm, and LBBB pattern. No treatment was started. At 2 months of age, she remained asymptomatic, and ECG was normal. At 1 year of age, her cardiac evaluation including ECG was normal.

Case 3

This full-term infant had fetal irregular HR and episodes of bradycardia. He was born with incessant broad QRS tachycardia with retrograde P waves. Physical exam was within normal limits. Twelve lead ECG demonstrated AIVR with left axis deviation, LBBB pattern, and HR of 154 bpm (Fig. 3A). Two-dimensional ECG was normal. He was started on Inderal. At 3 days, the ECG demonstrated SR and QTc of 524 msec (Fig. 3B). Later follow-up demonstrated SR and long QTc of 492 msec. Family history was noncontributory. Holter at 24 hours of age was abnormal, with monomorphic ventricular beats comprising 16% of the total. The average HR was relatively slow at 108 bpm and the maximum HR was 176 bpm. Inderal has been continued to date and the prevailing/dominant rhythm has been sinus. QTc was noted to be normal in follow-up ECG.
Fig. 3

(A) A 12-lead ECG showing broad QRS tachycardia, left bundle branch pattern, leftward axis, and apparent conduction 1:1 with upright P in V4R and V1. (B) A 12-lead ECG on Inderal with return to sinus rhythm and prolonged QTc

Case 4

This 2-kg premature infant was found to have broad QRS during routine ECG monitoring. ECG showed broad QRS with LBBB and suggested VA conduction, documented on esophageal ECG (Fig. 4). He had no cardiorespiratory symptoms, and by 1 week the arrhythmia resolved. SR returned without further AIVR arrhythmia.
Fig. 4

(A) A 12-lead ECG showing broad QRS tachycardia. (B) Left bundle branch pattern, leftward QRS axis, and apparent ventriculoatrial (VA) conduction 1:1 with upright P in V2. (B) This figure clearly identifies VA conduction. (C) Simultaneous surface and esophageal ECG showing VA conduction 1:1 (top 2) and spontaneous return to sinus rhythm with 1:1 AV conduction, corroborated by timing and polarity of the atrial electrogram on the esophageal lead

Case 5

This 2.8-kg infant, who presented with fetal tachycardia at 29 weeks of gestation with HR in the 180s, was treated with digoxin and procainimide without response but then responded to fleicainide. Assessment of the rhythm at 37 weeks demonstrated slow tachycardia with 1:1 atrioventricular (AV) conduction at rates of 165–175 bpm. Labor was induced at 37 weeks due to irregular fetal heart tones, with rates from 140 to 200 bpm. At birth, the infant presented with arrhythmia, and physical exam was otherwise unremarkable. ECG soon after birth demonstrated AIVR, with an HR of 170–180 bpm (Fig. 5). Two-dimensional echocardiographic evaluation was normal. He was started on propanolol and AIVR was less frequent. He was discharged home on propanolol. Holter at 2 months of age was normal.
Fig. 5

A 12-lead ECG with broad QRS tachycardia with left bundle branch pattern pattern, variable ventriculoatrial conduction, and occasional sinus captures


Five newborns were diagnosed with AIVR. One patient had a VSD and four patients had isolated AIVR with structurally normal hearts. Cases 3 and 5 had fetal tachycardia. Case 3 required no therapy during fetal life but was born with incessant tachycardia and was treated with propanolol. The fetal events were thought to be AIVR as per electrophysiologic evaluation in this case. Case 5 was treated in utero for slow SVT with 1:1 atrioventricular conduction, and AIVR was diagnosed at birth. These two cases most likely had AIVR in utero and continued to have it after birth. Other cases of fetal AIVR have been cited [1, 4].Ages at presentation varied from prenatal to 2 weeks, and there were two female and three male patients.

AIVR rates ranged from 150 to 180 bpm within 10% of the preceding SR. The longest recorded run was 216 bpm in case 1. QRS configuration was of LBBB, with AV dissociation consistent with right ventricular origin. Adenosine was helpful in diagnosing the rhythm in case 1, who was successfully treated with amiodarone. Case 3 was treated with propanolol, and once AIVR was treated, long QT was found but it normalized on follow-up. Case 5 was treated with digoxin and flecainide for prolonged fetal tachycardia. Cases 2 and 4 received no drugs and the arrhythmia resolved spontaneously. Although treating such a rhythm is usually not necessary, we elected to treat case 1 because of her VSD, which was believed to have the potential to develop congestive heart failure, and we decided to be proactive in restoring AV synchrony. Inderal was continued in case 3.

Reviewing the literature, we found at least 31 patients reported, with ages of presentation ranging from 1 day to 6 months. Four patients had a VSD and 1 had Ebstein’s, VSD, and pulmonary atresia (Table 1). One newborn had AIVR associated with myocarditis [13]. Another case showed association with maternal consumption of cocaine [5]. Eleven patients were treated, and 1 patient showed recurrence. Previous findings indicate some association with VSD [7, 8, 9] and we found one case.
Table 1

Patients with AIVR reported in the literature


Age at presentation

Age at resolution



Associated events


Bisset et al. [2]

9 hours

6 months

Lidocaine and propanolol


History of irregular heart rate



4 hours

24 hours






8 hours

10 hours





Scagliotti et al. [11]

7 patients, 0–48 hours

2–14 days

Lidocaine and propanolol



Yes, 1

Yokota and Wada [13]

0 hours

2 months



Elevated CK, LDH


Geggel et al. [5]

0 hours

4 days





Nakagawa et al. [9]

6 hours

30 days



VSD closed at 84 days



7 days

30 days






7 days

42 days


VSD pm

VSD still present at follow-up


Kuratobi et al. [7]

1 hour

45 days






10 hours

18 days





Van Hare and Stanger [12]

12 patients, <1 month


5 of 12 treated




Fouron [4]

30 weeks


Healthy pregnancy


Anatolliotaki et al. [1]


4 months





ASD, atrial septal defect; CK, creatine kinase; LDH, lactate dehydrogenase; PA, pulmonary atresia; VSD, ventricular septal defect

Presentation is common during the first day of life [2, 7, 9, 10, 11, 12, 13]. One case of AIVR in fetal life was reported by Fouron et al. [4], and a second case was reported by Anatolliotaki et al. [1].

AIVR is commonly seen in adults postinfarction; in myocarditis, digitalis toxicity, and right ventricular dysplasia; postoperatively; and s/p ablation [10]. In children, it is seen predominantly in normal hearts and with congenital heart diseases, such as tetralogy of Fallot s/p repair, s/p Fontan, and VSD with subAs, and in transplanted patients [1, 8]. Although this rhythm is well tolerated, it is not known if it will accelerate to a dangerous degree; hence, pediatric cardiologists feel compelled to treat it, which may not be necessary.

Several medications have been tried in the past, including mexiletine, propanolol, verapamil, digoxin, and quinidine. Verapamil was the only medication demonstrated to work in 1 patient [10]. All patients do not require treatment.

In reviewing the literature, it seems that no comments have been made regarding the site of origin of the rhythm (right ventricle) as the ECGs show LBBB pattern. The mechanism responsible for AIVR is unknown, but it is generally attributed to an enhanced automatic focus, most likely in the right ventricular outflow tract; this focus competes with the sinus pacemaker [6]. AIVR is easily converted to SR by atrial pacing at a faster rate, but it can neither be induced nor interrupted by ventricular pacing or programmed stimulation of the right ventricle [3]. These rhythms seem to occur in the right ventricle and may be the marker for future ARVD, especially when the QRS indicates a right ventricular infundibular origin [3]. Further follow-up of additional patients with AIVR may be useful to determine if this is the case; however, the current experience supports a benign and good prognosis.



We thank Dr. SuChiung Chen, Cardinal Glennon’s Children Hospital, Saint Louis University.


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Copyright information

© Springer Science+Business Media, LLC 2007

Authors and Affiliations

  1. 1.The Heart Institute for Children North and South Campuses— Lutheran General HospitalPark RidgeUSA
  2. 2.Hope Children’s HospitalOak LawnUSA
  3. 3.Saint Louis University, Cardinal Glennon Children’s Hospital, Pediatric Cardiology R A515St. LouisUSA

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