Step 7 of 8

Arrhythmias

Compromising arrhythmias are very common and may be an intrinsic feature of certain defects: e.g. some children have two AV nodes, AV block is common in the AV canal, and WPW syndrome in Ebstein’s anomaly. It may also be linked to surgery, e.g. AV block after perimembranous VSD correction, supraventricular tachyarrhythmias after ASD correction or Fontan procedure. Since the compliance of children’s heart is low, cardiac output is highly dependent on heart rate. The minimum tolerable heart rate is 70 bpm for neonates (up to 28 days old), 60 bpm for children aged < 2 years and 50 bpm in children aged up to 10 years. In contrast, heart rates > 170 bpm are associated with low ventricular filling pressure and decreased cardiac output. Arrhythmias occurring in children during surgery must be treated aggressively from the outset, since they have a strong tendency to deteriorate into malignant arrhythmias.

The incidence of non-surgery-related intraoperative cardiac arrest is almost 10 times higher amongst those suffering from congenital heart disease (21:10,000) than in children without heart disease (3:10,000) [7,8]. This incidence is 6 times higher in cardiac surgery (127:10,000) than in non-cardiac surgery (2.9:10,000) because the risk is linked to surgery itself [4]. The incidence attributable to anaesthesia is only 1-2:10,000.
 
Atrial tachyarrhythmias

Atrial tachycardia is characterised by a heart rate of 180-300 bpm and a narrow QRS (< 0.08 seconds in children < 6 months and < 0.10 seconds over 6 months). In addition to fibrillation (AF) and atrial flutter, some arrhythmias are particularly common in the postoperative recovery period of an open-heart procedure [1].
 
  • Junctional ectopic tachycardia (JET) is observed exclusively in children after cardiac surgery. It is due to an automatic discharge from the AV node or proximal bundle of His, with a ventricular rate that is higher than the atrial rate (> 150 bpm). It presents as fixed narrow-complex tachycardia. Although JET is highly resistant to traditional antiarrhythmic treatments (adenosine, cardioversion), it generally responds fairly well to hypothermia (local cold saline solution, hypothermia at 34°C) and to overdrive pacing if the heart rate allows for it. It may be sensitive to amiodarone, procainamide and magnesium.
  • Ectopic atrial tachycardia is characterized by a single non-sinus focus (the shape of the P wave varies according to its location) and an above-average heart rate for the patient’s age. Amiodarone and fast pacing generally curb it.
  • Multifocal atrial tachycardia is identified by a chaotic atrial rhythm, P waves of constantly changing morphology, and irregular PP, PR and RR intervals. It responds to amiodarone and digoxin.
  • Atrial tachyarrhythmias are common in children who have distended atria or have undergone atriotomies.
These supraventricular tachycardias (particularly JET) are very resistant to the usual treatments. Vagal manoeuvres are effective if the sinus node is still in control of the atrial rhythm, but this is rarely the case. The pharmacological treatment administered to children includes generally several steps [2].
 
  • Amiodarone (Cordarone® 5 mg/kg IV short infusion, followed by an infusion of 5-15 mcg/kg/min over 24 hr, maximum 1.2 g/24 hr) prolongs repolarisation and the refractory period for atrial, nodal and ventricular tissue; it has little negative inotropic effect. It is indicated in atrial and ventricular tachyarrhythmias. It is particularly useful for controlling JET.
  • Adenosine (0.05 mg/kg IV bolus dose, to be repeated by doubling the dose up to a maximum of 0.5 mg/kg) is the primary choice for tachyarrhythmias involving the AV node, but is ineffective for AF, flutter or JET. It is contraindicated in case of bronchospasm and may cause a sinus arrest in a denervated, transplanted heart, but has no negative inotropic effect in case of ventricular failure.
  • Esmolol (Brevibloc® 0.5 mg/kg IV, infusion 25-300 mcg/kg/min) is a short-acting betablocker (9 minutes) which slows sinoatrial and atrioventricular conduction.
  • Procainamide (0.4 mg/kg/min IV for 25 minutes, infusion 20-80 mcg/kg/min, maximum 2g/24hr) slows down atrial conduction and prolongs QRS and QT.
  • Magnesium for a serum level of 1.5 - 2.5 mM/L.
  • Lidocaine (Xylocaine® IV) may be useful in some resistant cases. It is used as an IB antiarrhythmic agent, affecting ventricular depolarisation and Purkinje fibre automaticity. It is sometimes necessary to repeat administration of this fast-acting, quickly metabolized drug (1-1.5 mg/kg IV repeated every 2-5 minutes), or administer it in a continuous infusion (20-50 mcg/kg/min).
  • Synchronised cardioversion 0.5-1.0 J/kg.
 
Ventricular tachyarrhythmias

Ventricular tachycardia (wide QRS) is always dangerous, for three reasons.
 
  • It occurs in the event of an abnormal myocardium, ventriculotomy scar, and often dilatation or ischemia;
  • It easily degenerates into ventricular fibrillation;
  • The fast ventricular rate prevents the ventricles from filling properly.
It can occur in all diseases, but is especially common in corrected Fallot patients who develop respiratory failure and RV dilatation [5]. The treatment is cardioversion (0.5 - 1.0 J/kg), lidocaine (1 mg/kg IV) and amiodarone (5 mg/kg in 1 hr).

Bradycardia

Sinus bradycardia is not uncommon after cannulation of the superior vena cava or after procedures involving long sutures in the atria, such as Mustard, Senning or Fontan operations. AV blocks are common after correction of membranous VSD or AV canal defects or after tricuspid surgery. These blocks are often temporary and last only a few days. Bundle branch blocks are common in children who have developed ventricular hypertrophy. Implanted pace-makers are indicated at a heart rate of < 60 bpm for children aged < 2 years and < 50 bpm for children aged up to 10 years [2]. In the post-operative phase, at least 7 days are allowed before fitting a permanent pacemaker, since many blocks resolve spontaneously.

Pacemaker

Although pacemakers for children and adults use the same technology and operate in the same way (see Chapter 20 Pacemakers), children’s pacemakers exhibit some distinctive features [6].
 
  • Endocavitary pacemaker leads are too large and do not stretch with growth. On the other hand, endovenous placement of electrodes is often impossible due to anatomical changes linked to the malformation. Therefore, epicardial electrodes are implanted by mini-thoracotomy or subxiphoid incision under general anaesthesia. The same applies to resynchronization therapy in case of ventricular dysfunction. The device casing is implanted subcutaneously in the abdominal area.
  • Cracked leads are the most common complication. The lower the age of implantation, the shorter their lifespan. The battery life expectancy is also shorter, because it is dependent on the baseline heart rate, which is higher in children.
  • Rate modulation is routinely used. Any acceleration requirements are detected by a motion sensor (accelerometer) or breathing sensor (thoracic impedance).
Indications for permanent pacemakers for children are more restrictive than for adults [3.6].
 
  • Congenital or postoperative complete AV block (3rd degree) (continuing beyond day 7 post-op) if the rate is < 70 bpm.
  • Sinus bradycardia (< 40 bpm or pauses > 3 secs) in congenital heart disease.
  • Atrial reentrant tachycardia in congenital heart disease.
Procedures on the atria (Mustard, Senning, Fontan, etc.) and adjacent to the AV node (VSD, Tetralogy of Fallot, L-TGA corrections) are most frequently involved.

Children with pacemakers are managed in a similar way to adults: asynchronous programming before the procedure (preferable to using a magnet during the surgery), use of bipolar diathermy, remote distance of the cautery pad from the device case, placement of defibrillation patches, monitoring of peripheral circulation (SpO2, arterial catheter). Substances which inhibit sinus function such as dexmedetomidine and remifentanil should be avoided. The stimulus threshold is raised by hyperkalaemia, alkalosis, acidosis, hypothermia, and hyperglycaemia.

 
 
Arrhythmias
Atrial tachyarrhythmias (HR > 180 bpm, end QRS, regular rhythm)
    - JET (junctional ectopic tachycardia), after open-heart surgery, very resistant
    - Multifocal, or ectopic atrial tachycardia, AF, flutter
    - Amiodarone (5 mg/kg short IV), adenosine (0.05 mg/kg), esmolol (0.5 mg/kg), procainamide (max 10 mg/kg IV in 25 mins), synchronised
      cardioversion 0.5 - 1.0 J/kg

Ventricular tachycardia (wide QRS, risk of fibrillation)
    - Cardioversion (0.5 - 1.0 J/kg), lidocaine (1 mg/kg IV), amiodarone (5 mg/kg in 1 hr)

Bradycardia
    - Pacemaker if HR < 70 bpm for children aged < 2 years and < 50 bpm for children aged < 10 years; isoprenaline (0.05-0.5 mcg/kg/min)
 

© BETTEX D, BOEGLI Y, CHASSOT PG, June 2008, last update May 2018



References
  1. BOHN D. Anomalies of the pulmonary valve and pulmonary circulation. In: LAKE CL. Pediatric Cardiac Anesthesia, 2nd edition, Appleton & Lange, Norwalk, 1993, 295-323
  2. BOTERO M, DAVIES LK. Diagnosis and management of arrhytmias in children after cardiac surgery. Semin Cardiothorac Vasc Anesth 2001 ; 5 : 122-33
  3. BRIGNOLE M, AURICCHIO A, BARON-ESQUIVIAS G, et al. 2013 ESC Guidelines on cardiac pacing and cardiac resynchronization therapy. Europace 2013; 15:1070-118
  4. FLICK RP, SPRUNG J, HARRISON TE, et al. Perioperative cardiac arrests in children between 1988 and 2005 at a tertiary referral center. Anesthesiology 2007; 106:226-37
  5. GATZOULIS MA, BALAJI S, WEBBER SA, et al. Risk factors for arrhythmia and sudden cardiac death late after repair of tetralogy of Fallot: a multicentre study. Lancet 2000; 356:975-81
  6. NAVARATNAM M, DUBIN A. Pediatric pacemakers and ICDs: how to optomize perioperative care. Pediatr Anesth 2011; 21:512-21
  7. ODEGARD KC, DiNARDO JA, KUSSMAN BD, et al. The frequency of anesthesia-related cardiac arrests in patients with congenital heart disease undergoing cardiac surgery. Anesth Analg 2007 ; 106 :335-43approach to pulmonary vascular disease. Circulation 1978; 58:1007-22
  8. RAMAMOORTHY C, HABERKERN CM, BHANANKER SM, et al. Anesthesia-related cardiac arrest in children with heart disease : data from the Pediatric Peiroperative Cardiac Arrest (POCA) Registry. Anesth Analg 2010 ; 110 :1376-82
 
14. Anesthesia for paediatric heart surgery