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Learning objectives
Recognise important ECG characteristics of common arrhythmias in adults with congenital heart disease (CHD).
Identify salient differences in clinical presentation of acute arrhythmia in this group.
Develop a management approach to the patient with CHD with acute arrhythmia.
Introduction
Before the advent of central shunts and cardiopulmonary bypass, the natural history studies characterising mortality in those with complex congenital heart disease (CHD) described dismal long-term outcome statistics with few reaching adulthood.1 Subsequent to these innovations—and coupled with outstanding advances in surgical techniques and cardiological care—the practising community has witnessed the emergence of a new population of survivors. Mortality has dropped profoundly; yet with the improved longevity, most of the patients with CHD with moderate/severely complex lesions (table 1) remain at high risk for recurrent haemodynamic issues.2 Yet, the most frequent cause for hospitalisation is arrhythmia, and sudden cardiac death and heart failure remain the primary causes for mortality.3–8 It is more the rule than the exception that the first presentation of these rhythm disturbances is acute as opposed to chronic. It is therefore crucial that the clinician recognise the important differences in managing this group of patients compared with those with acquired heart disease or a normal heart.
Common congenital heart disease lesions, their complexity and associated arrhythmias
Even the more ‘benign’ atrial arrhythmias, which frequently are well tolerated in the normal heart, can result in marked haemodynamic compromise for the patient with CHD and limited cardiac reserve. Atrial arrhythmias alone are associated with an almost 50% increase in mortality compared with those patients without atrial arrhythmias4 and are by far the most common type of arrhythmia and cause of morbidity.9 Ventricular arrhythmias are up to 100-fold more common in patients with CHD than in age-matched controls, but are lesion specific.10 Those repairs which entail ventricular incisions/patches or significant systemic ventricular dysfunction predominate.7
Typically, secondary to prior repairs, the adult with CHD is also at an increased risk of acute bradycardic events compared with the unoperated heart.7 11–15 Although these events are a less common cause of sudden death, the acute management can be particularly challenging in the context of venous occlusion and in those with intracardiac shunting.
This review is aimed at providing a very practical approach to managing these complex patients highlighting the salient differences in physiology and management. The indications for permanent pacing, defibrillators, conversion surgery and long-term anticoagulation are outside of the scope of this article.
ECGs and clinical presentation
In any adult with CHD presenting emergently with an acute arrhythmia, the importance of a thorough clinical history and grasp of the patient’s underlying anatomy is crucial and cannot be more emphasised. As soon as haemodynamic stability has been ensured, this background should be carefully explored, given that it will often dictate the long-term management approach for arrhythmia, but is also cardinal for the patient who may need urgent temporary pacing or cardioversion (see Cardioversion and Placement of Defibrillation Pads sections). Acute bradycardic events can present as dyspnoea, effort intolerance, presyncope or syncope. The ECG of sinus arrest or complete heart block should not present any difficulty from a diagnostic point of view, but the acute management can be especially difficult. Accessing the heart and decisions regarding anticoagulation in those with intracardiac shunting are complex and are discussed below in Management section.
Ventricular tachycardia (VT) is perhaps the most important tachyarrhythmia to recognise in the acute setting; yet, it does not commonly present as a sustained wide complex rhythm. More frequently, this malignant arrhythmia will present with palpitations, near-syncope, syncope or even resuscitated out-of-hospital cardiac arrest. Although the vast majority of wide complex tachycardia in patients with adult congenital heart disease (ACHD) represents atrial arrhythmias with bundle branch block, all haemodynamically unstable presentations should be addressed with prompt cardioversion. Elucidation of the underlying aetiology of the wide complex rhythm can then be determined later at an electrophysiological study, and this approach has been well validated in this group.16 17 Given that most ventricular arrhythmia in CHD is re-entrant in nature, patients with a history of ventricular scars are at higher risk for VT.18–20 On a mechanistic level, the incisional scar and/or patch can form a discrete boundary that allows for the propagation of an electrical wavefront around the obstacle that prevents it from extinguishing itself (figure 1). It is important to remember that the presence of any scar within the ventricle is likely to also influence the QRS morphology in normal sinus rhythm or any other conducted arrhythmia. It typically manifests on the ECG as a delayed/fragmented QRS or an unusual bundle branch block pattern (figure 2). This is important as one tries to decipher the nature of a wide complex tachycardia in the patient with CHD. The presence of atrioventricular (AV) dissociation is a cardinal feature that one should look for on the ECG to help with the diagnosis of VT. As markers of AV dissociation, fusion and captured beats should also be looked for, but these only occur in a very small percentage of patients. The fragmented abnormal QRS found commonly in this patient group is very often misinterpreted as VT, in patients with a rapid supraventricular rhythm such as atrial flutter. In addition, given the potential for abnormal septal activation and scar, aberrancy can also result in quite bizarre QRS morphologies (figure 3). In the acute management of this clinical scenario, one should be guided by the patient’s haemodynamics and symptoms, and if there is any significant hypotension, one should move ahead with electrical cardioversion as a priority. The stable patient with a wide complex rhythm can be treated like any other patient with acquired heart disease or a normal heart. Prior ECGs are especially useful in the setting so that one can compare the wide complex tachycardia with the QRS morphology in sinus rhythm. If there is no discrepancy one can make the case that this is an supraventricular tachycardia conducting with the patient’s typical bundle branch block pattern.
Depiction of the transventricular operative approach for complete repair of tetralogy of Fallot. From an arrhythmia point of view, each scar can form a boundary for re-entrant ventricular tachycardia, creating isthmuses between the scars and valves.
An ECG from a patient with a double outlet right ventricle and prior Rastelli repair demonstrates a quite bizarre QRS morphology. The patient does have a right bundle branch block pattern, but the unusual QRS morphology with prolongation and fragmentation (signifying myocardial conduction delay) is derived primarily from ventricular scar/fibrosis.
(A) An ECG from a patient with d-transposition of the great arteries and prior Mustard repair. Diagnosed presumptively as ventricular tachycardia (VT), but confirmed to be an atrial tachycardia with an unusual pattern of right bundle branch block aberrancy. With such abnormal myocardial conduction, very unusual bundle branch block type patterns can be seen and should be treated as VT unless the clinician is absolutely sure this is a bundle branch block pattern. (B) An ECG taken from the same patient with d-transposition (figure 7A), who has atrial flutter/re-entrant atrial tachycardia. The atrial tachycardia P waves are now seen more easily (specifically in lead II), yet the slow cycle length is allowing every other P wave to be partially buried in the ST segment and not readily seen in all leads.
The presentation of atrial arrhythmias in CHD can also be different, and this is based primarily on the cycle length of the atrial flutter. Atrial arrhythmias are also more commonly re-entrant and similar to the re-entrant VT from a mechanistic point of view. They are more common in patients with prior atrial surgery/atriotomy and scars which form boundaries that allow perpetuation of the re-entrant circuit (figure 4). The commonly abnormal atrial tissue can have abnormal conduction velocity through the diseased areas, and with concomitant atrial dilatation and larger circuits, the atrial flutter (often labelled intra-atrial re-entrant tachycardia) is frequently slower. The slower atrial flutter allows for better recovery of AV node refractoriness and hence paradoxically conducts to the ventricle in a more rapid manner. The slower atrial rate frequently allows for 2:1 conduction and the second P wave is easy to miss as it tends to fall on the QRS or T wave (figure 3A). Frequently, this results in the arrhythmia being misdiagnosed as sinus tachycardia, and clinicians should be aware that patients with CHD should not exhibit rapid sinus rates unless this is driven by a haemodynamic or metabolic stressor. Review of the patient’s ambulatory recordings can sometimes expose this phenomenon: AV node conduction is facilitated by exercise and higher circulating catecholamine levels, resulting in an abruptly step up from a 2:1 ratio to a 1:1 ratio. An exercise stress test can also help with this diagnosis, as can vagal manoeuvres or even adenosine: as they can reveal the underlying flutter waves.
Illustration of two of the potential circuits for intra-atrial re-entrant tachycardia. The scars/patches act as discrete boundaries, providing a fundamental component for the initiation and maintenance of re-entrant atrial arrhythmia. Similar to typical atrial flutter in the normal heart, the most common atrial arrhythmia in this group also relies on the isthmus of atrial tissue between the subpulmonic atrioventricular valve and the IVC. CS, coronary sinus; IVC, inferior vena cava; SVC, superior vena cava; TV, tricupsid value.
Specific arrhythmias
Acute bradycardia
Certain syndromes by virtue of the location of the defect are inherently associated with vulnerable conduction systems, such as the sinus node (20% of patients with sinus venosus atrial septal defect (ASD)) or AV node (around a third of those with congenitally corrected transposition).21 22 Sinus node dysfunction is also commonly seen as a late complication of the Mustard or Senning operation—occurring in up to half of this group.23 Frequently though, repeated atriotomies or atrial repairs affect conduction through the development of fibrous tissue in and around the conduction system, and sinus arrest or heart block can be seen in any syndrome.24
Ventricular tachycardia
Patients with tetralogy of Fallot (ToF), aortic stenosis, left ventricular outflow tract obstruction and transposition of the great arteries are most studied in this setting and appear to be at highest risk for VT (figure 5).1 The incidence of sustained VT in ToF may be as high as 15% of patients, with a risk of sudden death of around 0.2% per annum.10 27 For this particular anomaly, several important risk factors have been identified, yet no single risk factor is highly specific, and each patient requires an individualised approach.25 28 29 The clinician should be aware that those patients with ToF who have left ventricular systolic or diastolic dysfunction,27 30 increased QRS duration (>180 ms),31 history of older age at which the ToF was initially repaired,31 significant pulmonary regurgitation,25 prior palliative shunts31 and ventriculotomies32 pose the highest risk of developing VT, and many of these also serve important criteria for risk stratification when considering primary prevention implantable cardioverter defibrillator (ICD) implantation.33 Specific risk factors have not been elucidated for other types of CDH lesions; yet, for all patients who did not present with a reversible cause for their out-of-hospital cardiac arrest, secondary prevention ICD implantation is indicated.15 Primary prevention ICD implantation in the less common syndromes is tailored to the individual and any patient presenting with syncope or a sustained wide complex arrhythmia should be referred to a specialist centre and potentially considered for electrophysiological study.15 33
An ECG recorded from a patient in incessant ventricular tachycardia (VT). The clinical background included tetralogy of Fallot, which had been repaired as an infant and re-repaired as an adult, involving closure of a ventricular septal defect, right ventricular outflow tract reconstruction and pulmonary valve replacement. There is no obvious AV dissociation to confirm that this is VT, and the two are innocent morphology being positive in the inferior leads (II, III, aVF) suggest an origin that is an area and high; the negative complexes in lead, a VR and ADL, suggest that the origin is within the outflow tract; yet, the right bundle branch block pattern suggest that the exit of the VT is on the left side. The tachycardia was in fact ablated successfully in the left ventricular outflow tract below the aortic valve.
Atrial arrhythmias
The most common atrial arrhythmias in adults with CHD are intra-atrial re-entrant tachycardias (IART).34 These scar-related/incisional atrial flutters can present with very rapid ventricular rates and can be highly symptomatic. Any patient with atrial dilatation or any prior history of an atriotomy is at higher risk for any type of atrial arrhythmia, with the overall lifetime incidence approaching 40% by the age of 50 years.4 This is considerably higher in certain forms of CHD where more scar and atrial dilatation predominates, such as Ebstein’s anomaly, atrial-switch procedures for d-transposition and the classic right atrium to pulmonary artery Fontan.4 35Patients with tetralogy of Fallot also commonly present with these arrhythmias.27Patients with left-sided cardiac disease, such as that involving the mitral valve or left ventricular outflow tract more commonly develop atrial fibrillation as the index arrhythmia. Included in this group are those with significant left ventricular filling abnormalities, such as the hypertrophic cardiomyopathic patient. The pathophysiological mechanism here is not scar-related re-entry, but presumably atrial and pulmonary vein substrate changes secondary to the high left atrial pressure and dilatation.
Pre-excitation
Accessory pathways are more common in certain congenital syndromes such as Ebstein’s anomaly (occurring in up to a third of patients in some series), and even though multiple pathways may be present, the same triad of arrhythmias prevail. These encompass orthodromic reciprocating tachycardia (conduction down the AV node and retrograde up the accessory pathway), antidromic reciprocating tachycardia (conduction down the accessory pathway and retrograde via the AV node) and atrial fibrillation.
Acute management of symptomatic bradycardia
The patient with CHD with long pauses and near-syncope/syncope who is unable to maintain their blood pressure should undergo sedation and transcutaneous pacing. More frequently in CHD, the level of the AV block is below the AV node, and atropine is therefore ineffective, or can potentially even worsen the degree of AV block. Consistent with Advanced Cardiac Life Support guidelines, epinephrine and dopamine should be considered initially, but if ineffective transcutaneous method adopted. This serves as a temporising strategy only necessary until such time as the patient can undergo placement of a temporary transvenous lead. As alluded to above, access to the heart can be a major limitation, and review of the surgical records or CT/MR/catheterisation angiograms to understand the access to the heart is imperative. Any patient with a bidirectional cavopulmonary anastomosis or Glenn procedure usually has no direct route to the heart from the superior vena cava (SVC) and the veins of the upper extremities—with the SVC draining directly into the lungs, bypassing the right atrium. The standard internal jugular or subclavian approach is therefore not possible and a femoral approach is necessary. Those patients with an interrupted inferior vena cava or more commonly occluded femoral veins (from prior venous access as a child) frequently have no access from an inferior or peripheral approach, and review of prior cardiac catheterisation films is vital. Patients with non-fenestrated extracardiac Fontan’s may also have no transvenous access for atrial or ventricular pacing. Yet, those with lateral tunnel or atriopulmonary connection Fontan connections can at times be paced from portions of the remaining viable atrial tissue.
As important, systemic thromboembolism from pacing leads is a major concern in patients with intracardiac shunting. Thrombus quickly develops on the intravascular pacing leads and can embolise into the systemic circulation and result in stroke or other peripheral embolic phenomena if any right to left shunt is present.36 37 Eisenmenger physiology/large ventricular septal defect (VSD)/ASD or even the Mustard/Senning patient with a baffle leak are especially at risk, and a temporary pacing lead is deemed life-saving in the acute setting, the patient should be heparinised and anticoagulated as soon as sheaths are in situ to minimise this risk. The patient should then be referred for permanent epicardial lead placement.
It is also critical for the operator to realise that in the patient with a prior atrial-switch procedure (Mustard or Senning), the SVC baffle is commonly stenosed or may even be occluded.38 39 Emergency or urgent placement of a temporary lead via this route may therefore not be possible, and an alternative approach (typically femoral) may be necessary until a solution for a permanent lead can be devised.
Acute management of tachyarrhythmias
Cardioversion
For any patient presenting with tachycardia and associated haemodynamic compromise, synchronised direct current (DC) cardioversion should be performed without delay (see algorithm—figure 6). In the elective patient, who has developed an acute tachyarrhythmia yet emergency cardioversion/defibrillation is not necessary, appropriate anticoagulation and transoesophageal echocardiography guidance should be pursued in a controlled setting (as discussed below). If performed appropriately, DC cardioversion can be safely performed in adults with CHD, without higher incidence of cardioversion or postcardioversion complications40 41
The algorithm, which is focused specifically on tachyarrhythmia management for patients with congenital heart disease. The basic premise is to avoid treating a sinus tachycardia which is appropriate for the patient’s haemodynamic situation. Any haemodynamically compromising arrhythmia should undergo cardioversion. Wide QRS arrhythmias should be treated as if they are ventricular tachycardia, although SVT with aberrancy is not uncommon, and adenosine can reveal or terminate this. The most common arrhythmia is IART and typically can be rate controlled acutely, although this may require intravenous amiodarone. IART, intra-atrial re-entrant tachycardia; IV, intravenous; DC, direct current.
Atrial antitachycardia pacing
Because of the slower atrial cycle lengths, atrial flutter/IART is especially difficult to rate control with intravenous AV nodal blocking agents and given that it is such a fixed circuit, it is also unlikely to break spontaneously. This mechanism of atrial arrhythmia (which is distinctly different from atrial fibrillation) allows for interruption of the circuit and termination using atrial antitachycardia pacing. A prerequisite is that the patient has a permanent pacemaker with an atrial lead in situ. Some devices have this capability inherent in the software of the device, but most standard pacing systems can deliver sequences of rapid bursts or ramps which can frequently terminate re-entrant atrial tachycardias at the bedside via the device programmer and thereby avoid the need for sedation and cardioversion.42 43 However, the same precautions regarding anticoagulation, transoesophageal echo and thromboembolic risk prevail.
Anticoagulation differences
If cardioversion is necessary because of haemodynamic compromise, there should be no delay. For more elective cases, standard prevention of thromboembolism should be undertaken with anticoagulation for at least 3 weeks before and 4 weeks after cardioversion for an arrhythmia of unknown or >48 hours’ duration. If the clinician is concerned that this delay will result in a progressive clinical decline, cardioversion with transoesophageal guidance should be undertaken. During the first 48 hours, the need for anticoagulation should be based on the patient’s risk of thromboembolism.15 There is a valid concern that the complex patient with CHD presents a more thrombogenic milieu (figure 7)44 and it is probably safest to obtain a transoesophageal echo in all of the higher risk more complex patient if possible.15 45 Specifically, if elective cardioversion is chosen for patients with a classical Fontan, transoesophageal echocardiography is sensible in this higher risk group, regardless of their anticoagulation history.15 Frequently subjected to very sluggish flow, clot may be present within the conduit (see figure 8), despite the use of chronic anticoagulation.44 45 Cardioversion in this setting can therefore potentially have lethal complications as a large Fontan thrombus can dislodge and embolise to the pulmonary vasculature.
A postmortem specimen displaying evidence of old thrombus adherent to an atrial septal defect patch and highlighting why anticoagulation of this patient group is specifically different from the unrepaired heart.
A postmortem specimen of a single ventricle/classic Fontan displaying layered mural thrombus with the Fontan itself. This image serves to alert the clinician as to the risks of cardioversion in this patient group, which can potentially result in fatal thromboembolic complications.
Placement of defibrillation pads
Also important for the clinician to remember is that the patient with CHD does not necessarily have laevocardia. Therefore, placement of the defibrillation pads should be guided by whether mesocardia or dextrocardia is present. Typically, the most ideal vector is found with anterior–posterior placement of the pads which ‘sandwich’ the heart.
Pharmacological cardioversion
The use of drug therapy in the acute setting is reserved for the haemodynamically stable patient and varies with each arrhythmia. For the acute narrow complex arrhythmia, adenosine should be administered rapidly in escalating doses until AV block is seen or the arrhythmia terminates. Although 6 mg as a single dose may be successful, higher doses are often needed in larger patients and especially those with sluggish Fontan circulation through the lungs. The goal of this blockade is either termination of the tachycardia or exposition of the background atrial tachyarrhythmia. Pharmacological cardioversion with procainamide or ibutilide can be used for the patients with pre-excited atrial fibrillation, who are haemodynamically stable.46 It is crucial to also remember that adenosine and amiodarone are specifically contraindicated in this scenario, as it may result in atrial fibrillation conducting preferentially down the accessory pathway and translating into ventricular fibrillation. Ibutilide for atrial arrhythmia termination can also be considered in the monitored setting. It is safest that this drug be administered to the patient who has no history of QT prolongation, and pretreatment with magnesium appears to reduce the risk of torsades de pointes (typically occurring in around 3% of cases).46 47
Arrhythmia management following cardioversion
Although a detailed review of chronic management is beyond the scope of this review, the clinician should be aware of some fundamental differences when discharging these patients from hospital. Unlike the patient with a normal heart, adults with CHD commonly also have ventricular scar or ventricular dysfunction. Class Ic drugs administered in this context are more likely to result in re-entrant VT and are viewed as potentially proarrhythmic48 and should be avoided (Class III).15 The class III potassium channel blocking agents (such as sotalol and dofetilide) present a safer alternate in this group and have been studied in several ACHD cohorts.49–51 Studied specifically in this patient group and also extrapolated from patients with acquired heart disease, dofetilide can be considered as first-line treatment15 given that it lacks any depressant effect on the sinus and AV nodes (elements which are commonly abnormal in the patient with ACHD).52–55 Amiodarone can be considered as a first-line or second-line agent for atrial or ventricular arrhythmia prophylaxis, depending on the degree of ventricular dysfunction and the presence of comorbidities,15while recognising the potential for iodine-related toxicity. In the younger patient, ablation is frequently considered early, so as to avoid long-term pharmacological therapy (Class IIa).15
Acute management of ventricular arrhythmia
Given the bizarre QRS morphologies often seen in CHD, and if the underlying mechanism for a wide complex tachycardia cannot be discerned, it is the authors’ opinion that it would be prudent to err on the side of caution and treat these wide complex tachycardias as VT. For patients with recurrent ventricular arrhythmias despite cardioversion or defibrillation, adjunctive intravenous antiarrhythmics should be initiated. Amiodarone should be the initial drug of choice (unless there is a history of any of the congenital Long QT Syndromes), given as a bolus then followed by a transfusion. Lidocaine can be added, as can procainamide—with there being some evidence that the latter is potentially better for the patient with re-entrant VT.56 In the setting of the VT storm, intravenous beta blockade should be quickly instituted and titrated against the blood pressure, which can be maintained with vasopressors such as phenylephrine and vasopressin. Beta-stimulants such as norepinephrine/epinephrine and dopamine should specifically be avoided because of proarrhythmia. Early sedation, intubation and muscle paralysis should also be considered early on, and if ventricular arrhythmia still persists, haemodynamic support should be sought earlier than later.
Referral
Fundamental to the acute management of the arrhythmia is appropriate referral to a centre specialising in the management of adults with CHD.15 57 Very often new-onset or worsening arrhythmias herald a decline in haemodynamics,27 30 34 58 59 and a comprehensive evaluation needs to concentrate on all aspects of the cardiovascular system and not the arrhythmia alone. Although the CHADS2 and CHA2DS2Vasc scoring systems have not been validated in adults with CHD, it is critical to realise that this group of patients is at much higher risk of thromboembolic stroke (probably in the order of 10-fold to 100-fold).60 It is recommended that the scoring systems be used as a guide; yet, patients with moderate to complex CHD should likely receive anticoagulation at this juncture (following an acute episode of atrial arrhythmia), and a decision about long-term management can be taken at a later date.15
Psychological issues
It is essential that the element of patient anxiety is not ignored. The majority of these patients have had multiple cardiac procedures and hospital visits. Palpitations, dyspnoea, the need for cardioversion or anticoagulation or even discussion of any potential invasive approach can be an enormous source for anxiety and concern. Events such as ICD shocks, which are not uncommon in this group, are associated with significant debility from a psychological standpoint and follow-up with psychotherapy/psychiatry is crucial.61
Conclusion
Arrhythmias are very common events in the adult with CHD and there are distinct differences in the management of each arrhythmia. Background knowledge of prior repairs and cardiovascular anatomy is invaluable and should be sought as a priority. The wide complex tachycardia should be treated carefully, and the patient discharged only after a definitive diagnosis is concluded. Important differences exist in the anticoagulation and pacing of this group, but acute management could be initiated in any centre. Referral to an ACHD centre is mandatory given the inter-relationship with concomitant haemodynamic issues.
Key messages
Arrhythmias are the most common cause of morbidity and mortality in this group.
Acute haemodynamic deterioration can be heralded by an arrhythmia.
Acute management should be guided by evidence of haemodynamic compromise.
Detailed knowledge of anatomy is crucial.
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References
Footnotes
Contributors CJM is the sole contributor.
Competing interests None declared.
Provenance and peer review Commissioned; externally peer reviewed.
Author note References which include a * in the reference list have been identified as a key reference.