Summary
Supraventricular arrhythmias are an important and increasing cause of morbidity in adults with congenital heart disease, requiring specific management strategies. Pharmacological treatment has limited efficacy, and is often associated with some side-effects. Major improvements in catheter ablation techniques have opened new opportunities to better understand underlying mechanisms of supraventricular arrhythmias, offer better therapy, and eventually improve symptoms and quality of life in these patients. An array of tools and techniques are necessary to access relevant anatomical areas to address the arrhythmogenic substrate. The mechanism of these arrhythmias is mostly related to macroreentry around surgical scars or cavotricuspid isthmus-dependent flutter. The efficacy of catheter ablation is mainly dependent on the underlying congenital heart condition, with the most complex cases typically being associated with atrial switch and Fontan surgeries. Although relatively high rates of recurrence are seen after a single procedure, additional attempts are often helpful to decrease recurrences and improve symptoms. Catheter ablation in such patients continues to present many unique challenges that are best addressed by experienced multidisciplinary teams, at centres equipped with the proper catheters, imaging capabilities, mapping systems and support staff needed to maximize safety and success. Consensus indications have emerged that often support ablation as first-line therapy in these patients. In this comprehensive review, we aim to describe the specific issues associated with ablation of supraventricular arrhythmias in adult congenital heart disease, assess the results in contemporary practice and, finally, review the current indications.
Résumé
Les arythmies supraventriculaires sont une cause importante et croissante de morbidité chez les adultes porteurs d’une cardiopathie congénitale. Elles nécessitent une prise en charge spécifique. Le traitement médical a une efficacité limitée et reste associé à des effets secondaires significatifs. Les progrès majeurs de l’ablation par cathéters apportent de nouvelles données sur les mécanismes de ces arythmies, permettent de les traiter en améliorant les symptômes et la qualité de vie. Le mécanisme est le plus souvent une macroréentrée dépendante de l’isthme cavo-tricuspidien ou d’une large cicatrice. L’efficacité de l’ablation par cathéter est dépendante de la cardiopathie sous-jacente. Les cas les plus complexes sont représentés par les switch atriaux et les chirurgies de Fontan. Malgré des récidives après une première procédure, des reprises peuvent être proposées pour améliorer le succès à long terme et les symptômes. L’ablation des arythmies supraventriculaires chez ces patients comporte beaucoup de challenges et spécificités. Elle sera au mieux réalisée par des équipes multidisciplinaires expérimentées, dans des centres équipés des différentes modalités d’imagerie et de cartographie avec différents types de cathéters disponibles afin de diminuer le risque de complication et d’améliorer les résultats. Des indications consensuelles ont été proposées, positionnant souvent l’ablation en première intention chez ces patients. Nous décrirons dans cette revue les particularités de l’ablation des tachycardies supraventriculaires chez les adultes porteurs de cardiopathie congénitale, les résultats actuels et les indications retenues.
Background
The prevalence of adults with congenital heart disease (CHD) has been increasing continuously over the past decades, with improved surgical and interventional procedures leading to better survival. Nowadays, adults with complex CHD account for 60% of all patients with CHD . Nevertheless, even in simple CHD, life expectancy remains lower than in the general population.
Arrhythmias, including supraventricular arrhythmias (SVAs), form an important component in the care of adult CHD (ACHD). Even by 2009, data from the USA had indicated that SVAs occur in 15% of adults with CHD. Furthermore, the prevalence of SVA increases with age, and > 50% of patients with severe CHD who reach the age of 18 years go on to develop atrial arrhythmias by the age of 65 years . SVA incidence and type are dependent on the underlying CHD ( Table 1 ). SVAs are associated with a near 50% increase in mortality. The risk of stroke and heart failure is twice as high as in an age/sex-matched general population. Arrhythmias are also the main cause of emergency admissions . The relationship between SVA and sudden death has been well demonstrated in Wolff-Parkinson-White syndrome . SVAs may rapidly provoke poor haemodynamics in ACHD, as in transposition of the great arteries and atrial switch. SVAs with relatively slow cycle lengths can be conducted to the ventricle in a 1:1 fashion with poor tolerance . The occurrence of SVAs is favoured by surgical atrial scar, pressure or volume overload of cardiac chambers, accessory atrioventricular pathways or dual/atrioventricular node physiology. Mostly, they are related to intra-atrial reentrant tachycardia (IART) around surgical scars or natural anatomical barriers, such as cavotricuspid isthmus-dependent flutter. The incidence of atrial fibrillation (AF) increases with age and CHD complexity .
| Type of ACHD | IART | AP | AF | Atypical AVNRT |
|---|---|---|---|---|
| ASD | +++ | ++ | + (primum ostium) | |
| VSD | + | |||
| AVCD | ++ | + | + | |
| Congenital aortic stenosis and coarctation | ++ | |||
| TOF | ++ | + | ||
| dTGA and atrial switch | +++ | + | ||
| Ebstein’s anomaly | ++ | +++ | ||
| ccTGA | + (++ with double switch) | ++ | + | + |
| Fontan surgery with atriopulmonary connection | ++++ | + | + | |
| TCPC | ++ | + |
The treatment of SVAs in ACHD remains challenging, and clinical experience indicates that pharmacological treatment is of limited efficacy. Studies objectively evaluating the efficacy of medical treatment in this setting are still scarce. Flecainide is associated with a risk of proarrhythmia in patients with cardiomyopathy , and its safety – with potential unstable haemodynamics, as in the majority of complex CHDs – is questionable. Amiodarone has many long-term systemic effects , and is therefore undesirable in young patients with ACHD. Moreover, rhythm control efficacy seems lower in ACHD . Considering the above facts, percutaneous catheter ablation holds great promise with regards to definitive and potentially curative treatment. Nevertheless, the challenging anatomy, further compounded by previous surgery, often leads to a need for complex procedures that must be handled by multidisciplinary experienced teams.
General consideration of percutaneous ablation of arrhythmias in CHD
Since the early 1990s, percutaneous catheter ablation of arrhythmias in ACHD has expanded with improvements in knowledge and technology, leading to better efficacy. Three-dimensional mapping systems allow volume reconstruction with real-time navigation of the ablation catheter in three-dimensional spaces, and are of particular interest in those patients with complex anatomy. Anatomical landmarks such as the atrioventricular groove and venous connexions can be precisely located and marked. The position of the conduction network, frequently displaced in CHD , can be tagged to avoid damage during ablation. Voltage maps allow delineation of areas of scars that can be the substrate of arrhythmias. Activation maps can show the arrhythmia circuit and help to find the ablation target. Remote magnetic navigation may be helpful to increase catheter manoeuvrability and stability, and to decrease fluoroscopic time in patients with limited access and mapping difficulty . The quality of ablation lesions can be improved by the use of irrigated catheters and contact force monitoring . Cryoablation can also be of value to increase the safety of the ablation when working close to the atrioventricular node or coronary arteries . Interventional techniques have emerged to allow access to the critical substrate with transbaffle punctures , transconduit punctures , transhepatic venous access or transthoracic access . Transseptal access after septal closure devices can also be performed . Three-dimensional transoesophageal echocardiographic guidance may be useful for punctures. Surgical ablation also has its role, mostly performed concomitantly with other surgery to improve haemodynamics . Case-by-case multidisciplinary input is required to choose the best option in CHD patients.
Ablation of atrioventricular tachycardia
Atrioventricular tachycardias include atrioventricular reentrant tachycardia, related to an accessory pathway (AP), as well as atrioventricular nodal reentrant tachycardia with single or twin atrioventricular nodes. It appears that despite the difficulties of unusual anatomical landmarks and abnormally positioned conduction systems, most APs and slow pathways in ACHD can be safely and effectively ablated. Catheter ablation is therefore generally preferred over long-term antiarrhythmic drug therapy. A recently published consensus document has recommended catheter ablation for recurrent symptomatic and/or drug-refractory supraventricular tachycardia related to accessory atrioventricular connections or twin atrioventricular nodes in symptomatic ACHD, for ventricular preexcitation and high-risk or multiple APs, as commonly encountered in Ebstein’s anomaly, and/or drug-refractory atrioventricular nodal reentrant tachycardia ( Table 2 ).
| 1. Preoperative electrophysiological testing/ablation of AP or double atrioventricular node, where vascular or cardiac chamber access is restricted after surgery |
| 2. Systematic electrophysiological testing of manifest AP associated with ACHD and ablation in first-line therapy in cases of multiple APs and/or short refractory period; ablation can be proposed in cases of inducible supraventricular tachycardia alone and easy access to the pathway |
| 3. Atrioventricular reentrant tachycardias with AP, intranodal mechanism or twin atrioventricular node with haemodynamic compromise in first-line therapy |
| 4. Recurrent symptomatic atrioventricular tachycardia with AP, intranodal mechanism or twin atrioventricular node with easy access to dedicated cardiac chamber in first-line therapy or after failure of medical therapy in complex anatomy or limited vascular access |
| 5. Recurrent symptomatic IART in first-line therapy; discussion of first-line medical therapy (rhythm or rate control) in complex anatomy/difficult access to cardiac chamber |
| 6. In AF refractory to medical treatment, pulmonary venous antrum electrical isolation is recommended in selected cases after discussion of rhythm versus rate control |
| 7. Ablation of atrioventricular junction with permanent pacemaker implantation in selected cases with supraventricular permanent arrhythmias associated with symptoms of heart failure and insufficient rate control |
Atrioventricular reentrant tachycardia
Whereas catheter ablation of atrioventricular reentrant tachycardia is feasible in most patients with CHD, short- and long-term success rates are lower than similar procedures performed in patients with normal cardiac anatomy. The acute success rate is about 80–85%, and the recurrence risk is as high as 15–20% . Complication rates remain reasonable (5%), although they are estimated to be approximately twofold higher compared with non-CHD procedures. It is generally agreed that attempts should be made to ablate such pathways ahead of any surgical correction, as catheter access to an area of interest may become difficult following repair, and intraoperative AP interruption during subsequent surgery may be offered as a second-line option in case of failure. APs are associated with a variety of CHDs ( Table 1 ), most frequently with Ebstein’s anomaly and congenitally corrected transposition of the great arteries. Acquired APs can also be encountered exceptionally in patients with modified Fontan surgery (Bjork’s surgery) with atriopulmonary connection for tricuspid atresia . The electrophysiology of the APs in patients with CHD is not unique. However, the physiological and clinical implications of the tachycardia may be markedly different in these patients. Abnormal anatomy and atypical conduction systems may also enhance the difficulty and risks of catheter ablation. In addition, electrocardiogram localization algorithms may be misleading, and should be interpreted with caution in CHD . Although Ebstein’s anomaly accounts for < 1% of all CHDs, the prevalence of APs in patients with this anomaly is much higher than in other CHDs . Approximately 25% of patients with Ebstein’s anomaly have an AP (mostly manifest AP), and they are prone to having multiple APs (up to 50% of cases). A right bundle branch block pattern is typically present because of posteroseptal conduction delay, and its absence should raise suspicion of the presence of an AP. The localization of APs (usually right-sided and located along the posterior part of the dysplastic portion of the tricuspid annulus) is often difficult because of a massively enlarged right heart, the expanded tricuspid annulus region caused by displacement of the tricuspid valve and distortion of anatomical landmarks, all of which can make catheter stability difficult . Overall, catheter ablation is particularly challenging, and has an estimated success rate of about 75% in experienced centres. Special long sheaths are often required, and different techniques can be used to visualize the true atrioventricular groove, including selective angiography or intracoronary mapping of the right coronary artery. The use of three-dimensional navigational tools or intracardiac echocardiographic guidance may be helpful in these cases. In Ebstein’s anomaly, catheter ablation carries an increased risk of coronary injury because of the thin atrialized portion of the right ventricle adjacent to the atrioventricular groove. The use of cryoenergy may lower this risk, and has advantages for catheter stability because of the cryoadherence of the ablation catheter tip.
APs are found in 2–5% of patients with congenitally corrected transposition of the great arteries, and are typically located along the left-sided atrioventricular valve annulus, which is the anatomical tricuspid valve. During the procedure, the coronary sinus serves as an important anatomical landmark for the orientation of the tricuspid valve.
Atrioventricular nodal reentrant tachycardia
The variations in anatomical locations as well as the possibility of “twin” atrioventricular nodes represent unique aspects of atrioventricular nodal reentrant tachycardia in ACHD. Indeed, patients with CHD have less predictable atrioventricular node locations . In patients with atrioventricular canal defects, for instance, the node develops outside the triangle of Koch in a region inferior to the mouth of the coronary sinus, whereas in those with congenitally corrected transposition of the great arteries, the atrioventricular node is usually displaced to a superior location medial to the right atrial appendage. The atrioventricular node may also be left-sided in some patients with dextrocardia or heterotaxy syndrome. Even if the node is not actually displaced, the landmarks for the triangle of Koch will be distorted in conditions such as tricuspid atresia, Ebstein’s anomaly or abnormalities of the coronary sinus. Furthermore, surgical patching can complicate catheter positioning near the nodal extensions after the Mustard or Senning operation for d-transposition of the great arteries ( Fig. 1 ) or after the Fontan operation for single ventricle . Careful attention must be given to locating the normal conduction system, which cannot be mapped precisely in up to 10% of single ventricles, and therefore precludes radiofrequency ablation. Atrioventricular reciprocating tachycardia mediated by twin atrioventricular nodes can be a source of recurrent supraventricular tachycardia in complex CHD (especially in congenitally corrected transposition of the great arteries, atrioventricular canal defect and right isomerisms) . It consists of an anterior atrioventricular node and His bundle at the right atrial-mitral annulus junction, and a second posterior atrioventricular node and His bundle close to the remnant of the inferior interatrial septum, sometimes in the left-sided atria ( Fig. 2 ). The diagnosis can be suspected from a surface electrocardiogram if spontaneous alternations of superior and inferior QRS-axis are noted in the basic rhythm. During the electrophysiological study, pacing from different atrial sites, programmed ventricular stimulation during atrioventricular reentrant tachycardia and careful mapping of the entire atrioventricular groove can be used to objectively identify two distinct and separate areas with His bundle signals. The atrioventricular nodal system with reduced conduction capacity typically serves as the retrograde limb of the interatrioventricular nodal reentry tachycardia, and is targeted in most cases. Clearly, an extensive understanding of the anatomy and electrophysiology should be obtained in such patients before proceeding to ablation. Furthermore, a lack of clarity in defining the anatomy of atrioventricular conduction in these patients suggests that the ablation should first be undertaken using cryotherapy, which can facilitate cryomapping before the definitive ablation to avoid any damage to the conducting system in cases of inappropriate location of the ablation catheter. Radiofrequency energy can be used in cases of unsuccessful cryoablation or after a recurrence. The one caveat to this recommendation is that low-power radiofrequency application may be helpful in identifying the location of the anterior and posterior atrioventricular nodes through the occurrence of accelerated junctional rhythm.
