Impact of preoperative electrophysiological intervention on occurrence of peri/postoperative supraventricular tachycardia following Fontan surgery

Impact of preoperative electrophysiological intervention on occurrence of peri/postoperative supraventricular tachycardia following Fontan surgery

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Takeuchi D, Toyohara K, Kudo Y, Nishimura T, Shoda M.
Heart Rhythm. 2020 Aug 8:S1547-5271(20)30756-6. doi: 10.1016/j.hrthm.2020.08.003. Online ahead of print.
PMID: 32781159

Take Home Points:

  • 34% of patients undergoing Fontan procedure with a prior episode of supraventricular tachycardia (SVT) will have SVT during or within the 1st year after surgery
  • 70% of patients will have SVT due to AV nodal reentrant tachycardia or AV reentrant tachycardia due to an accessory pathway or twin AV nodes
  • Catheter ablation for SVT prior to Fontan surgery has a high acute success rate (91%) with the majority requiring only a single procedure (93%)
  • Use of a pre-operative EP study and catheter ablation resulted in a significant reduction in peri-/post-operative SVT after Fontan surgery (11% vs 43%)
  • Pre-operative EP study and catheter ablation should be considered in Fontan patients with high risk for SVT

Dr Akash Patel

Comment from Dr. Akash Patel (San Francisco), section editor of Congenital Electrophysiology Journal Watch.  Supraventricular tachycardia (SVT) in patients who undergo Fontan palliation can result in symptoms, compromised hemodynamics, and poor outcomes. Catheter ablation for SVT after the Fontan procedure can be challenging due to limited vascular and cardiac chamber access.  The utility of pre-operative EP studies and ablation prior to surgery has been shown effective in select congenital heart lesions. The data on this approach in Fontan patients is limited but important due to procedural challenges and clinical impact of SVT as mentioned. This study aimed to assess the 1) incidence, 2) impact of pre-operative EP study guided intervention, and 3) risk factors associated with peri-/post-operative SVT within 1 year after surgery in Fontan patients at high risk for SVT.

This was a retrospective single center study of all patients who underwent Fontan procedure and had a history of supraventricular tachycardia (≥ 1 episode) prior to surgery.  All patients underwent Fontan procedure between January 1987 and April 2017.  EP evaluation and management varied during this time frame. Prior to 1989, no EP studies or catheter ablation were performed. After 1989, all patients deemed high risk for supraventricular tachycardia underwent and EP study and if arrhythmia was diagnosed underwent ablation – surgical ablation (prior to 1997 or if unsuccessful catheter ablation) or catheter ablation (after 1997).  The patients were then divided into three cohorts (EP study not attempted, EP study without catheter ablation, and EP study with catheter ablation) and followed clinically for at least 30 months.

SVT was defined as atrioventricular reentrant tachycardias (AVRTs) associated with the accessory pathway or twin atrioventricular nodes (AVNs), atrioventricular nodal reentrant tachycardia (AVNRT), atrial tachycardias (ATs), and atrial flutter (AFL). Atrial fibrillation and junctional tachycardia with AV dissociation were excluded. Peri-operative was defined as during or ≤ 30 days after surgery.  Post-operative was defined as ≥31 days to <1 year  after surgery. All non-sustained SVTs were excluded.

The overall study group included 109 patients who underwent Fontan procedure and had a history of supraventricular tachycardia (≥ 1 episode) prior to surgery.   There were 44 (40%) patients who did not undergo an EP study,  22 (20%) patients who had a EP study without catheter ablation, and 44 (40%) patients who had a EP study with catheter ablation.

Typical EP study protocols were used with multiple diagnostic catheters in all cases and 3D electroanatomic mapping in 25%. Ablation was performed via radiofrequency in 38 (86%), irrigated radiofrequency in 7 (16%) ,  and cryoablation in 1 (2%) .

Fontan procedures were performed ≤ 6 months after the last EP study and catheter ablation.  Fontan types included atriopulmonary (77%), lateral tunnel (7%), and extracardiac conduit (16%). Intraoperative arrhythmia surgery was performed in 11 patients which included AVN modification and accessory pathway ablation (10 were included in the EP study only group, and 1 in the EP study with catheter ablation group).

The median age at Fontan procedure was 8.8 years with 11.4 years of follow-up. The EP study with catheter ablation group were significantly younger (3.8 years).   There was no differences in the type of Fontan, presence of heterotaxy, presence of AV discordance, or type of congenital heart disease between the groups. See table below.

patient characteristics

The incidence of peri-/post-operative SVT within 1 year after Fontan surgery was 34% (37/109) with most occurring peri-operatively (91%). All were sustained or incessant with symptoms and hemodynamic instability which required intervention. See figure below. Of note, 22% of the peri-operative SVT recurred after 1 month.

incidence of svt

There were 71 SVTs diagnosed in 65 patients.  The majority of SVT was due to AVRT due to twin AV nodes (44%) followed by AVNRT (17%), atrial tachycardia (17%), AVRT due to accessory pathway (10%), atrial flutter (10%) , and junctional tachycardia (1%).  See figure below. Twin AVNs were present or suspected in 67% of patients who underwent an EP Study. Of note, this cohort had  a high percentage with heterotaxy (50%).

bar chart AVRT

Catheter ablations (49) were performed in 44 patients before Fontan surgery.  41 (93%) only required 1 ablation with 3 (7%) required multiple procedures. The acute success rate was 91% after the initial procedure. The overall success rate after all catheter ablation(s) for SVT before Fontan surgery was 97% (43/44) of patients and 98% (52/53) of induced SVTs.  Catheter ablation was safe with no major complications such death, major hemorrhage, systemic thrombosis, and/or lethal arrhythmia.

The incidence of all SVTs within 1 year after Fontan surgery was 50%  (22/44) in the no EP study group, 47%  (10/21) in the EP study without ablation group, and 11% (5/44) in the EP study with catheter ablation group. The majority of SVT  (89%) was due to AV reciprocating SVTs and only 11% due to “atrial muscle” SVT (i.e. atrial flutter/tachycardia). Of note, there was the lack of “atrial muscle” SVTs in the catheter ablation group.  The incidence of AV-reciprocating SVT was significantly lower  (11%) in EP study with catheter ablation group compared to the EP study only (43%) or no EP study group (43%) (p< 0.05). See figure below.


bar chart n group eps group ca group

Risk factors for peri-/post-operative SVT within 1 year after Fontan surgery were analyzed and only a lack of or unsuccessful pre-operative catheter ablation was shown to be associated with increased risk (OR 4.43). See table below.

Risk factors of peri postoperative SVT

Long term follow-up after Fontan surgery was done for a median of 11.4 (5.0–19.8) years. There were 8 early deaths (≤ 1 month after surgery) and 18 late deaths.  The causes of late death included sudden death (8), heart failure (7), systemic embolism (2), and hemodynamic collapse due to SVT (1). Of note, 5 of the late deaths occurred within 1 year after surgery due to sudden death (4) and SVT (1). All of these were in the no EP study group.

Late arrhythmia occurrence was seen in 26 patients (27%) at a median of 13.5 (5.0–18.0) years after Fontan surgery.  The majority were atrial tachycardias (19) followed by SVT (9).  Of note, 1/3rd had history of SVT within 1 year of Fontan surgery.  In the catheter ablation group, there were 6 atrial tachyarrhythmias and 3 SVTs.  Of note, only 3 patients in the total cohort underwent repeat EP study with ablation and 2 were found be recurrence of prior AV reentrant tachycardia. Also, 10 patients underwent Fontan conversion during follow-up for various reasons which may have impacted arrhythmia substrate during follow-up.

Overall, this study demonstrated a high incidence of SVT (34%) during and after Fontan surgery in those patients with a history of SVT before surgery. The incidence of SVT peri-operatively (during or <1 month after surgery) was 91%, post-operatively (1 month to 1 year after surgery) was 9%, and late (>1 year) was 27%.  Catheter ablation was shown to significantly reduce the risk of peri-/post-operative SVT within 1 year of surgery (11% vs. 43%).  Clearly, SVT is associated with increased early and late comorbidities including in rare instance sudden death in single ventricle patients as noted in this study. The utility of pre-operative EP studies with catheter ablation carried high acute success rates (91%) with no major complications in this population.

This study adds support to and is consistent with the 2016  PACES/HRS expert consensus statement on the use of catheter ablation in children and patients with congenital heart disease. This guideline states that ablation can be useful to reduce peri-/post-operative risk for SVT when surgery will result in restriction of vascular or chamber access.  In particular, this is an important consideration as post-Fontan ablations may carry additional procedural risks such as need for transbaffle puncture or limitations in access reducing acute success rates.

Clearly more data and larger sample sizes are needed to determine whom should be considered for pre-operative EP study prior to Fontan as only a lack of /or unsuccessful ablation was associated with increased risk for peri-/post-operative arrhythmia. In particular, this study had a high proportion of heterotaxy syndrome and atriopulmonary Fontans.  In addition, the impact of ablation on length of stay and  other post-operative outcome measures would be important to investigate. Finally, this study noted significant late arrhythmia occurrences of whom the majority did not have a prior EP study or ablation done.  This raises the potential for long-term benefit of a pre-Fontan EP study and ablation in a subset of patients.

Management of SVTs in Fontan patients is critically important to reduce potential comorbidities such as stroke, heart failure, thrombosis, and in rare instances death.   A pre-Fontan EP study and ablation can be useful to reduce peri-/post-operative SVT in high risk patients and the long term impact of this strategy requires further investigation.