Predictors of Early- and Late-Onset Supraventricular Tachyarrhythmias After Fontan Operation
Background—The objectives of our study were to determine the frequency of supraventricular tachyarrhythmias (SVTAs) among modifications of the Fontan operation and identify risk factors for developing SVTA.
Methods and Results—The population consisted of all patients who had any modification of the Fontan operation at the Mayo Clinic between 1985 and 1993. Clinically significant SVTAs were those requiring initiation or change of antiarrhythmic treatment, and they were divided into early SVTAs (<30 days after the operation) and late SVTAs (≥30 days after the operation). Clinical histories were reviewed, and health status questionnaires were sent. Four hundred ninety-nine patients had various modifications of the Fontan operation. Frequency of early SVTA was 15%. Risk factors identified by multivariate analysis for early SVTA were AV valve regurgitation, abnormal AV valve, and preoperative SVTA. Frequency of late SVTA was 6% by 1 year, 12% by 3 years, and 17% by 5 years. Risk factors for late SVTA were age at operation (<3 or ≥10 years) and systemic AV valve replacement. By univariate and multivariate analysis, the type of Fontan operation was not a significant risk factor for late SVTA when all 6 modifications were considered. However, when we analyzed the frequency of late SVTA for the 2 recently used modifications, we found a lower frequency of late SVTA in patients with atriopulmonary connection with lateral tunnel compared with those with total cavopulmonary connection.
Conclusions—Postoperative SVTA continues to be a significant problem. Risk factors for SVTA are AV valve regurgitation, abnormal AV valve, preoperative SVTA, and age at operation. Frequency of SVTA does not appear to be related to type of Fontan procedure except for slightly lower frequency in patients with atriopulmonary connection with lateral tunnel compared with those with total cavopulmonary connection.
In 1971, Fontan et al1 reported the first successful procedure for total diversion of systemic venous return to the lungs without use of a ventricle in patients with tricuspid atresia. The concept was that the right atrium would act as a pump in place of a right ventricle. Early modifications of this operation included elimination of the Glenn anastomosis, elimination of valves in the inferior vena cava, and performing a direct atriopulmonary connection. Later modifications included closure of the right AV valve, placement of a baffle in the right atrium, and use of intra-atrial lateral tunnels and intra-atrial conduits or extracardiac conduits to treat other complex anomalies.2 3 4 5 6 7 8
All operations resulting in total right heart bypass are now included under the general heading “Fontan operation.” Survival has steadily improved for this operation.9 10 However, the development of late-onset supraventricular tachyarrhythmias (SVTAs) continues to be a problem.11 12 13 Various investigators8 13 14 15 16 17 have postulated that by altering the surgical technique one may decrease the incidence of SVTA. The 2 most popular modifications of the Fontan operation at our institution recently have been the total cavopulmonary connection (TCPC)6 8 14 and the atriopulmonary connection (APC) with lateral tunnel modification (APC-lat). It has been suggested that TCPC may lower the incidence of SVTA,8 but other investigators believe that TCPC provides a substrate for developing atrial tachyarrhythmias.18
The objectives of the present study were (1) to determine the frequency of early and late clinically significant SVTA after the Fontan operation, (2) to compare the frequency of SVTA among the various modifications of the Fontan operation, and (3) to identify the risk factors for SVTA after the Fontan operation.
The patient sample consisted of all patients who had a Fontan operation at the Mayo Clinic between January 1, 1985, and December 31, 1993. This period was chosen for 2 reasons: (1) it represents a time during which TCPC, APC with or without lateral tunnel, and other modifications were being performed concurrently, and (2) it allows at least 2 full years of follow-up.
Types of Modifications of the Fontan Operation
APC (Figure 1A⇓) involves a direct connection between the atrium and pulmonary arteries, closure of any atrial septal defect, and, if necessary, patch closure of the right AV valve.
Total Cavopulmonary Connection
In TCPC (Figure 1B⇑), the superior vena cava is divided, and the superior end is anastomosed to the superior aspect of the right pulmonary artery. The inferior part of the superior vena cava is anastomosed to the inferior aspect of the right pulmonary artery. A partial tubelike baffle is formed by a prosthetic patch attached with a suture line on the free wall of the right atrium along the crista terminalis and extended superiorly to the superior vena cava–right atrial junction.
Atriopulmonary Connection With Lateral Tunnel Modification
The APC-lat (Figure 2⇓) is a connection between the systemic venous atrial appendage and the pulmonary arteries combined with a prosthetic baffle sutured posteriorly and parallel to the medial border of the venae cavae. At the superior end, the baffle suture line deviates leftward to the atrial appendage. The anterior side of the baffle is sutured anteriorly and away from the crista terminalis on the free wall of the right atrium. A generous pericardial patch is used to construct the sides and roof of the connection.
Heterotaxy surgery was performed for patients who had either asplenia or polysplenia syndrome and who required extensive rerouting of systemic venous return, often with the aid of an intra-atrial baffle or conduit.
For an intra-atrial conduit, a prosthetic (usually polytetrafluoroethylene) tube is interposed between the inferior vena cava and the superior vena cava–right atrial junction or the APC.
Other types of connections included all those not classified above, such as from the systemic venous atrium to a diminutive right ventricle.
The presence of SVTA was ascertained from review of the Mayo Clinic medical history and included correspondence with referring physicians and patients. ECGs and 24-hour ambulatory ECGs contained in the Mayo medical record were reviewed. In addition, a detailed health status questionnaire was sent to each known survivor whose follow-up data could not be obtained or whose arrhythmia status could not be ascertained from the Mayo Clinic medical history. A second questionnaire was sent to any patient who did not return or complete the first questionnaire. If the second questionnaire was not returned or completed, the patient or next of kin was contacted by telephone. We also requested the death certificate for patients whose underlying cause of death could not be obtained by the above methods. Local physicians were contacted only if all of the above efforts failed to identify the status of the patient.
The types of SVTA included in the analysis were (1) atrial flutter or atrial tachycardia and (2) supraventricular tachycardia (including AV reciprocating tachycardia, atrioventricular nodal reentry tachycardia, automatic atrial tachycardia, but not sinus tachycardia).19 We also identified the underlying cardiac rhythm from the surface ECG in each patient as (1) normal sinus rhythm or (2) sinus node dysfunction, which included sinus bradycardia (below the normal sinus rate expected for age20 ) and junctional rhythm.
For the purpose of the present study, a clinically significant SVTA was defined as SVTA for which any of the following treatments were initiated or changed: (1) antiarrhythmia drug treatment (digitalis was included only if the primary reason for using it was for rhythm control), (2) synchronized direct current cardioversion, or (3) atrial overdrive pacing (transvenous or transesophageal).
Arrhythmias that occurred within 30 days after the operation were defined as early postoperative arrhythmias, and arrhythmias that occurred at or beyond 30 days after the operation were defined as late postoperative arrhythmias. Patients who had early SVTA were classified as having late SVTA if they had an additional documented episode beyond 30 days.
A detailed database for patients who had the modified Fontan operation at the Mayo Clinic has been maintained and repeatedly updated.9 10 21 22 23 This database includes preoperative and postoperative variables of interest for the present study (Table 1⇓).
Statistical analysis was performed by Fisher exact test, χ2 test of association for comparing proportions, Wilcoxon rank sum test, Kaplan-Meier survival curve estimates, log-rank tests to compare survival curves, and Cox proportional hazards model for assessing multivariate associations between late arrhythmic status and risk factors. All deaths, regardless of cause, that occurred after the initiation of the operation were considered in the survival analysis irrespective of whether they occurred during the operation, during the postoperative hospitalization, or after hospitalization. Deaths that were not preceded by evidence of an arrhythmia were censored at the time of death and not counted as having the SVTA event. We also censored the follow-up period in any patient whose Fontan connection was taken down or who underwent cardiac transplantation. The SVTA status was determined up to this time. In the multivariate analysis, we used backward elimination for deletion of nonsignificant variables. Logistic regression was used for assessing multivariate factors associated with early SVTA. Two-tailed values of P≤0.05 were taken as evidence of differences not attributable to chance. The SAS statistical software system was used throughout.
Patient Sample and Follow-up Status
A total of 499 patients had a modified Fontan operation during the study period. Their ages at operation ranged from 8 months to 39 years (mean±SD, 10±7.5 years). There were 308 males (61.7%). Of the 399 patients alive at last contact, follow-up ranged from 2 months to 10.6 years (mean, 5.9±2.7 years; median, 6.2 years), with 89.4% of patients having follow-up for >2 years. There were 316 patients (63.3%) who had at least 5 years of follow-up. Eleven patients were lost to follow-up during the 30-day postoperative period. Table 1⇑ shows the demographic variables and hemodynamic variables for all 6 types of Fontan operation. Five patients had preoperative SVTA.
One hundred patients are known to have died. Overall early mortality (<30 days after the operation) was 9% (45 of 499). The 5- and 10-year mortality rates (excluding early mortality within the first 30 days after the operation) were 13% and 18%, respectively. Of the 100 deaths, there were 29 patients whose cause of death was classified as sudden cardiac death, including 1 patient who died during the operation, 45 patients with nonsudden cardiac death, 19 patients with noncardiac death, and 7 patients with unknown or another cause of death not listed above.
Excluding 1 patient who died during the operation, the underlying cardiac rhythm in the remaining 498 patients during the early postoperative period was normal sinus rhythm in 414 patients (83.5%), sinus bradycardia in 12 patients (2.4%), and junctional rhythm in 44 patients (8.8%); 26 patients (5.2%) required permanent pacemaker implantation (24 for high-grade second-degree or third-degree AV block, symptomatic bradycardia, or junctional rhythm and 2 for placement of antitachycardia pacemaker).
Early-onset SVTA occurred in 74 (15%) of 498 patients. SVTA included atrial flutter or atrial tachycardia in 38 patients (7.6%), supraventricular tachycardia in 23 patients (4.6%), and both in 13 patients (2.6%). The frequency of early postoperative SVTA was slightly higher in the group that had intra-atrial conduit (25%) compared with other groups. The type of Fontan operation was not one of the predictive factors for early-onset SVTA by univariate or multivariate analysis.
Table 2⇓ shows different types of congenital heart lesions and frequency of early-onset SVTA. Univariate risk factors for early SVTA were AV valve replacement (P=0.002), AV valve regurgitation (P=0.011), abnormal AV valve anatomy (AV valve atresia or common AV valve) (P=0.024), preoperative SVTA (P=0.025), older age (≥10 years old) at operation (P=0.038), and direct hepatic vein drainage to atrium (P=0.049).
In the multivariate model, 3 predictive factors were identified: (1) AV valve regurgitation (P=0.014), (2) preoperative SVTA (P=0.019), and (3) abnormal AV valve anatomy (P=0.031). The frequency of early SVTA in 112 patients who had none of these predictive factors was 8.9%; in 117 patients who had only abnormal AV valve anatomy, 11.3%; and in 123 patients with only AV valve regurgitation, 12.4%. However, in the 146 patients with both abnormal AV valve anatomy and AV valve regurgitation, the frequency of early SVTA increased to 22.8%.
There were 443 patients (88.8%) who survived the early postoperative period and were available for follow-up. Normal sinus rhythm was the underlying cardiac rhythm in 335 patients (75.6%), sinus bradycardia in 15 patients (3.4%), and junctional rhythm in 27 patients (6.1%). There were 37 patients (8.4%) whose underlying cardiac rhythm could not be determined from the available data. There were 6 additional patients who required pacemaker implantation after the 30-day postoperative period. The total number of patients who required pacemaker implantation at the time of last follow-up (excluding deaths and Fontan procedures reversed) was 29 patients (6.5%). Twenty-five patients had a pacemaker implanted for high-grade second-degree or third-degree AV block, symptomatic bradycardia, or junctional rhythm, and 4 patients had an antitachycardia pacemaker implanted.
The frequency for late-onset SVTA was 6% at 1 year, 12% at 3 years, and 17% at 5 years after the operation. Figure 3⇓ shows the time course for freedom from SVTA for all patients during the late postoperative period. Although the cumulative frequency of late-onset SVTA increased over time, the annual rate for developing late SVTA, which ranged from 2% to 6%, did not seem to increase during the first 6 years of follow-up.
Freedom from clinically significant late-onset SVTA relative to the type of Fontan operation is shown in Figure 4⇓. Patients who had an intra-atrial conduit type of Fontan operation had the highest frequency of SVTA (21%) at 5 years. There was no significant difference by univariate and multivariate analysis in the frequency of late-onset SVTA among patients who had various types of Fontan operation. However, when pairwise comparisons were performed among each group of the Fontan operations, we found a small but significant difference between the 2 most recently and widely used types. The patients who had APC-lat had a slightly lower frequency of late SVTA at the end of 5-year follow-up than did patients who had TCPC (P=0.046).
Table 3⇓ shows the results of analysis of risk factors for late-onset SVTA. Univariate risk factors for late SVTA were age at operation of <3 years and ≥10 years (P=0.001) and early postoperative SVTA (P=0.05). In a multivariate model, the strongest risk factor associated with late-onset SVTA was age at operation of >10 years (P<0.001). Other significant risk factors were AV valve replacement (P=0.029) and age at operation <3 years (P=0.036).
Although early and late mortality have decreased for the modified Fontan procedure,9 10 the late development of SVTA has continued to be a problem.11 12 13 14 15 16 17 The occurrence of SVTA after the modified Fontan operation has been reported to range from 20% to 37.5% in follow-up periods of up to 15 years.12 24 In the present study, the late occurrence of SVTA at 5 years after the operation was 17%. The reported differences in incidence may be explained in part by the diverse groups of patients operated on in several eras by different surgeons. Also, the definition of clinically significant arrhythmia is different across studies. Additionally, patients in the present study were operated on in a more recent era than patients in some of the previous studies, and the techniques of operation were often different.
It has been suggested that exclusion of the majority of the right atrium from elevated systemic venous pressure may reduce the incidence of atrial tachyarrhythmia.8 Exclusion of all but the lateral wall of the right atrium from the systemic venous to pulmonary artery pathway (“lateral tunnel technique”) was reported by King et al.5 In 1987, Puga et al6 described a technique whereby the superior vena cava was divided and the cephalad and cardiac ends were anastomosed to the right pulmonary artery; a septation patch within the right atrium parallel to the medial borders of the venae cavae (lateral tunnel) completed cavocaval continuity (TCPC).
Short to intermediate follow-up has suggested a lower incidence of late-onset SVTA after TCPC compared with APC.15 16 Gelatt et al16 reported that the frequency of atrial arrhythmia was 14% after the lateral tunnel Fontan (TCPC) compared with 29% after the APC. However, others13 17 have not found any significant difference in the frequency of late-onset SVTA between the 2 types of Fontan operation. Our data indicate that over a median follow-up of 6.2 years, there was no difference by univariate and multivariate analyses in the frequency of SVTA among patients who had the various modifications of the Fontan operation. However, when we analyzed the frequency of late SVTA for the 2 most recently and widely used modifications of the Fontan operation, we found a significant difference in the frequency of late SVTA in patients who had APC-lat (7% at 5 years) compared with patients who had TCPC (17% at 5 years) (P=0.046). This observation suggests that with respect to late-onset SVTA, the location of incisions and suture lines may be important.
Kurer et al25 have reported that intra-atrial reentry is the most common mechanism of atrial flutter after the modified Fontan operation. This type of primary atrial tachycardia has been termed intra-atrial or “incisional” reentrant tachycardia (IART) by some authors.26 Rodefeld et al,18 using an acute dog model, demonstrated IART after placing sutures in the right atrium from the superior to the inferior vena cava to simulate the suture lines of a TCPC Fontan procedure. IART could be induced as a result of anatomic block of the atrial activation sequence occurring along the free wall segment of the lateral tunnel suture line corresponding to the site of the crista terminalis. The atriotomy and the septal portion of the lateral tunnel suture line had no impact on the normal atrial activation sequence or IART cycle. There appeared to be a critical isthmus of atrial tissue between the portion of the suture line on the free wall of the right atrium and the tricuspid valve anulus that served as a substrate for the IART.18 Our findings are supported by this animal research. Patients with the TCPC type of Fontan repair appear to be at the same risk for early and late SVTA as patients with other types of Fontan surgery.
Predictive Factors for Early-Onset SVTA
We found that the most powerful predictive factors for developing early SVTA were AV valve regurgitation and abnormal AV valve (AV valve atresia or common AV valve morphology). If both AV valve regurgitation and abnormal AV valve were present, frequency of early SVTA increased to 22.6%. This observation lends support to the theory that atrial distension from AV valve regurgitation is one of the factors contributing to SVTA. Acute and chronic atrial distension and stretch of atrial fibers are known to be factors for developing atrial arrhythmias in animal models and in humans with other forms of congenital heart disease.14 27 28 29 Preoperative SVTA was also one of the predictive factors for early SVTA, as previously described.16
Predictive Factors for Late-Onset SVTA
Although the cumulative frequency for late-onset SVTA increased over time, the annual rate for those who developed late SVTA, which ranged from 2% to 6%, did not appear to increase for the first 6 years. Using multivariate analysis, we found that risk factors for developing late SVTA were age at operation (<3 years or ≥10 years) and AV valve replacement. Gewillig et al17 found that older age was a significant predictive factor for developing late SVTA; this supports the theory that long-standing atrial distention is one of the key factors for developing SVTA, as previously noted in other postoperative congenital heart patients.14 27 28 29 Although, in our series, the patients’ age distribution may be different from those of other studies, with the large number of patients we believe that this would provide a large enough patient population to draw valid statistical conclusions. Previous studies15 16 have suggested that early-onset SVTA is a predictor for late-onset SVTA; however, in our review we found that this correlation was significant only by univariate analysis.
The association of sinus node dysfunction and atrial tachyarrhythmia has been a topic of interest for several years. Kurer et al25 found that 57% of postoperative Fontan patients had sinus node dysfunction during intracardiac electrophysiological study. We found that 11.9% of our patients during the first 30-day postoperative period and 11.1% of our patients during the late postoperative period (≥30 days) had an underlying cardiac rhythm other than normal sinus rhythm (excluding patients with pacemaker or lost to follow-up), which suggests some degree of sinus node dysfunction. The apparent lower occurrence of sinus node dysfunction in the present study is related in part to the fact that we did not use 24-hour ambulatory ECG monitors for most patients. Clinically obvious sinus node dysfunction was not predictive for developing SVTA in this review.
At our institution, the overall cumulative frequency of late-onset SVTA after the modified Fontan operation was 17% by 5 years after operation. By univariate and multivariate analysis, the frequency of early- and late-onset SVTA was no different among the 6 types of Fontan operation. However, when we analyzed the frequency of late SVTA for the 2 recently used modifications of the Fontan operation, we found a lower frequency of late SVTA in patients with APC-lat compared with those with TCPC. Abnormal AV valve anatomy, AV valve regurgitation, and preoperative SVTA were significant risk factors associated with early-onset SVTA. Age at operation of <3 years and ≥10 years was strongly associated with late-onset SVTA, and systemic AV valve replacement was also a significant risk factor for late SVTA.
This study was supported by a grant from Mayo Foundation, Rochester, Minn.
- Received February 9, 1998.
- Revision received May 5, 1998.
- Accepted May 6, 1998.
- Copyright © 1998 by American Heart Association
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Oh JK, Holmes DR Jr, Hayes DL, Porter CB, Danielson GK. Cardiac arrhythmias in patients with surgical repair of Ebstein’s anomaly. J Am Coll Cardiol. 1985;6:1351–1357.We determined the frequency of and identified risk factors for developing clinically significant supraventricular tachyarrhythmias (SVTAs) in patients who had various modifications of the Fontan operation. Risk factors for developing early SVTA by multivariate analysis were AV valve regurgitation, abnormal AV valve, and preoperative SVTA. Risk factors for developing late SVTA by multivariate analysis were age at operation and systemic AV valve replacement. Type of Fontan operation is not a risk factor for early or late SVTA by univariate or multivariate analysis.