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Modern Incidence of Complete Heart Block in Patients with L-looped Ventricles: Does Univentricular Status Matter? M. Abigail Simmons, MD,* Nancy Rollinson, APRN,* Steven Fishberger, MD,* Li Qin, PhD,† John Fahey, MD,* and Robert W. Elder, MD‡ *Section of Pediatric Cardiology, Department of Pediatrics, ‡Section of Pediatric Cardiology, Departments of Pediatrics and Internal Medicine, Yale University School of Medicine, and †Center for Outcomes Research and Evaluation, Yale University/Yale-New Haven Hospital, New Haven, Conn, USA ABSTRACT

Objective. Individuals with L-transposition of the great arteries and two normally sized ventricles are at risk for complete heart block. Little is known about the incidence of complete heart block in those with a single ventricle L-transposition of the great arteries. In this study, we compare the incidence of complete heart block in a modern cohort of patients with L-looped single ventricle anatomy to patients with L-transposition of the great arteries and two ventricles. Methods. We conducted a retrospective cohort study of patients with L-transposition of the great arteries who were seen at Yale-New Haven Hospital between 2001 and 2013. Patients were classified as having isolated L-transposition of the great arteries (group I), L-transposition of the great arteries and major cardiac defects with two-ventricle anatomy (group II), or L-transposition of the great arteries and single ventricle anatomy (group III). We recorded the age of onset and the circumstances of CHB in each group. We calculated the incidence rate of complete heart block and compared this between the groups. Results. We identified 64 patients with L-transposition of the great arteries, median age of 21 years (range 6 months–52 years): 21 in group I, 15 in group II, and 28 in group III. In total, 15 subjects developed complete heart block, incidence of 21.9% and rate of 1.3% per person years. Although group III patients were significantly less likely to develop complete heart block than dual ventricle patients (7.1% vs. 33% and 40%, P = .01), this difference is not significant when only spontaneous complete heart block was analyzed (P = .16). Conclusion. All patients with L-transposition of the great arteries have similar risk of spontaneous complete heart block and should be routinely screened for this complication. Key Words. L-transposition of the Great Arteries; Atrioventricular-ventriculoarterial Discordance; Congenitally Corrected Transposition of the Great Arteries; Complete Heart Block; Complete AV Block; Third Degree Heart Block

Introduction

L

-transposition of the great arteries (L-TGA), also known as congenitally corrected transposition, is a rare condition accounting for approximately 0.05% of all congenital heart defects. The anomaly occurs when the primitive cardiac tube loops to the left (L-looped ventricles) instead of to the right (D-looped ventricles), thereby bringing the morphologic left ventricle to the right and creating atrioventricular and ventriculoarterial discordance.1 L-TGA occurs both in isolation and

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in association with other cardiac abnormalities, the most common being ventricular septal defect (VSD), left ventricular outflow tract obstruction (pulmonary stenosis), and anomalies of the leftsided tricuspid valve (TV). L-TGA is also found in a subset of patients with functionally univentricular hearts, particularly those with double inlet left ventricle. Pathologic examination of patients with L-TGA reveals not only abnormal ventricular looping but also an abnormal atrioventricular conduction system that is more susceptible to the Congenit Heart Heart Dis. 2015;10:E237–E242 Congenit Dis. 2015;••:••–••

E238 2 development of complete heart block (CHB).2 Although several studies have investigated the incidence of CHB in patients with L-TGA and two ventricles, few studies have studied CHB in single ventricle patients with L-TGA. Furthermore, to our knowledge, no study has compared the incidence of CHB in patients with two ventricle physiology compared with those with a functionally univentricular heart. Our study aimed to determine the incidence of CHB in patients with L-TGA and compare the differences between CHB in patients with a single ventricle vs. those with two ventricles. Methods

We performed a retrospective chart review of patients with L-TGA seen at Yale-New Haven Hospital and Yale-New Haven Children’s Hospital between October 2001 and October 2013. We used International Classification of Diseases, 9th revision (ICD-9) billing codes to search institutional databases to identify patients for study inclusion and reviewed individual records to confirm the presence of L-TGA. When necessary, we used primary data including echocardiography and cardiac catheterization to verify the diagnosis. Additional data collected included the presence of other cardiac defects, age of onset of CHB, circumstance of CHB, and need for pacemaker implantation. Patients with insufficient records were excluded. We obtained institutional review board approval prior to the collection of data. We considered the L-TGA population both according to underlying anatomy and to number of functional ventricles. For anatomical subgrouping, we divided patients into three groups: group I: isolated L-TGA including L-TGA with minor defects (atrial septal defect, small VSD, mild pulmonary stenosis, and mild tricuspid regurgitation); group II: L-TGA with major defects and two ventricles (large VSD, pulmonary stenosis, pulmonary atresia, moderate or severe tricuspid regurgitation, and Ebstein-like anomaly of tricuspid valve); and group III: L-TGA with L-looped single ventricle. This classification is similar to that used by Graham et al. in their multi-institutional study of long-term outcomes in patients with L-TGA.3 For the purpose of comparing CHB in patients with two vs. one functional ventricle, groups I and II were combined and compared with group III. We defined CHB as the onset of persistent complete AV dissociation with the atrial rate faster than the ventricular rate. We classified the circum2015;10:E237–E242 Congenit Heart Dis. 2015;••:••–••

Simmons et al. stance of CHB as either spontaneous or postsurgical (occurring within 30 days of surgery). We considered late spontaneous CHB as CHB occurring >30 days after surgery.

Statistical Analysis Data analysis consisted of mean and standard deviation for continuous variables, and frequency and percentage for categorical values. For the incidence of third degree heart block, we calculated the person-year rate. For P value calculations, we used analysis of variance or t-test for continuous variables, and chi-square test or Fisher’s exact test for categorical variables. We determined the survival free from CHB from birth to the time of diagnosis of CHB using Kaplan–Meier survival and applied log-rank test for comparisons between/among L-TGA types. We used SAS software version 9.3 (SAS Institute, Cary, NC, USA) to complete all analyses. We considered two-sided P < .05 statistically significant. Results

In total, we identified 64 patients with L-TGA. At latest follow-up, the median age was 21 years (range 6 months–52 years). Fifty-three (82%) had been seen within 1 year of the end of the study. Table 1 reports baseline characteristics of the patients as well as the incidence and details of CHB according to subgroup. Fifteen patients developed CHB yielding an overall incidence of CHB of 21.9% with an incidence rate of 1.3% per 100 person-years. The mean and median age of onset of CHB for the entire patient cohort was 10.4 and 4 years, respectively. CHB occurred spontaneously in 10 subjects yielding an incidence of 15.6% and rate of 0.79% per 100 person-years. Figure 1 shows the Kaplan– Meier survival analysis of freedom from spontaneous CHB for the entire patient cohort. All 15 subjects who developed CHB required treatment with permanent pacemaker. When we considered the incidence of CHB (inclusive of spontaneous and perioperative CHB) according to anatomical subgroup (group I vs. II vs. III), we found that single ventricle patients (group III) were significantly less likely to develop CHB than those in groups I or II (7.1% vs. 33% and 40%, respectively, P = .01). This difference was further accentuated when single ventricle patients (group III) were compared with those with two functioning ventricles (groups I + II combined) with incidence of 7.1% vs. 36.1%, respec-

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Complete Heart Block in L-TGA Table 1.

Patient Characteristics and Incidence of CHB According to Subgroup Anatomal Subgroup

Age at last visit: mean ± SD Male: n (%) Surgical intervention: n (%) CHB: n (%) Incidence rate of CHB (per 100 person-years) Spontaneous CHB: n (%) Incidence rate of spontaneous CHB (per 100 person-years) Mean age of spontaneous CHB: mean ± SD Perioperative CHB: n (%) Late spontaneous CHB*:n (%)

Ventricular Subgroup

Group I (n = 21)

Group II (n = 15)

Group III (n = 28)

P Value

Groups I + II (n = 36)

Group III (n = 28)

P Value

24.8 ± 16.7 15 (71.4) 4 (19.1) 7 (33.3) 1.66

24.1 ± 13.6 11 (73.3) 13 (86.7) 6 (40.0) 2.32

19.0 ± 12.1 18 (64.3) 27 (96.4) 2 (7.1) 0.39

.31 .83

Modern Incidence of Complete Heart Block in Patients with L-looped Ventricles: Does Univentricular Status Matter?

Individuals with L-transposition of the great arteries and two normally sized ventricles are at risk for complete heart block. Little is known about t...
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