1. Boston Children’s Hospital, Harvard Medical School
Impact of Pacing on Systemic Ventricular Function in L-Transposition of the Great Arteries
Sophie C. Hofferberth, MBBS, Mark E. Alexander, MD, Douglas Y. Mah, MD, Victor Bautista-Hernandez, MD, Pedro J. del Nido, MD, Francis Fynn-Thompson, MD
Introduction remarks
Boston Children’s Hospital, Harvard Medical School
AATS 2015

2. Disclosures
None of the authors in this study have any commercial relationships to disclose

3. Congenitally Corrected Transposition of the Great Arteries (ccTGA)
ccTGA is a complex cardiac anomaly defined by atrioventricular (AV) and ventriculoarterial discordance
Native ccTGA physiology leaves morphological RV to support systemic circulation
Late onset RV dysfunction
Systemic AV regurgitation
Surgical management has evolved to anatomical repair
Excellent perioperative/intermediate outcomes
late systemic ventricular dysfunction remains significant problem1,2
1. Hiramatsu et al . EJCTS 2012;42(6): ; 2. Bautista-Hernandez et al. JTCVS. 2014;148(1):254-8.

4. Pacing and Systemic Ventricular Dysfunction
ccTGA has high incidence of spontaneous and procedure-related heart block
Pacemaker insertion associated with late-onset systemic ventricular dysfunction post anatomical repair1,2
Univentricular (single site) pacing shown to be significant risk factor for ventricular dysfunction
Biventricular pacing (BiVP) appears to preserve systemic ventricular function
-It is well recognized that l-tga pts have a high incidence of spontaneous and procedure-related hb.
-recent reports from our institution demonstrate that pacemaker insertion is assoc with late onset syst vent dysfxn in ltga pts post anatomical repair, more specifically these earlier reports showed univentricular (single site ) pacing is a major RF for ventricular dysfxn, while conversely pts who received biventricular pacing (CRT) appeared have have p
Bautista-Hernandez et al. Ann Thor Surg. 2006;82(6): Bautista-Hernandez et al. JTCVS. 2014;148(1):254-8.

5. Methods
Aim
Compare the impact of univentricular versus biventricular pacing on systemic ventricular function in all pts with ccTGA
Methods
Retrospective analysis of all pts with diagnosis of ccTGA who received pacemakers between 1993 and 2014
Study endpoints
Timing and indication for pacemaker insertion
Location of ventricular lead(s)
Qualitative ventricular function
Clinical outcomes

6. Baseline Patient Characteristics
Variable
Number (%) or Median (range)
Total number of pts 53
Male/Female
31/22
Median age at initial pacer insertion
1.8 years (6 days - 42 years)
Median weight, Kg
10.8 (3.5 to 69.0)
Segmental anatomy
S,L,L
49 (92)
I,D,D
4 (8)
Associated CV anomalies
VSD
42 (79)
Pulmonary stenosis
25 (47)
Pulmonary atresia
10 (19)
Ebstein-like anomaly
9 (17)
Single coronary artery
3 (6)
This study included a 53 pts and the demographic and co-morbidity profiles of this cohort is representative of the contemporary surgical population of L-TGA patients.

7. No further pacing intervention
Pacing Details
Primary univentricular pacing
42 pts
Epicardial lead location
- Anatomic LV, n = 28
- Anatomic RV, n = 11
- Ambiguous data, n = 3
Primary biventricular pacing
11 pts
No further pacing intervention
N = 25
Upgraded to BiV pacing
N = 17

8. Timing of Initial Pacemaker Insertion
Spontaneous heart block, n = 8
Time of surgical intervention preparing for anatomical repair, n = 9
PA Banding, n = 8
BT shunt, n = 1
Time of anatomical repair, n = 8
Post anatomical repair, n = 28

9. Outcomes: Primary Univentricular Pacing
Initial univentricular pacer
N = 42
Systemic ventricular dysfunction
N = 22
No ventricular dysfunction
N = 20
Upgrade to BiVP
N = 14
No further pacing intervention
N = 8
Upgrade to BiVP
N = 3
No further pacing intervention
N = 17
Persistent systemic ventricular dysfunction
N = 7
Improved systemic ventricular function
N = 7
2 late deaths (heart failure)
Important additional comments:
22 pts with significant systemic vent dysfunction8 pts had no further pacing intervention, of these 2 late deaths, remaining 6 pts 1 pt listed for transplantation, BiV pacing, further anatomical repair
14 upgraded to CRT, explain outcomes of 7 with persistent systemic vent dysfunction, 7 pts demonstrated improved ventricular function No major CV events amongst this group, improved QOL/exercise tolerance
20 pts with no significant ventricular dysfunction, of these 17 pts had no further pacing intervention, no significant late CV events in this group. 3 pts in this gp were upgraded to CRT at the time of anatomical repair. This was decision was made at the discretion of the operating surgeon and took place during the past few yrs as our experience shifted
1 in-hospital death (heart failure)
1 late death (heart failure)
1 transplant

10. Lead placement & Systemic Ventricular Function
Initial univentricular pacing, N = 42
Systemic ventricular dysfunction
N = 22
Lead placement on anatomic LV
N = 13
Lead placement on anatomic RV
N = 9
Sub-systemic lead
N = 6
Sub-pulmonary lead
N = 7
Sub-systemic lead
N = 4
Sub-pulmonary lead
N = 5
No difference in risk of systemic ventricular dysfunction based on initial lead location whether analyzed by ventricular morphology or physiologic function

11. Outcomes: Primary Biventricular Pacing
Median age = 1.2 yrs (range, 5 mths to 16 yrs)
Median weight = 10.9 kg (range, 5 to 59 kg)
6 male, 5 female
No perioperative complications
No major CV complications
(i.e. no mortality/heart failure/transplantation)
None of the pts treated with primary biventricular pacing developed systemic ventricular dysfunction at latest follow up

12. Univentricular versus Biventricular Pacing
We next performed a life-table analysis which demonstrated a striking difference in late outcomes between univentricular vs BiV paced pts.
Freedom from systemic ventricular dysfunction was 100% at 10 years for pts who received primary BiV pacing compared to just over 40% for those pts who underwent primary univentricular pacing.

13. Late Follow-up Primary biventricular pacing (n = 11)
Overall median follow up = 3.7 yrs (range, 4 days yrs)
Primary biventricular pacing (n = 11)
Median follow up = 3 yrs (range, 4 d - 9 yrs)
Primary univentricular pacing (n = 42)
25 pts: no further pacing intervention
Median F/U = 4.2 yrs (range, 4 d - 16 yrs)
17 pts: upgraded to BiVP
Median time from initial univentricular pacer insertion to BiVP upgrade = 3 yrs (range, 3 mths - 22 yrs)
Median time from upgrade to demonstrated improvement in ventricular function (6 pts) = 8 wks (range, 2 – 20 wks)

14. Limitations Retrospective, single-center analysis
Extended follow-up in univentricular pacing cohort may display natural history of systemic RV in addition to consequences of single site pacing
Variable location of biventricular leads driven by uncertainty over exact site of latest electrical activation and limited surgical access
Some pts upgraded to biventricular pacing at time of further anatomic correction
Subjective classification of ventricular function in paced ventricles

15. Conclusions
ccTGA pts have a high frequency of both AV block and late ventricular dysfunction
While ventricular pacing is clearly required, single site ventricular pacing appears to contribute to earlier ventricular dysfunction
Neither morphologic nor physiologic consideration of single lead placement predicts late ventricular dysfunction
Upgrade to BiVP offers a reasonable (50%) chance of short term normalization of ventricular function
Primary BiVP prevents (or at least delays) development of ventricular dysfunction
Based on the results of studies we believe that BiV pacing should be the primary mode of pacing in all pts with ccTGA who develop heart block in order to mitigate the risks of developing systemic ventricular dysfunction.

16. Thank you