Impact of temporary interruption of right ventricular pacing for heart block on left ventricular function and dyssynchrony.
BACKGROUND
The increasing data suggest an association between chronic right ventricular (RV) and left ventricular (LV) dysfunction. We sought to determine the effect of temporary interruption of long-term RV pacing on LV function and mechanical dyssynchrony in children and young adults with complete heart block.


METHODS
Twelve patients aged 20.0 + or - 7.4 years with congenital heart block (group I) and six patients aged 22.7 + or - 11.0 years with surgically acquired heart block (group II) with RV pacing were studied. The pacing rate was reduced to less than patient's intrinsic heart rate and maintained for 5 minutes. The LV ejection fraction (EF), three-dimensional systolic dyssynchrony index (SDI), two-dimensional global longitudinal strain and strain rate, and Doppler-derived isovolumic acceleration before and after interruption of RV pacing were compared.


RESULTS
The LVEF and GLS increased while QRS duration decreased after the pacing interruption in both the groups (all P < 0.05). While SDI decreased in both groups I (6.8 + or - 2.3%- 3.8 + or - 0.8%, P = 0.001) and II (9.2 + or - 4.1%-5.0 + or - 1.6%, P = 0.032), it remained higher in group II than in group I (P = 0.046) after the pacing interruption. The prevalence of LV dyssynchrony (SDI > 4.7%) decreased in group I (83%-25%, P = 0.006) but not in group II (67%-50%, P = 0.50). The %increase in LVEF correlated positively with %reduction of LV SDI (r = 0.80, P = 0.001).


CONCLUSIONS
Temporary interruption of chronic RV pacing acutely improves LV dyssynchrony and systolic function in children and young adults, the magnitude of which is greater in patients with congenital than those with surgically acquired heart block.
Department of Paediatrics and Adolescent Medicine, Division of Paediatric Cardiology, Queen Mary Hospital, The University of Hong Kong, Hong Kong.
Wen-Jing
WJ
Hong
Tak-Cheung
TC
Yung
Kin-Shing
KS
Lun
Sophia Jessica
SJ
Wong
Yiu-Fai
YF
Cheung
D002304:Cardiac Pacing, Artificial; D004452:Echocardiography; D018618:Echocardiography, Doppler, Color; D019560:Echocardiography, Three-Dimensional; D004562:Electrocardiography; D005260:Female; D006327:Heart Block / Q000151:congenital / Q000628:therapy*; D006801:Humans; D008297:Male; D018487:Ventricular Dysfunction, Left / Q000209:etiology*; D016277:Ventricular Function, Left / Q000502:physiology*; D055815:Young Adult