right ventricular based pacing ( rvp ) has been standard therapy for children with advanced second - degree and complete atrioventricular ( av ) block during the last several decades .
nevertheless , congestive heart failure ( chf ) and dilated cardiomyopathy ( dcm ) may rarely occur in children undergoing chronic rvp systems ( 1 , 2 ) .
there are numerous clinical trials on crt that show the effectiveness of it when dealing with or treating adult patients with refractory chf and dcm ( 3 , 4 )
. however , most reports on crt and its effectiveness have paid attention to adult patients rather than child patients . not many studies on crt with young children have been conducted .
some researches on the issue that were carried out only dealt with heterogeneous populations that are not capable of being generalized ( 5 - 7 ) .
we present a case of progressive left ventricular ( lv ) dysfunction following chronic right ventricular ( rv ) epicardial pacemaker for congenital complete av block whose lv dysfunction was improved after crt .
a 9-yr - old boy was transferred to our hospital because of progressive lv dysfunction on march 14 , 2007 .
he was delivered by caesarean section at 39 weeks of gestation and his birth weight was 3.2 kg .
after birth , bradycardia due to congenital heart block was noted . at the age of 3 days ,
a permanent vvi pacemaker was implanted due to a resting heart rate of 50 - 60 beats / min , which was accompanied by lv dilatation and low - lv ejection fraction ( ef ) of 41% .
after vvi pacing , lv dilatation and dysfunction had been improved . at the age of 9 yr ,
the new york heart association ( nyha ) class was ii or i , occasionally .
electrocardiogram showed vvi paced wide qrs complex of 164 msec with left bundle branch block ( lbbb ) pattern of qrs morphology and superior axis at frontal plane .
test weaning of ventricular pacing revealed intrinsic rhythm of complete heart block with wide qrs escape beats ( fig .
there was significant intraventricular dyssynchrony as follows : septal to lateral delay was 136 msec and all segment delay measured by tissue synchrony image ( tsi ) was 219 msec .
chest radiography showed a cardiomegaly , of which cardiothoracic ( ct ) ratio was 0.61 ( fig .
the level of plasma b - type natriuretic peptide ( bnp ) was 111 pg / ml .
screening for fluorescent antinuclear antibodies ( fana ) and anti double - stranded deoxyribonucleic acid ( ds - dna ) antibodies was negative .
both anti - ssa / ro and anti - ssb / la antibodies were also negative .
when we have examined his mother , the results were as follows : fana 1:40 , anti ds - dna antibodies 6.0 and anti - ssa / ro and ssb / la antibodies ( + ) .
because lv ef remained below 30% on echocardiography in spite of medical treatment for 1 yr , we decided to use crt in an attempt to improve cardiac function and acquire the reversed remodeling .
he received an epicardial biventricular pacing system with bipolar leads ( insync iii model 8042 , medtronic inc . ,
the epicardial bipolar atrial lead and the bipolar ventricular lead were placed on the right atrial ( ra ) appendage and the rv apex , respectively .
the left lead was placed on the lv posteriolateral wall , between the posterior descending artery and the branches of left circumflex artery . in choosing pacing sites , in order for optimal synchronization in lv walls , we considered tsi by intraoperative transesophageal echocardiography and arterial pressure monitoring that brought about minimal dyssynchrony and maximal arterial pressure .
the pacing thresholds of ra and lv were 1.0 v and 1.5 v respectively with 0.4 msec pacing width .
minimum intraventricular dyssynchrony was achieved with the setting of lv earlier by vv delay 4 msec .
twelve months after implantation , electrocardiogram showed atrial - sensing and ventricular - pacing qrs complex of 148 msec ( fig .
now , 18 months later from the implantation , he shows the improved exercise tolerance .
he has been followed up at the outpatient department and observed on a regular basis .
prolonged ventricular dyssynchrony induced by long - term rvp is associated with deleterious lv remodeling , which are lv dilatation and lv asymmetrical hypertrophy ( 2 , 8 , 9 ) .
a recent small series study documented that crt was effective in improving lv function in young patients with rvp induced cardiomyopathy ( 10 , 11 ) .
very few children with idiopathic dcm meet the published criteria found predictive of a positive response in adult subjects ( lbbb , lv dysfunction [ ef < 35% ] , and prolonged qrs duration [ > 125 msec ] ) ( 3 , 4 , 7 ) .
rvp induced cardiomyopathy seems to be one consistent subset of children and adolescent patients that seems eligible for crt . in this case with congenital heart block , rv paced qrs duration was prolonged ( 164 msec ) and lv dysfunction was obvious ( lv ef=25.1% ) .
although the heart failure was not severe , the lv dysfunction in this patient was considered to be caused by chronic rv pacing and intraventricular dyssynchrony .
the underlying disease and life expectancy in children are different from those in adult , current indication for crt in adult patients may not be strictly applicable to children .
( 5 ) described the use of biventricular pacing in one infant with congenital complete av block and dcm that had been previously paced for complete av block .
( 6 ) reported an improved clinical status and lv ef following crt in four of five patients previously paced for surgical complete av block . in some study of resynchronization therapy in pediatric patients ( 7 , 12 ) ,
the authors reported the patients with av block who exhibited an average improvement in lv ef .
our patient showed an improving lv ef and septal to lv lateral delay on tsi .
similar to the improvement in lv function , our patient exhibited reduction in the plasma bnp level .
the change of bnp has rarely been described in pediatric patients with dilated cardiomyopathy undergoing crt ( 13 ) . in adult patients ,
bnp levels are deemed as a useful index to reflect different degrees of lv reverse remodeling ( 14 ) . meanwhile ,
( 15 ) reported anti ssa / ro and anti ssb / la antibodies were one of the risk factors for development of dcm in patients with congenital complete av block .
even though our patient 's anti ssa / ro and anti ssb / la antibodies were negative , his maternal anti ssa / ro and anti ssb / la antibodies were positive .
maternal antibody may result in not only the damage of the conduction tissue but also contracting myocardium of the fetal heart .
direct association between rvp and development of severe dcm and overt heart failure in the young has not yet been demonstrated in korea .
this case is expected to play a significant role in rvp induced electromechanical dyssynchrony in the development of lv dysfunction irrespective of av block etiology .
long term follow - up studies are also needed to determine not only beneficial effects and but also crt - related late adverse effects in young children . in summary , despite early institution of cardiac pacing , some patients with congenital av block develop lv cardiomyopathy .
patients with congenital av block have to be closely monitored not only their heart rate and rhythm but also ventricular function even after pacemaker implantation .
upgrading to crt by biventricular pacing should be considered in the patient who has progressive lv dysfunction after rvp .
 cardiac resynchronization therapy ( crt ) has been proven its value in adult patients with congestive heart failure of low ejection fraction and wide qrs duration . 
 contrast to adult patients , crt has been rarely applied for young patients . 
 we report on a 9-yr - old boy with progressive left ventricular ( lv ) dilatation and dysfunction following chronic vvi pacemaker therapy for congenital complete atrioventricular block associated with maternal anti - ssa / ro and ssb / la antibody . 
 his lv dysfunction was improved after epicardially established crt . 
INTRODUCTION
CASE REPORT
DISCUSSION