Download Reduction of QRS duration following pulmonary valve replacement

European Heart Journal (2005) 26, 863–864
doi:10.1093/eurheartj/ehi206
Editorial
Reduction of QRS duration following pulmonary valve
replacement in tetralogy of Fallot: implications
for arrhythmia reduction?
Elizabeth A. Stephenson and Andrew N. Redington*
Division of Cardiology, Hospital for Sick Children, 555 University Avenue, Toronto, Canada M5G 1X8
Online publish-ahead-of-print 21 March 2005
This editorial refers to ‘Reduction of QRS duration
after pulmonary valve replacement in adult Fallot
patients is related to reduction of right ventricular
volume’† by B. Hooft van Huysduynen et al., on page
928
Tetralogy of Fallot is the commonest form of cyanotic
congenital heart disease, and early outcomes following
surgical repair are steadily improving. Nonetheless,
these patients remain at risk for late-onset arrhythmias
as well as sudden death.1,2 Increased QRS duration and
right ventricular (RV) dilation secondary to pulmonary
regurgitation have both been described as markers for
increased risk of ventricular arrhythmias and sudden
death.3–5 Pulmonary valve replacement (PVR) in these
patients has been shown to stabilize the QRS duration
and, when combined with cryoablation, to decrease the
incidence of ventricular arrhythmias.6
Hooft van Huysduyen et al. 7 present a retrospective
series of adult patients with tetralogy of Fallot, who
were assessed before and after PVR with both electrocardiograms (ECG) and cardiac magnetic resonance
imaging. In their series, patients demonstrated a significant decrease in both RV end-diastolic volume and QRS
duration, with reasonable correlation between these
two values. This is the first paper to demonstrate a
decrease in QRS duration, rather than simply stabilization. Interestingly, not all patients showed a reduction
in QRS duration, but there was a non-significant trend
toward greater reduction in RV volumes in those patients
with a decrease in QRS duration. QRS duration measurement was performed using averaged beats rather than
the more standard technique of using maximal QRS
* Corresponding author.
{
E-mail address: [email protected]
doi:10.1093/eurheartj/ehi140
length in any lead on a standard ECG. Although this
may have influenced absolute values of QRS, it is unlikely
to have biased the results, as it is the change from preoperative to post-operative rather than the absolute
value of the QRS that was considered.
The findings of this study are, at least to some degree,
different from those reported previously. Therrien et al. 6
showed no overall difference in QRS duration at a mean
of 4 years post-operatively, in a group that appeared to
have significant reduction in RV dilatation by echocardiogram. In comparison, a control group showed a small but
consistent increase in QRS duration. If these data are
considered individually, one finds a highly heterogeneous
response following PVR, with both substantial increases
and decreases in QRS within the study population. The
follow-up ECGs in Hooft van Huysduyen’s study patients
were performed at a median of 14.3 months (IQR 3.8–
20.1 months); a much shorter follow-up period than
that of the Therrien study. This raises the concern
that the reduction in QRS duration is transient; the
reason these two papers reached different conclusions
was that they considered the populations at two different
time intervals and that by 4 years the average QRS duration has returned to the pre-operative value. The
answer to this question lies in serial review of large
numbers of ECGs following PVR, from immediately postoperatively to the latest available. If the QRS response
continues to appear heterogeneous, it would be important to consider what factors may be influencing this
variability.
When the relationship between RV dilation, QRS
prolongation, and malignant arrhythmias was first recognized, the so-called mechano-electric interaction, it was
unknown whether PVR would alter this relationship or
whether mechanical and electrical reverse remodelling
could occur. The current data are encouraging in this
regard. If, indeed, there is true reversal of QRS
& The European Society of Cardiology 2005. All rights reserved. For Permissions, please e-mail: [email protected]
864
prolongation following PVR, this may indicate reduced
arrhythmia vulnerability. Currently, most centres are
only performing PVR on patients who are symptomatic
with exercise intolerance or clinical arrhythmia, or
those with the most severe RV dilation. If, indeed,
there is a threshold above which RV mechanical and
electrical reverse remodelling is less likely, and the risk
of malignant arrhythmia is reduced following PVR if
performed before this threshold is reached, it would be
reasonable to liberalize the indications for valve replacement. However, before any such conclusion can be
drawn, more information is required as perioperative
mortality and morbidity is not zero, and the insertion
of a conduit will essentially guarantee the need for
repeated interventions (albeit possibly by transcatheter
techniques) in the future.
We have come a long way over the past 15 years.
Chronic pulmonary regurgitation after repair of tetralogy
was once considered benign. It is now known that it leads
to RV dilation in many, with concomitant development of
exercise intolerance, congestive heart failure, and atrial
and ventricular arrhythmias.8 It may be that timely
reduction in RV volume and QRS duration will protect
against irreversible dysfunction and the development of
clinical arrhythmia. The results of large-scale prospective
studies are eagerly awaited.
Editorial
References
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with repair of tetralogy of Fallot: 36-year follow-up of 490 survivors of
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2. Harrison DA, Harris L, Siu SC et al. Sustained ventricular tachycardia in
adult patients late after repair of tetralogy of Fallot. (See comment).
J. Am Coll Cardiol 1997;30:1368–1373.
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7. Hooft van Huysduynen B, van Straten A, Swenne CA et al. Reduction of
QRS duration after pulmonary valve replacement in adult Fallot
patients is related to reduction of right ventricular volume. Eur
Heart J 2005;26:928–932. First published on February 16, 2005,
doi:10.1093/eurheartj/ehi140.
8. Wang Z, Taylor LK, Denney WD et al. Initiation of ventricular extrasystoles by myocardial stretch in chronically dilated and failing canine
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