Decreased inappropriate shocks with new generation ICDs in
children and patients with congenital heart disease
Stephanie A. Goldstein MD
Martin J. LaPage MD, MPH
Brynn E. Dechert RN, CPNP
Gerald A. Serwer MD
Sunkyung Yu MS
Ray E. Lowery BS
David J. Bradley MD
University of Michigan Congenital Heart
Center, Ann Arbor, Michigan, USA
Stephanie Goldstein, University of Michigan
Congenital Heart Center, 1540 East
Hospital Dr., Ann Arbor, MI 48109.
Objective: Inappropriate implantable cardioverter defibrillator (ICD) shocks in children and patients
with congenital heart disease (CHD) remain a major complication of device therapy, occurring in as
many as 50% of children with ICDs. New generation devices include algorithms designed to mini-
mize inappropriate shocks. This study aimed to evaluate the effect of new generation ICDs on the
incidence of inappropriate shocks in the pediatric and CHD population.
Design: Retrospective study of patients with CHD or under age 25 receiving ICDs between 2000
and 2015. New generation ICDs were defined as those with Medtronic “SmartShock” algorithms.
Results: Two hundred eight devices were implanted in 146 patients. Rates of inappropriate shocks
were similar between diagnoses (P 5 .71). The rate of inappropriate shock was 15% over median
5.8 years follow-up. In the 36 patients (25%) with new generation ICDs, the rate of inappropriate
shock was 6.3% over 4 years. Comparing old to new generation ICDs, freedom from first inappro-
priate shock was 90.6% versus 97.1% at 1 year and 80.4% versus 97.1% at 3 years (P 5 .01). Lead
fracture was associated with having inappropriate shock (hazard ratio 8.5, P < .0001), and there
was no significant difference between the device groups when lead fractures were excluded. Clini-
cal actions were taken in 69% of patients after initial inappropriate shock (such as medication or
program change, system revision, or explant). When an action was taken, subsequent inappropriate
shock was reduced (5.3% vs 49.2% at 1 year; P 5 .002).
Conclusions: Pediatric and CHD patients are experiencing reduced inappropriate shocks with new
generation ICD systems, though reduced lead fracture may account for this improvement. Clinical
interventions after inappropriate shock favorably impact the subsequent rate of shocks once an
inappropriate shock occurs.
complication, congenital heart disease, ICD, inappropriate shock, lead fracture, pediatric
Inappropriate implanted cardioverter-defibrillator (ICD) shocks in chil-
dren and patients with congenital heart disease (CHD) remain a major
complication of this potentially lifesaving device therapy. Their inci-
dence is as high as 18%–50% in children, often a rate greater than that
for appropriate shocks.
Children and patients with CHD constitute
as little as 1% of the total population with ICDs, and thus the majority
of data available on factors contributing to inappropriate shocks and
approaches to decreasing them are from older populations with differ-
ent clinical characteristics.
Children have been shown to have sig-
nificant morbidity from inappropriate shock therapies, including post-
Abbreviations: CHD, congenital heart disease; HR, hazard ratio; ICD,
implantable cardioverter-defibrillator; IS, inappropriate shock; LF, lead
fracture; NG-ICD, new generation ICD; TWOS, T-wave oversensing.
Congenital Heart Disease. 2018;13:413–418. wileyonlinelibrary.com/journal/chd
2018 Wiley Periodicals, Inc.
Received: 21 September 2017
Revised: 17 November 2017
Accepted: 22 December 2017