Abbreviations:
ACEI: Angiotensin-converting-enzyme inhibitors
ARB: Angiotensin II receptor blockers
ARNI: Angiotensin receptor-neprilysin Inhibitors
AF: Atrial fibrillation
ATP: Anti-tachycardia pacing
CI: Confidence Interval
CRT: Cardiac ressyncronization therapy
CV: cardiovascular
-D: defibrillator
ECG: electrocardiogram
h: hour
HR: hazard ratio
ICD: implantable cardioverter-defibrillator
LVEF: Left ventricle ejection fraction
SCD: Sudden cardiac death
SVT: Supra-ventricular tachycardia
VF: Ventricular Fibrillation
VT: Ventricular tachycardia
TEXT
INTRODUCTION
The use of implantable cardioverter-defibrillators (ICD) is a well
stablished therapy1. It reduces the risk of sudden
cardiac death (SCD) and all-cause mortality in patients with symptomatic
heart failure (HF) and left ventricular ejection fraction (LVEF) of
≤35%, despite optimal medical therapy. Recent registries also
corroborate the ICD benefit in contemporary HF
patients2. However, increasing awareness of the
frequency and the adverse outcomes associated with avoidable ICD
therapies also emerged. Several studies 3-9 suggested
that increasing detection duration and/or detection heart rate resulted
in a reduction of inappropriate and unnecessary therapies and all-cause
mortality when compared with conventional programming. Based on these
studies and on a meta-analysis including all of
them10, generic device programming guidelines were
issued in a 2015 Consensus Statement11, intending to
be applied to devices from all manufacturers. Nevertheless, the cited
studies were specific to each manufacturer and extrapolating their data
to a uniform programming to be used in clinical practice is not
straightforward. In addition, concerns about failure of modern ICDs to
treat VF have been raised and complex and unanticipated interactions
between manufacturer-specific features and generic programming were
adressed12.
The authors intent to determine if a uniform programming of tachycardia
zones, independently of the manufacturer, result in a lower rate of
avoidable shocks without compromising efficacy in patients with a
primary prevention indication for a defibrillator. The authors also
aimed to find if programming high-rate or delayed therapies can have
some benefit over the other.
METHODS
Study design
The study was a single center, randomized clinical trial of two
defibrillator tachycardia programming strategies and included a
historical cohort of patients of the same institution, programmed at
physician consideration.
Study population
Eligible patients were >18 years of age and had a primary
prevention indication for a defibrillator [ICD or cardiac
resynchronization therapy (CRT) with a defibrillator (CRT-D)] without
a specific indication for individualized programming.
Prospective group included all consecutive patients that had presential
scheduled consult between July and December 2017 and also those who
implanted a defibrillator from July 2017 to July 2019.
The historical patients were all consecutive patients that had
presential schedule consult between July and December 2014 and also
those who implanted a defibrillator from July 2014 and July 2016. To
avoid selection bias, being part of the randomized group was not an
exclusion criterion for being included in the historical group.
Otherwise, “good patients” (patients with a more favorable clinical
profile and no previous therapies) would be excluded from the control
group.
Data collection
Demographic data, cardiovascular risk factors, cause of HF (ischemic and
non-ischemic), transthoracic echocardiograms (LVEF) and medications were
recorded at the time of enrollment. Clinical summaries, device-stored
electrograms, interval plots and episode logs were accessed during the
follow-up on a regular basis (remote monitoring quarterly and schedule
visits yearly). Data collection in historical patients were based on
registries in schedule visits during the follow-up period retrieved from
the national patient registry and from medical records or discharge
letters, validated by reviewing patients’ files. The same
characteristics were analyzed.
Programming
Patients enrolled in the prospective group were randomized to one of the
two programming configurations: high-rate detection or delayed detection
(in a 1:1 consecutive fashion). Tachyarrhythmia detection and therapy
settings were chosen to allow a uniform programming across all
manufacturers. The paramount difference between the 2 configurations are
a longer detection (from 12/18 to 30/40) and a lower threshold rate in
the zone 2 (from 200 to 188 bpm). Details are displaced in figure 1.
Programming of the VT/VF detection and therapy parameters in the
historical group was not specified. It has been left at the discretion
of the physician, variable from patient to patient and details were
unavailable. SVT discriminators were used in all patients (in both
groups), according to manufacturer´s recommendation. Bradycardia pacing
settings were programmed at the discretion of the physician.