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.