Slow VT treatment in a contemporary population of primary prevention ICD recipients

Abstract

Funding Acknowledgements Type of funding sources: None. Background Implantable cardioverter defibrillator (ICD) is an effective therapy for sudden cardiac death (SCD). 2015 HRS/EHRA/APHRS/SOLAECE expert consensus document suggests long VT detection, above 185 bpm, as optimal ICD programming to reduce unnecessary therapies in primary prevention (PP). Purpose The aim of our study is to evaluate incidence, safety and efficacy of ICD treatment for VT arrhythmias below 185 bpm, in a contemporary population of PP ICD recipients with long detection intervals (LDI), morphological discrimination algorithm and antitachycardia pacing therapies (ATP) before shock. Methods We conducted a single centre retrospective study enrolling 236 patients implanted with a primary-prevention indication from January 2013 to June 2019. Patients were implanted with single or dual chamber single-lead transvenous ICD. All patients had standard device setting with long (at least 20 s in VT and 7 s in VF) VT/VF detection above 150 bpm and therapies starting from 171 with up to 5 ATP and multiple shocks. PainFREE-like bursts and Schaumann-like ramps ATP were always set in VT zone. Of each patient we collected a detailed report of up to five appropriate events and three inappropriate events. Arrhythmia diagnosis was confirmed from 3 independent expert physicians. Date of the event, cycle length, type of morphology (polymorphic or monomorphic), therapies with their effect were collected. Results During a mean follow-up of 42 months, 47 (20 %) and 18 (8%) patients had at least one appropriate and inappropriate activation, respectively. The detailed-events analysis shows that 16 (7%) patients had 38 (30%) appropriate events with rate <188 bpm. At these rate ATP were 97% effective. 14 (38%) of inappropriate activations were caused by arrythmias with ventricular rate below 188 bpm and half of these received a shock; 30% of inappropriate shocks were due to arrhythmia with rate <188 bpm. 73% of treated events, with rate <188 bpm, were appropriate. Only 5.6% (n = 10) of ATP attempts cause arrhythmia acceleration. Conclusions One third of detected arrhythmias had a rate below 188 bpm and 73% were true VT. In this slow VT zone, ATP had a high success rate with low percentage of acceleration.