ClinicalVentricular TachycardiaProgressive implantable cardioverter-defibrillator therapies for ventricular tachycardia: The efficacy and safety of multiple bursts, ramps, and low-energy shocks
Graphical abstract
Introduction
The programming of an implantable cardioverter-defibrillator (ICD) directly influences the risk of inappropriate and avoidable shocks. Clinical trials have shown that strategies to reduce shocks are associated with reduced morbidity and mortality.1, 2, 3, 4, 5, 6, 7, 8, 9 One such strategy is limiting detection and therefore therapies to fast ventricular tachycardia (VT) or sustained arrhythmia by programming a longer duration (12 seconds) or higher detection window (30 of 40).6, 7, 8 Algorithms that aim to discriminate between VT and supraventricular tachycardia (SVT) through the onset or stability of the arrhythmia or analysis of the far-field signal can also reduce inappropriate therapies.10 Far-field analysis can also be used to discriminate between ventricular arrhythmia and oversensing.11 Finally, incorporating antitachycardia pacing (ATP) therapy has been shown to reduce the number of unnecessary and inappropriate shocks and to improve patient quality of life and device longevity.1,2,4 These strategies have been found useful for both primary and secondary prevention.6, 7, 8, 9,12 The 2019 Heart Rhythm Society, the European Heart Rhythm Association, the Asia Pacific Heart Rhythm Society, the Latin American Heart Rhythm Society (HRS/EHRA/APHRS/LAHRS) expert consensus statement on optimal ICD programming offers manufacturer-specific recommendations on how to program an ICD “out of the box.” For treatment of VT, programming at least 1 burst ATP therapy is recommended, followed by maximum-energy shocks.13 While widely applied, parts of the consensus statement await validation as many recommendations are based on limited evidence. For instance, VT zones are recommended up to 230 or even 250 beats/min, the number of ATP bursts to program is not specified, and ramp ATP and low-energy shocks are not advised.13
At our center, progressive therapies have historically been used for VTs up to 200 beats/min. A Multicenter Automatic Defibrillator Implantation Trial: Reduce Inappropriate Therapy (MADIT-RIT) study showed that for VTs <200 beats/min, syncope is a rare event (1 syncope vs 33 nonsyncope).12 This allows the ICD time to deliver multiple painless ATP therapies before delivering harmful shocks. We define progressive therapies as programming up to 6 ATPs (typically 3 bursts, followed by 3 ramps or by 3 bursts), followed by a low-energy shock before high-energy shocks (Figure 1). By analyzing VT episodes collected over the past decade through our remote monitoring center, we sought to explore the following questions: (1) Is a single burst of ATP as effective for VTs of 150–200 beats/min as it is for VTs of 200–230 beats/min? (2) What is the efficacy and safety of programming up to 6 bursts of ATP for VTs of 150–200 beats/min? (3) After 3 failed bursts, what is the efficacy and safety of programming 3 ramps compared with 3 more bursts? (4) What is the efficacy and safety of a low-energy shock vs a maximum-energy shock as first shock treatment of VT?
Section snippets
Study design
In this retrospective single-center study, we collected VT episode tracings via remote monitoring from all 5 major ICD vendors (Abbott, Abbott Park, IL; Biotronik, Berlin, Germany; Boston Scientific, Marlborough, MA; Medtronic, Minneapolis, MN; and MicroPort, Shanghai, China). Episodes were included if they demonstrated monomorphic VT at rates of 150–230 beats/min with at least 1 burst ATP therapy. For evaluations of progressive therapies, only VTs of ≤200 beats/min were considered. To limit
Patient and episode characteristics
In total, 1775 patients with ICDs who transmitted episodes labeled as VT or VF to our remote monitoring center were screened. We received and analyzed 1877 episodes with therapies labeled as VT or VF transmitted by 480 patients (27%). Two hundred thirty-nine episodes were wrongfully classified by the ICD as VT or VF (12%); they were SVT (189 episodes [10%]), oversensing of noise (26 episodes [1%]), or oversensing of physiological signals (24 episodes [1%]). Seventy-five of these misclassified
Discussion
In the present study, we evaluated the efficacy and safety of progressive ICD therapies by analyzing 1126 treated VTs sent to our remote monitoring center using all ICD vendors. Several important observations were made: (1) A single burst fails to terminate a third of VTs, <200 or >200 beats/min. (2) The cumulative rate of VT termination increases as more ATP therapies are delivered, which directly translates into an important reduction in shock therapy. However, each additional ATP therapy is
Conclusion
Programming up to 6 burst ATP therapies in a VT zone of 150–200 beats/min can avoid shocks in a substantial proportion of patients with ICDs. Ramp ATP therapies are not more effective than bursts. Low-energy shocks are less effective and more arrhythmogenic than high-energy shocks.
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Funding sources: This work received financial support from the French Government as part of the “Investments of the Future” program managed by the National Research Agency (ANR; grant reference ANR-10-IAHU-04).
Disclosures: Dr Ramirez was supported by a Canadian Institutes of Health Research Banting Postdoctoral Fellowship and a Royal College of Physicians and Surgeons of Canada Detweiler Travelling Fellowship.
The authors have no conflicts of interest to disclose.