**15. Summary/Conclusion**

(d)

156 Cardiac Defibrillation

(e)

(f)

**Figure 22.** a: Demonstration of an AF episode in a CRT-D device with dual chamber detection (Promote St. Jude Medi‐ cal) A>V with CL around 344 to 270ms. Depending of CL the device counts VT (T) and VF (F) beats for detection. In this device no SVT discrimination algorithms are allowed in VF zone. b: Same episode 12 seconds later. After detection VT episode (NID 12] first VT therapy (ATP) is given. c: Same episode 27 seconds later. After acceleration of AF a VF episode Avoiding of inappropriate therapy delivery is one of the major issues in ICD therapy. In the last decade several new algorithms were developed to improve sensitivity and specificity of tachycardia detection. Current recommendation for primary prevention patients is the pro‐ gramming of a fast VT zone from 187 to 250 bpm with long NID or DT [30/40] for Medtron‐ ic, 12 seconds for Boston, 18/24 for St. Jude Medical and Biotronik), is ATP prior or during charging followed by shock therapy. For devices that not allow SVT discrimination in this zone a separate VF zone above 250 bpm should be programmed to make SVT discrimination possible in a VT zone of 187 to 250 bpm. If a second VT zone around 150-187 bpm is pro‐ grammed, a long NID (minimum 25 beats or 60 seconds) with stability and morphology dis‐ crimination algorithm without time out rule is recommended. Algorithms for early detection of lead fracture, sinus/tachy ratio and impedance monitoring are recommended when available. In patients with long QT syndrome or other risk for primary VF a single zone over 220 bpm is recommended. In dual chamber ICDs stability, morphology and A-V-A (or equivalent) SVT discrimination algorithms are recommended in the analysis of V=A and V<A tachycardias. Implantation of dual chamber ICD for better SVT/VT discrimination only is not indicated by currently available studies.

No algorithm is sensitive or specific enough to substitute the individual adaptation of ICD detection and therapy for every patient. Detailed knowledge of ICD algorithms may provide the necessary basis for the cardiologist to program devices individualized for each patient. Stored episodes should be carefully evaluated at every follow-up visit to further improve discrimination of SVTs and VTs.

## **Author details**

Martin Seifert\*

Address all correspondence to: m.seifert@immanuel.de

Heartcenter Brandenburg and Immanuel Klinikum Bernau, Department of Cardiology, Ber‐ nau bei Berlin, Germany

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Tachycardia Discrimination Algorithms in ICDs

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**Chapter 10**

**Current Issues in ICD SVT-VT Discrimination: Pacing for**

The stored electrograms (EGMs) retrieved from the ICD provide a unique and useful source

Current ICD algorithms discriminate VT from SVT on the basis of **passive analysis** of detect‐

Despite this, the incidence of inappropriate therapies for SVT discrimination still remains high and varies from 16% to 31% as quoted in prior studies [2]. In many ways, the ICD bears a resemblance to a diagnostic electrophysiological study. The underlying cardiac rhythm is analysed and acted on often with the delivery of anti-tachycardia pacing (ATP) if the threshold is met. This therapeutic interaction by the ICD with the underlying arrhythmia can also be interpreted as a diagnostic manoeuvre similar to the pacing techniques employed in the electrophysiology laboratory before arriving at the diagnosis (figure 1). The success or failure

Anti-tachycardia pacing has been demonstrated to be a safe, effective and painless therapy in randomized controlled multicentre trials [3,4]. In the PAINFREE trial two sequences of ATP were delivered before a shock in the fast ventricular tachycardia (FVT) zone. A total of 446 FVT episodes with a mean cycle length of 301 ± 24 msec were documented in 52 patients. A total of 396 of these FVT episodes were terminated by ATP alone with an adjusted efficacy of 77% (95% CI 68% to 83%) [5]. Acceleration of the VT by ATP occurred in only 10 (4%) FVT episodes but these went on to delivery of a definitive shock aborting the episode (figure 2).

and reproduction in any medium, provided the original work is properly cited.

© 2013 Michael et al.; licensee InTech. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

© 2013 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution,

of information regarding the mechanism of the underlying arrhythmia.

ed **rhythms** with positive predictive values of greater than 90% [1].

of ATP to terminate the underlying rhythm may both have value.

**SVT-VT Discrimination**

Mark L Brown

**1. Introduction**

http://dx.doi.org/10.5772/55047

**1.1. Anti-tachycardia pacing**

Kevin A Michael, Damian P Redfearn and

Additional information is available at the end of the chapter
