**3. VT/VF zone**

In the last decade of ICD therapy the programming of a single detection zone {eg. SCD-HeFT[1]} have been replaced by the programming of up to three detection zones with differ‐

ent discrimination algorithms and therapies (table 1). Moreover, data on the programming of zones up to 260ms CL with a long detection time are also available {ADVANCE III study [2]}. Until now, no consensus is accepted concerning the number of detection zones (not at least in primary prevention indication), nor clear definition of detection windows is given. Until 2010 most ICDs had no SVT/VT discrimination algorithm available in the VF zone. In primary prevention a VT zone from 360ms CL with long detection time, SVT/VT discrimina‐ tion up to 260ms CL and anti-tachycardia-pacing (ATP) prior or during charging, along with a VF zone from 260ms CL without SVT/VT discrimination and maximal energy shock deliv‐ ery was widely recommended. Depending from device a FVT zone was needed to program an ATP prior or during charging shock up to 280-250ms CL. Newer devices have now inde‐ pendent discrimination algorithm for every detection zone (Medtronic), and provide SVT/VT discrimination algorithms also in VF zone. Furthermore, ATPprior or during charg‐ ing is available in all zones. In secondary prevention patients with documented VTs, the first zone should be programmed 10-20ms above (or 10 bpm below) its cycle length. In younger patients with channel rhythm disorders like long QT syndrome a single zone (<280ms) can be considered. Patients with secondary prevention, very low ejection fraction or repetitive syncope need an individualized, more conservative programming with shorter detection in‐ tervals and less ATPs. Different programming examples for tachycardia detection and thera‐ pies in recent studies with primary prevention patients with ICDs of different manufacturers are listed in table 1.

**zone VT FVT VF**

**manufactures 150bpm 200bpm 250bpm**

Rx – 188 bpm[12/16] ATPx2 → Shocks

167 – 188 bpm[18/24] ATPx3 → Shocks

150 – 200 bpm[16 beats) ATPx3 → Shocks

delay) discrimination free, therapy free or Monitor

[60s delay), Rhythm ID ATPx1

170 – 200 bpm

181 – 214 bpm [25 beats) SVT Discr. ATPx2 → Shocks

→ Shocks

167 – 182 bpm [32 beats) Monitor

MADIT II[6] 2002 Boston 170 – 200 bpm, [1-5 sec

**4. Inappropriate ICD therapy**

Shocks

only

ATPx2 → Shocks

ATPx1 → Shocks

ATPx1 → Shocks

during change

200 – 250 bpm

Shocks

no clear definition no clear definition

**Table 1.** Change in detection for defibrillation therapy over the last ten years in corner stone studies of different

Inappropriate ICD therapy is a delivered ATP and/or shock in absence of VT/VF episode. Inappropriate ICD therapy has serious consequences: proarrhythmic effect, reduced quality of life, psychological stress with depression, unnecessary hospitalisation, early battery de‐ pletion duration and even elevated mortality [3]. Up to 80% of inappropriate ICD therapies are registered in the first year following device implantation [4, 5] figure 2. Atrial fibrillation

187bpm [18/24 beats) only

188 – 250 bpm[12/16 beats)

188 – 250 bpm[18/24 beats) ATPx1 → Shocks vs Shocks

200 – 250 bpm[18/24 beats)

182 – 250 bpm[30/40 beats)

187bpm [30/40 beats) ATP

>200 bpm[1-3 sec delay)

[12 sec delay) Rhythm ID ATPx1 → Shocks

214 – 250 bpm[18 beats) ATPx1 → Shocks

>250 bpm[12/16 beats)

>250 bpm[18/24 beats)

>250 bpm[18/24 beats)

>250 bpm[30/40 beats)

>250 bpm[2.5 sec delay) Quick Convert ATP → Shocks

>250bpm [12 beats) Shocks only

Shocks only

Tachycardia Discrimination Algorithms in ICDs

http://dx.doi.org/10.5772/52657

139

Shocks only

Shocks only

Shocks only

**Study, date and**

SCD-HeFT[1] 2005 Medtronic

PAINFREE[13] I 2001

PAINFREE[14] II 2005

EMPIRIC[15] 2006 Medtronic

PREPARE[16] 2008 Medtronic

ADVANCE III[2] Medtronic 2012

MADIT CRT[18] 2011 Boston

PROVIDE St.Jude Medical ongoing 2008-"/> (NCT00743522]

MADIT[17] 1996 Boston

Scientific

manufactures.

Medtronic

Medtronic

**Figure 1.** Notice critical area of VT and VF discrimination in yellow and orange up to 460ms cycle length

Practically, devices in primary prevention patients can be programmed using either single or two zones with long detection intervals. The programming should be adjusted during the follow-up in case of arrhythmic events.


**Table 1.** Change in detection for defibrillation therapy over the last ten years in corner stone studies of different manufactures.
