Figure 1:

An example of inappropriate shock due to AF with a VT zone programmed at 370 ms due to previous monomorphic VT at this rate. In the top panel, PR Logic™ (Medtronic, Minneapolis, MN, USA) was used and AV dissociation was deemed to be present, likely due to the changing relationship between the atrial- and ventricular-sensed activities. The bottom panel shows that the morphology discriminator (Wavelet) detects that the QRS morphology is on average less than a 70% match for eight QRS complexes as compared with the template that was created. The rhythm is then deemed to be a double tachycardia with AF and VT as noted and antitachycardia pacing is subsequently delivered. Options to avoid repeat inappropriate therapy include decreasing the Match threshold for Wavelet. The VT zone could also be changed and the tachycardia onset discriminator could be turned off.