What does the the box plot show?
A) An inappropriate shock for AF
This is a single-chamber ICD and therefore there is no information from the atrium. At the beginning of the trace the RR intervals are irregular and relatively long (none are less than 400 ms). This is due to underlying AF. There is then a sudden increase to a regular tachycardia with a cycle length of 300 ms (rate 200 bpm) which is entirely consistent with VT. There are 18 of these beats before the device appropriately detects VT, marked with the word detection appearing at time point 0. The giveaway that ATP is delivered is the word ‘Burst’ being documented, but it can also be seen that 8 beats occur at a slightly shorter RR interval than the VT before the successful termination of the VT and a return to AF with a slower irregular RR interval. These 8 beats are the ATP being delivered. It is important to scrutinize all the information on the programmer printouts carefully as each manufacturer gives the information in a different format.