Patient 1 : A 71-year old male patient implanted with a triple-chamber Boston Scientific Autogen CRT-D revealed an episode of PMT during interrogation of the device.
Patient 2 : 69-year old male patient implanted with a triple-chamber Boston Scientific Autogen CRT-D revealed an episode of PMT during interrogation of the device.
Patient 1 :
Patient 2 :
These tracings correspond to two episodes of PMT induced by premature atrial contraction (A) or non-sustained VT (B). For a Boston Scientific device, the diagnosis of a PMT is made after the occurrence of 16 consecutive AS – VP cycles at the maximal tracking rate. The VA intervals are required to be stable; when one of the 16 VA intervals varies by more than 32 ms from the first VA interval of the tachycardia, the intervals are considered unstable and the counter (fixed at 16 consecutive cycles) is reset at zero. When the device diagnoses PMT, the PVARP is prolongated to 500 ms for one single cycle (corresponding to the 16th cycle).
Atrial or ventricular extrasystoles, isolated or in bursts, are major contributors for induction of PMTs since they cause an offset between ventricular and atrial depolarization. To avoid these types of episodes, the most suitable solution is probably to extend the PVARP so that it exceeds the retrograde conduction delay.
