Marker Annotation Misalignment on a Defibrillator Interrogation Printout

Abstract

A 47-year-old man with a past medical history significant for mitral stenosis, status post mitral valve replacement, and intraoperative Maze procedure for paroxysmal atrial fibrillation presented to our institution for heart failure management. He had a nonischemic dilated cardiomyopathy with an ejection fraction of 15%, New York Heart Association class III symptoms, and a left bundle branch block. Subsequently, he underwent implantation of Cardiac Resynchronization Therapy-Defibrillator (CRT-D) system (Guidant Contak Renewal 3 HE, model H177; Boston Scientific) in May 2005. Device interrogations during follow-up revealed thousands of atrial tachycardia response (ATR) episodes secondary to recurrent paroxysmal atrial fibrillation and atypical atrial flutter (AFL). Noncompliant with medical therapy, the patient received an inappropriate shock for an episode of atrial fibrillation with a rapid ventricular response. Atrioventricular (AV) node ablation was performed to avoid further inappropriate shocks and to ensure biventricular pacing. Three months later, the patient received another shock, at which time 69783 ATR episodes had been recorded. The device intracardiac event sequence is shown in Figure 1. Is the event associated with normal device function? DiscussionThe figure shows the stored intracardiac electrograms (EGMs) retrieved after the patient received a defibrillator shock. The three panels are continuous. Panel A shows an AFL with a CL of 220 msec, which is dissociated from a regular ventricular rhythm that has a cycle length (CL) of approximately 700 msec. This rhythm is consistent with the patient's documented clinical AFL with complete heart block and either ventricular pacing or a ventricular escape rhythm. In addition, it should be noted that there is evidence of atrial EGM dropout. Toward the end of panel A, a polymorphic ventricular tachycardia (VT) is initiated. The VT becomes regular and monomorphic in panel B with a CL of approximately 250 msec. During the VT, the CL of the AFL remains unchanged at 220 msec. The rhythm in panel B is consistent with a double tachycardia consisting of both an AFL and a VT. In panel C, it appears that a shock is delivered. The shock converts both the AFL and the VT to sinus tachycardia and a competing, irregular, slow VT. Toward the end of panel C, atrial sensing-ventricular pacing is delivered. The strips appear to be consistent with an appropriate defibrillator shock for VT.However, the confidence of the interpreting physician is challenged when the marker annotations are reviewed in context with the EGMs. The marker annotations in Panel A indicate a ventricular event detected in the VF zone with a cycle length of approximately 250 msec, while the ventricular EGM demonstrates a regular ventricular rhythm with a cycle length of 700 msec. This finding raises the question of whether this recording represents oversensing on the ventricular channel and thus, an inappropriately detected event. In addition, the interval annotation channel in Panel B indicates ventricula...

Significance of Missing Telemetered Markers in Implanted Cardioverter‐Defibrillators

“…Unusual manifestations of the telemetry function of pacemakers and ICDs have been rarely reported 1,2 . Some experts might consider our observations as curiosities with no clinical significance.…”

“…Unusual manifestations of the telemetry function of pacemakers and implantable cardioverter‐defibrillators (ICDs) are uncommon 1,2 . We have encountered three patients with St. Jude ICDs (St. Jude Medical, Sylmar, CA, USA) where telemetry revealed missing markers.…”

Electrograms and Marker Delay: Is There a Problem?

“…There has been one published case of misalignment between surface ECG and intracardiac EGM due to a software problem . Another case of misalignment of marker channel and stored events have been reported, also due to software issues as well . In both cases, there was no adverse effect on device function.…”

Unusual Marker Annotation: Something Shifty is Going On

“…Misalignment between the surface electrogram and the intracardiac electrograms is a rare occurrence and makes the interpretation of device system testing challenging. There has been one prior published case of misalignment between the recorded channels 1 . In that case, there was a discrepancy in the timing between the marker channel and all the intracardiac electrograms on a stored event during an episode of dual tachycardia (atrial fibrillation and ventricular tachycardia).…”

“…There has been one prior published case of misalignment between the recorded channels. 1 In that case, there was a discrepancy in the timing between the marker channel and all the intracardiac electrograms on a stored event during an episode of dual tachycardia (atrial fibrillation and ventricular tachycardia). This was attributed to a software problem in the device that may occur when an atrial tachycardia response episode and the electrogram segment storage end at the same time.…”