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Roy M. John, “Arrhythmia Diagnosis Following an ICD Shock
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Arrhythmia Diagnosis Following an ICD Shock
Arrhythmia Quiz 3
Roy M. John, MD, PhD, FRCP
Address for correspondence: Roy M. John, MD, PhD, Section of Cardiology, Lahey Clinic
Medical Center, 4І Mall Road, Burlington, MA 01805. Email: roy.m.john @ lahey.org
A 70 year old male with coronary artery disease, severe left ventricular dysfunction
(LVEF 20%), first degree AV block and underlying QRS of 154 msec underwent upgrade of
an existing dual chamber ICD system with a Medtronic Insync Model 7272. The device was
programmed to provide atrial synchronized biventricular pacing in the DDD mode. He
experienced significant improvement in heart failure symptoms following cardiac
resynchronization therapy. His ICD was programmed for single zone detection in the VF zone
at 182 bpm with first shock therapy of 24J. Pacing was programmed in the DDD mode with
lower rate limit of 70 and upper rate limit of 120ppm.
He presents with an ICD shock while seated watching television. He had minimal
prodromal symptoms prior to the shock although he admitted to being more dyspneic for the
past two days. Data recovered during ICD interrogation is shown below:
Figure 1: Electrograms and markers obtained during ICD interrogation. The top and bottom
panels show the onset and termination of arrhythmia respectively. In each panel, the following
information is displayed from top to bottom: atrial electrogram, ventricular electrogram, atrial
marker channel with cycle length and ventricular marker channel with cycle length.
Indian Pacing and Electrophysiology Journal (ISSN 0972-6292), 4(1): 43-44 (2004)