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Failure to Sense



This strip shows dual chamber pacing in DDD mode, with problems.   The first six beats are unexceptional, but the seventh is a fusion beat.  The eighth beat is the problem beat: after the atrial pacer spike, but before the ventricular spike, a native beat occurs.  The pacer should have sensed this, and withheld the ventricular stimulus.   The pacer is also failing to sense atrial activity throughout this strip.  Native P-waves can be seen marching through the paced rhythm if you look closely.