Figure 6.12a. From top to bottom: atrial electrogram, ventricular electrogram, and marker channel. Markers: AR = atrial refractory sense; AS = atrial sense; TF = tachycardia sense (fast ventricular tachycardia window); TS = tachycardia sense (ventricular tachycardia window); VF = ventricular fibrillation sense; VS = ventricular sense.
Detection: VF = 300 ms; fast VT via VF = 270 ms; VT = 430 ms. Discrimination: stability = 40 ms; PR Logic ON.
Therapy: VF = shock; fast VT and VT = antitachycardia pacing and cardioversion.
1. Presence of tachyarrhythmia?: No.
2. Presence of high-frequency noise on isoelectric baseline?: Yes.
3. Interval plot: the interval versus time plot shows AA intervals and VV intervals with cycle length of 100-150 ms. These short intervals are an indication of high-frequency noise due to non-physiological signals.
4. Description of the atrial and ventricular electrogram: the atrial and ventricular electrograms show large as well as sinusoidal deflections. The large deflections represent the baseline rhythm, cycle length ~ 850 ms. The sinusoidal deflections demonstrate high-frequency noise due to electromagnetic interference.
Diagnosis: external electromagnetic interference.
Action: instructions for the patient to avoid sources of electromagnetic interference. Grounding of the washing machine.
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