Case 12 A Shock at Washing

Patient: 46-year-old male with corrected Fallot's tetralogy. Index arrhythmia: sustained monomorphic ventricular tachycardia. Complaint: Shock when doing the laundry. Electrogram

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.

ICD pulse generator: Marquis DR 7274 (Medtronic Inc, Minneapolis, MN, USA).

Tachycardia settings

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.

Bradycardia settings

Figure 6.12b.

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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