PMC4706391_01
12-lead ECG of the patient with short QT. Below are shown the acceptable R/T ratio using the screening ruler both at implant (left) and at 1 year (right).
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After assuring an acceptable R/T ratio using the screening ruler (Fig. 1), the pulse generator was placed subcutaneously in the anterior axillary line with the electrode inserted subcutaneously parallel to the sternal midline.
Programmer telemetry recordings in the primary (A), secondary (B) and alternate (C) detection configurations at implant, during exertion and at rest at 1 year follow-up. S are the markers of the QRS complexes as sensed by the device (see text for detailed explanation).
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The device adequately sensed the R wave (Fig. 2) even if there are a few missed R waves at exertion in some configuration (arrows), especially when the R wave amplitude slightly decreases (the subcutaneous ICD uses a two peak average to adjust the detection profile dynamically, but in the presence of varying amplitudes such as during exertion, a few beats may be missed while adjusting to the underlying amplitudes). The latency sometimes observed after the R wave on markers (red circle) in the alternate configuration is an artifact of programmer telemetry's ability to process increased marker activity, for example, exertion scenario at follow-up (such a behavior is not observed in the ambulatory setting).