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Figure 2 Electrocardiogram during left ventricular (LV) pacing, showing fusion at AV1 but not at AV2, AV3, and AV4. From the electrocardiographic leads I, II, III, aVR, aVL, aVF, and V₁ are displayed together with telemetered right ventricular (RV) electrogram (EGM). Notice the change in the morphology of the RV EGM when fusion is lost completely; see also Figure 3.