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Figure 1 Temporary epicardial leads for pacing protocol. Standard right atrial (RA) leads, one active (–) and one indifferent (+) lead. Two right ventricular (RV) leads, RV base (–), RV apex (+). One left ventricular (LV) free wall lead (–). Atrial pacing (AOO) mode uses RA leads only. Conventional dual-chamber pacing (CDOO) uses RA and RV leads. Biventricular pacing (BDOO) uses RA, RV, and LV leads.