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Figure 2 Three-dimensional electroanatomic activation map (CARTO) of the right atrium. Spontaneous sinus tachycardia is shown after administration of esmolol (B) and following successful sinus node modification (C). Red represents early and purple represents late electrical atrial activation. (A) The earliest site of activation during inappropriate sinus tachycardia (IST) to be in the vicinity of the atrium-SVC junction. (B) A 3.5-cm caudal shift of the earliest activation site after administration of intravenous esmolol. A CARTO map after sinus node modification shows a 2.5-cm caudal shift in the earliest activation site along the crista terminalis. CS = coronary sinus; HIS = His-Bundle potential; SVC = superior vena cava; IVC = inferior vena cava; TV = tricuspid annulus.