In addition to the PVC burden, other characteristics like a longer PVC duration, presence of nonsustained VT, multiform PVCs and right ventricular PVCs might be associated with cardiomyopathy.

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Before creating a detailed 3-dimensional map of an arrhythmia, the electrophysiologist should already have a reasonable idea regarding which cardiac chamber contains either the focal site of origin of an automatic tachycardia or the relevant substrate for reentry. Typically, a combination of careful review of the ECG during tachycardia and knowledge of the location of abnormal substrate (such as myocardial infarction, atriotomy scar, etc) will allow focused mapping in the appropriate chamber.Prior teaching points have already discussed 1,2 the fact that an isolated "early site of activation" is essentially meaningless for guiding ablation of macroreentry. However, in some circumstances, even for a focal "automatic" tachycardia, the apparently early site is not a suitable site to target for ablation. Figure 1. Activation map of a focal tachycardia ablated in the supravalvar pulmonic area. In each map, colors reflect activation time relative to the QRS with earliest activation shown as red; yellow, green, blue, and purple indicate progressively later activation. A, Activation map of the right ventricle (RV) with earliest activation at the left anterior right ventricular outflow tract (RVOT) at Ϫ97 ms before the reference time. B, Activation map of a limited area of the left ventricular outflow tract (LVOT) has been added, showing that earliest activation remains in the RVOT at Ϫ97 ms. C, Activation map of the proximal pulmonary artery (PA) has been added. Earliest activation is now identified in this supravalvar region at Ϫ106 ms. D, Activation map of the aortic root (AO) is added. There is no further change in the earliest activation point, which remains above the pulmonary valve, identifying the successful ablation site.

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