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Figure 7 Atrial tachycardia originating from the left superior pulmonary vein (LSPV). (A) Surface echocardiogram and bipolar electrograms are depicted from sites shown in panel B. All bipolar electrodes registered the same activation cycle length (147 ms). The vein of Marshall (VOM) activations (red asterisks) occurred at longer cycle lengths than in the atria, suggesting intermittent conduction blocks from the left atrium (LA) to the VOM. Earliest activation (a) was found in the proximal LSPV, near the LA–LSPV junction.