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Figure 3 Adenosine-Insensitive Focal Atrial Tachycardia From a Patient With Muscular Dystrophy (Patient #5, Table 2)

After adenosine 12 mg, high-grade atrioventricular block occurs, but the tachycardia cycle length and activation sequence are unchanged. The earliest activation in the coronary sinus (CS) appears in the mid-posterior poles (CS 5,6). The right atrium (RA) is activated by wave fronts that fuse in the lateral wall. Note that conduction delay from the left atrium to lateral RA approximates the tachycardia cycle length.