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Figure 6 Accessory connection localization in mutant transgenic mice. (A) Vector analysis of surface six-limb lead ECG recordings from three TG^N488I mice. In each panel, the solid line is placed at the onset of pre-excitation, and the dotted line is placed 5 ms later, intersecting the preexcited waveform. The left panel shows a pattern consistent with an anteroseptal AV connection (leads I and aVL and leads II, III, and aVF are positive). The middle panel shows a pattern consistent with a left lateral AV connection (leads I and aVL are negative and leads II, III, and aVF are positive), and the right panel shows a pattern of a posteroseptal AV connection (lead I is isoelectric, lead aVL is positive, and leads II, III, and aVF are negative). (B) Masson trichrome-stained sections (x5) from one-week-old TG^N488I (left panels) and 2.5-week-old TG^N488I (right panels) hearts through the right paraseptal area anterior to the aortic outflow tract. The fibrous separation between the atrial and ventricular myocardium is intact in the mutant heart from the one-week-old animal, whereas there is physical contact between the atrial and vacuolated ventricular myocytes from the 2.5-week-old animal in the right anteroseptal region. Bottom inserts magnified x20.