Fractionated electrograms with ST-segment elevation recorded from the human right ventricular outflow tract

Figure 1. A: The traces show 4 different unipolar electrograms recorded at the right ventricular outflow tract (RVOT) and 2 corresponding bipolar electrograms (red). B: A photograph of the epicardial side of the wedge preparation showing the site recording at the proximal and distal RVOT and the corresponding unipolar recordings. Stimulation occurred at the right ventricle. The proximal electrode was located 2 cm from the site of stimulation and recorded activation at ∼45 ms. The distal electrode was located twice as far but activated at ∼250 ms, suggesting delayed activation of RVOT. The monophasic morphology in the distal RVOT coincided with the electrogram at the proximal RVOT. C: Unipolar electrograms recorded from the proximal and distal RVOT when stimulated on the distal RVOT. Note the sharp deflection and normal ST segment in the unipolar electrogram recorded from the distal RVOT. Dist = distal; prox = proximal; PT = pulmonary trunk; RV = right ventricle; stim = stimulation.

Figure 2. Top image shows a photograph of the transmural wall of the right ventricular outflow tract (RVOT) preparation at the location where we recorded electrograms. The images below show Masson’s trichrome staining, indicating fatty infiltration into the transmural wall of the RVOT. Panels a and b represent magnifications. PT = pulmonary trunk.

Figure 3. A: Simulation of a 2-dimensional myocardial sheet where the intracellular potential in the black region is clamped to -60 mV while the surrounding region is activated, showing a monophasic-like potential in the extracellular space. B: The black region is not clamped but is connected to the surroundings by small connections leading to conduction blocks, causing an ST-segment elevation in the extracellular space.