Characterization of the Effects of Single Ventricular Extrastimuli on Endocardial Activation in Human Infarct-Related Ventricular Tachycardia
Oliver R. Segal, MRCP,
Anthony W.C. Chow, MD, FRCP,
Vias Markides, MD, MRCP,
D. Wyn Davies, MD, FRCP, FHRS and
Nicholas S. Peters, MD, FRCP, FHRS*
Department of Cardiac Electrophysiology, St. Mary’s Hospital and Imperial College, London, United Kingdom.
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Figure 1 VT Circuit Depiction, Placement of Reconstructed Electrograms, and Resetting Definitions
(A) Schematic representation of an infarct-related ventricular tachycardia (VT) circuit with the central common pathway bordered by presumed scar and a line of functional block. A figure-8 re-entrant native cycle is shown. Reconstructed electrograms were placed parallel and adjacent to this line of block to calculate the local temporal excitable gap within the circuit. (B) A single ventricular extrastimulus arising from the site of stimulation (pacing symbol) preexcites the circuit leading to an extrastimulated wavefront. Collision with the native cycle wavefront in the DP is shown. See text for discussion. DP = diastolic pathway.
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Figure 2 Example of a Single Ventricular Extrastimulus Pre-Exciting a VT Resulting in Resetting
At the top are electrocardiographic (ECG) leads aVR and V1 showing ventricular tachycardia (VT) with a cycle length of 520 ms. At the bottom is a reconstructed electrogram within the systolic portion of the circuit showing pre-excitation at 386 ms. The return cycle electrogram occurs 468 ms later, and the VT has been reset by 176 ms.
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