Key result
Ventricular fusion beats simulating A, B, and C types of WPW syndrome were produced in dogs by varying the site of ventricular stimulation and the interval between atrial and ventricular pacing.
Experimental ventricular fusion beats in dogs demonstrate that the site and timing of ventricular pre-excitation determine the resulting QRS morphology, simulating WPW syndrome types A, B, and C.
Animal data on fusion beats simulating WPW leave open human mechanistic relevance; no clinical implications.
1) The ventricular fusion beat was produced in dogs with atrial pacing and the stimulation of various sites of ventricle. The interval between atrial and ventricular stimulation was controlled by a preset timer with a step of 1msec.2) The limit of the range of the AV stimulation interval (D1 and D2) for the fusion beat was related to the normal activation time of the location of the ventricular stimulation.3) The QRS morphology corresponding to the A type of WPW syndrome was obtained from the stimulation of posterior and lateral wall of the LV, that to B type from the base of the RV, and that to C type from the septal area of the LV, the posterior basal part and tha apical 2/3 of the RV.4) The longer interval of the atrial and ventricular stimulation caused the B type QRS at any site of the ventricular stimulation.
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UEDA et al. (1974) studied WPW Syndrome (simulated) (n=26). Atrial and ventricular pacing was evaluated on QRS morphology of ventricular fusion beat. Ventricular fusion beats simulating A, B, and C types of WPW syndrome were produced in dogs by varying the site of ventricular stimulation and the interval between atrial and ventricular pacing.
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