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Focal atrial tachycardia arising from the mitral annulus

Electrocardiographic and electrophysiologic characterization

^* Department of Cardiology, Royal Melbourne Hospital, and the Department of Medicine, University of Melbourne, Melbourne, Australia

View larger version (39K): [in a new window]   Figure 1 The tachycardia P-wave morphology of three patients is shown here. The P-wave in precordial leads is characteristically biphasic, with an inverted component followed by an upright component. The upright component is most prominent in lead V1 but diminishes with transition across the precordium. The limb leads are all of low amplitude, with a minor positive deflection in the inferior leads.

View larger version (56K): [in a new window]   Figure 2 (A) An example of the typical atrial activation sequence with the ablation signal at the successful site. The first beat is a sinus beat showing earliest activation at the high crista terminalis (CT). The second beat is a spontaneous atrial ectopic originating from the tachycardia focus. Earliest activity on the right atrial and coronary sinus (CS) catheters is at the proximal His bundle pair. However, the mapping and ablation (MAP) catheter located at the superior mitral annulus (MA) reveals a much earlier signal, which was 40 ms ahead of P-wave onset. Note the atrial-to-ventricular ratio is indicative of an annular location. (B) Graphic representation of the mean activation times at each of the recorded endocardial sites for the seven patients. Earliest endocardial activation on these standard catheters occurred at the His bundle region in all seven patients. HBE = His bundle. Numbers listed in catheter location refer to bipolar pair.

View larger version (79K): [in a new window]   Figure 3 Left anterior oblique and right anterior oblique projections of the catheter positions are shown with the mapping catheter at the successful ablation site on the mitral annulus in Patient #3. ABL = ablation catheter across transeptal puncture; CS = coronary sinus; CT = crista terminalis; HBE = His bundle.

View larger version (19K): [in a new window]   Figure 4 Schematic of the mitral annulus (MA) in the left anterior oblique projection showing the location of the seven tachycardia foci at the point of successful ablation. All were positioned superiorly between 11:00 and 12:00 when viewing the MA as a clockface. AV = aortic valve; CS = coronary sinus; HBE = His bundle; MV = mitral valve; TV = tricuspid valve.