Direction‐ and rate‐dependent fractionation during atrial fibrillation persistence: Unmasking cardiac anisotropy?

Figures

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  Figure 1. Epicardial mapping using a 64‐electrode spatula. With eight rows of eight unipolar electrodes, having an interelectrode distance of 2.5 mm, the spatula covers a mapping area of 17.5 × 17.5 mm. During epicardial mapping extracellular potentials of atrial tissue are recorded.

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  Figure 2. Premature atrial complex (PAC) causes unidirectional longitudinal block with corresponding low‐amplitude, fractionated potentials with long duration. At the top, the electrode 6 tracing demonstrates one sinus rhythm (SR) beat followed by a ventricular far‐field complex (V), together with one PAC with subsequent ventricular activation. During recordings the spatula was placed on the caudal pulmonary vein (PV) area. Color‐coded activation maps of both the SR beat and PAC are shown. The SR impulse arises from the right‐lower part of the mapping area and homogeneously propagates towards the left‐upper part, whereas the PAC exhibits inhomogeneous and slow conduction around several lines of block (∆local activation time ≥12 ms, visualized as thick white lines). The SR beat is characterized by high‐amplitude, biphasic and smooth extracellular potentials with short duration (80‐95 ms), whereas the PAC exhibits low‐amplitude, multiphasic potentials with long duration (160‐177 ms). CL, cycle length (ie, coupling interval of consecutive atrial impulses)

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  Figure 3. Pacing at shorter cycle length induces multiphasic fractionated potentials, due to a lower transverse conduction velocity in relation to longitudinal conduction velocity. With the spatula on the mid PV area, pacing from the right atrial appendage was performed. Three unipolar tracings of electrode 10 are shown, corresponding with pacing cycle lengths of 600, 500, and 333 ms (ie, 100, 120, and 180 beats per minute, respectively). In contrary to pacing at low rates, pacing at the highest rate (ie, cycle length of 333 ms) induced low‐amplitude, fractionated atrial potentials with prolonged durations. A, atrial complex; P, pacing; PV, pulmonary vein; V, ventricular far‐field complex