THE RELATION BETWEEN ATRIAL-FIBRILLATION WAVE-FRONT CHARACTERISTICS AND ACCESSORY PATHWAY CONDUCTION

Although the source-sink relationship for impulse propagation in cardi ac tissues has been demonstrated in vitro, there has been no verificat ion of this hypothesis in humans. Accordingly, eight patients undergoi ng surgical division of their accessory pathways were studied, A 56-ch annel (7 X 8) bipolar plaque electrode array was placed over the atrio ventricular groove on the accessory pathway and atrial fibrillation el ectrically induced, 10 episodes of QRS transition from consecutively p reexcited to nonpreexcited complexes were analyzed. This showed that c onsecutively preexcited QRS complexes were always associated with unif orm large atrial wavefronts, Immediately prior to QRS transition, four general types of changes were observed: (a) premature invasion by sec ondary wavefronts creating local conduction block (n = 5); (b) wavefro nt collision leading to wavefront curvature (n = 2); (c) transition fr om a uniform large atrial wavefront to multiple fractionated small wav efronts (n = 1); and (d) uniform atrial wavefronts ''marching'' into t he accessory pathway refractory period (n = 2), We conclude that local atrial wavefront characteristics are important factors influencing im pulse propagation through the accessory pathway, The findings that loc al wavefront collision, curvature, or fractionation often precede loss of accessory pathway conduction support the notion that source-sink r elationship is an important determinant of the safety factor for impul se propagation in the human heart.