Figure 4.

Control subject with action potential duration alternans only at very fast rates preceding atrial fibrillation. This patient showed no action potential duration alternans at (A) cycle length 500 ms to (B) cycle length 240 ms, (C) action potential duration alternans appeared at cycle length 210 ms during 1 : 1 and 2 : 1 avtioventricular conduction, (D) at cycle length 180 ms, action potential duration alternans amplified to 6.5% of action potential duration immediately preceding AF initiation. Electrical restitution curve slope > 1 at the fast rates of action potential duration alternans onset. Adapted with permission from Narayan et al.⁷