Figure 1.

(A) Initiation of EAD-mediated triggered activity in canine cardiac Purkinje fibers during acidosis (A) and hypokalemia (B). (A) The numbers 1–4 indicate progressive increase in the duration (2, 5, 7, 8.5 min) of acidosis (20% CO₂ and 80% O₂) as shown below each recording [from Corabeuf, 1953 (Coraboeuf and Boistel, 1953)]. (B) Action potentials in a canine cardiac Purkinje fiber exposed to hypokalemia (K⁺₀ = 2 mmol/L) of increasing duration. Notice that the 3rd beat shows four EAD-mediated action potentials. The 4th recording shows EAD-mediated triggered activity that end with repolarization failure (from Cranefield, 1977).