Fig. 5.
Microelectrode recordings of Vm in cat isolated Purkinje fibres showing stretch-induced (A) focal ectopic excitation (first and last AP − middle AP represents normal conducted excitation, as evidenced by faster AP upstroke), induced by a change in fibre length of 10% from resting, and (B) increase in DD rate, which resulted in focal tachycardia when the change in fibre length reached 30% (lower tracing). In both examples, measurements were made from the point of focal activity.
From Dudel and Trautwein (1954), with permission.