Figure 1.

An example of decremental conduction, unidirectional block, and induction of ventricular tachycardia (VT) from Jackson et al. [25]. During right ventricular pacing, local abnormal potentials can be seen on bipoles A to K. With the introduction of the first extrastimulus (S2), an important delay in bipoles A to J is observed. With S3, there is a block (*) of the local potential on bipole I and subsequently with S4 there is block (*) at the VT exit site (bipole J). Block at the VT exit site and conduction delay through the entrance of the channel set the basis for re-entrance. The mechanistic study by Jackson et al. showed that those late potentials that had decremental properties were more frequently co-localized with the VT isthmus.