What is the mechanism of ischemic ventricular tachycardia?

• A. Micro
• B. Macro
• C. Focal
• D. Hemodynamic

Answer: (B)

Ischemic ventricular tachycardia is driven by a macroreentrant circuit around scar tissue in the ventricle. After myocardial infarction, scar forms and creates an obstacle to normal conduction. Surviving myocardium in the border zone often conducts slowly and may have areas of block, allowing an impulse to travel around the scar in a looping path and re-enter the tissue that has already recovered excitability. This large looping circuit sustains the tachycardia, hence the term macroreentry. Focal VT would arise from a single active focus rather than a reentrant loop, and microreentry would involve a much smaller circuit, which is less characteristic of ischemic VT. Hemodynamic describes the effects rather than the mechanism.