Which remapping criterion is most appropriate when the tachycardia cycle length changes during mapping?

• A. Change in QRS morphology
• B. Increase in heart rate by 20%
• C. Decrease in cycle length by 50 ms
• D. Tachycardia cycle length change greater than 10%

Answer: (D)

When mapping tachycardia, you need a stable cycle length to accurately time activation across the map. If the tachycardia cycle length changes by a meaningful amount, the recorded activation times and the perceived circuit can shift, making the previous map unreliable. The most appropriate remapping trigger is a tachycardia cycle length change greater than 10%. This relative threshold balances sensitivity and robustness, flagging real circuit changes rather than minor fluctuations or measurement noise. Remapping under the new cycle length reestablishes accurate timing, ensuring the critical slow-conduction zone or isthmus is correctly located for effective ablation. Other cues like QRS morphology changes or fixed numeric changes (such as a 50 ms shift) are less reliable across patients and scenarios, and a simple 20% rate increase isn’t a standardized remapping criterion.