In pace mapping, the 12-lead ECG during pacing is compared to which reference?

In pace mapping, the 12-lead ECG during pacing is compared to which reference?

• A. 12-lead ECG recorded previously in VT
• B. Baseline 12-lead ECG during normal rhythm
• C. A 3-lead rhythm strip during pacing
• D. A 24-hour Holter ECG

Answer: (A)

Pace mapping relies on reproducing the VT pattern to locate the origin. The reference used is the 12-lead ECG recorded during the VT itself, because that VT morphology shows the exact activation sequence and exit vector you’re trying to match. When pacing from a site, you compare the paced QRS across all leads to the VT QRS; a close match suggests the pacing site is near the VT origin and a good target for ablation. Using the baseline rhythm would show normal conduction, not the VT pattern you’re trying to replicate, and a short 3-lead strip or a 24-hour Holter wouldn’t provide the full 12-lead comparison needed for accurate mapping.

Pace mapping relies on reproducing the VT pattern to locate the origin. The reference used is the 12-lead ECG recorded during the VT itself, because that VT morphology shows the exact activation sequence and exit vector you’re trying to match. When pacing from a site, you compare the paced QRS across all leads to the VT QRS; a close match suggests the pacing site is near the VT origin and a good target for ablation. Using the baseline rhythm would show normal conduction, not the VT pattern you’re trying to replicate, and a short 3-lead strip or a 24-hour Holter wouldn’t provide the full 12-lead comparison needed for accurate mapping.