A patient becomes hemodynamically unstable after VT induction during EPS. Which mapping techniques can help identify the site of origin while the patient is in sinus rhythm?

A patient becomes hemodynamically unstable after VT induction during EPS. Which mapping techniques can help identify the site of origin while the patient is in sinus rhythm?

• A. Activation Map
• B. Pace Map
• C. Voltage Map
• D. Pace Map and Voltage Map

Answer: (D)

When VT cannot be mapped because the patient becomes unstable, you turn to mapping strategies that work in sinus rhythm. Pace mapping uses pacing from different ventricular sites during sinus rhythm and compares the resulting QRS shapes to the clinical VT. If the paced QRS closely matches the VT, that site is likely near the origin or exit of the VT circuit, helping to localize the target without needing the patient to tolerate sustained VT. Voltage mapping complements this by highlighting scarred or diseased tissue—the substrate that often forms VT circuits. Low-voltage areas and the borders of scars point to regions where reentry is more likely to occur. Together, pacing in sinus rhythm to find a VT-like QRS pattern and voltage mapping to outline scar architecture give a practical and accurate way to identify the origin and plan ablation when VT cannot be mapped directly. Activation mapping during VT would require a stable VT, which isn’t available here, so relying on pace and voltage maps is the best approach.

When VT cannot be mapped because the patient becomes unstable, you turn to mapping strategies that work in sinus rhythm. Pace mapping uses pacing from different ventricular sites during sinus rhythm and compares the resulting QRS shapes to the clinical VT. If the paced QRS closely matches the VT, that site is likely near the origin or exit of the VT circuit, helping to localize the target without needing the patient to tolerate sustained VT. Voltage mapping complements this by highlighting scarred or diseased tissue—the substrate that often forms VT circuits. Low-voltage areas and the borders of scars point to regions where reentry is more likely to occur. Together, pacing in sinus rhythm to find a VT-like QRS pattern and voltage mapping to outline scar architecture give a practical and accurate way to identify the origin and plan ablation when VT cannot be mapped directly. Activation mapping during VT would require a stable VT, which isn’t available here, so relying on pace and voltage maps is the best approach.