Pace-Mapped Induction as a Surrogate for Entrainment Mapping in Ventricular Tachycardia

BACKGROUND: Entrainment mapping is the gold standard for identifying the critical isthmus in scar-mediated ventricular tachycardia (VT), but requires hemodynamic tolerance of the arrhythmia, which is absent in up to 70% of patients. CASE SUMMARY: An 84-year-old man with old anterior wall myocardial infarction, left ventricular apical aneurysm, and severely reduced ejection fraction (15%) presented with recurrent monomorphic VT. Pace-mapped induction (PMI) at a late-potential site within dense antero-apical scar produced a 12/12 morphologic match to the clinical tachycardia. The return cycle of the first spontaneous electrogram after the last paced stimulus approximated the tachycardia cycle length, mirroring formal entrainment criteria. Radiofrequency ablation at the PMI site terminated VT within 8 seconds; programmed stimulation with up to 4 extra-stimuli failed to reinstate any VT. The patient remained free of VT at 1-year follow-up. DISCUSSION: PMI appears to localize the obligate slow-conduction zone of the reentrant circuit with high specificity and provides functional information equivalent to entrainment, including morphologic matching, mid-diastolic activity, and return-cycle measurement. It is particularly valuable when VT is hemodynamically unstable. TAKE-HOME MESSAGE: PMI during slow-pacing substrate mapping could identify the critical VT isthmus and guide successful ablation without requiring sustained hemodynamically tolerated tachycardia.