Relationship Between Voltage Map “Channels” and the Location of Critical Isthmus Sites in Patients With Post-Infarction Cardiomyopathy and Ventricular Tachycardia
What is the most accurate sinus rhythm mapping technique for identifying an effective ventricular tachycardia (VT) ablation site within a post-infarction scar?
A critical isthmus in which radiofrequency catheter ablation successfully eliminated a clinical VT (mean cycle length 410 ms) was identified by entrainment mapping in 24 post-infarction patients (mean age 67 years, mean ejection fraction 33%). The endocardial voltage maps underwent post-hoc analysis to identify endocardial scar (voltage <1.5 mV) and isolated late potentials (ILPs). Voltage cutoffs were adjusted to identify channels within scar.
Thirty-seven channels were identified within scar in 21 of 24 patients (88%). ILPs were present within 17/37 channels (46%) in 11/24 patients (46%). Only 11/37 channels (30%) contained the critical isthmus at which the clinical VT had been successfully ablated. Voltage channels in which ILPs were recorded had a sensitivity of 78% for identifying a successful ablation site, and a specificity of 85%.
Channels identified by voltage mapping within post-infarction scars are not an accurate indicator of a critical isthmus at which VT can be successfully ablated. The value of a channel for identifying a critical isthmus is enhanced by the presence of ILPs.
The most accurate mapping techniques for post-infarction VT (e.g., concealed entrainment) require an ongoing episode of VT. In many post-infarction patients, the VT that is targeted for ablation is not hemodynamically tolerated. In these patients, mapping is performed during sinus rhythm using pace mapping, voltage mapping, and/or mapping of ILPs. This study demonstrates that voltage mapping to identify channels within scar are not clinically useful unless they contain ILPs.
Keywords: Infarction, Tachycardia, Ventricular, Cicatrix, Cardiomyopathies, Catheter Ablation
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