What is the clinical evidence from this study?

Study design: Cohort. Population: Scar-mediated ventricular tachycardia (n=44). Intervention: Pace-mapping identifying multiple exit sites (MES) vs. Absence of MES during pace-mapping. Primary outcome: Freedom from recurrent VT (p=0.024).

February 15, 2012Open Access

Functional Pace-Mapping Responses for Identification of Targets for Catheter Ablation of Scar-Mediated Ventricular Tachycardia

Key Result

Patients with scar substrates exhibiting multiple exit sites during pace-mapping had improved freedom from recurrent VT at 9 months compared to those without (74% vs 42%, P=0.024).

Study Design

Type

Cohort (n=44)

Structured PICO

Does the identification of multiple exit sites (MES) during pace-mapping predict improved freedom from recurrent ventricular tachycardia in patients undergoing catheter ablation for scar-mediated VT?

Population

44 consecutive patients with scar-mediated ventricular tachycardia undergoing mapping and catheter ablation

Intervention

Catheter ablation targeting sites with abnormal electrograms identified via high-density mapping and pace-mapping (specifically looking for multiple exit sites [MES] and pace-mapped induction [PMI])

Comparator

Patients without multiple exit sites (MES) observed during pace-mapping

Outcome

Freedom from recurrent ventricular tachycardia at 9 monthshard clinical

The presence of multiple exit sites and pace-mapped induction during pace-mapping identifies critical reentry sites and is associated with significantly improved freedom from recurrent ventricular tachycardia following catheter ablation.

Main Result

Absolute Event Rate: 74% vs 42%

p-value: p=0.024

Abstract

BACKGROUND: Myocardial scars harbor areas of slow conduction and display abnormal electrograms. Pace-mapping at these sites can generate a 12-lead ECG morphological match to a targeted ventricular tachycardia (VT), and in some instances, multiple exit morphologies can result. At times, this can also result in the initiation of VT, termed pace-mapped induction (PMI). We hypothesized that in patients undergoing catheter ablation of VT, scar substrates with multiple exit sites (MES) identified during pace-mapping have improved freedom from recurrent VT, and PMI of VT predicts successful sites of termination during ablation. METHODS AND RESULTS: High-density mapping was performed in all subjects to delineate scar (0.5-1.5 mV). Sites with abnormal electrograms were tagged, stimulated (bipolar 10 mA at 2 ms), and targeted for ablation. MES was defined as >1 QRS morphology from a single pacing site. PMI was defined as initiation of VT during pace-mapping (400-600 ms). In a 2-year period, 44 consecutive patients with scar-mediated VT underwent mapping and ablation. MES were observed during pace-mapping in 25 patients (57%). At 9 months, 74% of patients who exhibited MES during pace-mapping had no recurrence of VT compared with 42% of those without MES observed (P=0.024), with an overall freedom from VT of 61%. Thirteen patients (30%) demonstrated PMI, and termination of VT was seen in 95% (18/19) of sites where ablation was performed. CONCLUSIONS: During pace-mapping, electrograms that exhibit MES and PMI may be specific for sites critical to reentry. These functional responses hold promise for identifying important sites for catheter ablation of VT.