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Pace-mapping conduction delay at reentry circuit sites of ventricular tachycardia after myocardial infarction
T Harada1, Y Tomita, T Nakagawa
1St. Marianna University School of Medicine, Toyoko Hospital, Kanagawa, Japan.
Insights
This study found that conduction delay during ventricular tachycardia pace-mapping is significantly longer at sites proximal to the reentry circuit exit. These findings highlight slow conduction in specific areas following myocardial infarction.
Area of Science:
- Cardiology
- Electrophysiology
- Medical Imaging
Background:
- Ventricular tachycardia (VT) is a significant complication after myocardial infarction (MI).
- Understanding the electrophysiological substrate of VT is crucial for effective ablation strategies.
- Reentry circuits are a common mechanism for VT in post-MI patients.
Purpose of the Study:
- To investigate the relationship between conduction delay during pace-mapping and the location of reentry circuit sites in patients with post-MI VT.
- To differentiate conduction properties at various sites within and outside the VT reentry circuit.
Main Methods:
- Retrospective analysis of data from 40 patients undergoing catheter mapping and ablation for post-MI VT.
- Pace-mapping and entrainment pacing were used to identify 122 endocardial sites relative to the VT reentry circuit.
- Stimulus-to-QRS interval was measured to quantify conduction delay at different sites.
Main Results:
- Sites proximal to the VT reentry circuit exit exhibited significantly longer conduction delays (103 ms) compared to exit sites (57 ms), other circuit sites (57 ms), and bystander sites (57 ms).
- Pace-mapping indicated greater conduction delay at sites proximal to the reentry circuit exit, suggesting slow conduction.
- Exit and outer loop sites were frequently located at the infarct border with less evident conduction delay.
Conclusions:
- Conduction delay during pace-mapping is significantly increased at sites proximal to the ventricular tachycardia reentry circuit exit in patients with post-MI VT.
- Slow conduction is a key characteristic of regions proximal to the reentry circuit, likely contributing to VT maintenance.
- These findings enhance our understanding of VT substrate and may inform targeted ablation strategies.
Abstract:
This study was carried out to determine the relationship of conduction delay during pace-mapping, as indicated by the stimulus to QRS interval to different reentry circuit sites and bystanders, as identified by entrainment criteria, in patients with ventricular tachycardia late after myocardial infarction. Catheter mapping and ablation were performed in 40 patients with ventricular tachycardia after myocardial infarction. Data were retrospectively analyzed from 122 endocardial sites which met the following the criteria: a 12-lead electrocardiogram was recorded during pace-mapping, ventricular tachycardia was then induced and entrained by pacing to classify the type of the site relative to the reentry circuit exit. By entrainment criteria 77 sites were in the reentry circuit (28 exit sites, 49 other circuit sites) and 45 sites were bystanders not in the reentry circuit. The average stimulus conduction delay at central/proximal sites was 103 +/- 43 ms, which was significantly longer than at exit (57 +/- 31 ms), outer loop sites (57 +/- 32 ms), and bystander sites (57 +/- 37 ms); P < 0.05. Pace-mapping revealed evidence of greater conduction delay at sites proximal to the reentry circuit exit, consistent with slow conduction between these regions and the border of the infarct. Exit sites and outer loop sites were more likely to be located along the border of the infarct, with less conduction delay evident during pace-mapping.