Elsevier

Heart Rhythm

Volume 6, Issue 5, May 2009, Pages 644-651
Heart Rhythm

Original-clinical
Imaging/mapping
Infarct architecture and characteristics on delayed enhanced magnetic resonance imaging and electroanatomic mapping in patients with postinfarction ventricular arrhythmia

https://doi.org/10.1016/j.hrthm.2009.02.018Get rights and content

Background

Delayed enhanced magnetic resonance imaging (DE-MRI) can be used for the exact assessment of myocardial infarct scar. Electroanatomic (EA) mapping can identify the subendocardial extension of infarcts and is used to identify and eliminate areas critical for postinfarction ventricular arrhythmias.

Objectives

The purpose of this study was to correlate DE-MRI with EA mapping in postinfarction patients with ventricular arrhythmias to assess myocardial infarct architecture and its relationship to postinfarction ventricular arrhythmias.

Methods

EA mapping during sinus rhythm was performed in 14 postinfarction patients (10 men; age 64 ± 10 years; ejection fraction 0.33 ± 0.12) referred for ablation of ventricular arrhythmias. All patients underwent prior DE-MRI. Both DE-MRI and EA mapping data were registered in three-dimensional space. Presence of scar and its transmurality as well as scar core versus gray zone were assessed on DE-MRI and correlated with EA maps; furthermore, the electrogram characteristics of the EA map were correlated with the DE-MRI.

Results

Scar areas as assessed by bipolar and unipolar voltages in the EA map both correlated well with the scar as defined by DE-MRI. The best cutoff value to differentiate subendocardial scar from normal myocardium was 1.0 mV for bipolar voltage and 5.8 mV for unipolar voltage. Areas with DE had distinct electrophysiologic characteristics compared with nonenhancing sites. All identified sites that were critical for postinfarction ventricular tachycardia (31/31) and premature ventricular complexes (5/5) were located within areas of DE, with most (71%) being located in the core area of the scar.

Conclusions

DE-MRI can accurately predict the EA characteristics of corresponding subendocardial locations. Critical sites of postinfarction arrhythmias were confined to areas of DE. The scar information on MRI can be selectively imported into an EA mapping system to facilitate the mapping and ablation procedure.

Section snippets

Patient characteristics (Table 1)

Fourteen consecutive patients were included in this study. The study was approved by the institutional review committees of both institutions.

MRI

All patients had MRI studies within 2 weeks before the ablation procedure. The studies were performed on a 1.5 Tesla MRI scanner (Signa Excite CV/i, General Electric, Milwaukee, WI) with a 4- or 8-element phased-array coil placed over the chest of patients in supine position. Images were acquired with electrocardiogram (ECG) gating during breath holds.

Patient characteristics

The patient characteristics are described in Table 1. The subjects of this study were 14 consecutive postinfarction patients referred for radiofrequency ablation of recurrent VT (n = 9) or symptomatic frequent PVCs (n = 5) that were refractory to medical treatment. None of the patients had a cardioverter-defibrillator at the time of hospital admission. One patient was being treated with amiodarone, and the other patients were not taking antiarrhythmic drugs other than a beta-blocker or calcium

Main findings

The unique aspect of this study is the demonstration that sites critical to reentrant ventricular arrhythmias in humans are located within areas of DE by MRI. Scar can be selectively extracted from DE-MRIs and registered into the EA mapping system using customized software. Areas enhancing with DE-MRI have distinct electrophysiologic characteristics as compared with nonenhancing sites.

Scar extraction and registration

This study demonstrated a high degree of correlation between endocardial EA voltage mapping and scar as

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This study was supported by National Institutes of Health grant no. 7K23EB006481 (to BD).

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