Postinfarction Ventricular Tachycardia Substrate Characterization: A Comparison Between Late Enhancement Magnetic Resonance Imaging and Voltage Mapping Using an MR-Guided Electrophysiology System

Abstract

Catheter ablation of ventricular tachycardia (VT) is preceded by characterization of the myocardial substrate via electroanatomical voltage mapping (EAVM). The purpose of this study was to characterize the relationship between chronic myocardial fibrotic scar detected by multicontrast late enhancement (MCLE) MRI and by EAVM obtained using an MR-guided electrophysiology system, with a final aim to better understand how these measures may improve identification of potentially arrhythmogenic substrates. Real-time MR-guided EAVM was performed in six chronically infarcted animals in a 1.5T MR system. The MCLE images were analyzed to identify the location and extent of the fibrotic infarct. Voltage maps of the left ventricle (LV) were created with an average of 231 ± 35 points per LV. Correlation analysis was conducted between bipolar voltage and three MR parameters (infarct transmurality, tissue categorization into healthy and scar classes, and normalized relaxation rate R1). In general, tissue regions classified as scar by normalized R1 values were well correlated with locations with low bipolar voltage values. Moreover, our results demonstrate that MRI information (transmurality, tissue classification, and relaxation rate) can accurately predict areas of myocardial fibrosis identified with bipolar voltage mapping, as demonstrated by ROC analysis. MCLE can help overcome limitations of bipolar voltage mapping including long durations and lower spatial discrimination and may help identify the sites within scars, which are commonly believed to trigger arrhythmic events in postinfarction patients.

Distribution of abnormal potentials in chronic myocardial infarction using a real time magnetic resonance guided electrophysiology system

“…These findings are in line with findings of Nakahara et al [ 13 ], where a higher concentration of abnormal EGMs (late potentials) was found in the putative isthmus and also with Hsia et al [ 7 ], where the majority of these delayed and fractionated endocardial electrogram recordings were found in critical central pathway sites. In this study we did not report nor conduct a rigorous correlation study between low-voltage and MR-defined dense scar, since it was the focus of our previous publication [ 15 ].…”

“…Bipolar recordings were made with the distal electrode pair (1 and 2). The catheters were placed in the (right ventricle) RV or LV using active catheter tracking with MR-guidance as reported previously [ 15 ]. The catheters were advanced under full MR guidance with a 3D LV shell created from segmentation of SSFP-cine images acquired in the same session, with the animal resting in the same position; this eliminated the need for additional registration or alignment.…”

“…At each point of contact, the intracardiac signals and the three-dimensional spatial coordinates were recorded. As detailed in our previous study we calculated spatial error associated with fusion of EAM surface and EP points by measuring the average perpendicular distance between EP points and mesh surface [ 15 ].…”

Postmyocarditis Ventricular Tachycardia in Patients with Epicardial‐Only Scar: A Specific Entity Requiring a Specific Approach

“…NICM patients also display distinctive electrogram (EGM) characteristics: The distribution of LAVA in NICM is typically epicardial, since almost all LAVA appear in low‐voltage areas . Correlation between low‐voltage area, LAVA signals, and ischemic scar on MRI has been demonstrated …”

Physiological Assessment of Ventricular Myocardial Voltage Using Omnipolar Electrograms

“…D uring ventricular tachycardia ablation, bipolar electrogram voltage amplitude is widely used for myocardial substrate characterization and for determining relevant therapeutic strategies. [1][2][3][4][5] Josephson and Anter recently highlighted the pitfalls of interpreting bipolar electrogram voltages as a medium for substrate mapping by identifying myriad factors that significantly affect its measurement. 6,7 These factors can be classified into those that can and cannot be standardized.…”