Evaluation of a real-time magnetic resonance imaging-guided electrophysiology system for structural and electrophysiological ventricular tachycardia substrate assessment

Figures

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  Figure 1. Set-up of the real-time MR-EP system to enable electrophysiology studies inside a MRI scanner. ECG, electrocardiogram; EGM, intra-cardiac electrogram; iCMR, interventional cardiovascular magnetic resonance; MR-EP, magnetic resonance imaging-guided electrophysiology; MRI, magnetic resonance imaging; RF, radiofrequency; RT, real-time.

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  Figure 2. Representative depiction of image-guidance platform showing three orthogonal MRI views demonstrating location of catheter in relation to LV endocardium, three-dimensional segmentation of the left ventricle derived from MRI and scar segmentation from LGE images to guide EAM. EAM, electroanatomic mapping; LGE, late gadolinium enhancement; LV, left ventricular; MRI, magnetic resonance imaging.

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  Figure 3. Representative examples of intra-cardiac EGMs obtained using the MR-EP system in a region of normal myocardium (Point 1) and area of scar (Point 2) (A–C). The baseline noise level inside the MRI scanner was in the region of 0.1 mV (∼10-fold higher than that in the conventional electrophysiology laboratory). Dot plot showing signal-to-noise ratios obtained for intra-cardiac EGMs in normal myocardium and LGE-derived scar regions from 7 animals; *P < 0.0001 (D). EGMs, intra-cardiac electrograms; LGE, late gadolinium enhancement; LV, left ventricular; MR-EP, magnetic resonance imaging-guided electrophysiology; MRI, magnetic resonance imaging; RA, right atrium.

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  Figure 4. Representative examples of segmented LGE scar, voltage, and S-QRS maps obtained using real-time MR-EP system in two animals (A and B). LGE, late gadolinium enhancement; MR-EP, magnetic resonance imaging-guided electrophysiology; S-QRS, stimulus-to-QRS.

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  Figure 5. ROC curves (A and C) for prediction of LGE regions using voltage mapping and S-QRS. Frequency histograms (B and D) displaying the true positive, false positive, true negative, and false negative counts of voltage mapping and S-QRS measurements using the real-time MR-EP system to predict MRI-derived scar. Sensitivity, specificity, PPV, and NPV of measurements using the system using different normal voltage cut-offs and S-QRS times (E–H). LGE, late gadolinium enhancement; MR-EP, magnetic resonance imaging-guided electrophysiology; MRI, magnetic resonance imaging; NPV, negative predictive value; PPV, positive predictive value; ROC, receiver operator characteristic; S-QRS, stimulus-to-QRS.

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  Figure 6. Sorenson–Dice similarity co-efficient between MR-derived scar shells (far left panels) and endocardial voltage maps with varying normal voltage thresholds (right panels) in two representative animals. FWHM, full-width-half-maximum; MR, magnetic resonance; MRI, magnetic resonance imaging.

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  Figure 7. DSCs between MR-derived scar shells and endocardial voltage maps acquired using MR-EP system following application of normal cut-off thresholds of 0.5–3.5 mV. DSC is shown for overall similarity, similarity across scar nodes and normal myocardium nodes. DSC, Dice similarity co-efficients; MR, magnetic resonance; MR-EP, magnetic resonance imaging-guided electrophysiology.