3D delayed enhancement magnetic resonance sequences improve conducting channel delineation prior to ventricular tachycardia ablation

Abstract

Introduction: Delayed enhanced cardiac magnetic resonance using 2D sequences (CMR-2D) represents the standard for clinical characterization of myocardium. However, 2D images suffer from insufficient spatial resolution in the Z-axis and missregistration that preclude appropriate visualization of conducting channels (CC), which are critical for ventricular tachycardia (VT) ablation. We studied whether characterization using a free breathing 3D delayed enhanced navigator gated sequence (CMR-3D) proved to be superior than CMR-2D sequences. Methods: We included 30 consecutive patients with structural heart disease referred for VT ablation. Myocardial characterization was conducted prior to the ablation procedure in a 3T-scanner using CMR-2D and CMR-3D sequences, yielding a spatial resolution of 1.4 x 1.4 x 5 mm and 1.4 x 1.4 x 1.4 mm respectively. The scar components, core and border zone (BZ), were quantified in both datasets using the 60% and 40% threshold of maximum pixel intensity, respectively. The signal to noise ratio (SNR) and contrast to noise ratio (CNR) was analyzed in a representative slice in both sequences. For both set of images a 3D reconstruction of the scar was obtained and an electrophysiologyst identified potential CC and compared them to those depicted in the electroanatomic map (EAM). Results: We found no significant differences between the mass of the scar core in the 2D and 3D sequence (mean 7.33±6.56 vs 6.74±5.22 grams respectivelly, p=0.612). However, the BZ mass was smaller in the 2D than in the 3D sequence (9.38±7.72 vs 12.10±7.81 grams; p=0.019). The SNR was higher in the 2D dataset as compared to the 3D (42.93±27.34 vs 28.09±12.85; p=0.005) as well as the CNR (37.01±26.20 vs 20.15±11.41; p=0.001). The mean number of CC identified in the 3D dataset was higher than in the 2D, and closer to those depicted in the EAM (1.06±0.75 for CMR-2D vs 2.63±1.41 for EAM, p=0.005; and 2.06±1.25 for CMR-3D vs 2.63±1.41 for EAM p=0.088). Conclusion: Despite the higher SNR and CNR of standard CMR-2D images, the higher spatial resolution provided by CMR-3D images improved the overall delineation of CC prior to VT ablation.