Impact of ICD artifact burden on late gadolinium enhancement cardiac MR imaging in patients undergoing ventricular tachycardia ablation.

BACKGROUND: Cardiac magnetic resonance imaging (CMRI) is the gold standard for myocardial scar evaluation. Although ideal for substrate assessment in ventricular tachycardia (VT), most patients have an implantable cardioverter-defibrillator (ICD) at presentation for ablation. This study evaluates the ICD artifact burden during standard late gadolinium enhancement CMRI (LGE-CMRI) evaluation of myocardial scar in VT patients with ICDs. METHODS: Thirty-one patients with ICD and cardiomyopathy underwent LGE-CMRI using 1.5-T magnetic resonance scanner before VT ablation. Using the American Heart Association (AHA) 17-segment model, short-axis LGE series were analyzed for artifact burden localization and assessment. RESULTS: Preablation CMRI was performed in 31 patients with single chamber (n = 13), dual chamber (n = 11), and biventricular (n = 7) ICDs. Pre- and post-MRI ICD parameters were unchanged. All patients had susceptibility artifact and 51.6% (256 of 496) of segments were affected by artifact. The artifact area (178 ± 136 cm(2) ) resulted in an artifact burden of 54 ± 21% of the LV myocardial area (327 ± 15 cm(2) ). The anterior wall was most affected by artifact (89%) compared with 52%, 49%, and 23% in the lateral, septal, and inferior walls, respectively (P < 0.0001). The apical segments had more artifact burden (66%) than the mid (49%) and basal (44%) segments (P = 0.0005). Artifact area correlated with ICD-heart distance on anteroposterior chest radiograph (r = 0.42, P = 0.021) and body mass index (r = -0.48, P = 0.008). CONCLUSIONS: Current clinical LGE-CMRI scar imaging protocols produce ICD artifacts that affect >50% of the LV myocardium and correlate with the ICD-heart distance. This significantly limits the application of CMRI for image-guided VT ablation.