Feasibility of Cardiac Magnetic Resonance Wideband Protocol in Patients With Implantable Cardioverter Defibrillators and Its Utility for Defining Scar

Abstract

Implantable cardioverter defibrillators (ICDs) have been a relative contraindication to cardiovascular magnetic resonance imaging. Although cardiovascular magnetic resonance provides valuable information regarding scar in patients with ventricular arrhythmias or cardiomyopathy, ICDs in these patients frequently cause artifacts hindering accurate interpretation of both cine and late gadolinium enhancement (LGE) images. We sought to quantify the frequency and severity of artifact on LGE images and assess whether a modified wideband LGE protocol could improve the diagnostic yield of scar identification in agreement with invasive electroanatomic mapping (EAM). Forty-nine patients with ICDs and ventricular tachycardia (VT) or cardiomyopathy underwent CMR (Philips 1.5T), including standard and wideband LGE imaging. A safety algorithm was followed throughout the protocol. Standard and wideband LGE short-axis images were graded using an artifact score on a per-slice basis. LGE on wideband images was compared with EAM in 27 of 49 patients who underwent VT ablation. There were no adverse patient- or device-related events. With standard LGE imaging, 84% of patients demonstrated some degree of hyperenhancement artifact, which persisted in 22% on wideband LGE but with much less extent. Wideband LGE imaging resulted in an increase from 48% to 94% diagnostic-quality slices, with a significant reduction in artifact score, and correlated with EAM in 21 of 27 patients (78%). In conclusion, assessment of standard LGE is markedly limited by artifact in patients with ICD. The use of wideband LGE significantly improves image quality and can accurately localize myocardial scar before VT ablation.

Figure 1.

Patient safety algorithm. This demonstrates the clinical decision-making that determined patient eligibility for CMR with acceptable safety, and device and patient monitoring performed before, during and after the CMR exam. CMR = cardiovascular magnetic resonance.

Figure 2.

Optimal patient positioning. This example demonstrates a significant 4 cm displacement of ripple artifact from the ICD generator, due to a maneuver in which the ipsilateral arm of the ICD generator was raised above the head for the duration of the CMR exam. ICD = implantable cardioverter defibrillator.

Figure 3.

Selection of optimal frequency shift. 4-chamber view (top row) and 2-chamber (bottom row) views at three pre-selected frequency shifts (−1500 Hz, 0 Hz and +1500 Hz, respectively) were utilized before contrast administration. Optimal frequency shift was identified by the image with the least prominent hyperenhancement artifact. Asterisk (*) represents the artifact from the ICD generator itself or its effects on the extracardiac and orange arrows represents how this artifact affects the myocardium. In this example, artifact is least prominent at +1500 Hz and was selected as the appropriate frequency shift for the wide band late gadolinium enhancement images.

Figure 4.

Example: Hyperenhancement artifact simulated anterior wall LGE (middle) but was completely resolved with WB imaging (right). This correlated with epicardial voltage mapping (left) showing normal voltage patterns and no electroanatomic evidence of scar (purple denotes normal myocardium, whereas scar area would be depicted by gray, which is absent in this image; see examples in Figures 5 and 6). LGE = late gadolinium enhancement; WB = wideband.

Figure 5.

Example: The presence of concomitant hyperenhancement artifact (yellow arrows) can obscure true scar, as evidenced in this patient for whom there was underlying severe basal to mid lateral wall scar (orange arrows) made more evident by WB imaging. This correlated with clinical VT and focus of catheter ablation findings (right, gray region indicating scar in the epicardial/endocardial basal lateral walls). VT = ventricular tachycardia.

Figure 6.

Example: Severe and transmural inferolateral and anterolateral wall infarct (right panels) was well-correlated with voltage mapping of scar (left, gray region indicating scar in the epicardial/endocardial basal lateral walls).