Abstract
A 73-year-old woman with presyncope and frequent episodes of symptomatic 2:1 atrioventricular block underwent implantation of a dual-chamber MRI-conditional pacing system (Advisa MRI SureScan pacing system, Medtronic, Minneapolis, MN) to facilitate cardiovascular magnetic resonance (CMR) assessment of apparent isolated right ventricular (RV) hypertrophy seen on transthoracic echocardiography (Figure 1 and online-only Data Supplement Movies I and II). The ventricular lead was positioned in the outflow tract. This pacing system is approved, outside of the United States, for MRI without isocenter restriction, provided certain conditions are fulfilled, including a static magnetic field strength of 1.5 T, a maximum gradient slew rate ≤200 T/m per second, whole body average specific absorption rate levels <2.0 W/kg, and a minimum period of 6 weeks between implantation and scanning. Within the United States, the isocenter is presently required to be either superior to C1 or inferior to T12 vertebrae. Figure 1. Parasternal long-axis ( A ) and short-axis ( B ) echocardiogram images showing apparent right ventricular wall thickening. CMR assessment was performed in accordance with the stated conditions. The impact of pacing on the activation pattern and regional deformation of both ventricles, and aortic and pulmonic forward flow, were studied by imaging in unpaced and paced (VVO; 75 bpm) modes. On balanced steady-state free precession imaging marked susceptibility artifact led to almost nondiagnostic image quality (Figure 2A and online-only Data Supplement Movie III). Switching to a spoiled gradient echo sequence greatly improved image quality (Figure 2B and online-only Data Supplement Movie IV) and reduced the specific absorption rate. Figure 2. Marked susceptibility artifact from the right ventricular pacing lead is seen in the 3-chamber view acquired using balanced …
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