Assessing myocardial circumferential strain using cardiovascular magnetic resonance after magnetic resonance-conditional cardiac resynchronization therapy.

Nondrug therapy for arrhythmia patients had been developed dramatically until recent years. Cardiac resynchronization therapy (CRT), a nondrug therapy for arrhythmia, is especially utilized for the treatment of left ventricular (LV) severe heart failure caused by cardiac dyssynchrony. Prolonged QRS duration (≧130 ms) is strongly used as a CRT indication criterion, but QRS is not the direct clinical index of mechanical contraction delay of the LV myocardium. Therefore, identifying the presence of dyssynchrony by diagnostic imaging is necessary. Echocardiography is widely used for the assessment of dyssynchrony as a standard diagnostic imaging. Several studies have addressed the efficacy of cardiovascular magnetic resonance feature tracking (CMR-FT) in the diagnosis of dyssynchrony for arrythmia patients. In addition, cardiac implantable electronic devices (CIEDs) were not available to examine CMR until recent years; however, new MR-conditional CIEDs have become available for use before and after CRT. Recently, diagnostic imaging using CMR-FT has been attracting attention for the assessment of dyssynchrony. However, a strong metal artifact caused by CIEDs may make the analysis difficult after CRT implantation. Strain analysis using short-axis (SA) cine CMR overcame this issue of artifact by enabling slice selection by avoiding artifact. Moreover, circumferential strain has superiority over other strain methods with respect to sensitivity, and we focused on these advantages. This case illustrates that circumferential strain with CMR-FT using SA cine CMR is useful in the assessment of improvement of myocardial motion after CRT and can provide useful additional information with imaging to determine the responders of CRT.