Beat to beat volumetric analysis in arrhythmia using real time CMR

Abstract

Background ECG-gated cardiac MRI is the gold standard for volumetric evaluation of patients, and clinically, ejection fraction is used as a surrogate for function. We hypothesized that the use of arrhythmia rejection in the presence of ectopic beats compromises the accuracy of hemodynamic measurements. Real-time MRI, coupled with ECG telemetry and semi-automated LV endocardial segmentation, can be used to identify multiple beat morphologies and derive global hemodynamic measurements for each beat. Methods Short-axis golden angle radial bSSFP projections (8000 projections/slice) were reconstructed using Gadgetron (non-Cartesian, iterative SENSE) with 34 projections per frame, and slice volume was measured via segmentation of LV endocardial contour with ITK-SNAP. ECG was synchronously recorded with the acquisition, and each image frame was assigned a time point on the ECG (~22 seconds/slice). QRS detection was used to identify cardiac cycles, and similar beats (across slices) were grouped via RR-duration of the beat of interest as well as the previous (loading) beat. The use of the loading beat duration allowed for accurate grouping of premature ventricular contractions (PVCs). For each beat morphology, global volume was obtained by summation of slice volume curves allowing for hemodynamic evaluation via EDV, ESV, SV, and EF.