ARKS for a patient with a severe arrhythmia using a 4-16-57 scheme (shots-segments-projections). A) Signal buffer SS with the most recent physiologic data (1-2 heart beats). B) Large buffer SL storing history of the physiologic signal. 4 similar periods of the signal are labeled (red). C) Cross-correlation between SS and SL. Local maxima are labeled (red). Lags for the first 4 local maxima are used to label the ECG in B. D) For the first 3 shots, 16 radial projections are acquired and labeled -8 to 7, with the 0 projection corresponding to the lag index in C. 8 projections are acquired in the last shot. These 56 projections determine the angle of the 57th projection. E) 57 k-space radial projections. Projection color corresponds to the shot index in D. F) Simulated image from radial projections prescribed in E. G) Time-varying ventricular volume from the line in F.