Introduction: 4D data (time-series images) inundate the viewer, so conventional 2D slice image review for decision making verges on impracticality. A multiplexed composite presentation was developed to facilitate review of the 4D cardiac data for diagnostics. Methods: Data were collected by MRI as time-series: 4D data (beating volume), and bolus transit contrast studies. Space-time maps were produced by extracting heart muscle in short axis views, remapping it from polar to Cartesian, so that the annular muscle formed a vertical strip, tiled into a 2D image in which vertical distance represents distance around the myocardium, and horizontal distance represents time. Results: Space-time maps enabled instant recognition and rapid measurement of size and timing of abnormalities, validated by microsphere distributions (r equals 0.86), ex vivo CT imaging (r equals 0.95), and correspondence to treatment effect (p less than 0.01). Multiplexed space-time maps enabled rapid recognition and rapid measurement of both the spatial extent and timing of transient changes. These maps summarize a massive amount of time-varying data in static images. Conclusion: Multiplexing obviates the need for accurate edge detection, and facilitates observer evaluation of data confidence and error propagation. Diagnostic information extraction and quantification is accelerated markedly with improved reproducibility and accuracy. The method is very noise tolerant.