This document summarizes a method for segmenting left ventricular contours in tagged magnetic resonance images. The method uses a predictor-corrector scheme with a semantic descriptor to preprocess images and multiple external forces to drive segmentation. Validation on 21 test images showed segmentation errors less than 2 pixels on average and average global rotation errors below 0.5 degrees, indicating accurate segmentation. Future work will analyze inter-observer variability, pathological cases, and additional clinical measures.