A system for diagnosing a heart condition comprises an imaging system (102) arranged to acquire two images of the heart at respective points in the cardiac cycle, and locating means, which may be manually operated or automatic, for locating a series of pairs of points on the images. Each pair of points indicates the respective positions of a single part of the heart in the two images. The system further comprises a processor (108) arranged to calculate from the positions of said pairs of points a value of at least one parameter of the deformation of the heart. It may further be arranged to compare the value of the at least one parameter with reference data to generate a diagnostic output.