Radioisotopic imaging of the heart, especially of the muscular contraction of its walls and of its ejection fraction. Red blood cells are withdrawn and labeled with an isotope of technetium. A sequence of images is taken immediately after the radiolabeled blood is reinjected into a peripheral vein and allowed to circulate. The images are timed to begin with each ventricular depolarization (with each R wave of the electrocardiogram). Normally the ejection of blood from the heart occurs at the same time and with the same strength from all muscle segments. Areas of the heart affected by infarction may not move normally (they may be “akinetic” or “hypokinetic”) or they may move paradoxically (e.g., when a ventricular aneurysm is present, they may be “dyskinetic”).