Keto Pure Trim -. - - around the bundle of His and coronary sinus). Their task is to register and analyze the electrical potential of the heart, and due to the fact that it happens inside the heart, they can be evaluated very accurately.Read also: X-ray of the chest - what does it look like? Preparation for the studyThe electrodes are also used to send stimuli - the heart is stimulated to cause arrhythmias under controlled conditions.