You may be confusing EKG with an echocardiogram. Sometimes there is a small hole in the wall that separates the heart chambers. The bubble test is given to view for any bubbles going from one chamber to the other chamber. When a bubble is seen in the adjacent chamber during the test it indicates passage of blood from one chamber to the other chamber and not immedicately in circulation. Often it is considered medically insignificant and there is no progression. If it is significant, there is a procedure to patch the opening.