There are no risks or complications to a cardiac MRI without contrast agent. If you do have contrast, risks are related to possible allergic reaction to the contrast or kidney damage as your body tries to excrete it. The risk of kidney problems is greater for people who have decreased kidney function or kidney transplant. The magnetic field when the MRI scanner is on can cause serious problems if you have metal implants or objects in or on your body. The magnetic field could cause the metal parts to move inside your body or they may heat up from the energy. You may need to a have a different type of heart scan if you have a pacemaker, defibrillator, or neurostimulation device. Speak with your doctor about your options.