Magnetic resonance imaging (MRI) has been around for decades, but it's only within the past several years that physicians have begun using the technology on a regular basis to examine the heart.

For years the ultrasound-based echocardiogram was the standard option for capturing an image of the heart at work. It remains the go-to procedure, but cardiac MRI is an increasingly common and often more accurate alternative.

Nearly identical to a traditional MRI, cardiac MRI is a noninvasive procedure that entails lying on a bed scanner for 45 to 90 minutes. The magnetic fields and radio waves used in cardiac MRI are harmless, although the procedure can disrupt the functioning of pacemakers and implantable defibrillators and is therefore off-limits to patients with those devices.

Thanks to new technological advances, the test is now widely used to diagnose numerous cardiovascular conditions, including congestive heart failure, coronary heart disease, and the extent of heart muscle damage caused by heart attacks (some of which may go unrecognized with less sensitive technology).

MRIs help predict sudden cardiac death
A research team from Johns Hopkins used MRI scans to determine in 2005 that the thickness of scar tissue resulting from a heart attack was an accurate predictor of the risk of sudden death from arrhythmia and could prove valuable in identifying patients in need of an implantable defibrillator or other aggressive treatment.

The high-quality images of heart muscle from cardiac MRI also help physicians determine the probable success of operations to restore heart function (a process known as revascularization), which in turn helps patients avoid ineffective and possibly harmful surgery.

The cost of cardiac MRI
While a cardiac MRI can produce 3-D images that are far more detailed and precise than fuzzy, 2-D echocardiograms, the procedure is also about five times more expensive. Insurers often resist the use of the technology for screening purposes, but it's usually covered in serious cases. "Generally one can get reimbursed if there's a suspected pathology," says Raymond Stainback, MD, the medical director of noninvasive cardiac imaging at the Texas Heart Institute, in Houston. "Insurers have become much more open to that."

But patients shouldn't start demanding MRI just yet. Echocardiography machines are portable, very quick, and usually quite sufficient to diagnose and monitor a heart condition. "The echocardiogram is still going to be the workhorse," says Dr. Stainback.