Biomedical engineers at the Johns Hopkins University have extended magnetic resonance imaging (MRI) into cardiac surgery for the first time with a new procedure to help prevent rapid and irregular heart rates.
The novel technique uses MRI instead of X-rays to guide radio frequency cardiac ablation, a minimally invasive surgical procedure that blocks abnormal electrical pathways in heart muscle. The MRI technique makes catheter-based intervention more accurate and reliable, which should reduce overall costs, and eliminates the current hazard of radiation exposure.
MRI has been used primarily for diagnosis throughout the human body, and is increasingly being used to guide therapy. Until now, however, MRI-guided therapies have not targeted the heart. The new approach, says lead investigator Albert Lardo, Ph.D., represents "a significant shift away from X-ray-guided techniques and establishes the feasibility of performing cardiovascular intervention under MRI guidance." Lardo presented some of his findings at a scientific conference of the American Heart Association in New Orleans last month. The new technique was also described in a recent issue of the AHA journal Circulation.
In recent years, radio frequency (RF) cardiac ablation has become a standard therapy to treat basic types of arrhythmia, or abnormal heart rate. The procedure benefits about one out of every 13 arrhythmia patients each year in the United States. During RF ablation, doctors make a small incision in the arm or leg and insert a special electrode catheter, essentially a long, flexible wire, through an artery to the heart and close to the trouble spot. As radio frequency energy passes through the catheter, the tip of the wire heats up and burns the heart tissue, creating a small, elongated lesion. The lesions and subsequent scar tissue, which do not conduct electrical impulses, essentially form roadblocks for the abnormal impulses responsible for the arrhythmia.