"X-ray is inherently a two-dimensional projection imaging technique," says Lardo, "which means that there is a lot of anatomic ambiguity. It's very difficult to know in 3-D where you are." Also, as the lesions are made, X-rays are deficient at distinguishing between the lesions and the heart tissue.
"Although we have bioelectric feedback, we're just kind of shooting in the dark," he says.
Not surprisingly, arrhythmia reoccurrence rates are high, says Lardo. Physicians may try to tilt the odds in their favor, sometimes creating as many as 50 to 60 lesions in only a 2- to 3-millimeter space, "but the goal is to make as few lesions as possible and still achieve conduction block," he says.
"With MRI, you can overcome all those limitations," says Lardo. "We know precisely where the catheter is so we gain a lot of confidence in being able to put the lesion in the right spot. Not only that, but we have a way to monitor the formation of the lesion s it happens, and watch it grow. If the image tells us that the lesion isn't big enough, we can go back to the same spot and deliver another burn."
Fewer and more precise and effective lesions should reduce the overall costs of the surgery, says Lardo. The time to perform the procedure should be reduced, and the need for a second procedure nearly eliminated.
MRI is generally considered a safe technique because no X-rays are used, thus eliminating any radiation exposure to the patient and physician. Also, the electromagnetic fields do not, by themselves, cause tissue damage. But despite MRI's advantages, Lardo had to overcome several hurd
Contact: Mark Bowman