To treat atrial fibrillation, a procedure called ablation is frequently employed in which the source of a patient’s heart arrhythmia is mapped and destroyed, often leaving behind a small electrically inactive scar. Despite the prevalence of the procedure, locating the precise area for treatment has often been a challenge. Seeking to overcome such challenges by determining new ways to detect abnormalities in cardiac conduction, researchers at Columbia University (New York) have developed a noninvasive technique called electromechanical wave imaging (EWI). This technique could eventually help doctors determine precisely where to ablate using medical devices found in nearly every hospital or clinic in the world.
Arrhythmia repairs typically involve the insertion of a catheter through a vein and subsequent ablation by applying radiofrequency energy, applying electrical energy, or freezing the offending area, which can cause permanent damage to the heart. Unfortunately, it is a fairly common occurrence that the initial ablation does not target the correct spot—or even the correct chamber—often making repeat procedures necessary, according to Elisa Konofagou, an associate professor of biomedical engineering and radiology at Columbia and EWI research leader.
The EWI technology, she notes, could eliminate this problem. By comparing the EWI images of compressions seen in normal heart activity with those taken in a patient with abnormal electrical activity, cardiologists can see a more detailed map of problem areas that require ablation. “The EWI process will help guide ablation catheters to the correct part of the heart, avoiding unnecessary damage to healthy heart tissue,” Konofagou explains.
As a noninvasive process, EWI further eliminates the opportunity for scarring or damage to the patient. Unlike other cardiac arrhythmia measuring techniques that involve either invasive electrode contact or noninvasive, but unreliable, mathematical modeling based on remote measurements, the EWI technique employs conventional ultrasound equipment that can be modified at little or no cost.
This novel imaging technique requires that the patient take a deep breath and hold it for several seconds, during which the heart is imaged at a rate about five times faster than standard echocardiography. By looking at a region of just a few square millimeters, the scientists measure the stretching or compression that takes place every 0.002 seconds. “We sped up the imaging taken by a standard ultrasound to look at the minute deformations following the electrical activation of the heart,” Konofagou states.
Citing a larger clinical trial as the next step for the EWI technology, Konofagou’s team has already begun to image patients with arrhythmias and compare their measurements with catheterization and noncontact electrode measurements. She estimates that this technology could potentially be available to doctors treating cardiac patients in the next two to five years. Capitalizing on the low cost, portability, and safety of ultrasound equipment, Konofagou envisions a future in which doctors could use a pocket-sized ultrasound scanner during a routine visit to map heart activation.
Published in MPMN, September 2011, Volume 27, No. 7
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