Medical device developer Medtronic has commercialized a 252-electrode vest that can map the heart’s electrical system. The device could help doctors pinpoint the locations of electrical malfunctions in the heart that cause irregular heartbeats.
Doctors began using the system commercially last week after the US Food and Drug Administration (FDA) in November approved the vest, Medtronic announced.
Irregular heartbeats, or arrhythmias, are caused by electrical malfunctions of the heart. The malfunctions can bring on a range of problems, from the disconcerting sensation of a fast, irregular heartbeat, to a fatal cardiac arrest.
In order to treat an arrhythmia, doctors must pinpoint the location of the electrical malfunction. That typically involves inserting a catheter with an electrode tip into a blood vessel in the groin, and snaking it up to the heart. By touching the tip to different places on the heart doctors can create spatial and electrical maps.
But those maps are usually incomplete. The catheter can’t reach every part of the heart, leaving some areas of the map blank. The invasive procedure also comes with some risk.
Medtronic’s vest, called the CardioInsight, aims to provide a more complete map—without the snaking groin catheter. The patient puts on the 252-electrode vest and gets into a computed tomography (CT) scanner. The system then creates a three-dimensional electroanatomical map of the heart by combining the vest’s electrocardiogram (ECG) signals and the anatomical image from the CT scan.
The technology has been in development for nearly 25 years, says David Steinhaus, medical director of Medtronic’s cardiac rhythm and heart failure division. Advancements in computing power in recent years made the device possible, he says. “You’re taking a complex 3D image from a digitized CT scan, and a 252-point surface electrical reading,” and then combining the two using complex mathematics. “So you can imagine the computing power that is required to do that,” Steinhaus says.
Medtronic acquired the technology two years ago when it bought Cleveland-based CardioInsight Technologies for $93 million. CardioInsight had developed a version of the vest that received regulatory clearance in the US in 2014 and in Europe in 2012.
Medtronic enhanced the stability of the software to enable it to be commercialized, and last year submitted the upgraded version to the FDA through the agency’s premarket notification, or 510k process. That regulatory pathway is for devices that are similar to previously approved technologies, and don’t require evidence of clinical benefit.
Cardiologist P. Boon Lim, at Imperial College London who has studied the vest in a clinical trial, found it to be accurate. In an email to Spectrum, he said that because the CardioInsight vest is non-invasive and can be worn for several hours, it is particularly useful when arrhythmias need to be induced. For example, there’s a type of heart rhythm abnormality called ventricular ectopy where the arrhythmia is brought on by exercising. That’s hard to capture with conventional, catheter-based mapping, where patients are typically lying flat on a laboratory table.
Lim said ventricular ectopy patients can wear Medtronic’s vest while exercising on a treadmill in the lab, enabling him to induce, map and pinpoint the electrical abnormality. In his study of these patients, the vest was 96% accurate in finding the site of problem, and led to successful treatment.
The electroanatomical maps are generated in near real-time and can find the problem in just one heartbeat. “You literally get to watch the heart’s electrical system work. It’s fascinating,” says Steinhaus. "It's almost as if there's an electrical wiring diagram inside the heart."
Fascinating indeed. The system is coordinated so that electrical signals reach different regions of the heart at different but precise times. For example, the pulses cause the atria—the upper chambers of the heart—to beat slightly ahead of the ventricles—the lower chambers—allowing them to fill with blood.
The heart even generates its own electrical pulses. They start in a specialized area of the heart called the sinoatrial node. There, cells spontaneously depolarize, creating electrical pulses that are carried along certain cell pathways across the heart.
The sinoatrial node is located in the upper right atrium. From there the electrical pulses spread across the right atrium to the atrioventricular node, which connects the right atrium to the right ventricle. Then the specialized His-Purkinje system transmits the signals quickly to the ventricles, causing them to contract.
Problems arise when abnormal cells or connections form, knocking the system out of whack. “When that happens the heart cannot beat in a coordinated way and it can stop,” says Steinhaus.
Doctors treat the problem by destroying the cells that are electrically malfunctioning. The procedure, called ablation, allows the heart to get back to its normal rhythm.