Running wires to the left side of the heart is a notorious weakness of advanced pacemakers and heart-rhythm devices.
Such wires may fracture, decay or lead to infection. Sometimes do-over procedures are needed to place them in a narrow vein outside the heart muscle. Misplaced wires near the left heart may trigger hiccups by stimulating the nerve that controls the diaphragm, or deliver energy to damaged tissue that doesn't respond to the therapy.
The result is billions of health care dollars wasted on ineffective pacing of the left heart. However, a California medical device company with Minnesota financial backing, EBR Systems, says it has invented a device it calls the WiSE System to pace the left side of the heart using sound waves directed to a pacemaker electrode the size of a grain of rice.
The 9-millimeter electrode is implanted inside the heart's left ventricle, where scar tissue permanently embeds it in the heart. The electrode does not contain a battery, but rather converts ultrasound energy into electricity. The ultrasound waves come from a pulse generator implanted between the ribs and powered by a third component, a replaceable battery, also under the skin.
The current design requires the patient to have a traditional pacemaker or implantable defibrillator for the right ventricle that determines when the left-ventricle device should fire. Typically, those devices need a wire in the heart's coronary sinus vein to pace the left heart, which limits where the power can be applied. The WiSE System is said to work better because its location is not limited to where the vein goes, and because pulses delivered inside the heart are more effective than outside it.
EBR Systems received permission to sell this complicated medical device for heart failure last fall in Europe. The company is now in talks with the U.S. Food and Drug Administration about starting a clinical trial involving hundreds of U.S. patients.
The technology would fall within a fast-growing niche of experimental, ultrasmall pacemakers that don't use wires to pace the heart. Medtronic and St. Jude Medical are both testing inside-the-heart pacemakers called the Micra and Nanostim, respectively.
So far, 47 WiSE systems have been implanted in humans worldwide, and U.S. approval is at least three years away. But private investors have stuck with the firm, even after it canceled its first clinical trial in Europe and spent more than a year redesigning the catheter that implants the electrode in the left ventricle.
