An Inventor at Heart
At the Boston Museum of Science, audiences gather around the Van de Graaff generator to watch as two million volts crackle between twin metal spheres while the operator, who stands nearby inside a simple cage, remains unaffected. This lightning show demonstrates a Faraday cage, an enclosure that keeps electrical charges from getting in—or out. In 1999, when Ronald Berger ‘81, SM ‘83, PhD ‘87, took his kids to the Boston spectacle, it wasn’t just for fun. He was in the midst of a plot to fit a Faraday cage around the human heart.
If Berger can make it work, his device will improve conditions for patients with heart problems. Sudden cardiac arrest, a leading cause of death, results from a severe arrhythmia called ventricular fibrillation. In this emergency, the only way to restore normal rhythm is with a defibrillator, which delivers a chest-seizing wallop of hundreds or thousands of volts. For more than three decades, patients considered at risk for heart attacks have been able to get an internal cardiac defibrillator (ICD) installed beneath the skin to detect irregular heartbeats. A wire that passes from the ICD into the heart through a vein delivers shocks as needed. However, the shocks are painful, and patients often live in dread of them or choose to forgo treatment because of them. “It’s an important problem,” Berger says. “I’ve been very interested in making defibrillation painless.” And a type of Faraday cage could be the answer.
Berger, who is co-director of cardiac electrophysiology at Johns Hopkins, earned three MIT degrees in electrical engineering and computer science and then completed his MD through the Harvard-MIT Division of Health Sciences and Technology in 1987. Mirroring his education, he is both engineer and doctor. More specifically, he is a cardiac electrophysiologist—one who understands that “we can actually fool Mother Nature and interrupt the propagation of the [electrical] impulse in hearts,” as he puts it. Berger spends 75 percent of his time at Johns Hopkins teaching, serving as an administrator, and performing procedures to quiet cardiac electrical dysfunction, or arrhythmia. The rest of the time, he researches and invents.
Berger has always invented. For his undergraduate thesis at MIT, he designed a new way to steer and deflect laser beams through crystals. The result, recalls his thesis advisor, EECS professor Cardinal Warde, “was one of the best undergraduate theses ever done in my laboratory.” Soon after Berger met his best friend, Joseph Smith, SM ‘82, PhD ‘85, in the lab of MIT biomedical engineer Richard Cohen in 1980, they turned a black-and-white handheld TV into an EKG machine capable of reading the heart’s electrical activity at the surface of the body. Today, Berger has been issued 25 patents for cardiology methods and equipment.
Fifteen years ago, Berger became fixated on the pain that ICD shocks caused his patients. He knew that the pain wasn’t coming from the heart. The organ itself has so little capacity for pain sensation that patients can stay wide awake as cardiologists perform ablation, burning away chronically malfunctioning heart tissue with a wire that’s been snaked up through a blood vessel. So Berger concluded that electrical pulses from the ICD must leak out as the nerves and muscles of the chest wall activate.
Something clicked. “I said to myself, wouldn’t it be cool if there was a way to keep the electrical activity confined to the heart?” Berger says. That’s when he was reminded of a lesson on the Faraday cage from 8.022, Electricity and Magnetism, a class he had taken with Professor Claude Canizares back in 1977. Berger wondered if it would be possible to sheathe the heart inside a Faraday cage to contain a shock that halted arrhythmia.
One problem, however, is that a Faraday cage around the heart would not just keep electricity confined to the heart; it would also block electricity from another source from entering. This meant that patients would be unable to get emergency external defibrillation if their heart failure were extreme enough to require a bigger shock. To deal with that, Berger began to think about a configuration of metal panels that would not be entirely contiguous. They would merely be close enough to act as a Faraday cage when electricity passed through them. He recalls that a research fellow mentioned the idea to his wife, who suggested sewing the metal mesh into a nylon stocking. She even produced a prototype. It was a Faraday cage—or, more accurately, a Faraday sock.
In practice, the sock would fit around the heart and serve as one electrode of the shock delivery circuit; when an attached sensor detected abnormal heart activity, an electrical coil implanted inside the heart would deliver the jolt. In 2005, when Berger and his research team tested the prototype in dogs, the device reset the heartbeat using less energy than a standard ICD. Most important, the dogs’ chest muscles contracted much less, meaning that less electricity was seeping out and causing pain.
Berger and Johns Hopkins colleagues have refined the design in the past year, using mathematical modeling to find the optimal spacing for the panels. In the most recent version, the panels electrically unite into a contiguous shield and act as a Faraday cage only in the 10 milliseconds right before and during the moment in which the shock is delivered.
Despite the progress, some cardiac experts question the sock’s potential. Bioengineer Igor Efimov at Washington University in St. Louis points out that covering the heart with the mesh would require major open-chest surgery. “Who would agree to such a dramatic surgery with unclear clinical benefits?” he says. He also predicts that scar tissue would encrust the device’s wire slats and prevent them from opening. “Unless there is a breakthrough in biomaterials, I don’t think it could be used,” he says. Berger agrees that scar tissue could be a problem, but he holds out hope that his invention can work. He notes that private companies have already invented socks made of elastic mesh to reduce heart muscle stress in patients with heart failure. Berger suggests that his Faraday cage might be built into one of those socks. Heart patients who already need invasive surgery to implant the sock could get a two-for-one solution.
Berger and his friend Smith, who is now chief medical officer for West Wireless Health Institute, have spent many a Baltimore night discussing the Faraday sock and how Berger might bring it to fruition. “It’s one of those things that only comes from a bright engineer being able to understand the problem from a physics perspective but also see the clinical applications,” Smith says.
These two complementary talents started to meld not long after Berger began at MIT in 1976. One day, he walked into the office of his advisor, George W. Pratt, and noticed a large painting of a horse. He was puzzled until Pratt, a horse-racing enthusiast, began drawing chalk diagrams of electrical resistors and capacitors to model the equine blood system; the heart was acting like a battery and the blood vessels like a charged capacitor. For Berger, these lessons are still a revelation 35 years later. He says, “It’s an amazing thing—the principles of electrical engineering underlie how one native impulse in the heart gets from one cell to the next.”
Today Berger is trying to improve defibrillation in the very place the technique was born. In 1933, a New York electric company funded efforts by Johns Hopkins researchers to find solutions for the frequent electrocution accidents of the era; after studying what happens when a heart’s rhythm is off course, these men were the first to get a dog’s heart to stop fibrillating. Hopkins physicians implanted the first ICD into a patient in 1980.
But though the technology has its roots in the Johns Hopkins clinic, Berger says his mind goes back to MIT every day. “I always say that performing ablation reminds me very much of my undergraduate course 6.082, where we would move the probe from point to point within a circuit to debug it,” he says. He thinks of those lab projects each time he inches the catheter’s tip to the right place in a patient’s heart and watches the arrhythmia disappear as he delivers the burn.