|
|
     |
|
|
|
Medical technology started with a pacemaker.
by Keira Thrasher and Michael Franklin
In the 1950s, a revolution in medical technology began when University of Minnesota physician C. Walton Lillehei asked Earl Bakken, a local electronics repairman, to redesign the machine that Lillehei was using to restore patients’ heart beats after surgery.
The machine Bakken built was a wearable, battery-operated pacemaker, and with this invention, Bakken’s small business, called Medtronic, was catapulted into high gear, and an era of technological innovation was born in Minnesota. Physicians began collaborating with Bakken and his staff to create innovative new medical technology, and Medtronic became a fertile training ground for engineers and other industry professionals who went on to found other well-known Minnesota-based medical device manufacturers and health care organizations. Now Minnesota is known for its “medical alley,” a wide ribbon of innovative medical businesses that runs from Rochester to Duluth.
The Humble Beginnings
Earl Bakken was an electrical engineering graduate student at the University of Minnesota and a hospital repairman who was known for his ability to fix the hospital’s sensitive equipment that other electricians could not service. Recognizing an opportunity, Bakken and his brother-in-law, Palmer Hermundslie, started a company that began by selling and servicing hospital equipment. That company was Medtronic.
Operating out of a garage, Bakken and Hermundslie modified and designed equipment at their customers’ requests, but those innovations were primarily custom-built, single-use devices. Once Bakken designed the wearable pacemaker in 1957, Medtronic began to grow, prosper, and profoundly influence the health care industry.
Pacemakers and the Heart
The heart is a large muscle that pumps blood through the body by contracting at regular intervals. These contractions are controlled by electrical impulses that are produced by chemical reactions in the sinoatrial (SA) node, a collection of specialized cells in the heart that have been called the heart’s “natural” pacemaker. Each impulse sets off a reaction that spreads through the heart, causing its chambers to contract rhythmically. These rhythmic contractions push the blood through the heart, to the lungs for oxygenation, back to the heart, and out to the rest of the body.
In order for the heart to beat normally, electrical impulses must move through the heart at proper intervals and along particular pathways. If the SA node malfunctions, or if there is a block in the heart’s electrical pathways, the heart suffers from irregular, interrupted, or misdirected rhythms. This stimulation frequently means that the heart can no longer pump an adequate supply of blood through the body, and the person’s life may be in jeopardy. For hearts that beat too slowly, too quickly, or irregularly, pacemakers can either maintain or restore a healthy rhythm by delivering electrical impulses to the heart tissue at proper intervals.
Since 1803, physicians have known that electricity could be used to stimulate the heart. Although some physicians had been developing means to deliver electrical impulses to the heart, Dr. Albert Hyman coined the term “artificial pacemaker” in the 1930s for an apparatus he built that delivered impulses to the right atrium via a thoracic needle electrode.
In the early 1950s, Dr. C. Walton Lillehei pioneered open heart surgery at the University of Minnesota. He soon found that about 10% of his open heart surgery patients experienced problems when the sutures interrupted the proper transmission of electrical impulses through the heart. Dr. Lillehei used an AC-powered, vacuum-tube pacemaker to restore normal heart rhythms for these patients. Although this pacemaker was effective, patients were subject to power failures and electrocution. In fact, one of Dr. Lillehei’s pediatric patients died in a city-wide power outage. In addition to power source problems, these pacemakers were bulky, desk top devices that rendered patients immobile because they had to stay tethered to a wall socket while they recuperated.
To solve these problems, Dr. Lillehei knew he needed a pacemaker that operated on battery power. He decided to ask a graduate student to create a smaller device that would use batteries to deliver a low voltage current at an adjustable rate between 50 and 110 pulses per minute. Six months later the student still wasn’t successful. Dr. Lillehei decided to ask Bakken for help.
Bakken was on a routine visit to the hospital to fix the EKG when Dr. Lillehei presented him with his pacemaker problem. Within just six weeks of Dr. Lillehei’s request, Bakken modified a metronome circuit design he found in Popular Electronics and created a box that used mercury batteries to deliver a 9-volt DC pulse. A day after the device was tested, Dr. Lillehei used it to successfully restore a child’s heartbeat to a normal rhythm. Because Dr. Lillehei continued to have such success with Bakken’s new wearable pacemaker, he referred many of his colleagues to Bakken. Medtronic quickly expanded, and their pacemaker came to be used throughout the world.
While the wearable pacemaker enabled heart surgeons to save more lives on the operating table, it was also becoming clear that heart attacks were frequently caused by problems with the heart’s natural electrical system and that artificial pacemakers could be used for long-term treatment as well as surgical recovery periods.
The wearable pacemaker was uncomfortable and inconvenient for patients’ long term use. In addition, the wires that carried the electrical current from the pulse generator to the electrodes in the heart had to be threaded through an incision in the patient’s skin. As a result of the incision, it was sometimes difficult to prevent infections from taking hold. To solve these problems, various physicians and engineers across the country started trying to develop an implantable pacemaker.
By 1960, Drs. William Chardack and Andrew Gage collaborated with electrical engineer Wilson Greatbatch to successfully design an implantable pulse generator in New York state. Soon after the device was thoroughly tested and successfully implanted in a human patient, Medtronic met with the developers and obtained exclusive rights to produce and market it.
While the implantable pacemaker was being developed, Medtronic engineer Norman Roth and Dr. Samuel Hunter from St. Joseph’s hospital in St. Paul were busy improving the electrodes that conduct electricity to the heart. They devised an electrode that doctors could strategically position and suture securely within the heart’s chambers. With this innovation, the pacemaker required less current to effectively stimulate the heart muscle to contract. Medtronic combined their new electrodes with their newly acquired implantable pulse generator and began production immediately to meet the large demand for implantable pacemakers.
Since then, Medtronic has continued to develop and improve pacemaker technology. For example, pulse generators can now sense a person’s level of physical activity and automatically adjust the pulse rate. Also, leads have been developed that enable the physician to maneuver them through veins and into the heart instead of opening up the chest. (Leads are the wires along which current travels to the electrodes and the heart.)
Minnesota and Medical Technology
Medical research and innovation started to boom at the University of Minnesota in the 1950s after Dr. Lillehei pioneered open heart surgery and collaborated with Bakken to devise the wearable pacemaker. The collaboration between Dr. Lillehei and Bakken enabled Medtronic to grow, innovate, and develop new talent. Medtronic employees went on to start 35 more companies, which in turn have contributed to Minnesota’s reputation as a leader in the healthcare industry.
Dr. Lillehei and his medical colleagues continued their collaboration with Medtronic and the companies that sprang from it. For example, Dr. Lillehei fostered the development of blood oxygenators that take over the heartís work during open heart surgery and helped create several artificial heart valves that were marketed by various Minnesota companies.
Manuel Villafana and CPI
The story of Manuel Villafana is one striking example of the chain of events that followed the advent of the wearable pacemaker and led to the enormous success of the health care industry in Minnesota.
Villafana began as a Medtronic employee and went on to found several biomedical companies in Minnesota. Medtronic had been reluctant to embrace lithium batteries as a power source because of the potentially explosive nature of lithium. Yet lithium batteries lasted up to ten times longer than standard mercury batteries. Villafana was convinced that lithium could be safely used in pacemakers, and he left Medtronic to start Cardiac Pacemakers, Inc. (CPI), and CPI soon became very successful in its own right.
Villafana sold CPI in 1975 and founded a new company, St. Jude Medical. Their new product, which became the leading heart valve, was based on some of Dr. Lillehei’s work eight years earlier. Dr. Lillehei had perfected an artificial heart valve in 1968 in collaboration with a surgical resident named Bhagavant Kalke. The first implant of the Kalke-Lillehei valve appeared to be successful, but the patient died two days after surgery for unknown reasons, and the valve was forgotten until St. Jude Medical picked it up.
Since then, Villafana has also started both Golden Valley Medical and Helix Bicore. Villafana is just one of the many entrepreneurs, engineers, and health care professionals who were associated with Lillehei and Bakken and who founded Medical Alley, now a trade organization that represents hundreds of health care companies.
The success of Minnesota’s medical device industry is widely attributed to that first collaboration between Bakken and Dr. Lillehei. On October 8th, the Institute of Electrical and Electronic Engineers (IEEE) recognized the significance of Earl Bakken’s invention when it designated his transistorized, wearable pacemaker as an “IEEE Electrical Engineering Milestone.”
