In just the past year, at least 28 cases have been identified, with hospitals in Iowa, Michigan and Pennsylvania reporting infections. Numerous infections also have been reported in patients in Europe; some were diagnosed almost four years after surgery.
The device in question is a piece of medical equipment known as a heater-cooler unit, an essential part of life-saving surgeries because it helps keep a patient’s organs and circulating blood at a specific temperature during the operation. It is used in an estimated 250,000 heart-bypass procedures in the United States every year. About 60 percent of these procedures use the German-made model that has been linked to the infections.
The bacteria, known as nontuberculous mycobacterium, or NTM, are commonly found in nature and aren’t typically harmful. But NTM can cause infections in patients who have had invasive procedures, especially when they have weakened immune systems.
Symptoms of infection are often general, such as night sweats, muscle aches, weight loss, fatigue or unexplained fever. As a result, diagnosis can be missed or delayed, making the infection more difficult to treat. Treatment involves a specific antibiotic combination because routine antibiotics won’t be effective against the slow-growing germ.
During the past year, the Centers for Disease Control and Prevention and the Food and Drug Administration have notified hospitals and doctors about the potential link between the machines and infection. But recently completed genetic fingerprinting has provided the strongest evidence so far that the machines were contaminated at a single source — during their production in Germany. That means many more machines could be contaminated with the bacteria than have been identified so far, placing thousands more patients at risk.
Federal officials want to raise awareness of the issue among doctors and patients.
“Although thousands of patients in the United States have been notified regarding potential exposure to contaminated heater-cooler devices, the number who were exposed might be much larger,” according to a CDC report released Thursday.
In a statement Thursday, the FDA said information "strongly suggests" that contamination occurred at the production facility, affecting models made before September 2014. On Thursday, the FDA issued an updated safety communication to help health care providers prevent the spread of infection related to the use of the device.
The equipment in question does not come into direct contact with the patient or the patient’s blood. But the device has a water reservoir, and bacteria can grow there. During use, some of the water evaporates or gets sprayed into the air of the operating room. It can then get into a patient’s open chest during the surgery.
In U.S. hospitals where the infection has been identified, officials say the risk remains low — between 1 in 100 and 1 in 1,000, according to Mike Bell, CDC deputy director of health care quality promotion. While these infections can be severe, and some patients in this investigation have died, officials said it's unclear whether the infection was a direct cause of death. Patients who had valves or prosthetic products implanted are at higher risk of these infections, the CDC said.
Medical devices have been implicated in infections before. In 2015, lighted tubes known as duodenoscopes that are used during surgery were linked to more than two dozen outbreaks of antibiotic-resistant infections that sickened at least 250 patients in the United States and Europe.
With both pieces of equipment, health officials say design flaws didn’t take into account how difficult the equipment is to clean.
In the case of the heater-cooler device, “some smart engineer designed it because surgeons said they need to keep this cool and that warm,” Bell said. “But no one probably said, it needs not to have a fan because it wasn’t part of the calculation. The person who wanted this machine, they weren’t thinking about maintenance and repair.”
The risk of these slow-growing infections is much lower than the more common surgical site infections, according to the CDC and FDA. And for someone facing a massive heart attack or an aneurysm that is about to rupture, the risk of NTM infection “becomes vanishingly small in comparison to the very real concrete risk that those medical emergencies pose to a patient who needs surgery,” Bell said.
But the CDC wants any patients with post-surgical symptoms to be aware that if other explanations have been ruled out, “they and their clinicians need to think about” a possible NTM infection.
There is no test to determine whether a person has been exposed to the bacteria. Infections can be diagnosed by growing and analyzing the bacteria by laboratory culture. But the slow-growing nature of the bacteria can require up to two months to rule out the infection, the CDC said.
To date, eight hospitals in four states have notified about 15,000 of their patients who underwent an open-chest procedure, in some cases going back to 2011.
WellSpan York Hospital in York, Pa. was the first hospital in the country to identify a cluster of NTM infections in July 2015. Hospital staff, working with the CDC and the Pennsylvania health department, reviewed all the facility’s open-heart surgery cases and sent letters to about 1,300 patients who may have been exposed going back four years.
Twelve patients have infections most likely linked to the devices, including six who have died, hospital spokesman Brett Marcy said. Those who died also had complex medical conditions.
The Stöckert 3T heater-cooler devices have been available in the United States since 2006, according to the FDA. The manufacturer is LivaNova PLC, formerly Sorin Group Deutschland GmbH. The FDA estimates there are close to 2,000 devices in the United States.
The company has received complaints about patient deaths related to NTM infections and the devices since January 2014, according to the FDA.
Last year, the company notified hospitals to update cleaning instructions for the machines. But the FDA found the new guidance to be inadequate for reducing the risk of infection. In December, the agency placed an import alert on the devices, to restrict the import of the devices into the United States.
These are the six hospitals that have reported infections in Pennsylvania, Iowa and Michigan, the number of at-risk patients who were notified, the number of patients identified with NTM infections, and the dates of surgery:
• WellSpan York Hospital – 1,300 notified; 12 cases; 10/1/11 to 7/24/15
• Penn State Hershey Hospital – 2,300 notified; 5 cases; 11/5/11 to 11/5/15
• Penn Presbyterian Medical Center - 1,100 notified; 4 cases; 10/1/13 to 12/17/15
• University of Iowa – 1,500 notified; 3 cases; 1/1/12 to 1/22/16
• Mercy Medical Center in Iowa - 2,600 notified; 2 cases; 7/1/12 to 7/1/16
• Spectrum Health Medical Center in Michigan – 4,500 notified; 2 cases; 1/1/12 to 11/10/15