The Life-Saving Device That’s Made To Last
Research and Innovations With patients living longer, fuller lives, a cardiac expert explains how new ICDs are being designed to last long-term.
ardiac arrest — when the heart suddenly stops functioning — used to mean certain death. Today, physicians are able to implant small, lifesaving defibrillators directly into patients who are at risk for cardiac arrest to help reset the heart in case of emergencies.
Implanted cardiac defibrillators, commonly known as ICDs, deliver a shock to the heart when they detect an abnormal heart rhythm. These devices are currently the gold standard for helping treat cardiac arrest — which occurs an estimated 40,000 times in Canada each year, according to the Heart and Stroke Foundation. However, these devices are not built to last as long as patients are now living.
“When we first started doing defibrillators in people, we weren’t thinking of them living for another 20, 30, or 40 years,” says Dr. Soori Sivakumaran, an electrophysiologist and an associate clinical professor at the University of Alberta. “But, as cardiac therapies improve, people are living longer. I’ve put devices in when patients were in their 70s and they’re now 90.”
In ICDs, electric wires that connect the defibrillator to the heart are called the leads —Dr. Sivakumaran refers to them as “the Achilles heel of the system.”
These leads run through blood vessels into the heart, which can subject them to infections. Dr. Sivakumaran recently had a patient who was admitted with a urinary tract infection that spread to the blood and settled on the leads of the patient’s ICD. “So, for the infection to clear, we had to take out the device and the leads,” says Sivakumaran, adding that because these leads often get attached to the veins and the heart, removal is much easier said than done.
In addition, traditional ICDs have leads that are prone to wear and tear over time.
“Those leads are subjected to a lot of stresses because they’re in a liquid environment that can seep in through the lead, and the lead is flexing and extending with every heartbeat, so there’s mechanical strain,” he says, adding that once a lead is 10–15 years old, it has a higher rate of failure.
Dr. Sivakumaran has a patient in his early 20s with a rare heart condition that puts him at risk for cardiac arrest. Since the patient is young, the doctor is opting for a different type of ICD.
A subcutaneous ICD (S-ICD) serves the same purpose as its predecessor, but instead of being implanted inside the heart, the leads are run outside of the rib cage — from the left armpit across the chest, just under the skin. With this device, physicians do not have the same concerns surrounding risk of infection in the heart, possible damage to blood vessels, or whether the leads will last.
“We don’t have to have the same degree of worry we would with a standard defibrillator,” says Dr. Sivakumaran, which is particularly important now that patients are living longer. “The younger patients are, the better the benefit may be from S-ICDs, because they basically need a defibrillator for the rest of their lives.”
With patients living longer than ever before, S-ICDs offer a solution that, like cardiac patients, can keep on going for years to come.