On the right beat for artificial hearts
The need
Heart failure is the , accounting for , according to the World Health Organization. Heart transplants are the most effective treatment for ischaemic heart disease, where the heart is starved of oxygen due to a reduced blood supply, but there are not enough heart transplants available for everyone. Instead, people receive ventricular assist devices or artificial hearts to help pump their blood, but these do not respond to the body’s changing needs.
The solution
Developing left ventricular assist devices (LVAD) and artificial hearts (TAH) with adaptive control systems would improve their performance and provide a better quality of life for recipients. The devices would automatically respond to the body’s changing needs, pumping the optimal amount of blood at every moment. They would also send data to clinicians to remotely monitor patients.
Making artificial hearts ‘smarter’ is simple to say, but complex to do – and a goal for biomedical engineer Dr Michael Stevens.
, where reduced blood supply starves the heart of oxygen, is the top cause of human death worldwide. Replacing that heart with a donated organ is the gold standard of treatment, but that’s not always possible.
There is a huge shortage of heart transplants available – just in Australia in 2022. Patients may instead receive a left ventricular assist device (LVAD) or artificial heart to pump their blood. This may be an alternative to a transplant or to keep them alive while they wait for one.
, but there are shortcomings.
“Unfortunately, those artificial hearts are pretty dumb,” says Michael. “They don't really know what the body is doing. They don’t really know how much blood you need at any one time.”
Even a healthy person has a plus or minus 20 to 30 percent difference in their blood pressure or flow rate through the day, depending if they’re sleeping or sneezing or walking up stairs, he points out.
His research focuses on identifying what blood flow the body needs at a particular moment, and telling the device.
Even if you could make like a 2 percent improvement on someone's life, it's really worth coming in to work every day
As a first step, the device would send data to clinicians to remotely monitor patients. Patients could then see clinicians as needed, rather than having to travel to a set appointment every month to check and adjust a device’s parameters.
Ultimately, the device will automatically adjust blood flow, using an adaptive control system that mimics the natural responses of the human heart. This could provide a much better experience for patients.
“As my old supervisor used to say, we can add years to people's life, but what about adding life to those people's years?” Michael says.
A cardiovascular system sourced from Bunnings
Michael’s team is cooperating with partners from Monash University, Queensland University of Technology, University of Queensland and others through the , supported by the . But one of his testing tools is sourced from his local Bunnings hardware store.
“We have a benchtop simulator of the cardiovascular system, which is just a bunch of pipes and plumbing from Bunnings. But that set-up can generate flow that moves with the same pressure and flow rate as blood in the human body.”
The team can dial in numbers from a patient’s chart to the system, and the “big pulsing apparatus” then simulates the patient.
“Then we can connect our artificial heart and say, okay, for this patient, what parameters are we getting? How do we adjust our device to respond to this patient?” Michael explains. “We’re using as much computing power as possible to cover the broadest range of potential situations we might encounter, which surprisingly, no one's really done in this space before.”
In one experiment, Michael’s team ran over 100,000 different simulated combinations of patient conditions and device conditions.
The project is now moving to testing with animal models, which is required by the Therapeutic Goods Administration (TGA). This will involve working with clinicians at St Vincent’s Hospital on ‘real world’ analysis with pigs or sheep.
From an engineering perspective, I think the human body is one of the greatest machines you’ve ever seen. We’re nowhere close to getting anything that mimics it, but we try our hardest, and that's kind of a fun challenge.
Collaborators from engineers to literary experts
The project involves a huge variety of disciplines, from cardiothoracic surgeons to mechanical engineers designing pumps to electrical engineering for signal processing and analysis. Michael is also working with humanities scholars to see how artificial hearts are represented in literature, to better understand patient experiences.
“I love solving problems that have potential to make someone's life just that little bit better,” he says. “Even if you could make a 2 percent improvement on someone's life, it's really worth coming in to work every day. I also love the human body. From an engineering perspective, I think the human body is one of the greatest machines you’ve ever seen. We’re nowhere close to getting anything that mimics it, but we try our hardest, and that's kind of a fun challenge.”