Researchers say new insights into blood flow patterns could explain why some heart failure patients with implanted pumps are more likely to suffer strokes.
Left ventricular assist devices (LVADs) – mechanical pumps used when the heart can no longer circulate blood effectively – are often the final treatment option for people with advanced heart failure. More than 14,000 people currently have one implanted, and with heart failure affecting around 26 million people globally, use of the devices is expected to grow.
However, people with LVADs face an 11 to 47 per cent higher risk of developing blood clots that can travel to the brain and cause strokes, compared to the general population.
Researchersused digital simulations to investigate how patterns of blood flow – known as haemodynamics – might influence this risk.
The findings suggest that altered flow dynamics could help explain why some patients go on to suffer strokes, while others do not.
The researchers created 3D computer models, or “digital twins”, of 12 people with LVADs, using detailed imaging of their aortas (the body’s main artery), nearby blood vessels, and the point at which the LVAD connects to the heart.
Six of the patients had suffered a stroke after receiving the device; six had not.
Debanjan Mukherjee is senior author of the study and assistant professor in the Paul M. Rady department of mechanical engineering at CU Boulder.
The researcher said: “We are in an age where there is quite a bit of data that we have access to, and we know a lot about how fluid moves through the arteries and veins.
“We are looking at blood flow patterns as information that currently is not incorporated in clinical practice.”
Heart failure occurs when the heart is too weak to pump enough blood to meet the body’s needs.
In a healthy heart, the left ventricle contracts to push oxygen-rich blood into the arteries. In patients with advanced heart failure, this chamber can become ineffective.
An LVAD is a mechanical pump that attaches directly to the heart and diverts blood from the weakened left ventricle into the aorta.
While this helps restore circulation, it can also create regions – particularly in the bypassed left ventricle – where blood flow slows or stagnates, increasing the likelihood of clot formation.
If a clot dislodges and travels to the brain, it can block an artery and cause a stroke by interrupting blood supply to part of the brain.
In the study – supported by the US National Institutes of Health and CU’s AB Nexus initiative – the researchers integrated patient-specific clinical data, including heart rate and blood pressure, into their models. They also simulated blood flow in the same individuals before they received their LVADs.
Mukherjee said: “We are basically digitally recreating something that’s going on inside the body.”
The team observed differences in blood flow patterns between patients who experienced strokes and those who did not, both before and after implantation.
The LVADs also altered flow by creating a jet of blood entering the aorta at a different angle than natural heart function would produce.
These variations could lead to localised areas of slower flow, where platelets are more likely to stick to protein networks in the blood and form clots.
Jay Pal, professor and chief of cardiac surgery at the University of Washington, and a co-author of the study, said: “Knowledge gained from this study can help us develop patient-specific implant techniques to reduce the likelihood of stroke in patients with durable LVADs.”
The findings could enable clinicians to personalise how LVADs are surgically implanted and monitored, better anticipate individual stroke risk, and tailor treatment plans accordingly.
