New discoveries on where plaque can form and what can trigger a heart attack.
Researchers from the Harry Perkins Institute of Medical Research have published new findings that turn the scientific understanding of cardiovascular-disease-causing plaque on its head.
Fatty deposits of cholesterol and other substances in our arteries, which are known causes of stroke, heart attack and even amputation of limbs, have long been thought to occur only in the inner layer of blood vessels.
But Perth researchers have found plaque can build up in the middle layer, weakening the blood vessel and making it susceptible to rupture.
They have also discovered that pressure exerted on blood vessels, from exercise over several years, can cause injury to the middle layer and lead to the build-up of plaque.
Lead researchers on this study, PhD candidate Hanane Belhoul-Fakir, Associate Professor Juliana Hamzah, and vascular surgeon and Perkins researcher Professor Shirley Jansen, said medical consensus had been that plaques first develop in the inner layer of blood vessels, but this new study has shown something entirely new.
“We created an artificial injury in the middle layer of an abdominal aorta and then tested that injury after 12 weeks of a high-fat diet,” said Ms Belhoul-Fakir.
“The study showed that plaque accumulated in the injury site, in the middle layer of the vessel.
“The significance of this is that the amount of plaque in the middle layer can be far greater than the amount tested for in the inner layer.
“Patients may have far higher amounts of plaque than that tested for.
“We discovered a third of Sir Charles Gairdner Hospital patient samples that we tested had a much greater amount of plaque than the amount seen in the inner layer.
“It had been thought that the inner layer was the only site where plaques first grow.
“The accumulation of fat in this middle layer of arteries may lead to a dangerous disease, making it more susceptible to rupture, leading to cardiovascular events such as stroke,” A/Professor Hamzah said.
“In real life, this means that long-term vigorous exercise, which exerts high mechanical forces in the arterial wall, may lead to the arterial wall becoming more prone to injury and ultimately to cardiovascular disease,” Ms. Belhoul-Fakir said.
Professor Jansen said damage in the wall of an artery caused by forces from blood pressure, particularly at the point where a vessel branches into two, are a known catalyst for fat build-up or ‘atherosclerotic plaque’, which is a hardening of blood vessels.
Blood vessels are made up of three layers, and the medical consensus has been that risk factors such as high blood cholesterol, blood pressure and smoking lead to plaques beginning to first develop in the inner layer of the blood vessels but this new study has shown it can also build-up in the middle layer.
“We also found that the carotid arteries in your neck that supply blood to your brain, contained a high accumulation of fat in the middle vessel layer in more than 30% of SCGH patient samples tested,” said Professor Jansen,
This work was published in the journal Frontiers in Cardiovascular Medicine and was generously funded by the Miles family and Cook Foundation.