Next time you take an exercise class it might be worth consulting your doctor beforehand, certain conditions could make the increased heart rate tied to exercise very dangerous.
New research has shown that an elevated heart rate can induce a stroke in patients with highly blocked carotid arteries. However, for healthy patients with only slightly blocked arteries, exercise was shown to be beneficial for maintaining healthy blood flow.
Carotid arteries, located on both sides of the neck, supply blood flow to facial tissues and the brain. When fat, cholesterol, and other particles build up the inner carotid walls, they form a plaque that narrows the artery.
This narrowing is known as stenosis and it often proves difficult to detect the early stages of plaque accumulation. Stenosis is particularly dangerous as it limits the blood flow to the brain.
In healthy patients, an elevated heart rate increases and stabilises the drag force blood exerts on the vessel wall, reducing stenosis risk.
The researchers found that this may not the case for patients already experiencing stenosis.
The study authors used a specialised computational model to stimulate blood flow in carotid arteries at three stages of stenosis: without blockage, with a mild 30 per cent blockage, and with a moderate 50 per cent blockage. They compared the effect of an exercise-induced heart rate, 140 beats per minute, and resting heart rates of 67 and 100 bpm.
Contours of oscillatory shear index (OSI) on healthy, 30% stenosis, and 50% stenosis carotid arteries for the normal (67 beats per minute), moderate (100 bpm), and high exercise (140 bpm) heart rates.
In health and mild cases, the exercise condition improved the health of the simulated carotid.
For the moderate blockage, the results were a cause for major concern.
Study author, Somnath Roy, says: “Intense exercise shows adverse effects on patients with moderate or higher stenosis levels.
“It substantially increases the shear stress at the stenosis zone, which may cause the stenosis to rupture. This ruptured plaque may then flow to the brain and its blood supply, causing ischaemic stroke.”
In addition to this, an elevated heart rate could increase the likelihood of another stenosis forming.
Whilst many factors contribute to stenosis and heightened risk of stroke, the authors recommend arterial health checks regularly for those doing intense workouts. Furthermore, they also recommend a carefully prescribed exercise regimen for people with moderate to severe stenosis or with a history of stroke.
