This article is first seen at Medscape.
Citation: Intense Exercise May Be Risky in Moderate to Severe Stenosis – Medscape – Jun 30, 2023
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New research suggests that intense physical activity could heighten the risk of stroke among patients with moderate to severe stenosis.
Using a sophisticated computational model of the internal carotid artery (ICA), researchers simulated blood flow across three stenosis stages: no blockage, mild blockage (30%), and moderate blockage (50%). They compared the impact of exercise-induced elevated heart rate (140 bpm) with two resting heart rates (67 and 100 bpm).
As anticipated, vigorous exercise proved beneficial for patients with healthy arteries and those with mild stenosis. However, it displayed the potential to negatively impact arteries in patients with moderate or higher stenosis due to an increase in arterial wall shear stress (WSS) at the stenosis site.
According to Somnath Roy, PhD, a study investigator and associate professor at the Indian Institute of Technology, Kharagpur, the heightened shear stress at the stenosis site could lead to stenosis rupture, potentially resulting in plaque traveling to the brain through the internal carotid artery (ICA) and causing ischemic stroke. The study was published online in Physics of Fluids on June 20.
Physics-Driven Prediction
The study authors explain that arterial behavior is significantly influenced by local hemodynamics, closely tied to atherosclerosis development. Disturbed flow in the post-stenotic region further exacerbates arterial dysfunction by activating genes promoting atherosclerosis and inflammation in endothelial cells.
Arterial sites subjected to low or oscillatory WSS are considered atherogenic. Two hemodynamic parameters, time-average WSS and oscillatory shear index (OSI), are widely used to quantify low and fluctuating WSS behavior in arterial flow.
Stenosis within internal carotid arteries can disrupt cerebral blood supply, potentially leading to ischemic stroke, Roy explains. While previous research indicates beneficial changes in arterial stress due to exercise for healthy or mildly affected arteries, this complexity increases when considering patients with stroke history or arterial blockage.
Noting instances of sudden vascular strokes during intense exercise, Roy highlights the inadequate exploration of flow behavior in arteries with stenotic blockage at high heart rates.
For the study, researchers observed flow patterns and wall stress levels in a human carotid model at heart rates corresponding to rest and exercise conditions.
Roy states that their computational model enabled them to “solve the mass and momentum equation of blood flow in the virtual arterial domain,” producing a “physics-based prediction of what might happen in human artery under such conditions.”
Prescribing Exercise Cautiously
The researchers noted the development of strong recirculation, secondary velocity, and an OSI zone within a severely stenosed carotid artery at a normal heart rate.
While higher heart rates were observed to potentially improve arterial health by reducing OSI, this effect was only seen in the absence of stenosis or in cases of mild stenosis.
In contrast, heart rates exceeding 120 bpm worsened arterial health in severely stenosed arteries (≥50% blockage) by triggering flow instabilities. This intensified the recirculation zone’s extent and intensity, along with secondary velocity.
This led to a pressure drop across the stenosis and the spread of a high OSI (≥0.2) zone downstream. Moreover, severe stenosis cases saw a significant rise in WSS at the stenosis constriction, which could contribute to plaque rupture and thrombus formation.
While not directly studied, the stress distribution predicted for stenosed arteries at 120 bpm indicated a high risk of plaque rupture.
This ruptured plaque could travel to the brain via the ICA, leading to blood supply blockage and an ischemic stroke. Additionally, intense exercise heightens the risk of poststenotic zone stenosis formation by expanding the region exposed to high oscillating WSS.
Roy hopes a comprehensive understanding of flow patterns and stress distribution in stenosed carotid arteries at varying heart rates can aid clinicians in designing improved exercise plans.
He and his colleagues recommend regular monitoring of arterial health for individuals engaging in intense workouts or exercises.
Considering the study’s findings, Roy advises careful prescription of exercise routines for individuals with moderate to severe stenosis or a history of strokes, taking into account the identified risk factors.
Innovative Insights Dr. Seemant Chaturvedi, a neurology professor at the University of Maryland School of Medicine, comments that increased WSS in narrowed carotid arteries with higher heart rates is established. However, the new observation regarding variations with differing heart rates is novel.
Currently, there may not be a clear actionable directive for healthcare providers. Chaturvedi notes that higher heart rates can be advantageous, such as during exercise to prevent vascular disease. For those with extreme narrowing, avoiding very fast heart rates could be considered, but this decision should be made individually in consultation with a physician.
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