Role of Shear Stress in Hypertension
Dr. Kaizad Tamboli is an internist practicing in Gulfport, MS. Dr. Tamboli specializes in the medical treatment of adults. Internists can act as a primary physician or a consultant to a primary physician. They manage both common and rare diseases. Dr. Tamboli provides comprehensive care and manages treatment with surgeons... more
High blood pressure which is commonly known as hypertension has many causes and results in significant morbidity and mortality affecting multiple organs. At a basic level, it is about how the general principles of physics would apply in this scenario. The generally recognized formula for Shear stress, T, is the force, F, acting on a given section divided by the cross-sectional area, A, of the section, calculated in the direction of the force. T= F/A.
A simple way to compare this biological phenomenon is with the concept of a faucet and a hose. Imagine the heart to be the faucet that is attached to the hose which represents the major artery which is the aorta and its branches. The pressure in this loop can rise because either the faucet (the heart) has a high output or the hose (the aorta and branches) is rigid and stiff.
This creates inherent shear stress in the system which leads to a cascade leading to damage to the lining of the blood vessels, subsequent inflammation and reactive fibrosis, and further stiffening of the arteries. Downstream this process affects the major organs which are crucial in the regulation of blood pressure, namely the kidneys. A combination of high output and high shear stress forces exponentially increases the problem of high blood pressure.
Also, any increase in the volume of blood within this loop will add to the shear stress forces. That is why sodium and electrolyte balance and regulation is so crucial. Again, damaged kidneys will significantly contribute to this disruption in homeostasis.
The approach to high blood pressure control should take into account all of the above scenarios. Lower the volume coming out of the faucet (heart); lower the volume in the loop (blood volume) and lower the shear stress forces in the loop (the hose).
That is why the treatment approach to controlling high blood pressure is usually a combination approach with medications that work synergetically (together) with each other to achieve the ultimate goal. We will review these approaches and discuss their advantages.
The volume coming out of the faucet (heart) can be reduced by taking medications that slow the heart rate down and decrease the contractility of the heart to include beta-blockers and calcium channel blockers. Volume in the loop can be decreased by taking medications like diuretics. Shear stress forces in the loop (hose) can be decreased by taking medications like ACE inhibitors or ARBlockers.
A low sodium diet, strict fluid management, weight control, daily exercise, low-fat low cholesterol diet, restricted caffeine, and alcohol intake are crucial concurrent lifestyle changes and modifications that must be strictly adhered to and added to the medications will prevent further damage to the “loop”.
