Teachable moment in classrooms:

  1. cardiovascular system/ hemodynamics chapter – smooth muscle layer in arteries and veins
  2. cardiovascular system/ hemodynamics chapter – physiological regulation of blood pressure
  3. autonomic nervous system chapter – sympathetic innervation of the kidneys

The news item:  Recently this report appeared online

New Procedure Treats High Blood Pressure

The first renal denervation (RDN) procedure at Springhill Medical Center was completed last week by Dr. John Galla of Cardiology Associates. The blood pressure procedure is now offered for certain patients and was approved by the U.S. Food and Drug Administration (FDA) in 2023.

The article states that the Simplicity renal denervation procedure targets nerves near kidneys. During the procedure a catheter is introduced into an artery near the kidney, and energy is delivered to calm the excessive activity of nerves. The article also states that this procedure is approved for people with hypertension where lifestyle changes or medication did not sufficiently control blood pressure.

So, Why Do I Care??  High blood pressure (hypertension) is a disorder that affects about half the US adult population, almost 120 million people. There are over 600,000 deaths in the USA from causes that can be linked to hypertension. This is a huge health problem, and while medications can do a good job controlling hypertension, only 27% of patients take their medication, so new procedures do not depend on taking a daily pill can provide a practically useful alternative.

Plain English, Please!!! First, let’s talk about why high blood pressure develops. Normal blood pressure of 120/80 mmHg is carefully maintained in our bodies by hormones, and the nervous system. Hormones such as renin, angiotensin II, aldosterone, epinephrine, norepinephrine are used in our bodies to increase blood pressure. All those hormones act on the smooth muscle layer of small arteries and make them contract resulting in narrowing (vasoconstriction) of small arteries. The sympathetic nerves of the kidneys normally play a small role in lowering blood pressure. Overactive renal nerves, however, increase blood pressure by increasing renin and aldosterone production.

Second, let’s talk about why high blood pressure is damaging to our bodies. Chronic (long-duration) high blood pressure physically stretches and damages thinnest and weakest small arterioles. Those kinds of arterioles are found in the renal corpuscle, the retina, and in the healing wounds. Therefore, when patients don’t control their high blood pressure kidney failure develops, vision loss develops, and ulcers develop from non-healing wounds.

Third, let’s talk about how this new surgical procedure reduces blood pressure. In some individuals high blood pressure is exaggerated by the unusually high activity of the sympathetic nervous system. Overactive sympathetic nerves bring unusually high number of nerve impulses to the kidneys and make the cells of the kidney produce more renin, which, in turn increases aldosterone production in the adrenal glands. The situation in those individuals is similar to a car factory that makes 1000 cars every day and uses 100 cables to bring computerized instructions to 100 welding robots. The Simplicity procedure disables many sympathetic nerve axons in the kidneys. During the procedure a catheter is pushed near the sympathetic nerves of the kidney, and then radiofrequency waves from the catheter heat the nerves and destroy many of the axons. If in our car factory 50 cables are damaged, then only 50 welding robots will receive the instruction, and only 500 cars will be made that day. In the kidneys fewer sympathetic nerve impulses lead to lower renin production, and, thus, lower blood pressure.