The strange tale of high blood pressure and the cattle prod

By John Pickering 03/04/2012

This is a good news story for all with high blood pressure.  It may even get you and extra decade or two here on earth.  High blood pressure is a killer.  It leads to heart attacks, strokes, and, yes, kidney failure.   Funnily enough, it is the kidney which regulates blood pressure – more on that in a minute.  The good news story I have to tell you is one that was told by a cardiac surgeon (Dr Gerry Wilkins) at a meeting of the University of Otago Renal Theme I attended last week in Dunedin.  It begins thus ….

Have a look at this graph of Franklin Delano Roosevelt.  In the 1940s there was no way to control blood pressure.  There are two lines corresponding to the systolic (top) and diastolic (bottom) blood pressures.  Basically the bigger they are the harder your heart has to work to get the blood around the body. The top line begins at about 140 – a high blood pressure!  A good blood pressure would be about 120 mmHg or less.  What is yours?  Despite reassurances to the contrary when he was at Yalta trading countries in Europe with Stalin that his health was good, he had a massively high blood pressure which soon after the conference rapidly rose.

Franklin Delano Roosevalt’s blood pressure. From Bishop T and Fiueredo VM. Hypertensive therapy: attacking the renin-angiotensin system West J Med. 2001 August; 175(2): 119–124 (

The good news for us baby boomers was the invention of drugs which help lower blood pressure, and there are lots of them.  Dr Wilkins summed these up by stating if one drug causes a 10 mmHg drop in the systolic blood pressure it is hailed as a miracle drug.  Large studies have shown that the average decrease in blood pressure using drugs is around 12 mmHg and that takes a combination of more then three drugs on average to achieve that!  Some of these, of course, have side effects

The exciting news is that a cattle prod and a 25 minute procedure can reduce blood pressure by a massive 32 mmHg on average and it appears to work in almost everyone (so far).  The procedure is called renal denervation.  Basically a cattle prod is introduced inside the big artery bringing blood to a kidney (and it is HUGE… remember the kidney’s get 25% of the blood from each heart beat).  It then prods points on the inside of the artery and heats a spot… the heat extends to the outer wall of the artery and kills off a few nerves that happen to be passing that point.  Have a look at the great You Tube video showing this procedure.

So, how does this work?  Remember the kidney contains about a million tiny filters (glomeruli).  Each filter has a supply of blood coming into it and out of it.  See my diagram below.  The kidney works to maintain the blood pressure across the filter so that the plasma (water, proteins, and other junk) comes out of the blood vessel and can be cleaned up in the tubules before (most of it) is reabsorbed back into the blood vessels.  The blood vessels fore and aft of the filter are squeezed so as to maintain this pressure.  Each has nerves going to it.   Renal denervation effectively inhibits this process in some of the filters so that the kidney doesn’t raise the blood pressure too much.

Schematic of the blood vessels and nerves of the filter (glomerulus)

More trials are underway… this could be great news.  Just maybe it will also help some  on dialysis even though their kidneys don’t work well.  Watch this space…I shall keep you updated.

Tagged: high blood pressure, renal denervation