New post up on Cardiology Medscape: Lessons learned from the failure of Renal denervation for high blood pressure

Most people come by it honestly. They eat too much, move too little, skimp on sleep, take on too much stress and then succumb to buying larger clothes. The word we use in medicine is insidious.

High blood pressure (hypertension – HTN) is one of the leading cardiovascular problems of this time. Some have called treating HTN the holy grail of medicine. Think about why this may be. The human heart contracts 100,000 times per day. Each beat delivers a pressure load to the thousands of arteries in the body. Over days, weeks, months, years and decades, small elevations of high pressure can have devastating wear and tear effects. This is why high blood pressure leads to stroke (damage to brain vessels), kidney failure (damage to kidney vessels) and heart attack (damage to coronary arteries), among other problems.

It’s easy to see why treating high blood pressure is important. And the best way to treat high blood pressure is to exercise, eat well, sleep well and avoid obesity. Medicines are second-line choices. But even then, many patients remain hypertensive. This led to an idea. What if we could disconnect adrenaline-carrying nerves from the kidney–an organ central to blood pressure control?

Renal denervation showed promise. The technique involved placing an ablation catheter, similar to what we use in the EP lab, up to the kidney arteries and then deliver circular burns on the inside of the kidney vessels. These lesions would damage/reduce neural outputs to and from the kidney, effectively lowering sympathetic nervous system tone. The sympathetic nervous system is responsible for the adrenaline-dependent fight or flight response. Blocking the effect of adrenaline is the primary way beta-blockers exert their effect. Less sympathetic tone means lower blood pressure.

Preliminary studies of ablating kidney arteries (renal denervation) in patients with drug-resistant high blood pressure looked promising. Critics, however, pointed to the small numbers of subjects, implausible reductions of blood pressure and lack of robust control groups. But as it should be in science, small promising trials led to a bigger scientifically rigorous trial, which was called SYMPLICITY HTN-3.

Hopes were high. Imagine the stakes. If a simple procedure, like buzzing the kidney arteries, could control high blood pressure, well, that would be something.

This quote came from the lead investigator of one of the preliminary renal denervation trials and was featured in a 2012 AHA press release: “Studies will soon determine whether this procedure can cure mild hypertension, producing permanent drug-free normalization of blood pressure. Based on the blood-pressure declines achieved, reduction in heart attack and stroke rates of more than 40% is anticipated.”

Hype is defined by extravagant or intensive publicity or promotion. That statement, my friends, was hype.

Sadly, but for masters of the obvious, not surprisingly, Medtronic announced last week that its pivotal renal-denervation study, SYMPLICITY HTN-3 , failed to meet the primary efficacy end point—reduction of blood pressure at six months. In other words, renal denervation didn’t work.

This was huge news for the cardiology community. It was yet another negative trial, and yet another failure to treat acquired chronic disorders of lifestyle choices with a simple procedure or pill.

I saw 5 lessons to be learned from this news: principles like implausibility, the fog of hype, oversimplification of complex biology, the rule of minimal disruption and the importance of recognizing our own intervention bias.

You can read more by clicking on the title of the Medscape Cardiology post. Five Lessons to Be Learned From the Fall of Renal Denervation

JMM

BTW: My Novel Oral Anticoagulants vs Warfarin: The Truth is Relative post has over 80 comments and remained on the most-read list for weeks.