Removing the hype from hypertension

Earlier this year, Symplicity HTN-3, the world’s first blinded randomised controlled trial of renal denervation in hypertension, announced that it had failed to meet its targeted reduction in blood pressure.1 Before this announcement, three high profile publications—a case report2 and two unblinded trials3 4—had reported a consistent 30 mm Hg effect size, which was confirmed by more than two dozen reports of similar effect sizes. The intellectual property for the technology was sold for $800m (£480m; €582m).5 The various competing devices now number more than 50.

Symplicity HTN-3 faces scrutiny because the effect of renal denervation on blood pressure has fallen short of the target of about 10 mm Hg,6 which seemed modest given the results of the previous unblinded trials. However, unlike previous trials, Symplicity HTN-3 used a placebo controlled study design and blinded measurement of blood pressure. Therefore, the odd choice of study design was not that of Symplicity HTN-3, but rather the dozens of previous studies. Measurement of a noisy variable by unblinded optimistic staff …