PHILADELPHIA – Enthusiasm for catheter-based renal denervation as a potential nondrug treatment for hypertension is once again on the rise, Michael Bohm, MD, observed at the American Heart Association scientific sessions.
The field experienced “a big depression” in 2014 with the publication of the unexpectedly negative results of the Symplicity HTN-3 trial (N Engl J Med. 2014;370:1393-401), he said. But post hoc analysis of the trial revealed significant shortcomings in design and execution.
“All of the flaws of this trial have been eliminated and now there is a very tightly controlled program to show whether renal denervation will work or not,” according to Dr. Bohm, director of the department of internal medicine and professor of cardiology at Saarland University in Homburg, Germany.
Indeed, three randomized, double-blind, sham-controlled, proof-of-concept clinical trials – all with strongly positive results – were published in Lancet in 2017 and 2018: SPYRAL HTN-OFF (2017 Nov 11;390:2160-70), RADIANCE SOLO (2018 Jun 9;391:2335-45), and SPYRAL HTN-ON (2018 May 23;391:2346-55). Based on the encouraging findings, four large pivotal trials of renal denervation (RDN) for hypertension are ongoing: RADIANCE HTN, REQUIRE, RADIANCE II, and SPYRAL HTN-ON MED. In addition, the SPYRAL HTN-OFF MED pivotal trial has been completed and will be presented soon, Dr. Bohm said.
Defining who’s most likely to benefit
Treatment response has been quite variable within the various RDN trials. A reliable predictor of response would be an important advance because it would enable physicians to select the best candidates for treatment while sparing others from an invasive procedure – albeit a relatively safe one – that they may not benefit from. On this front, Dr. Bohm and colleagues have recently reported that a baseline 24-hour heart rate above the median value of 73.5 bpm in the SPYRAL HTN-OFF MED trial – a marker for sympathetic overdrive – was associated with a 10.7/7.5 mm Hg greater reduction in average ambulatory blood pressures post-RDN than with a sham procedure. In contrast, blood pressure changes in RDN recipients with a below-median baseline 24-hour heart rate weren’t significant (Eur Heart J. 2019 Mar 1;40:743-51).
“Although this is a little bit rough, there is no other really true and reliable marker,” the cardiologist observed.
A pressing need exists for a reliable intraprocedural indicator of success. Dr. Bohm noted that Australian investigators are pursuing a promising approach in animal studies: intraprocedural transvascular high-frequency pacing of the aorticorenal ganglia. Abolition of the pacing-induced increase in blood pressure may be an indicator of complete RDN (JACC Cardiovasc Interv. 2019 Jun 24;12:1109-20).
Applications other than hypertension
Renal denervation is under early-stage investigation for a range of other cardiovascular diseases in which sympathetic overdrive figures prominently.
“The truly interesting things in renal denervation are what happens beyond hypertension. There are a lot of potential applications,” according to Dr. Bohm.
For example, when RDN was performed alongside pulmonary vein isolation for treatment of paroxysmal atrial fibrillation in hypertensive patients, the arrhythmia recurrence rate was significantly reduced during 1 year of follow-up, compared with AF ablation alone, in the randomized, multicenter, 302-patient ERADICATE-AF trial, presented at the most recent meeting of the Heart Rhythm Society.
Also, a small, uncontrolled registry study of RDN in patients with cardiomyopathy and electrical storm suggests the procedure may have an immediate anti–ventricular arrhythmia effect.
Meanwhile, Dr. Bohm is pressing the German government to sponsor an independent randomized controlled trial of RDN for heart failure. He and others have shown in small pilot studies a promising signal that the treatment may improve myocardial function and the signs and symptoms of heart failure in both patients with reduced and preserved left ventricular ejection fraction – and without reducing their blood pressure, which is often already low.
Dr. Bohm and others have also been exploring the impact of RDN in patients with metabolic syndrome. The treatment has a sound pathophysiologic rationale because insulin resistance is dependent upon sympathetic nervous system activation. Preliminary reports show improved insulin sensitivity in response to RDN. Patients also report better quality of life, presumably because of the reduction in sympathetic overactivity.
A couple of small Chinese studies suggest denervating the pulmonary vein in patients with pulmonary hypertension leads to a salutary reduction in pulmonary blood pressures.
“We haven’t done that yet. There is no properly designed catheter. They’ve used a Spyra unipolar catheter. It could work, but it hasn’t been rigorously investigated,” the cardiologist said.
Dr. Bohm reported serving as a scientific adviser to Abbott, AstraZeneca, BMS, Boehringer Ingelheim, and Servier.