Renal Denervation's Structural, Functional Heart Benefits May Be Independent of BP

Marlene Busko

December 06, 2013

HAMBURG, GERMANY — In a small study of patients undergoing renal denervation for resistant hypertension, left-ventricular hypertrophy and diastolic function improved independently of changes in blood pressure and heart rate [1].

"The novelty of our findings is the independence of morphologic improvements [regression of LV hypertrophy] from hemodynamic changes (reduction of blood pressure and heart rate)," Dr Stephan H Schirmer (University of Saarland, Hamburg, Germany) told heartwire in an email. "If this is confirmed in larger trials, it might open up novel indications for the use of renal denervation, for example, in [diastolic] heart-failure patients, independent of blood pressure."

Dr Deepak L Bhatt (Harvard Medical School, Boston, MA) told heartwire that the study observations are "provocative" and "exciting" but stressed that they need to be confirmed in a blinded, larger, multicenter study before they could be accepted into clinical practice. Bhatt and Dr George Bakris (University of Chicago, IL) are co–principal investigators for the ongoing SYMPLICITY HTN-3 trial of bilateral renal denervation in patients with uncontrolled hypertension.

The study was published online December 4, 2013 in the Journal of the American College of Cardiology.

Are Renal Denervation Effects Always Tied to BP Change?

Renal denervation reduces heart rate and blood pressure in patients with resistant hypertension, and as reported by heartwire , a recent small study suggested that the procedure also reduces left-ventricular mass and improves diastolic function in such patients, Schirmer and colleagues write.

They hypothesized that renal denervation might affect cardiac structure and function, independent of the effect on blood pressure.

They enrolled 66 consecutive patients who underwent renal denervation using the Flex catheter system (Medtronic) at their center during 2010 and 2011 for treatment of resistant hypertension (office systolic blood pressure >140 mm Hg). Patients had a mean age of 64 years, and 55% were men. They were on a mean of 4.3 antihypertensive drugs. All were taking a diuretic, 89% were taking a beta-blocker, and 55% were taking an angiotensin-receptor blocker.

Six months after renal denervation, mean blood pressure decreased from 172.9/92.5 to 151.3/85.5 mm Hg, confirmed by 24-hour ambulatory monitoring, if available (n=50). Mean heart rate decreased from 67.7 to 60.5 bpm. Mean left-ventricular mass index decreased from 61.5 to 53.4 g/m2. Measures of diastolic function also improved.

The changes in cardiac function and ventricular size were not tied to the magnitude of the blood-pressure reduction, which "suggest[s] a direct effect of the sympathetic nervous system on myocardial morphology and function," Schirmer and colleagues write. They call for further research to investigate functional cardiovascular benefits of renal denervation beyond blood-pressure reduction.

Promising Early Benefit, Needs Confirmation

In an accompanying editorial [2], Bakris and Dr Sandeep Nathan (University of Chicago) commend Schirmer and colleagues "for providing promising early benefit of catheter-based renal denervation and for highlighting a possible blood-pressure–independent facet of this technique." However, they caution that although the findings are "intriguing," the study's limitations include that it was relatively small, conducted at a single center, lacked a sham control, and relied on echocardiography rather than magnetic resonance imaging.

Therefore, "these observations need confirmation before acceptance in clinical practice . . . and can only be applied to those with inclusion criteria used in their study," the editorialists conclude.

"It's an exciting, provocative result, and there's a good chance that it will stand the test of time, but I still think in general, it's best to be cautious about new technologies and relatively small studies, because time typically shows that they provide an overestimate of what the true effects will be," Bhatt commented when interviewed.

"Whether the reduction in left-ventricular mass is beyond what would be anticipated with blood-pressure and heart-rate reduction—certainly this analysis suggests that is a possibility—needs to be confirmed in larger studies," he added, echoing the authors and editorialists.

Potentially referring physicians, in the United States where the procedure is investigational, and even in Europe where it's approved, appear to be waiting for the results of SYMPLICITY HTN-3, Bhatt said. This blinded, randomized, multicenter trial will provide a clearer picture of what sort of blood-pressure reductions are achievable in patients with resistant hypertension who undergo renal denervation. Results are expected by mid-2014.

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