Over the past decades, clinical trials in HF have been unable to alter the natural history of cardio-renal compromise. Fluid retention accounts for the majority of admissions for acute decompensated heart failure, and salt and water removal using intravenous (IV) diuretics has been the mainstay of therapy applied to this population.1 Over 20% of hospitalized patients in the Acute Decompensated Heart Failure National Registry (ADHERE) had serum creatinine values greater than 2.0 mg/dL2 with the majority of congested patients presenting with significantly elevated systolic blood pressures rather than low-output states.1 Administration of IV loop diuretics further produces intravascular volume depletion and reduction in glomerular filtration rates3 as well as an increase in neurohormonal activation.4 This is true regardless of whether LVEF is impaired or preserved.5 However, despite relieving symptoms, acute drug administrations (such as adenosine receptor antagonists or natriuretic peptide analogues) for short durations have not changed the long-term cardio-renal outcomes in large clinical trials.
Recent recognition of different phenotypes of cardio-renal syndrome has provided better characterization of patient populations to evaluate specific treatment approaches or interventions.6 There is now greater appreciation that patients with congestive HF depend not only on an adequate glomerular function for renal glomerular filtration, but also on adequate tubular function for effective sodium handling that may or may not be dependent on glomerular filtration.7 Despite optimizing intracardiac filling pressures, many patients with August 28, 2013 Page 10 of 58 cardio-renal compromise remain symptomatic, complaining of breathlessness and fatigue often associated with concomitant increase in neurohormonal up-regulation (e.g. natriuretic peptides) and poor outcomes.8 Since the majority of patients present with hypertension, it points to the possibility that congestive HF is precipitated by heightened sympathetic drive.
Animal models have demonstrated that both blood pressure control and renal tubular function/glomerular filtration (as a function of renal blood flow) can be directly influenced by renal sympathetic nerve activity,9-12 which has evolved to provide cardiovascular support in the setting of hypovolemia or profound cardiovascular collapse. Specifically, HF animal models with denervated kidneys have demonstrated improvement in renal blood flow and natriuresis (with restoration of Na+-K+ ATPase at the loop of Henle, as well as epithelial sodium pumps at the distal tubules). However, our understanding of how persistently activated renal sympathetic outflow can lead to exaggerated neurohormonal up-regulation and chemoreceptor regulation in humans is still evolving. As heightened cardio-renal compromise leads to disease progression and congestive HF, it is conceivable that an approach to selectively modulate renal sympathetic outflow may improve cardio-renal compromise as well as the target mechanism leading to symptomatic improvement in at-risk patients.
By establishing the mechanistic role of renal sympathetic outflow in patients with impaired sodium handling as a contributor to congestion in HF, we may better understand why patients with HF develop symptoms, retain salt and water, and activate neurohormonal systems. This trial will be hypothesis generating and will serve to inform a larger clinical trial in patients with congestion related to HF.
The Data Safety and Monitoring Board (DSMB), an independent committee assigned by the sponsor to oversee the conduct and safety of this study, met on May 12, 2014 to review information that had become available from another study of the renal artery denervation procedure using the same investigational catheter as the PRESERVE study. Even though there were no concerns for the safety of subjects that had the renal artery denervation, the DSMB decided to stop the PRESERVE study.
Based upon agreement with the FDA, the protocol was amended to reduce subject participation from 52 weeks to 13 weeks and to only collect limited safety information.
