Results of a prospective, multicentre pilot trial of severe, symptomatic systolic heart failure patients treated with continuous spinal cord stimulation at the T13 level have shown the treatment is safe and feasible with the commercially available neurostimulation system (Eon Mini, St Jude Medical) and can potentially improve symptoms, functional capacity and cardiac function.
Hung-Fat Tse (University of Hong Kong, Queen May Hospital, Hong Kong) and others reported recently in HeartRhythm the results of the SCS HEART study. They said that after six months, there were no deaths and no cases of device-device interaction to cause spinal cord stimulation device or implantable cardiac defibrillator malfunction. The authors also noted that the efficacy composite score improved by 4.2±1.3, and 73% of the patients showed improvement in four or more than four of six efficacy parameters.
The efficacy results of this study differ from the preliminary results shown in the DEFEAT-HF (Determining the feasibility of spinal cord neuromodulation for the treatment of chronic heart failure) trial, which did not demonstrate clinical benefit or improvement in heart failure patients treated with spinal cord stimulation.
DEFEAT-HF, the first single blinded randomised controlled trial studying the safety and efficacy of spinal cord stimulation with the PrimeAdvanced Neurostimulator device (Medtronic), also showed that the procedure is safe with no increase in major adverse events. Results of this study were presented at the American Heart Association Scientific Sessions (AHA; 15-19 November 2014, Chicago, USA).
Commenting on the possible reasons of the differences in therapeutic efficacies between DEFEAT-HF and the SCS HEART study Tse et al told Cardiac Rhythm News: “The reasons for the difference are not clear but can be related to the differences in the methods of spinal cord stimulation we performed in our study with two leads (left and right) providing continuous stimulation at T13. In DEFEAT-HF, spinal cord stimulation was performed for just 12 hours per day using a single electrode at the T24 level.
In the SCS HEART study, 22 patients (all male with New York Heart Association [NYHA] class III) were enrolled between August 2011 and April 2013 at five centres in Hong Kong, Australia and Japan. Seventeen patients underwent spinal cord stimulation device implantation and also had an implantable cardiac defibrillator at baseline, eight of those had not responded to previous cardiac resynchronisation therapy. Four patients who did not fulfil the study criteria served as non-treated controls, two of those had an implantable cardiac defibrillator.
For the spinal cord stimulation procedure, the authors explain that the leads were placed subcutaneously below the left costal arch and connected to the permanent implantable pulse generator located in a subcutaneous pocket in the lateral abdominal region. Primary safety endpoints were death due to ventricular tachyarrhythmia of sudden unexpected death, myocardial infarction, or hospitalisation for heart failure during the first six months. The primary efficacy endpoint was based on a composite score, which included six efficacy parameters measured at baseline and at six months.
Tse et al note that thoracic spinal cord stimulation “is one of the therapeutic approaches that has been proposed to restore the homeostasis of the autonomic nervous system in heart failure and shown to improve cardiac function in a large animal model of heart failure…Our results demonstrated that chronic dual thoracic spinal cord stimulation leads targeted at the midline and to the left of the midline at the T13 level to provide spinal cord stimulation for 24 hours is safe and feasible.”
The authors report that at six months, two patients experienced ventricular tachyarrhythmia that required intervention and two were hospitalised for heart failure.
Fifteen of the 17 patients completed the efficacy endpoint assessments. The authors note that the efficacy composite score improved by 4.2±1.3, and 73% of the patients showed improvement in four or more than four of six efficacy parameters. They highlight that there was a significant improvement in the NYHA class efficacy parameter in 13 of 17 patients treated with spinal cord stimulation (3 vs. 2.1, p=.002). The Minnesota Living with Heart Failure Questionnaire efficacy parameter also showed improvement in 12 of 17 patients (42±26 vs. 27±22, p=.026). Ten of 15 patients improved the peak maximum oxygen consumption (VO2max) parameter (14.6±3.3 vs. 16.5±3.9 mL/kg/min, p=.013).
The left ventricular ejection fraction parameter also saw improvement in 14 of 16 patients (25%±6% vs. 37%±8%, p<.001). Eleven of 16 patients had better left ventricular end-systolic volume (174±57 vs. 137±37 mL, p=.002). There was no improvement in the N-terminal prohormone brain natriuretic peptide (NT-proBNP). The researchers comment that no improvements were observed in the non-treated controls.
They also suggest that future long-term randomised controlled trials with a larger patient cohort will be needed to assess long-term safety and efficacy of this procedure.
The study was funded by the Center for Innovation and Strategic Collaboration and St Jude Medical.