Restoration of normal sympathetic neural function in heart failure following baroreflex activation therapy: final 43-month study report

BACKGROUND: Baroreflex activation therapy (BAT) exerts in severe heart failure sympathoinhibitory effects, improving clinical variables and reducing hospitalization rate. The current follow-up study was aimed at determining the long-term effects of BAT, assessing whether BAT in heart failure allows to restore physiological levels of sympathetic function.

METHODS: Seven patients out of the 11 heart failure patients aged 66.5 ± 3 years (mean ± SEM) in New York Heart Association Class III with left ventricular ejection fraction 40% or less and impaired functional capacity recruited in the study survived at the final follow-up (43.5 ± 2.1 months). Measurements included muscle sympathetic nerve activity (MSNA, microneurography) and spontaneous baroreflex-MSNA sensitivity together with hospitalization rate, echocardiography, Minnesota score, New York Heart Association class and standard clinical data. Measurements were collected before and at 6, 21 and 43 months following BAT. Data were compared with those collected in 17 age-matched healthy controls. All assessments were made with the heart failure patient on optimal active therapy.

RESULTS: In the seven patients, BAT maintained its beneficial effects over 43.5 ± 2.1 months of follow-up. MSNA values underwent a progressive significant reduction from baseline to 21 and 43 months follow-up following BAT (from 46.2 ± 2.4 to 31.3 ± 3.0 e 26.6 ± 2.0 bursts/min, P < 0.05 at least), becoming almost superimposable to the ones seen in healthy controls (25.5 ± 0.8 bursts/min). Baroreflex-MSNA sensitivity improved, without achieving, however, a full normalization. Blood pressure and heart rate did not change. Left ventricular ejection fraction improved significantly from 32.3 ± 2 to 36.7 ± 3% (P < 0.05). Hospitalization rate decreased substantially when measured as days/year/patients it decreased from 10.3 ± 2.5 preimplant to 1.01 ± 1.4 at the 43.5th month follow-up (P < 0.02). No side effects were reported in the long-term period.

CONCLUSION: The current study provides evidence that BAT in heart failure with reduced ejection fraction allows not only to improve hemodynamic and clinical profile but also to exert profound sympathoinhibitory effects, allowing an almost complete restoration of physiological levels of the sympathetic neural function.