Response to Sustained Handgrip Exercise and Post‐Exercise Circulatory Arrest in Renal Denervation Responders and Non‐Responders

Abstract

PURPOSEHypertension is characterized by an exaggerated hemodynamic response to sympathoexcitatory stimuli such as exercise and metaboreflex activation. Renal Denervation (RDN) lowers blood pressure in some individuals with resistant hypertension, however the effect of RDN on reflex control of blood pressure remains unclear.METHODSA subset of subjects from the simplicity HTN‐3 study who underwent RDN (n=11) were classified as responders (R; n=7, 6M:1F, 61±10 years) or non‐responders (NR; n=4, 3M:1F, 57±4 years) based on a target decrease in office blood pressure of 20mmHg observed on at least 3 occasions post‐RDN (~27 months). Heart rate (HR), mean arterial blood pressure (MAP; plethysmography), and muscle sympathetic nervous system activity (MSNA, microneurography) were measured during supine rest, sustained handgrip exercise to fatigue (HGE; 40% maximal voluntary contraction), and post‐exercise circulatory arrest (PECA; 2 mins). Maximal changes (Δ) in HR, MAP, and MSNA (frequency: burst/min and total MSNA: AU/min) were calculated from baseline in response to HGE and PECA, and comparisons made using unpaired t‐tests and reported as mean ± SEM.RESULTSDuring supine rest, R had lower MAP (R: 97±7; NR: 118±8 mmHg, P<0.05), and similar HR (R: 70±4; NR: 75±9, P=0.26) and MSNA (R: 41.8±4; NR: 41±3 burst/min, P=0.50) compared to NR. During HGE, R had a similar rise in bursts frequency and a larger rise in total MSNA (ΔMSNA: R: 2897±825; NR: 382±573 AU/min, P<0.05) compared to NR. Despite this increase, the HR and BP response to HGE was similar between groups (ΔHR: R: 17±4; NR: 11±3 beats/min; ΔMAP: R: 33±8; NR: 27±7 mmHg, both P>0.05). During PECA, MSNA tended to remain elevated (ΔMSNA: R: 2345±687; NR: 775±493 AU/min, P=0.10) and HR was higher (ΔHR: R: 9±3; NR: −1±2 beats/min, P=0.02) in R compared to NR, while MAP was not different between groups (ΔMAP: R: 25±5; NR: 15±6 mmHg, P=0.21).CONCLUSIONR had a greater rise in MSNA in response to the same sympathoexcitatory stimuli (HGE, PECA) compared to NR. Despite this larger increase in MSNA, the HR and BP response to HGE and PECA was similar between groups. Thus, RDN may impact both central integration, and end organ responsiveness to sympathoexcitatory stimuli.