title: Baroreflex gain and vasomotor sympathetic modulation in resistant hypertension.
abstract: OBJECTIVE
  The aim of this study was to determine the gain and latency of arterial baroreflex control of heart rate in patients with resistant hypertension compared to patients with essential hypertension and normotensive subjects.
  
  
  METHODS
  Eighteen patients with resistant hypertension (56 ± 10 years, mean of four antihypertensive drugs), 17 patients with essential hypertension (56 ± 11 years, mean of two antihypertensive drugs), and 17 untreated normotensive controls (50 ± 15 years) were evaluated by spectral analysis of the spontaneous fluctuations of arterial pressure (beat-to-beat) and heart rate (ECG). This analysis estimated vasomotor and cardiac autonomic modulations, respectively. The transfer function analysis quantified the gain and latency of the response of output signal (RR interval) per unit of spontaneous change of input signal (systolic arterial pressure).
  
  
  RESULTS
  The gain was similarly lower in patients with resistant hypertension and patients with essential hypertension in relation to normotensive subjects (4.67 ± 2.96 vs. 6.60 ± 3.30 vs. 12.56 ± 8.81 ms/mmHg; P < 0.01, respectively). However, the latency of arterial baroreflex control of heart rate was significantly higher only in patients with resistant hypertension when compared to patients with essential hypertension and normotensive subjects (-4.01 ± 3.19 vs. -2.91 ± 2.10 vs. -1.82 ± 1.09 s; P = 0.04, respectively). In addition, the index of vasomotor sympathetic modulation was significantly increased only in patients with resistant hypertension when compared to patients with essential hypertension and normotensive subjects (4.04 ± 2.86 vs. 2.65 ± 1.88 vs. 2.06 ± 1.70 mmHg2; P < 0.01, respectively).
  
  
  CONCLUSIONS
  Patients with resistant hypertension have reduced gain and increased latency of arterial baroreflex control of heart rate. These patients also have increased vasomotor sympathetic modulation.
authors.affiliation: Cardiovascular Research Unit and Exercise Physiology, University Hospital and Faculty of Physical Education and Sports, Federal University of Juiz de Fora University Campus, Juiz de Fora, MG, Brazil. isabelleguedes@yahoo.com.br.
authors.forename: Isabelle Magalhães Guedes
authors.initials: IMG
authors.lastname: Freitas
authors.affiliation: Cardiovascular Research Unit and Exercise Physiology, University Hospital and Faculty of Physical Education and Sports, Federal University of Juiz de Fora University Campus, Juiz de Fora, MG, Brazil.
authors.forename: Leonardo Barbosa
authors.initials: LB
authors.lastname: de Almeida
authors.affiliation: Cardiovascular Research Unit and Exercise Physiology, University Hospital and Faculty of Physical Education and Sports, Federal University of Juiz de Fora University Campus, Juiz de Fora, MG, Brazil.
authors.forename: Natália Portela
authors.initials: NP
authors.lastname: Pereira
authors.affiliation: Cardiovascular Research Unit and Exercise Physiology, University Hospital and Faculty of Physical Education and Sports, Federal University of Juiz de Fora University Campus, Juiz de Fora, MG, Brazil.
authors.forename: Pedro Augusto de Carvalho
authors.initials: PAC
authors.lastname: Mira
authors.affiliation: Interdisciplinary Center for Studies, Research and Treatment in Nephrology (NIEPEN), Federal University of Juiz de Fora, Juiz de Fora, MG, Brazil.
authors.forename: Rogério Baumgratz
authors.initials: RB
authors.lastname: de Paula
authors.affiliation: Cardiovascular Research Unit and Exercise Physiology, University Hospital and Faculty of Physical Education and Sports, Federal University of Juiz de Fora University Campus, Juiz de Fora, MG, Brazil.
authors.forename: Daniel Godoy
authors.initials: DG
authors.lastname: Martinez
authors.affiliation: Heart Institute (Instituto do Coração), University of São Paulo Medical School, São Paulo, SP, Brazil.
authors.forename: Edgar
authors.initials: E
authors.lastname: Toschi-Dias
authors.affiliation: Cardiovascular Research Unit and Exercise Physiology, University Hospital and Faculty of Physical Education and Sports, Federal University of Juiz de Fora University Campus, Juiz de Fora, MG, Brazil.
authors.forename: Mateus Camaroti
authors.initials: MC
authors.lastname: Laterza
mesh_terms: D000368:Aged; D000959:Antihypertensive Agents / Q000627:therapeutic use; D001341:Autonomic Nervous System / Q000503:physiopathology; D017704:Baroreflex; D003329:Coronary Vasospasm / Q000503:physiopathology*; D004562:Electrocardiography; D000075222:Essential Hypertension / Q000188:drug therapy / Q000503:physiopathology; D005260:Female; D006321:Heart / Q000294:innervation / Q000503:physiopathology; D006339:Heart Rate; D006801:Humans; D006973:Hypertension / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D009131:Muscle, Smooth, Vascular / Q000503:physiopathology*; D013564:Sympathetic Nervous System / Q000503:physiopathology*
chemical_list: D000959:Antihypertensive Agents
keywords: Heart rate variability; Hypertension; Latency of baroreflex control