Controle autonômico e hemodinâmico em pré-hipertensos com histórico familiar de hipertensão arterial

Abstract

Introduction: Individuals with a family history of systemic arterial hypertension (SAH) or prehypertension have autonomic and vascular abnormalities, both at rest and in response to stressful situations. Considering that these changes are related to the development of SAH and that in individuals with a family history of SAH there is a high incidence of prehypertension, the understanding of these disorders in prehypertensive individuals with a history of SAH is of fundamental importance. Objective: To compare the autonomic and vascular functions in rest and the hemodynamic response during mental stress and isometric handgrip exercise the prehypertensive and normotensive patients with family history of SAH. Methods: Twenty-five young volunteers with family history of SAH (30±5 years, 24±4 kg/m²), 14 normotensive (SBP: 116 [105-119], DBP: 67[60-71] mmHg) and 11 prehypertensive subjects (SBP: 128[124-132], DBP: 75[7175] mmHg) were submitted to vascular function evaluation (reactive hyperemia, Hokanson®), and cardiac and peripheral autonomic modulation, quantified, respectively, by spectral analysis of heart rate (ECG) and systolic blood pressure (SBP, FinometerPRO®). The transfer function analysis was used to measure the gain and response time of baroreflex. Additionally, were recorded blood pressure, heart rate (Dixtal®) and forearm blood flow and calculated forearm vascular conductance (Hokanson®) for 3 minutes during rest and 1º, 2º and 3º minutes of the protocols of mental stress (Stroop Color Word Conflict Test) and isometric exercise at 30% of maximal voluntary contraction (Saehan®). Data were presented as mean ± standard deviation of the mean or as median [1º quartile – 3º quartile]. The statistical significance adopted was 5%. Results: Pre-hypertensive individuals, in relation to normotensive individuals, have higher forearm vascular conductance both at rest (3.48 ± 1.26 vs. 2.67 ± 0.72 units, p = 0.05, effect size (ES): 1.13) and peak reactive hyperemia (25, 02 ± 8.18 vs. 18.66 ± 6.07 units, p = 0.04, ES: 1.05). The indices of cardiac autonomic modulation were similar between the groups. However, in the peripheral autonomic modulation, greater variability was observed in prehypertensive patients compared to normotensive individuals (9.4 [4.9-12.7] vs. 18.3 [14.8-26.7] mmHg²; p < 0.01) and higher spectral components of very low (6.9 [2.0-11.1] vs. 13.5 [10.7-22.4] mmHg², p = 0.01) and low frequencies (1.7 [1.0-3.0] vs. 3.0 [2.0-4.0] mmHg², p = 0.04) of SBP. Additionally, we observed a lower gain of baroreflex control in prehypertensive patients compared to normotensive patients (12.16 ± 4.18 vs. 18.23 ± 7.11 ms/mmHg, p = 0.03, ES: 1.1), but similar delay time (-1.55 ± 0.66 vs. -1.58 ± 0.72 s, p = 0.90). During the protocols of mental stress normotensive and prehypertensive groups increased (deltas) significantly and similarly systolic blood pressure (time effect: p<0.01, interaction effect: p=0.70, group effect: p=0.58), diastolic (time effect:p<0.01, interaction effect: p=0.35, group effect: p=0.78) and mean (time effect: p<0.01, interaction effect: p=0.82, group effect: p=0.60), heart rate (time effect: p<0.01, interaction effect: p=0.68, group effect: p=0.66), forearm muscle blood flow (time effect: p<0.01, interaction effect: p=0.42, group effect: p=0.91) and forearm vascular conductance (time effect: p=0.01, interaction effect: p=0.47, group effect: p=0.84) in relation to the baseline. No differences were observed between group responses in any of the variables. Similarly, throughout the isometric exercise protocol, both groups increased (deltas) significantly and similarly systolic blood pressure (time effect: p<0.01, interaction effect: p=0.35, group effect: p=0.99), diastolic (time effect:p<0.01, interaction effect: p=0.93, group effect: p=0.79) and mean (time effect: p<0.01, interaction effect: p=0.89, group effect: p=0.89) and heart rate (time effect: p<0.01, interaction effect: p=0.65, group effect: p=0.79) in relation to the baseline. However, the forearm muscle blood flow increased from baseline only in the third minute time effect: p<0.01, interaction effect: p=0.62, group effect: p=0.98) and forearm vascular conductance (time effect: p=0.06, interaction effect: p=0.66, group effect: p=0.92) remained similar to baseline in both groups in all moments. No differences were observed between groups in any of the variables. Conclusion: Young prehypertensive patients with family history of SAH have autonomic dysfunction and increased forearm vascular conductance when compared to normotensive patients with the same risk factor. During mental stress and physical exercise, the groups studied had a similar hemodynamic response. Additionally, both groups present vascular dysfunction during exercise, characterized by the absence of vasodilation during this maneuver.