Função barorreflexa arterial espontânea da frequência cardíaca em pacientes com hipertensão arterial resistente

Abstract

Introduction: Resistant hypertension is characterized by damage in practically all blood pressure regulating mechanisms, resulting in significantly elevated blood pressure levels. These hemodynamic changes are associated with increased sympathetic modulation and baroreflex dysfunction of muscle sympathetic nerve activity. However, the power (gain) and duration of action (latency) of spontaneous arterial cardiac frequency baroreflex remains unknown in patients with resistant hypertension. Purpose: 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 4 antihypertensive drugs), 17 patients with essential hypertension (56±11 years, mean of 2 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 seconds; 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.