ABC | Volume 115, Nº1, July 2020

Original Article Macedo et al. Resistant hypertension in afrodescendants Arq Bras Cardiol. 2020; 115(1):31-39 the total population studied, with an average of 152.1±28.0 and 88.0±7.6 mmHg, respectively, for SBP and DBP. Participants used an average of 4.8±1.1 antihypertensive agents, 80.8% of whom received a prescription for the recommended combination of ACE inhibitors or ARB + CCB + thiazide diuretic, regardless of the association with other drugs. Good or moderate adherence to therapy according to the MMAS-8 questionnaire was found in 61% of patients. After evaluating the participants according to the phenotypic presentation of SAH, 51% were categorized as RfH. Age was significantly lower among patients with RfH when compared to patients with RH (mean age=59.4±11.7 years versus 64.1±12.2 years, respectively, p=0.02). Table 1 shows the distribution of patients according to the classification as RH or RfH. In our population, the RfH group had a higher proportion of individuals aged up to 60 years, dyslipidemia and a history of stroke. In addition, the RfH group had higher mean BP, and the mean time of diagnosis of SAH tended to be longer in patients with RfH; however, this did not reach statistical significance (Table 2). Regarding the use of antihypertensive drugs, there was a higher proportion of use of ARB and, therefore, a lower proportion of use of ACEi. There was also a higher frequency of use of CCB and beta-blockers in individuals with RfH, when compared to RH (Figure 1). Figure 2 shows that the use of the ACEi/BRA+BCC+thiazide diuretic combination was significantly higher in patients with RfH. Spironolactone was used by 49.3% of the participants. Among patients who used a thiazide diuretic, 34.5% of patients used chlortalidone as an option. Figure 3 shows that the use of chlortalidone and spironolactone was also significantly higher among individuals with RfH. Discussion The group of individuals predominantly of African descent with RH is a population with high CVR, which is shown by a high proportion of participants (51%) categorized as RfH, a phenotypic presentation associated with greater severity of SAH according to previous studies. 7,8,16,27 The prevalence of RfH has been estimated in a limited number of studies, ranging from about 3% in a general population of individuals with SAH to up to 31%, in individuals with true RH with follow-up in a specialized clinic. 7,8,16 These studies, however, did not use a standard definition of RfH. It is known that the predominance of black and brown ethnicities is related to the severity of hypertension and probably contributed to the high prevalence of RfH in our sample. Black ethnicity has often been associated with RH. Cushman et al. 28 reported an association between African American ethnicity and resistance to antihypertensive treatment, when evaluating data from the ALLHAT study. 28 This association was also described in the Brazilian study ELSA, where black ethnicity was associated with RH in a population undergoing treatment for SAH. 18 In turn, based on data from the REGARDS study cohort, where African- American ethnicity was the main predictor of RH, Calhoun et al. 7 reported that, compared to RH, the prevalence ratios for RfH were significantly higher in blacks (PR=3.00; 95% CI=1.68-5.37). 7 These data support our findings of a high prevalence of RfH in a population with the majority of individuals of African descent. The predominance of browns and blacks in our sample can be attributed to the fact that it is a public outpatient clinic, serving the low-income population, which in our region is composed of a majority of mixed and black ethnicities. The prevalence of obesity (36.1%), history of smoking (37%), diabetes mellitus (34.2%), and dyslipidemia (69.4%) reflects a population with a high CVR, as would be expected in individuals with RH. This high CVR in our population is also demonstrated by the evaluation of the FRS, where 61% of individuals were categorized as at moderate/high risk. These findings are consistent with other studies that demonstrated an association of RH with female gender, advanced age, and obesity. 18,29 Calhoun et al. 7 reported an average FRS of 17.5% in patients with RfH and 11.7% in patients with RH, with risk of coronary events and stroke in 10 years of 20.8% in RfH and 16.2% in individuals with RH, respectively. 7 Also contributing to the increase in CVR in the population of our study, there was a high prevalence of abnormal renal function, demonstrated by an estimated GFR of <60ml/min in 34.2% of the individuals and a high proportion of previous cardiovascular events (AMI and stroke). This suggests that the presence of target organ damage should be frequent in these patients. Muntner et al., 30 by comparing ALLHAT study participants with and without RH, also observed a high risk of coronary disease (RR=1.44; 95% CI=1.18-1.76), stroke (RR=1.57; 95% CI= 1.18-2.08), and end-stage kidney disease (RR=1.95; 95% CI=1.11-3.41) in those with RH. 30 In our study, like other publications, 7,8 there was a significantly higher prevalence of previous stroke in patients with RfH, who had significantly higher mean BP and a higher frequency of dyslipidemia. The frequency of other risk factors, as well as FRS and therapeutic adherence by MMAS-8 were similar in the two subgroups. These data suggest that the persistence of high BP, probably more than the other factors of CVR, seems to have a fundamental role in this unfavorable outcome in patients with RfH. Sympathetic hyperactivity, a mechanism proposed for the persistence of uncontrolled BP in patients with RfH, 14 could be associated with a higher incidence of stroke in these individuals. Dyslipidemia and its intimate association with atherosclerosis can also contribute negatively to the prognosis of patients with HRf and need to be better evaluated in other studies. Despite the high average age, a significantly lower proportion of individuals over 60 years of age was observed among patients with RfH, despite the trend for longer time of SAH diagnosis among them. Similar findings have been described in other studies. 14,15,27 These data are probably associated with the possible mechanisms involved in the pathophysiology of RfH, attributing to this group of individuals characteristics that imply in the earlier development and greater severity of SAH. Regarding the predominance of females, based on the ALLHAT study, Cushman et al. 28 found greater difficulty in 33