[Hypertension, coronary heart disease and stroke: should the blood pressure J-curve be a concern?]. / Hipertensão arterial, doença coronária e acidente vascular cerebral. A curva em J deve preocupar-nos?

The paradoxical increase in cardiovascular events in patients with treatment-induced low blood pressure (BP), particularly in hypertensives with pre-existing coronary artery disease, especially those with critically low diastolic BP, which conflicts with data from epidemiologic observational studies, is referred to as a J-curve. It was first described over 30 years ago and is still the subject of considerable controversy. Recent large clinical outcomes trials (INVEST, TNT, ONTARGET, PROVE IT-TIMI 22, SMART) and meta-analyses strongly support its existence for systolic and diastolic BP. The diastolic J-curve is commonly more pronounced. In contrast to cardiovascular complications related to coronary artery disease, no J-curve phenomenon was noted for stroke in most of these studies. This is explained by differences in cerebral and coronary autoregulation and because coronary perfusion occurs only during diastole. On the basis of this review, we suggest a cautious, individualized approach to treatment, particularly in hypertensive patients with coronary heart disease or high risk for impaired coronary blood flow. In these patients we advise against treatment that lowers systolic BP below 120-125 mmHg and, particularly, diastolic BP below 70-75 mmHg.

Decreased erythrocyte activity of methemoglobin and glutathione reductases may explain age-related high blood pressure.

OBJECTIVES: Erythrocytes may play an important role in regulating blood pressure as storage sites for nitric oxide (NO). The objective of this work was to determine whether factors related to variations in erythrocyte metabolism associated with NO bioavailability, such as the activity of two enzymes--methemoglobin reductase (MHbR) and glutathione reductase (GSHR)--may help explain age-related increased blood pressure. METHODS: The sample consisted of 468 individuals of both sexes, 237 hypertensive (HT) and 231 normotensive (NT), aged between 18 and 98 years (48.81 +/- 19.46). The activity of MHbR (micromol.g Hb-1.min-1) and of GSHR (micromol.g Hb-1.min-1) was determined in erythrocytes by spectrophotometry. The statistical methods used were the Mann-Whitney test, Spearman's correlation coefficient and binary logistic regression. RESULTS: In this population, age was a risk factor for hypertension (OR=1.055, 95% CI = 1.045-1.065, p < 0.001). There was a significant difference in erythrocyte activity of these enzymes between normotensive and hypertensive subjects, with lower values in hypertensives: MHbR-NT = 16.97 (3.82-34.63), HT = 16.26 (3.26-37.10), p = 0.012; and GSHR-NT=57.60 (21.59-96.58), HT = 39.26 (23.07-90.27), p < 0.001. Enzyme activity was inversely correlated with age (MHbR: r = -0.193, p < 0.001; GSHR: r = -0.757, p < 0.001). MHbR correlated directly with GSHR only in hypertensive patients (r = 0.343, p = 0.034), which was not observed in normotensives. CONCLUSIONS: Age was a risk factor for hypertension. The erythrocyte activity of glutathione and metahemoglobin reductases, essential for redox balance and nitric oxide bioavailability in erythrocytes, may contribute only partially to the increased prevalence of age-related hypertension, and other factors should be taken into consideration, such as nutrition and antihypertensive medication.