Correlation between office and 24-hour ambulatory measures of pulse wave velocity, central augmentation index and central blood pressure

Relationship of blood pressure measured in the calf with arm blood pressure and arterial stiffness: a general population study

AIM

Leg blood pressure (BP) measurement is needed when arm BP evaluation is not feasible, and calf BP, especially when measured in standing position, may have greater association with cardiovascular remodeling than arm BP. This study evaluated the relationship between calf and arm BP, and investigated whether calf BP would be superior to arm BP in predicting increased arterial stiffness [pulse wave velocity (PWV) > 10 m/s].

METHODS

We evaluated clinical and laboratory characteristics, BP measurements, and PWV in 1397 individuals resident in Baependi, Brazil, between 2017 and 2019. Arm BP was measured in the seated and supine positions while calf BP was measured in supine and standing positions using digital oscillometric devices. Carotid-femoral PWV was measured using a noninvasive mechanotransducer.

RESULTS

The sample had 62.7% females, age = 48.1 ± 15.4 years and 8.4% with PWV >10 m/s. Results of linear regression analysis showed that BP values of 140/90 mmHg measured in the arm in supine and seated position were equivalent to calf supine BP values of 164/81 mmHg and 166/78 mmHg and calf standing BP values of 217/137 mmHg and 221/137 mmHg, respectively. Calf-arm BP differences were associated with age, glomerular filtration rate, body mass index, smoking, low-density lipoprotein-cholesterol, diabetes and height. Furthermore, stepwise logistic regression analysis revealed that arm supine systolic BP, but not calf BP measurements, was independently associated with increased arterial stiffness.

CONCLUSION

Thresholds of ≈165/80 mmHg and ≈220/135 mmHg could be used for diagnosing hypertension when only calf measurements in supine and standing positions, respectively, are available. Conversely, calf BP was not superior to arm BP in predicting increased arterial stiffness.

Ambulatory blood pressure phenotypes and isolated elevation of office central or brachial blood pressure

Disagreements in office brachial and central blood pressure (BP) have resulted in the identification of novel hypertension phenotypes, namely isolated central hypertension (ICH) and isolated brachial hypertension (IBH). This study investigated the relationship of ICH and IBH with ambulatory BP phenotypes among 753 individuals (mean age = 47.6 ± 15.2 years, 48% males) who underwent office and 24-hours brachial and central BP measures using a Mobil-O-Graph PWA monitor. Thresholds for elevated office central and brachial BP were 130/90 and 140/90 mm Hg. Results of multivariable analysis adjusted for potential confounders showed that ICH (n = 25) had 3.71-fold (95% CI 1.48-9.32; P = .005) greater risk of masked hypertension than normal brachial/central BP (n = 362), while IBH (n = 20) had 4.65-fold (95% CI 1.76-12.25; P = .002) greater risk of white coat hypertension compared with combined brachial/central hypertension (n = 346). These findings suggest that the diagnosis of ICH and IBH might be useful in identifying individuals at higher risk of presenting discordant office and ambulatory BP phenotypes.

Reference values of office central blood pressure, pulse wave velocity, and augmentation index recorded by means of the Mobil-O-Graph PWA monitor

Assessment of central blood pressure (BP), pulse wave velocity (PWV), and augmentation index (AIx) measurements may improve cardiovascular risk stratification. This study aimed to establish reference office values for central BP, PWV, and AIx by means of a Mobil-O-Graph PWA monitor and to evaluate the impact of cardiovascular risk factors (CVRFs) on these measurements. We cross-sectionally evaluated clinical characteristics, central BP, PWV, AIx, and peripheral BP measurements among 867 apparently healthy individuals (age = 46.0 ± 15.5 years, 39% males) who were free of obesity, hypertension, active smoking, dyslipidemia, and diabetes (CVRF-No) and 5632 individuals (age = 57.0 ± 14.7 years, 44% males) with at least one of these major CVRFs (CVRF-Yes). Reference values for central BP, PWV, and AIx were provided for the CVRF-No and CVRF-Yes groups, stratified by age and sex. PWV and AIx exhibited curvilinear increases with age, and there was an interaction between age and sex for central systolic BP and PWV in both the CVRF-No and CVRF-Yes groups. The results of a multivariable analysis including the whole sample (n = 6499) showed that obesity had a direct association with central BP, while diabetes was directly related to PWV. In addition, alcohol intake was directly associated with central BP, while performance of physical activity was inversely related to AIx. In conclusion, values of office-measured central BP, PWV, and AIx obtained in an apparently healthy population and in a population with CVRFs are now available according to age and sex and may be useful to build thresholds for use in clinical practice.

Impact of hypertension phenotypes on the office and 24-h pulse wave velocity and augmentation index in individuals with or without antihypertensive medication use

Data on the association of blood pressure (BP) phenotypes with office and out-of-office markers of vascular stiffness and pressure wave reflection are sparse. This study investigated office and 24-h measures of brachial BP, pulse wave velocity (PWV), and central augmentation index (AIx) across hypertension phenotypes among individuals not using BP-lowering medications [normotension (NT), white-coat hypertension (WH), masked hypertension (MH) and sustained hypertension (SH)] and those using BP-lowering medications [controlled hypertension (CH), white-coat uncontrolled hypertension (WUCH), masked uncontrolled hypertension (MUCH) and sustained uncontrolled hypertension (SUCH)]. We evaluated 454 untreated (age = 45 ± 15 years, 50% males) and 238 treated (age = 52 ± 15 years, 45% males) individuals who underwent office and 24-h brachial BP, PWV, and AIx measures using a Mobil-O-Graph PWA monitor. In the analysis adjusted for age and sex, WH had higher (p < 0.05) office PWV (7.53 ± 0.09 vs 6.89 ± 0.05), office AIx (27.9 ± 1.3 vs 23.8 ± 0.8), and daytime AIx (24.6 ± 0.7 vs 22.7 ± 0.4) compared with those of NT, while WUCH had higher (p < 0.05) office PWV (8.28 ± 0.11 vs 7.43 ± 0.08) and 24-h PWV (7.54 ± 0.09 vs 7.21 ± 0.07) than those of CH. MH had higher (p < 0.05) 24-h PWV (7.00 ± 0.09 vs 6.69 ± 0.04) and 24-h AIx (24.3 ± 0.9 vs 21.9 ± 0.4) than those of NT, whereas MUCH had higher (p < 0.05) 24-h PWV (7.64 ± 0.13 vs 7.21 ± 0.07) than that of CH. Lastly, SH or SUCH had significantly higher office and 24-h PWV and AIx than those of NT and CH, respectively. In conclusion, these results suggest that individuals with masked BP phenotypes are more predisposed to have adverse out-of-office vascular characteristics, while individuals with white-coat phenotypes have adverse office and out-of-office vascular characteristics compared with those of individuals with normal BP levels.

The hypothalamus and hypertension

Most forms of hypertension are associated with a wide variety of functional changes in the hypothalamus. Alterations in the following substances are discussed: catecholamines, acetylcholine, angiotensin II, natriuretic peptides, vasopressin, nitric oxide, serotonin, GABA, ouabain, neuropeptide Y, opioids, bradykinin, thyrotropin-releasing factor, vasoactive intestinal polypeptide, tachykinins, histamine, and corticotropin-releasing factor. Functional changes in these substances occur throughout the hypothalamus but are particularly prominent rostrally; most lead to an increase in sympathetic nervous activity which is responsible for the rise in arterial pressure. A few appear to be depressor compensatory changes. The majority of the hypothalamic changes begin as the pressure rises and are particularly prominent in the young rat; subsequently they tend to fluctuate and overall to diminish with age. It is proposed that, with the possible exception of the Dahl salt-sensitive rat, the hypothalamic changes associated with hypertension are caused by renal and intrathoracic cardiopulmonary afferent stimulation. Renal afferent stimulation occurs as a result of renal ischemia and trauma as in the reduced renal mass rat. It is suggested that afferents from the chest arise, at least in part, from the observed increase in left auricular pressure which, it is submitted, is due to the associated documented impaired ability to excrete sodium. It is proposed, therefore, that the hypothalamic changes in hypertension are a link in an integrated compensatory natriuretic response to the kidney's impaired ability to excrete sodium.