Increased Sympathetic Activity in Patients with Masked Uncontrolled Hypertension
Not all hypertensive patients who have normal blood pressure readings in the doctor's office actually have controlled hypertension. Recent studies suggest that so-called masked uncontrolled hypertension may be linked to increased sympathetic activity.
Masked Uncontrolled Hypertension
The term masked uncontrolled hypertension (MNH) is used for patients who, despite taking antihypertensive medication and having normal blood pressure readings in the doctor's office, have an average daytime blood pressure (BP) ≥ 135/85 mmHg or a total average ≥ 130/80 mmHg when monitored continuously over 24 hours (ABPM). It is more commonly seen in older individuals, diabetics, patients with chronic kidney disease, post-kidney transplant patients, or black patients. The prevalence of MNH in treated hypertensive patients ranges from 30-50%, and it has been shown to have a greater impact on overall and cardiovascular mortality than treatment-controlled hypertension, and even more than persistent uncontrolled treated hypertension.
Findings from a Prospective Study
A prospective study recently published in the journal Hypertension provided new information about increased sympathetic activity outside the doctor's office in these patients. The study included 237 treated hypertensive patients, of which 169 had normal BP readings in the doctor's office. Of 156 who underwent ambulatory BP monitoring, 74 (47.4%) had controlled hypertension outside the office (mean 24-hour BP 122.1 ± 7.5/68.9 ± 6.9 mmHg), while the remaining 82 (52.6%) had masked uncontrolled hypertension (mean 24-hour BP 145.9 ± 11.9/79.9 ± 8.3 mmHg).
A one-time assessment of plasma catecholamine and plasma and urinary metanephrine levels during a doctor's visit showed no significant difference between the two groups. In contrast, 24-hour urine catecholamine and metanephrine evaluations demonstrated significantly higher values in patients with MNH. Additionally, patients with MNH exhibited significantly higher BP variability and lower heart rate variability.
Discussion
The higher excretion of catecholamines and metanephrines in the urine of patients with MNH indicates increased sympathetic activity, which may be one cause of MNH. It is known that sympathetic tone is higher in diabetic patients—there were significantly more diabetics in the MNH group compared to the truly controlled hypertension group (41.8% vs. 22.4%). Other factors such as obesity or smoking can also affect sympathetic activity; however, the study found no significant differences in their prevalence between the groups.
Additionally, a significantly higher number of patients with MNH than those with controlled hypertension used mixed α/β-blockers (carvedilol, labetalol). There was no significant difference in the use of other sympathicus-influencing medications (calcium channel blockers, β-blockers, and α2-agonists).
Clinical Significance of the Findings
This is the first study to provide evidence of increased sympathetic activity outside the doctor's office as one possible cause of MNH. Choosing antihypertensives that act centrally and specifically affect sympathetic function could potentially improve hypertension control in these patients.
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Source: Siddiqui M., Judd E. K., Jaeger B. C. et al. Out-of-clinic sympathetic activity is increased in patients with masked uncontrolled hypertension. Hypertension 2019; 73 (1): 132−141, doi: 10.1161/HYPERTENSIONAHA.118.11818.
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