Approximately 35% of occult hypertension can develop into persistent hypertension and has a higher cardiovascular risk. Numerous studies have found that individuals with covert hypertension have varying degrees of target organ damage, are at greater risk for cardiovascular events than white coat hypertension, and have a higher cardiovascular mortality rate, not significantly different from persistent hypertension. In addition, occult hypertension is often underdiagnosed and has a poor prognosis. Therefore, increased attention should be paid to early detection and treatment.
Pay attention to screening: early detection, early treatment
Currently, the prevalence of occult hypertension in many countries is over 8% or even higher, but the detection rate is only 7.6% to 15.7%. If you rely only on incidental blood pressure measurement, you may miss a serious diagnosis and miss the opportunity for early treatment.
Among patients with grade 1 hypertension diagnosed by office blood pressure measurement, patients with white coat hypertension account for 20% to 30%. For white coat hypertension, because of its high office blood pressure, it is easy to draw the clinician’s attention and follow-up is easy to perform. In contrast, patients with covert hypertension have normal office blood pressure and are therefore more likely to be underdiagnosed. In one report, 1153 residents over 18 years of age were selected from the urban resident registry and their blood pressure was measured 12 times a week, using both office and home measurements.
It was found that the prevalence of covert hypertension in the general population was 8.9% and that of white coat hypertension was 3.6%, suggesting that the prevalence of white coat hypertension is lower than that of covert hypertension. Possible factors affecting the prevalence of covert hypertension include age, sex, smoking, alcohol consumption, birth control pills, sedentary lifestyle and centripetal obesity. Recent findings also suggest that occult hypertension is also more common in children, with a prevalence of 10%-15% in healthy children, and a higher prevalence of occult hypertension than white coat hypertension. It has also been suggested that boys are more likely to have covert hypertension than girls. Of 136 children with hypertension, 15 had covert hypertension, 19% of whom were boys and 5% of whom were girls, with no significant difference in younger (≤15 years) and older (>15 years) individuals.
Patients with covert hypertension often have elevated total blood cholesterol and LDL cholesterol, elevated blood glucose, increased heart rate, obesity, left ventricular hypertrophy, atherosclerosis, carotid atherosclerosis, and other cardiovascular risk factors, and often have a family history of hypertension. Therefore, even those who occasionally have normal blood pressure should have 24h ambulatory blood pressure monitoring or insist on self-measurement at home. The pathogenesis of occult hypertension is not well understood. Studies suggest that its pathogenesis may be related to postural reflexes, dysregulation of vasoactive substance balance, increased sympathetic excitability, 25-hydroxylated vitamin D levels, low Ni levels, and poor lifestyle.
Clinical features: there is no specificity, but occult hypertension can be found to be similar to the clinical manifestations of general essential hypertension, except that it is easily overlooked. Although the patient occasionally measures normal blood pressure or normal high blood pressure, on closer inspection, there are often varying degrees of multiple risk factors intertwined. Compared with healthy individuals, patients with covert hypertension have significantly higher body mass index, proportion of alcohol consumption, serum total cholesterol and LDL cholesterol concentrations, suggesting that patients with covert hypertension have more risk factors for cardiovascular disease. The proportion of males in patients with covert hypertension was higher than that in patients with essential hypertension, and the average age of patients with essential hypertension was greater than that of patients with covert hypertension. The proportion of alcohol consumption was significantly higher in patients with covert hypertension, and the mean age and proportion of smoking were higher than normal in ambulatory blood pressure suggesting abnormal changes.
Ambulatory blood pressure in both covert hypertension and essential hypertension revealed significantly higher mean 24h systolic and diastolic blood pressure, daytime and nighttime ambulatory blood pressure than the normotensive group. Occasional blood pressure was significantly higher in the primary hypertension group than in the concealed hypertension group, but there were no significant differences in 24-h mean systolic and diastolic blood pressures and daytime ambulatory blood pressure between the two groups.
These hemodynamic alterations may increase the risk of cardiovascular disease systolic vascular factor activity augmentation plasma levels of thromboxane (TXA) and neuropeptide (NPY) were higher in patients with covert hypertension than in the normotensive group. In contrast, plasma levels of prostacyclin (PGI) and calcitonin gene-related peptide (CGRP) were lower in the covert hypertension group than in the normotensive group and higher than in the normotensive group. By multiple linear regression analysis, daytime systolic blood pressure levels were linearly correlated with TXA and NPY levels; daytime diastolic blood pressure levels were linearly correlated with thromboxane A2 (TXA2) levels in patients in the covert hypertension group. The vasoactive substances TXA2, PGI, NPY, and CGRP were different in patients with covert hypertension than in normotensive individuals, showing increased systolic vascular factor activity and decreased diastolic vascular factor activity, suggesting that these vasoactive substances may be involved in the development and progression of covert hypertension.
Dual cardiovascular and renal damage
Patients with covert hypertension had increased central arterial pressure, significantly increased left ventricular wall thickness and left ventricular weight, and the detection rate of carotid atherosclerosis was not significantly different from that of patients with essential hypertension; atherosclerosis and its compliance were decreased in patients with covert hypertension, and the results were similar to those of patients with hypertension. This suggests that covert hypertension can cause target organ damage and increase cardiovascular risk. Covert hypertension is closely related to the development of systemic atherosclerosis, and changes in arterial function occur before the diagnosis of hypertension and are independent of changes in age and blood pressure. Carotid intima-media thickness was lower in patients with occult hypertension than in patients with essential hypertension, but higher than in patients with white coat hypertension and healthy subjects. Renal damage in patients with covert hypertension was manifested by increased urinary β2 microglobulin and microalbumin levels, which were higher than in patients with white-coat hypertension and healthy subjects. Therefore, it is believed that occult hypertension can lead to a certain degree of renal damage, the extent of which is linearly correlated with daytime blood pressure levels.
Clinical diagnosis: taking into account blood pressure and coexisting risk factors
The diagnosis of covert hypertension lacks a characteristic clinical presentation, but most present with a strong elevated blood pressure response to stressful situations or exercise. It is important to pay attention to patients with normal blood pressure on occasional measurements, but with a combination of multiple risk factors and target organ damage.
Blood pressure diagnostic cut points
Evidence suggests that covert hypertension is an independent risk factor for target organ damage and cardiovascular events, and there is increasing interest in the diagnosis of covert hypertension. The criteria for diagnosing covert hypertension are usually <140/90 mmHg on incidental clinic measurements and ≥135/85 mmHg on ambulatory or home self-measured daytime blood pressure.
Occasional blood pressure normal with multiple risk factors
Studies have shown that the incidence of dyslipidemia and excessive alcohol consumption is higher in men with incidentally normal blood pressure. Therefore, people with cardiovascular risk factors (men, advanced age, dyslipidemia, obesity, smoking, family history of cardiovascular disease, etc.) should be given priority attention and self-monitoring and ambulatory blood pressure monitoring should be performed. Patients with normal blood pressure with target organ damage and high values of blood pressure, and patients with target organ damage such as heart, brain and kidney, should further do 24h ambulatory blood pressure or home self-measurement blood pressure. If ambulatory blood pressure or home self-measured daytime blood pressure is ≥ 135/85 mmHg, the diagnosis of occult hypertension can be made.
Prevention and treatment countermeasures: lifestyle and drug treatment should be used in parallel. First, patients should be followed up closely to observe the natural regression and the impact on target organs. All patients with covert hypertension should adhere to a therapeutic lifestyle. Patients with target organ damage should be treated as primary hypertension and treated with a combination of antihypertensive drugs along with poor lifestyle intervention. Pay attention to screening for covert hypertension
Continue to raise awareness of the prevention and treatment of hypertension, regular health checkups, attention to standardized blood pressure measurement, and ambulatory blood pressure monitoring when indicated. Clinicians should pay attention to the combination of ambulatory blood pressure, self-measured blood pressure and office blood pressure for comprehensive analysis, so as not to miss patients with “hidden hypertension” that cannot be detected by office blood pressure measurement alone. In addition, attention should be paid to ambulatory blood pressure screening and home blood pressure monitoring in patients with transient elevations. Attention should be paid to screening for covert hypertension in those with poor lifestyle, especially when clinic blood pressure is already at high normal values
Attention should be paid to the rising trend of pharmacogenic hypertension among secondary hypertension: this group of people is often in the stage of covert hypertension for a certain period of time. Knowledge of hypertension prevention and treatment should be disseminated to high-risk groups, and lifestyle interventions should be carried out to establish healthy habits.
Active treatment of occult hypertension to improve the control rate First, individualized treatment is taken for the condition. Long-acting calcium antagonists, angiotensin-converting enzyme inhibitors, angiotensin receptor antagonists, β-blockers and vasodilators are commonly used. Second, in order to improve the therapeutic effect, treatment with optimal combination of medications should be used. In general, the combination of long-acting calcium antagonists with angiotensin-converting enzyme inhibitors, angiotensin receptor antagonists, and β-blockers is mostly used to improve the efficacy and reduce side effects.
Emphasis on early intervention of multiple risk factors for cardiovascular disease: Occult hypertension is a special type of hypertension that often combines multiple risk factors, target organ damage, and cardiovascular disease. Comprehensive interventions appear to be important for the treatment of occult hypertension, including: establishing a healthy lifestyle and, depending on the patient’s condition, the application of anticoagulant drugs such as aspirin, statin lipid-regulating drugs, anti-atherosclerotic and vasodilating nitrates. This not only improves the control rate, but also reduces the disability and mortality rates.