OVERVIEW
Pseudohypertension is a condition in which the blood pressure measured by plain cuff tonometry is higher than that measured directly by arterial puncture.The 2013 European Guidelines on Hypertension suggest that pseudohypertension is a condition in which blood pressure measurements are falsely elevated due to severe atherosclerosis that prevents compression of the brachial artery, and that it is more common in older adults, especially those with severe arterial calcification.
To date, the epidemiology of pseudohypertension is still unclear as there are fewer epidemiologic studies, the number of cases studied is limited, and the definition of pseudohypertension is not uniform across studies.
Etiology
1. Physiologic factors
Direct measurement of blood pressure in the upper extremities is significantly different from simultaneous measurement of blood pressure in the aorta, with higher SBP and lower DBP in the periphery. This progressive change from proximal to distal is related to the intensity and time course of the pulse wave reflection.
2. Technical factors
The accuracy of brachial blood pressure measurement, whether by direct pressure measurement by arterial puncture or by cuff method, is limited by a number of technical details. Many studies have found that cuff manometry overestimates blood pressure values, with SBP and DBP about 5 mmHg and 5-10 mmHg higher, respectively.
3. Principles of cuff-inflated hypertension
Cuff inflation hypertension is a rise in blood pressure during cuff inflation, a phenomenon that is neurally mediated and occurs only in a small number of individuals by an unknown mechanism.
Pathophysiology
Pseudohypertension occurs in elderly, uremic, diabetic, and severely atherosclerotic patients due to thickening and hardening of the intima of the brachial artery, and occasionally due to encapsulated fibrosis, resulting in “severe clenching pressures” on the wall of the artery, which causes an associated faulty auscultation reading resulting in systolic pseudohypertension.
The mechanism of diastolic pseudohypertension is due to the premature disappearance of the Koch sound before the cuff pressure reaches the intra-arterial DBP. This is due to the fact that the production of the Koch sound is associated with “flaccid oscillations” of the arterial wall, and if the increased stiffness of the arterial wall reduces the oscillations caused by the mechanical stimulus, then the oscillations of the arterial wall will be aborted at higher pressures when the cuff is deflated, resulting in an auscultation reading of a higher DBP than the intra-arterial DBP.
Symptoms
Pseudohypertension is clinically categorized into three types:
1. Systolic pseudohypertension
As mentioned above, “severe clenching pressures” may cause erroneous auscultation readings to produce systolic pseudohypertension. In addition, arterial wall thickening, such as calcific sclerosis of the Menkeberg artery, can also occur, and even the inability to measure blood pressure with a mercury sphygmomanometer due to the incompressibility of the brachial artery, which is common in the elderly.
Notably, some adolescents also present with pure systolic hypertension, mostly males, taller, nonsmokers, athletic, and with a higher difference between central and brachial arterial pressure than normotensive controls. This phenomenon was once thought to have a favorable prognosis, but as studies have grown in size, there is increasing evidence that this group of patients with both elevated brachial and central arterial pressures have a higher cardiovascular risk than normotensive controls, but long-term follow-up studies are needed to further confirm this.
2. Diastolic Pseudohypertension
It is commonly believed that the standard of diagnosis for DBP is the disappearance of the Koch sound, and diastolic pseudohypertension is the early disappearance of the Koch sound. 1993 Society for the Advancement of Medical Instrumentation (SAMEI) evaluated 5 studies comparing cuffed brachial arterial pressure to the gold standard of blood pressure, brachial arterial pressure, and found that: for systolic blood pressure, the intra-arterial blood pressure was higher than the auscultatory pressure by 3-4 mmHg, however, the auscultatory blood pressure was higher than the intra-arterial blood pressure by about 10 mmHg for diastolic blood pressure.
3. Cuff inflation hypertension
Blood pressure rises during cuff inflation, a phenomenon that occurs only in a small number of patients.
Examination
1. Osler maneuver: When the cuff pressure exceeds the patient’s SBP, if the patient’s radial artery or brachial artery can be clearly palpated, the Osler maneuver is positive, and vice versa. 65% of the patients with positive Osler maneuver have a cuff DBP 10 mmHg higher than that of trans-arterial pressure, which is quite common among the elderly, and the tendency is to increase with the increase of age, and the sensitivity and specificity of Osler maneuver are higher than that of the cuff pressure. Sensitivity and specificity are poor.
2. Automatic infrasound blood pressure detector can better reflect the intra-arterial blood pressure. A study suggests that the diagnosis of diastolic pseudohypertension can be excluded if there is no difference between the DBP of blood pressure measured by infrasound blood pressure detector and standard auscultation.
3. Direct manometry uses a catheter inserted into the artery to measure aortic blood pressure directly. This invasive test is not suitable for routine medical work or clinical trials, but it is a gold indicator for diagnosing pseudohypertension. Currently there is a very small probe at the tip of the catheter that can be inserted directly into the brachial artery for measurement.
4. Measurement of central arterial pressure Aim the pulse wave sensor at the obvious point of radial artery pulsation, collect the pulse wave graph for 30 seconds, and record the brachial artery blood pressure at the same time, the central arterial pressure detecting device can automatically calculate and display the central arterial pressure.
5. Angiography shows calcification of the forearm artery.
Diagnosis
1. Clinical diagnosis
Pseudohypertension is mostly seen in old age, uremia, diabetes mellitus, severe arteriosclerosis patients. When hypertensive patients show ineffective antihypertensive drug treatment and long-term hypertension or severe hypertension without target organ damage, especially in old age and patients with large pulse pressure, pseudohypertension should be suspected, and the combination of noninvasive central arterial pressure detection can be used to make a preliminary diagnosis.
2.Diagnostic criteria
Final diagnosis of pseudohypertension requires intra-arterial pressure measurement along with cuff blood pressure measurement. 2010 Chinese Hypertension Prevention and Control Guidelines state that pseudohypertension is defined as a phenomenon in which the blood pressure measured by cuff method is higher than the intra-arterial pressure measurement, with systolic blood pressure (SBP) ≥10mmHg or diastolic blood pressure (DBP) ≥15mmHg.
Treatment
Treatment of pseudohypertension should be determined by the patient’s clinical condition. In some patients, the risk of cardiovascular events is elevated due to increased arterial stiffness and atherosclerosis of the vessels of the organs, and therefore often accompanied by inadequate blood supply to the organs. Therefore, the diagnosis of pseudohypertension does not imply treatment or not, but rather the discovery of an appropriate treatment population and antihypertensive goals. For example, the presence of a J-curve in blood pressure lowering is likely to be due to excessive lowering of blood pressure by adjusting the target value according to the blood pressure value measured by the cuff method, with consequent serious complications. Therefore, patients with pseudohypertension should not be treated with antihypertensive therapy before a reasonable antihypertensive target is determined. After diagnosis, atherosclerosis and insufficient blood supply to organs should be evaluated at the same time, and comprehensive interventions targeting predisposing factors for atherosclerosis should be carried out to monitor the blood pressure and thus protect the function of important organs such as the brain, the heart, and the kidneys.
Prevention
When hypertensive patients present with ineffective antihypertensive drug therapy and prolonged hypertension or suspected severe hypertension and lack of target organ damage, they should be alerted to the possibility of pseudohypertension, and should undergo further relevant investigations in order to confirm the diagnosis at an early stage.