True and False Hypertension —— Several Special Types of Hypertension

Text | Li Qing, Tianjin TEDA Hospital

Hypertension is one of the most dangerous factors of cardiovascular disease, and accurate measurement of blood pressure is very important for correct diagnosis of hypertension and monitoring the effect of antihypertensive treatment.

At present, the diagnosis of hypertension is still based on the blood pressure measured by doctors in the clinic. The diagnostic standard of hypertension in the United States is ≥130/80 mmHg, and other countries still use the previous ≥140/90 mmHg.

However, there are also some disadvantages in measuring blood pressure in the clinic, such as doctor’s operation error, inconsistent measurement methods, patients’ nervousness when measuring blood pressure, and the inability to obtain blood pressure values outside the consultation time, which leads to the phenomenon of true and false hypertension: some hypertension may not be found, while some normal people may be mistaken for hypertension.

Ambulatory blood pressure monitoring (ABPM) is a noninvasive and automatic blood pressure measurement technology, which can record blood pressure continuously for 24 hours. ABPM has a history of 40 years. In the past 20 years, big data proved that the blood pressure measured by ABPM has a stronger correlation with the target organ damage of hypertension compared with the blood pressure in the clinic.

The significant benefit of ABPM is that it can collect multiple blood pressure measurements, provide more comprehensive blood pressure information, identify "true and false hypertension" and accurately evaluate the antihypertensive effect. At present, clinical application is becoming more and more popular.

Common special types of hypertension are:

1. White coat hypertension and white coat effect

Because of the influence of environment and nervous factors when seeking medical treatment, the blood pressure measured in most patients’ clinic is often higher than the average blood pressure measured outside the clinic.

Without taking antihypertensive drugs, the blood pressure in the clinic is in the range of hypertension, but the blood pressure outside the clinic is not high, which is called white coat hypertension; In patients taking antihypertensive drugs, the blood pressure in the clinic is higher than that outside the clinic, which is called the white coat effect.

It has been observed that white coat hypertension accounts for 15% ~ 30% of the patients diagnosed with hypertension in the clinic [1]; In patients taking antihypertensive drugs, 30% ~ 40% have white coat effect [2].

Most studies (but not all studies) show that white coat hypertension itself brings little cardiovascular risk [2].

It is not clear whether antihypertensive therapy can reduce the risk of cardiovascular disease in patients with white coat hypertension. However, white coat hypertension may develop into persistent hypertension faster than normal people, so patients with untreated white coat hypertension should be monitored regularly and followed up.

2. Concealed hypertension

Concealed hypertension means that the blood pressure in the clinic is normal, < 140/90 mmHg, but it is indicated as hypertension through ambulatory blood pressure monitoring or home self-test blood pressure (the average blood pressure during the day is ≥135/85 mmHg).

According to statistics, about 15% ~ 30% of the adult population with normal blood pressure (< 140/90 mmHg) in the clinic are artificial occult hypertension [3]. In some groups, such as patients with chronic kidney disease and apnea, the proportion of occult hypertension is higher.

The risk of target organ damage and cardiovascular disease in occult hypertension is 1.5 ~ 3.0 times higher than that in normal people or patients with well-controlled blood pressure, and its risk is equivalent to that in patients with persistent hypertension.

3. Night hypertension

Nocturnal hypertension is characterized by elevated blood pressure during sleep.

Ambulatory blood pressure monitoring is the main method to find this type of hypertension.

It is estimated that 20% of whites and 40% of blacks suffer from nocturnal hypertension, and the prevalence of nocturnal hypertension in patients with diabetes and chronic kidney disease is also high.

Because ambulatory blood pressure monitoring will affect the quality of sleep when the cuff is inflated at night, it is not clear to what extent the ambulatory blood pressure monitoring machine will lead to the increase of blood pressure at night.

A large meta-analysis and several studies show that the increase of blood pressure during sleep is related to the increased risk of cardiovascular events.

4. Spoon blood pressure and non-spoon blood pressure

Most people’s blood pressure gradually rises from 6: 00 in the morning, reaches a peak around 10: 00, and then gradually drops steadily, and the blood pressure at noon is relatively low; From 14: 00, blood pressure gradually increased again, and peaked again from 16: 00 to 18: 00, and then slowly decreased; Blood pressure reached a low point at 0: 00-2: 00 in the morning, and then rose slightly, and maintained until 6: 00 to start the next day’s circulation. The whole day’s blood pressure shows a long-handled spoon-shaped curve with two peaks and one valley, so it is called spoon-shaped blood pressure. See the picture.

According to the decrease rate of blood pressure at night (22: 00 ~ 8: 00) compared with that at daytime (8: 00 ~ 22: 00), the circadian rhythm of blood pressure can be divided into:

Spoon blood pressure: the rate of blood pressure drop at night is 10% ~ 20%;

Non-spoon blood pressure: the rate of blood pressure drop at night is less than 10%;

Super spoon blood pressure: the rate of blood pressure drop at night is > 20%;

Reverse spoon blood pressure: blood pressure at night is higher than blood pressure during the day.

Compared with spoon-type blood pressure, the cardiovascular risk of target organ damage such as left ventricular hypertrophy and carotid intima thickening in non-spoon-type and anti-spoon-type blood pressure is significantly increased, while the extra-spoon-type blood pressure may not be related to the increase of cardiovascular risk.

5. Peak blood pressure in the morning

No matter whether the blood pressure is normal or hypertensive, the blood pressure will rise rapidly after waking up in the morning and returning to the upright position, and reach a higher level in a short time (2 ~ 4 hours). This phenomenon is called morning peak blood pressure.

Generally, the average systolic blood pressure of 2 hours after waking up is used, and the average blood pressure of 1 hour including the lowest systolic blood pressure at night (that is, the average of the lowest blood pressure and its two blood pressures before and after) is subtracted. If it is ≥35mmHg, it can be diagnosed as morning peak hypertension.

In recent years, more and more clinical studies have confirmed that there is a close relationship between blood pressure fluctuation and cardiovascular complications. It is found that the high incidence of cardiovascular events such as angina pectoris, myocardial infarction, sudden cardiac death and cerebrovascular accident is from 6: 00 to 10: 00 every morning, accounting for about 35% to 40% of the whole day, and the morning peak of blood pressure plays an extremely important role.

Note:

[1]Franklin　SS,　Thijs　L,　Hansen　TW,　et　al.　Whitecoat　hypertension:　　new　insights　from　recent　studies.　Hypertension.　2013; 62:　982–987.　doi:　10.1161/HYPERTENSIONAHA.113.01275

[2]　Muntner　P,　Booth　JN　3rd,　Shimbo　D,　et　al.　Is　white-coat　hypertension　associated　with　increased　cardiovascular　and　mortality　risk? 　　J　Hypertens.　2016; 34:1655–1658.　doi:　　10.1097/HJH.0000000000000983

[3]　Peacock　J,　Diaz　KM,　Viera　AJ,　et　al.　Unmasking　masked　hypertension:　prevalence,　clinical　implications,　diagnosis,　correlates　and　future　directions.　J　Hum　Hypertens.　2014; 28:　521–528.　doi:　　10.1038/jhh.2014.9