When blood pressure is above normal levels
The question
What is meant by the word high blood pressure?
Answer: In strictly semantic terms, the word hypertension is composed of the prefix 'hyper' meaning too much and tension meaning pressure so the literal meaning of the compound word is excess pressure. Since this excess refers to the pressure that is measured within the arterial tree, hypertension is defined as arterial. This aspect has a relevant clinical element because the concept of hypertension is a generic entity that also applies to other districts in the vascular sphere such as, for example, the portal circle (abdomen) and the pulmonary circle (lungs) or in the extra-vascular sphere such as glaucoma characterised by ocular hypertension.
The definition of arterial hypertension or more appropriately 'systemic' hypertension identifies a condition characterised by an increase in blood pressure above the normal levels described in the previous sections. In particular, all consensus documents agree in considering pressure values greater than or equal to 140/90 mmHg as elevated, considering that the diagnosis can also be made in the presence of only one of the two values above the normal limit. In terms of classification, systolic hypertension is defined as hypertension characterised by a simultaneous increase in maximum and minimum pressures.
If only one of the two values is outside the normal limits, this is referred to as isolated systolic or diastolic hypertension. In percentage terms, 90% of the hypertensive population belongs to the two types of hypertension with an isolated systolic component or combined with an increase also in the minimum blood pressure.
The diagnosis of hypertension must be adapted to the way in which blood pressure is measured, which can also be performed according to alternative procedures to the typical ambulatory one such as home measurement and 24-hour monitoring. In particular, under conditions of personal home measurement high blood pressure values are set for levels greater than or equal to 135/85 mmHg while for pressure measured during ambulatory blood pressure monitoring ("ABPM") pathological values are defined for levels of 130/80 mmHg when considering the average of the entire 24-hour profile with a significant difference between normal daytime values (>135/85 mmHg) and nighttime normal values (>120/70 mmHg) on the basis of a significant difference in the pressure profile between the phases of the day generated by differences mainly in the activation of the autonomic nervous system.
The diagnosis of hypertension also applies to two other particular clinical forms of pathological increases in blood pressure also associated with an increased risk of cardiovascular complications.
The first is 'white-coat' hypertension, which is characterised by a pathological increase in blood pressure during ambulatory measurement while blood pressure values appear completely normal outside the healthcare setting. Its clinical significance derives from the fact that the same abnormal blood pressure behaviour is also found in stressful and emotionally charged situations in everyday life. White-coat hypertension must be differentiated from the white-coat effect, which is that transient rise in blood pressure that coincides with a blood pressure measurement and is quickly extinguished by multiplying the serial number of measurements and is the basis for the need for repeated blood pressure measurements described above in order to acquire a reliable value.
The second particular form of hypertension is what is known as 'masked' hypertension, which is characterised by normal blood pressure values in the outpatient setting and elevated values during everyday life. This form of hypertension is also potentially dangerous in clinical terms because it is associated with the development of target organ damage (especially cardiac and renal) and major cardiovascular complications.
From a diagnostic point of view, it is important to point out that the possibility of ascertaining the presence of these particular forms of arterial hypertension is conditioned by the performance of ambulatory 24-hour blood pressure monitoring (ABPM), the only method that allows one to dissociate the opposite pressure changes that the subject may undergo throughout the day.