Long-term blood pressure monitoring: apparatus, results

Nowadays, it is difficult to surprise anyone with high blood pressure. A dangerous tendency is that people treat this condition as a given, guided by the principle: I'll have a rest, and everything will be fine. But high blood pressure, even if situational, can be a harbinger of a dangerous disease - hypertension. But how can you find out whether the increase in blood pressure is caused by some provoking factors (stress, weather conditions, meteosensitivity) or is it the result of a pathological condition of the heart and blood vessels? A one-time pressure measurement does not answer this question. But monitoring blood pressure for 24 hours or more can quite clarify the situation.

The procedure of non-invasive measurement of blood pressure, lasting a day or more, is abbreviated as ABPM. Daily monitoring of blood pressure is considered the most reliable method for determining true blood pressure readings, which is simply impossible to do in a couple of minutes. At the same time, the procedure is not burdensome, because the patient does not have to be in the clinic all this time. And those small requirements that the doctor insists on him to follow during monitoring will seem like a trifle compared to the diagnostic value of the procedure.

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Indications for the procedure

Let's start with the fact that in order to conduct blood pressure monitoring, it is not at all necessary to have documented heart and vascular diseases. For preventive purposes, such a procedure can be performed by any person who is zealous about their health.

Let's say that the same hypertension is a rather insidious pathology, and for a certain period of time it may not manifest itself in any way. Up to 30 years old, a person may not even suspect that he has this disease, and then incomprehensible fluctuations in blood pressure begin, a deterioration in well-being is noted during physical exertion, pronounced weather dependence appears, etc.

But if only that were all. If left untreated, hypertension leads to persistently high blood pressure, which in turn is a risk factor for dangerous complications such as stroke, myocardial infarction, arrhythmia, and angina. Against the background of high blood pressure, doctors often diagnose vascular atherosclerosis, diabetes, and other pathologies associated with impaired blood supply to organs, and therefore with impaired nutrition and breathing.

The danger of hypertension, which causes difficulties in diagnosing the pathology, is also in the fact that it can have various forms and manifestations that require completely different approaches to treatment:

• Latent hypertension, which occurs virtually asymptomatically, meaning that the patient may not even suspect that he or she has the disease.
• Working day hypertension (also known as office arterial hypertension), when an increase in blood pressure is observed in connection with the performance of work duties, and when visiting a doctor who takes blood pressure measurements, the pressure readings are close to normal.
• Nocturnal hypertension. An insidious type of pathology, when blood pressure readings rise, seemingly out of nowhere: at rest in the evening and at night.
• Persistent hypertension, resistant to antihypertensive therapy. In this case, single measurements 2-3 times a day do not provide a complete clinical picture.
• White coat syndrome. A peculiar variant of situational hypertension, when the anxiety caused by visiting a clinic or hospital, where people in white coats (a figurative expression denoting the uniform required in medical institutions) are scurrying about, causes a temporary increase in blood pressure, which is recorded by the doctor's device. The anxiety is most likely associated with an unpleasant childhood experience of communicating with doctors.
• Fluctuations in blood pressure, which cause patients to experience a significant deterioration in their well-being.
• Symptomatic hypertension, an increase in blood pressure in which is provoked by strong excitement, fear, anxiety, etc. (strong emotional factors).
• Borderline arterial hypertension, when the pressure is at the upper limit of the norm, but in some situations it can even cross the line.

All these situations are very difficult to detect by taking one-time blood pressure measurements when a person consults a doctor about a deterioration in health or undergoes a routine medical examination. If atypical forms of hypertension, which we have discussed, are suspected, doctors prescribe long-term blood pressure monitoring to observe changes in blood pressure readings over the course of a day. In some cases, a longer study may even be needed to professionally assess the situation and develop measures to stabilize the patient's condition.

Indications for the ABPM procedure include not only various types of arterial hypertension, but also the diagnosis of the possible development of the disease, where the following plays a major role:

• hereditary factor of the disease (this type of diagnostics is relevant in case of hereditary predisposition, if there were cases of hypertension in the family),
• pregnancy (hormonal changes can cause fluctuations in blood pressure),
• risk factors (excess weight, smoking, exposure to stressful situations, hormonal imbalances, autoimmune, allergic, infectious pathologies) that can provoke the development of hypertension even at a young age,
• pathologies that occur with increased blood pressure (for example, diabetes mellitus, cardiac ischemia and heart failure, vascular pathologies of the brain, sleep apnea syndrome, severe forms of vegetative-vascular dystonia, etc.),
• age (older patients are more prone to hypertension due to the physiological characteristics of this age group and the baggage of diseases accumulated over many years).

In this case, a person can go to the clinic to undergo the ABPM procedure themselves or with a doctor’s referral.

Monitoring blood pressure will be useful not only for those with high blood pressure, but also for patients with hypotension (persistent decrease in blood pressure due to constitutional features or provoking factors).

Doctors perform this procedure not only for purely diagnostic purposes. The study provides information when selecting patients who need drug treatment. For example, the advisability of antihypertensive drug therapy for "white coat" syndrome or office hypertension is extremely questionable. In this case, psychological assistance and correction of the work and rest regimen will be more effective. However, such people have a certain predisposition to increased blood pressure (hypertension), so they are prescribed ABPM regularly 2-4 times a year.

Monitoring blood pressure for 24 hours or more helps to assess the effectiveness and safety of drug therapy (for example, some antihypertensive drugs with slightly elevated blood pressure can lower it below normal, which is no less dangerous to health). It can be used to determine the degree of effectiveness of prescribed drugs in each specific case. If no improvement is observed within several procedures, this indicates resistance to drug treatment. Individual treatment regimens for arterial hypertension are developed for such patients.

If the patient is forced to take medications strictly at the allotted time (chronotherapeutic regimen of drug therapy), a very important indicator is the daily rhythm of arterial pressure, which is individual for each person. Sometimes it is the violation of the circadian rhythm that hides the deterioration of the patient's condition, pressure surges and even the ineffectiveness of the prescribed course of therapy. The ABPM method provides complete information on this issue.

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Preparation

Blood pressure monitoring is one of those diagnostic and treatment procedures that do not require any special preparation on the part of the patient. However, an important task for the doctor is to convey to the patient information about the goals of blood pressure monitoring and behavior during the procedure. The accuracy of the results of the tests and the effectiveness of further treatment depend on the awareness of the importance of this diagnostic method and the correct fulfillment of all medical requirements.

Another particularly important point in preparation for the long-term blood pressure monitoring procedure is the preparation of the 24-hour blood pressure monitoring device and the selection of a cuff of the appropriate size based on the patient's constitution.

Daily monitoring of blood pressure can be carried out using invasive and non-invasive methods. Within the framework of the non-invasive method of monitoring blood pressure, two methods are considered: auscultatory and oscillometric, which has recently become increasingly widespread, since it is free from the shortcomings of the previous method.

Invasive method: blood pressure measurements are taken in a hospital setting. In this case, a needle connected to a sensor is inserted into the patient's artery, which continuously records the information coming from it onto a magnetic tape.

The auscultatory method is still used in some clinics and involves listening to Korotkov's tones using a special microphone, which is applied to the site of vessel pulsation in the cuff area. The oscillographic method of measuring blood pressure is a diagnostic measurement of average systolic and diastolic pressure by small pulsations of air pressure in the cuff.

Both of these methods can be used both in hospital and outpatient settings. Fortunately, today there is no shortage of equipment for non-invasive measurement of daily blood pressure on the medical equipment market. Both domestic developments and foreign technologies are presented there. Therefore, it is not difficult at all to select equipment in accordance with your wishes and needs.

These can be regular tonometers that measure blood pressure (for example, the Hungarian-made AVRM-02/M model with battery charge control). But many clinics prefer to use multifunctional devices (Cardio Tens made in Hungary simultaneously records blood pressure and ECG readings, and the Japanese TM-2425/2025 system also regularly measures air temperature, human body position, increased physical activity by accelerating movement, etc.). Devices for long-term blood pressure monitoring are called Holters, hence the other name SMAD - Holter monitoring of arterial pressure.

24-hour blood pressure monitoring implies a continuous cycle of specialized equipment. And since all such devices in outpatient settings operate on batteries (or regular batteries), before starting the procedure, the doctor must check whether the battery charge is sufficient to conduct ABPM for the required time. Recharging on site is impossible in this case.

The blood pressure monitoring device consists of a recorder, a display and a cuff, which are connected to each other and work as a single unit. First, the recorder is initialized by connecting it to a PC. A special program allows you to enter individual patient information into the recorder's memory, set the data recording periods and intervals at which blood pressure measurements should be taken, enable or disable the sound signal function before each measurement, and mark the need to display blood pressure and pulse data on the display.

The device does not record blood pressure data continuously, but at certain intervals. The following standards are accepted: during the daytime, the device measures blood pressure and pulse every 15 minutes, and at night – every half hour. If necessary, the device can be programmed for other time intervals.

After the recorder has been initialized, a cuff is selected for the device. Devices of this type are usually supplied with several cuffs that differ in length and width. A child's cuff is 13-20 cm long. For adults, these figures may vary greatly. When selecting the optimal length and width of the cuff, it should be taken into account that it should cover at least 80% of the limb along the perimeter.

The cuff is applied to the upper limb in the shoulder area according to the leading side of the body. For most people, the cuff is attached to the left arm, and for left-handers, to the right.

There is a special mark on the cuff that indicates that the device is attached correctly if it coincides with the point of greatest pulsation.

Since the pressure measurement is carried out over a long period of time, and the patient lives a normal life, i.e. is in motion, the cuff can shift slightly. This should not be allowed, because the measurement results will be distorted in this case. To prevent the device from shifting relative to the arm, it is recommended to use special discs with a double-sided adhesive coating (like double-sided tape).

Then control measurements are taken (about 4-6 measurements with an interval of 2 minutes). To do this, first attach a pneumatic cuff to the patient's shoulder, then use special fasteners to attach a recorder with a display and a sphygmomanometer to it, based on which the average indicators of the doctor's and instrumental values are calculated. The permissible differences between these indicators are 10 mm Hg (for systolic or upper pressure) and 5 mm Hg (for lower pressure indicators).

If the difference in readings exceeds the permissible limits, it is necessary to check the correct placement of the cuff, change the arm on which the blood pressure will be measured, or change the type of device for daily blood pressure monitoring.

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Technique blood pressure monitoring

As already mentioned, the device for daily blood pressure monitoring takes measurements during the time set by the program, recording the measurements in the device's memory. That is, a person does not remove the tonometer during the entire procedure (sometimes a day, sometimes more), and even at night.

The patient is warned in advance that the blood pressure measuring device must not be wet. Like any electrical device, it must be kept away from sources of moisture and electromagnetic radiation. It is prohibited to independently adjust the height of its fastening (there is a risk of incorrectly fastening the device on the arm, which will distort the results of the study), disconnect the cuff from the recorder, remove or change the batteries, or repair the allegedly broken device. It is important to ensure that the parts fastening the cuff to the recorder are not pinched by clothing or squeezed during sleep.

If the device has slipped down significantly, you can adjust it, leaving a distance of about 2 cm between its lower edge and the elbow.

During blood pressure monitoring, it is not recommended to change your daily routine and habits, the only thing that should be limited is physical activity on the day of monitoring. It is clear that sports, fitness, etc. should be postponed until another day.

You should try to forget about the device during the procedure (especially since it is quite light and is not attached to the dominant hand, which means it does not cause any particular inconvenience), think less about possible bad results of the study, try to see the readings on the display. Such thoughts and actions cause a state of anxiety and worry, which can affect the results of the study in the form of increased blood pressure.

Night sleep should also be calm, not burdened by thoughts about the device readings and possible pathologies. Any nervousness distorts night measurements and, of course, the final indicators. But the results of measuring the night drop in blood pressure are very important in terms of diagnosing hypertension. Patients are even classified into 4 groups based on the SNAD indicator (the degree of nighttime decrease in blood pressure).

An important duty of the patient during the procedure is to keep special records in the ABPM diary. But in their records, a person should display not the blood pressure values and time intervals between measurements (this information is stored in the device's memory), but their detailed actions during blood pressure monitoring and changes in well-being. All emerging symptoms should be noted in the diary, indicating the time of appearance and disappearance of the symptom.

During the day, the device measures blood pressure every 10-15 minutes. Before taking a measurement, it gives a beep. This function can be turned off, but for the convenience of the patients themselves, doctors advise using it. The thing is that it is advisable not to move during the blood pressure measurement (if the signal sounds while walking, you need to stop and wait until the second signal sounds, indicating the end of the measurement). The arm on which the device is attached should be lowered down, and the muscles should be relaxed as much as possible. These requirements are not imposed by chance, because their violation can adversely affect the accuracy of the measurements.

At night, the patient moves little and is quite relaxed, so there is no need to monitor the time of measurements.

ECG and BP monitoring

If a patient complains of irregular heartbeat and high blood pressure when visiting a doctor, but a one-time electrocardiogram and blood pressure measurement do not show anything suspicious, the doctor still has many questions. These questions can be answered using a fairly simple procedure - measuring ECG and blood pressure over a longer period of time. In this case, ECG and blood pressure monitoring can be carried out for 24 hours, and sometimes the device is left on the patient's body for a longer period of time.

24-hour Holter ECG monitoring is prescribed for the following patient complaints:

• pressing pain in the heart area, which appears episodically, mainly during physical exertion,
• a feeling of palpitations, anxiety, discomfort behind the breastbone and a deterioration in well-being,
• shortness of breath against the background of the above symptoms,
• the appearance of unexplained weakness and dizziness, fainting, accompanied by the appearance of cold sweat on the face and body,
• feeling of exhaustion, fatigue and loss of strength in the morning hours (without physical activity),
• a disturbance of the heart rhythm that is accompanied by a brief loss of consciousness, a sensation of palpitations, or a feeling that the heart is stopping,
• attacks of angina pectoris,
• metabolic pathologies: diabetes mellitus, thyroid dysfunction,
• period after myocardial infarction,
• increased sensitivity to weather changes (increased blood pressure, heart palpitations, noticeable deterioration in general well-being when the weather changes).

Long-term monitoring of ECG and blood pressure can also be performed to evaluate antiarrhythmic and antihypertensive therapy.

This type of heart monitoring makes it possible to track any changes on the cardiogram during the day, those changes that cannot be reflected in a short period. The development of this method belongs to the American scientist N. Holter, in whose honor the method was named.

Daily ECG monitoring is carried out in a similar way to long-term blood pressure monitoring. A portable electrocardiograph, which is about the size of a mobile phone, is attached to the patient's belt, and the electrodes are on his chest. The device can be on the patient's body for 24 hours or more, as prescribed by the doctor.

It has become quite a popular practice recently to simultaneously conduct daily monitoring of both blood pressure and ECG. In this case, the patient will not have to undergo the procedure twice. In addition, in both cases, the main requirement is to keep a diary in which the patient's activities and changes in his or her well-being during the period of diagnostic measurements should be noted.

Joint monitoring allows you to immediately obtain complete information about the condition of the heart and blood vessels, including:

• cardiovascular response to exercise,
• information about the work of the heart and blood vessels during night rest,
• fluctuations in blood pressure depending on physical and emotional stress,
• information about heart rhythm for 24 hours or more,
• cardiac conduction study.

Such an extensive study makes it possible not only to identify episodes of increased (decreased) blood pressure, loss of consciousness, etc., but also to establish the cause of these changes, for example, disturbances in heart rhythm or blood supply to the myocardium of the heart.

Normal performance

The device for long-term monitoring of arterial pressure remains fixed on the patient's shoulder for a certain period of time, after which it is removed and connected to a computer. Information is read from the Holter's memory using a special computer program supplied with the device. The same program was used to initialize the device.

On the computer screen, the doctor sees the processed information in the form of tables and graphs, which can be printed on a sheet of paper. On the graph, you can see the curved lines of systolic (SBP), diastolic (DBP) and mean (MAP) arterial pressure, as well as the pulse rate. Which indicators have a special prognostic value for doctors?

First of all, these are the average values of BP, DBP, MAP and HR (pulse). The calculation of average values can be carried out for a day or certain periods of time (wakefulness from 7 am to 11 am, night time from 11 pm to 7 am). It is the average values of the above values that provide valuable information about the blood pressure of a particular person.

Normally, the average daily pressure is considered to be 130/80 mm Hg. If it increases to 135/85, doctors talk about hypertension. For daytime and nighttime blood pressure, the norm is considered to be 135/85 and 120/70, respectively. Doctors diagnose hypertension if these figures rise to 140/90 and 125/75. As a difference between a healthy person and a sick person, an increase in average blood pressure by only 5 mm Hg.

It is by analyzing the change in average values that one can judge the degree of effectiveness of antiherpetic therapy.

Another important indicator is the frequency of increased blood pressure (FAP). This indicator may be called pressure load or hypertensive load, as well as time index in different sources. It is the number of blood pressure readings that are above the upper limit of the norm, expressed as a percentage. During the daytime, this limit is 140/90, and at night, the threshold is within 120/80 mm Hg.

The NBP indicator allows making forecasts for the future and creating effective therapeutic schemes. At not very high blood pressure indicators, NBP is expressed as a percentage as the number of times the norm is exceeded, and at greatly increased blood pressure values - as the area under the graph of the dependence of pressure on the time of day and night, limited by the same 140/90 mm Hg.

Of great importance in the diagnosis of cardiovascular pathologies are not only individual blood pressure indicators, but also changes in these indicators during the day. Pressure variability is determined by deviation from the daily rhythm chart.

STD is the standard deviation indicator from the mean arterial pressure chart. It can be measured both per day and during the day or night. If the STD of systolic pressure at any time of the day is equal to or exceeds 15 mm Hg (for diastolic, the daytime indicator is greater than or equal to 14 mm Hg, and the nighttime indicator is 12 mm Hg), this indicates developing hypertension. If only one of the indicators is exceeded, this indicates increased variability of blood pressure, which may be associated with left ventricular myocardial hypertrophy, carotid artery atherosclerosis, pheochromocytoma, renal hypertension, etc.

Changes in BP variability can be used to judge the effectiveness of antihypertensive drugs. Hypertension therapy should ideally lead to a decrease in BP variability; if this does not happen, a revision of the prescriptions is needed.

The daily index is also considered a very important diagnostic indicator. The change in the daily (circadian) rhythm of arterial pressure can be judged by the degree of nighttime decrease in blood pressure (SNBP). For systolic blood pressure, this indicator is calculated using the formula: (average SBP during the daytime - average SBP at night) x 100% / average SBP during the daytime. SNBP is calculated similarly for diastolic pressure, but instead of SBP values, DBP values are used.

Normal SNSAD values are within 10-22% (60 to 80% of people who belong to the Dippers group). Insufficient and excessive reduction of SNSAD have values of less than 10% and more than 22%, respectively (Non-dippers and Over-dippers groups). A negative SNSAD value indicates a stable increase in blood pressure (Night-peakers group).

If daily blood pressure monitoring shows insufficient reduction of blood pressure at night, doctors may assume the following consequences: frequent episodes of strokes, high probability of left ventricular hypertrophy and ischemic heart disease, high risk of developing microalbiminuria, which will proceed with more pronounced symptoms. Acute myocardial infarction in such patients often ends in death.

As we can see, daily blood pressure monitoring is an extremely important diagnostic procedure, which in many cases helps to save a person’s health and life, facilitating the timely and effective implementation of therapeutic measures to improve the functioning of the cardiovascular system and prevent various unpleasant and even dangerous complications.

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