ELEVATED blood pressure is associated with significant risks if untreated. Research has been better able to quantify the cardiac and vascular risk associated with increasing levels of blood pressure.

Decades ago it was a common belief that the rise in blood pressure with age was a normal phenomenon and that it was not necessary to treat systolic blood pressure up to 160mmg of mercury. It is now clear that, as both systolic and diastolic blood pressure rises, cardiovascular risk rises, regardless of age. There is some debate among cardiac and hypertension societies of the level at which hypertension should be diagnosed (American guidelines suggest 130/80 and Europeans suggest 140/90) but both agree that normal or optimal blood pressure is less than 120/80. It is estimated that of the US population, if 130/80 is the upper limit of normal, then 47 per cent of the adult population would meet the criteria for the diagnosis of hypertension, that is, the measured blood pressure exceeds a systolic pressure of 130, a diastolic pressure of 80, or the patient is currently taking medication for hypertension. The 2016/2017 Jamaican Health and Lifestyle survey suggests that one in three Jamaican adults have hypertension. Ominously four in 10 Jamaican patients with hypertension are unaware of the diagnosis and many of those with known hypertension are not under optimal treatment. Of those treated, many are not well controlled.

How is hypertension diagnosed?

It is important to remember that we do not diagnose hypertension with a single finding of elevated blood pressure unless there are other findings that would support a chronic elevation in blood pressure. For example, thick heart muscle, changes on the EKG, changes on eye examination, etc. Blood pressure is not a number but is a range with the blood pressure rising and falling throughout the day in response to several factors. There is physiologic variation in the blood pressure throughout the 24-hour period. The blood pressure tends to be highest in the morning prior to awakening and tends to be lowest in the late evening. The level of the blood pressure at any one time can be affected by exercise, emotional stress, smoking, drinking alcohol, cold weather, caffeine, and various medications. When we make a diagnosis of hypertension, effectively what we are saying is that the blood pressure is elevated most of the time it is measured. Another important note to make is that the effects of hypertension on the body are related to the level of blood pressure elevation and the duration. So that extremely high levels of hypertension can have deleterious effects in days to months, while mild levels of hypertension make take decades to have clinical effects. Lastly, we should remember that, for the majority of hypertensive individuals, hypertension is clinically silent despite the common misconception that an elevated blood pressure is always associated with headache. The only way to know that hypertension is controlled is to measure it.

Why should we measure blood pressure at home?

A major change in the management of hypertension over the past 20 years is the recognition of the importance of measuring blood pressures at home, in addition to the traditional office measurement. Measurement of blood pressure at home has been shown to be a better predictor of morbidity and mortality from hypertension for several reasons. The simplest explanation may be that, with home blood pressure readings, a greater number of readings can be generated over any period. Over the course of a year a patient may have as few as two to four measures of blood pressures in the physician’s office or health centre. While at home it is possible for a patient to check and record blood pressure one to two times per day. With more frequent measurement there is greater accuracy in assessment of blood pressure control and the ability to titrate medications to improve blood pressure control or to reduce the risk of side effects from too much medication.

The use of home blood pressure measurement also allows for the diagnosis of white coat hypertension and masked hypertension. It is common knowledge that the blood pressures measured in the doctor’s office may not be reflective of the blood pressures that the patient experiences in day-to-day life. White coat hypertension in which the blood pressures are only elevated in the office can occur in 10-30 per cent of patients who are diagnosed with hypertension only based on office measurement. These patients do not need anti-hypertensive treatment if their blood pressures can be documented to be normal at home. The other condition of concern is so-called masked hypertension, in which the blood pressures are normal in the office but elevated at home. These patients need treatment as their risk of complications from elevated blood pressure is the same as patients with garden variety hypertension.

How is home blood pressure monitoring done?

Home blood pressure monitoring can be done in two ways. Patients can buy a home blood pressure machine, of which there are several types (most commonly manual and automatic), or an ambulatory blood pressure monitor can be ordered by a physician. Some societies, including the American College of Cardiology, suggest that a diagnosis of hypertension should be confirmed with a 24-hour ambulatory blood pressure monitor. The current recommendation of most cardiology and hypertension societies is that patients diagnosed with hypertension should have their own blood pressure machines and should make a practice of recording their blood pressures. Most societies recommend automatic cuff-based machines that measure the pressure at the arm as opposed to the wrist or finger as these tend to give more reliable readings. In terms of what machine to buy, some hypertension societies have validated specific machines for home use. Lists of these machines can be found at validatebp.org (American Heart Association), Stridebp.org (European Society of Hypertension), and the British and Irish hypertension society.

It is recommended that blood pressure be checked at roughly the same time every day. For 30 minutes prior to measurement patients should not exercise, drink alcohol or caffeine, or smoke. Ideally, they should sit quietly five minutes prior to measurement and the bladder should be empty. Patients should sit straight with the back supported and feet flat on the floor. Legs should not be crossed. The arm should be on a flat surface at the level of the heart. Blood pressure should be taken (some societies recommend at least two readings, one minute apart) and recorded. When going to see the physician in the office these readings should be brought along.

Ambulatory blood pressure recording

Ambulatory blood pressure measurement is ordered by a physician and the patient wears a blood pressure cuff for 24 hours. Blood pressures are taken usually twice per hour during the day and hourly at night. When the machine is returned to the health-care facility or physicians office the readings are downloaded and graphed. An average blood pressure for the 24-hour period with daytime and night-time averages can be obtained. The results are considered the gold standard for the diagnosis of hypertension and can be very useful in assessing control and need for medication adjustment. It is consistent with best practice standards for doctors to request a 24-hour ambulatory blood pressure monitor to confirm a diagnosis of hypertension prior to initiating treatment and to check 24-hour ambulatory blood pressure monitor at intervals to assess the impact of treatment or adjust medication doses over time. Appropriate use of 24-hour ambulatory blood pressure monitoring ensures that patients with pseudo hypertension (about one in four patients with elevated blood pressure in the doctor’s office) are not unnecessarily treated.

Hypertension remains one of the most common risk factors for cardiovascular disease. Treatment of hypertension has been demonstrated to reduce the risk of heart disease, vascular disease, kidney disease, and stroke. Measurement of blood pressure at home adds to diagnostic certainty when making an initial diagnosis of hypertension, plays a significant role in maintaining control and adjusting medications, and gives data that is supplemental to office blood pressure readings. Most importantly, it does appear that patients who are checking blood pressure at home do better over the long term than those who are managed with office readings only.

Dr Ernest Madu, MD, FACC and Dr Paul Edwards, MD, FACC are consultant cardiologists for Heart Institute of the Caribbean (HIC) and HIC Heart Hospital. HIC is the regional centre of excellence for cardiovascular care in the English-speaking Caribbean and has pioneered a transformation in the way cardiovascular care is delivered in the region. HIC Heart Hospital is registered by the Ministry of Health and Wellness and is the only heart hospital in Jamaica. Correspondence to info@caribbeanheart.com or call 876-906-2107