Interpretation Of Blood Pressure Measurements

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Several important points need to be kept in mind in the interpretation ofblood pressure recordings.Diagnosis of hypertension requires demonstration of sustained elevations of blood pressures under normal resting conditions. The normal upper level of blood pressure for adults regardless of age is 140/80. In fact, some newer studies suggest that mortality and cardiac events are less frequent in those with blood pressures of less than 125/75. Present recommendations suggest the blood pressure in diabetics be controlled to 130/80, and if renal disease or microalbuminuria is also present the pressure should be 120/70 or lower. It appears that lower is better as long as the patient does not suffer any symptoms or adverse effects of hypotension and remains asymptomatic. Documentation of sustained elevations of blood pressures therefore requires more than one observation. Sometimes self-recorded pressures at home and/or recordings using an ambulatory monitoring system may have to be resorted to, particularly in nervous and anxious individuals. In addition, one may also have to look for evidence of end-organ damage, such as the presence of retinal changes and electrocardiographic and/or echocar-diographic evidence of left ventricular hypertrophy.

While one cannot make a diagnosis of hypertension in a patient with one isolated elevation in blood pressure, the significance of such elevations nevertheless should be interpreted in relation to the clinical problem. For instance, an elderly patient who has exertional angina or dyspnea with a resting blood pressure of 130/80 mmHg may have been noted to have a blood pressure reading of 180/90 soon after undressing himself, untying his shoe laces, and getting on the examining couch. Although one may not label this patient as hypertensive on the basis of that one recording of high pressures, it nevertheless indicates that the elevation in blood pressure in this patient was inappropriate to the level of exercise and most likely is a contributing factor to the exertional symptoms. Lowering ofthe pressure with the use of medications such as an angiotensin-converting enzyme inhibitor and/or a ^-blocker would be an appropriate management strategy for such a patient.

In young patients because of peripheral amplification secondary to reflected waves in the more muscular stiffer vessels in the extremities, the systolic blood pressure obtained may not correctly reflect the systolic central aortic pressure and may in fact be 50% higher. In these patients, the diastolic pressure may more accurately reflect the diastolic pressure in the central aorta.

In the elderly because of arteriosclerosis and stiffened aorta and arteries in general, the pressure pulse wave travels faster. The wave reflection therefore tends to arrive early in the central vessels, augmenting the systolic pressure. In these patients no peripheral amplification is noted, and the brachial systolic pressure more accurately reflects the central aortic systolic pressure (26-30).

In atherosclerosis there may be significant differences between the upper and lower limb pressures. Because atherosclerosis tends to involve the lower extremities more, one may actually find in these patients decreased pulse amplitude together with lower blood pressure in the lower limbs compared to the arms. This is in contrast to the usual findings in the young and/or normal patients, where the pressures in the legs are in fact 10-20 mmHg higher than the brachial pressures.

In patients without any evidence of hypertensive end-organ damage, significantly elevated systolic blood pressures may be obtained in doctors' offices. These high office blood pressure readings are at times associated with normal blood pressure readings throughout the day when 24 h ambulatory blood pressure monitoring is carried out. Not surprisingly, the first and the last readings (normally readings taken in the laboratory in the presence of the technician) during these recordings also show significant blood pressure elevations. This white coat syndrome is likely related to an anxiety reaction on the part of the patient. Generally this condition is felt to be relatively benign, although there always is a concern that patients may become hypertensive in the future.

White coat hypertension has been defined and classified (31,32) into three groups:

1. White coat hypertension: Abnormal office systolic blood pressure >150 mmHg and daytime average systolic blood pressure <140 mmHg. (Patients not on antihyper-tensives).

2. White coat syndrome—normotensive: Patients' blood pressures controlled on anti-hypertensives. Their daytime average systolic blood pressure <140 mmHg and office blood pressure reading of >150 mmHg.

3. White coat syndrome—hypertensive: Patients may be on or off antihypertensive medications with daytime average systolic blood pressure of >140 mmHg and office systolic blood pressure measurement of >150 mmHg, which is at least 15 mmHg higher than the average daytime systolic blood pressure.

White coat hypertension syndrome may not be as benign as once thought (33). There appears to be higher incidence of increased mean albumin levels in the urine of some of these patients. Some show increased albumin/creatinine ratios of >30%.

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Blood Pressure Health

Blood Pressure Health

Your heart pumps blood throughout your body using a network of tubing called arteries and capillaries which return the blood back to your heart via your veins. Blood pressure is the force of the blood pushing against the walls of your arteries as your heart beats.Learn more...

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