New Classification of Blood Pressure

New Classification of Blood Pressure

Hypertension had been classified in different ways. Clinical classification is dependent on severity of systolic as well as diastolic blood pressure. A new classification have been introduced by Joint National Committee of America (JNC-7) by the end of 2003 where Mild and Moderate types of hypertension is ignored. The term Pre-hypertension is introduced first time. Stage-3 or very severe hypertension is included within stage-2 hypertension, because of same precaution and treatment is needed for the patient.

High blood pressure is a trait as opposed to specific disease and represents a quantitative rather than a qualitative deviation from the norm. Systemic blood pressure rises with age and the incidence of cardiovascular disease (particularly stroke and coronary artery disease) is closely related to average blood pressure at all ages even when blood pressure readings are within "normal range".

Moreover, a series of randomized controlled trials have demonstrated that anti-hypertensive therapy can reduce the incidence of stroke and, to a lesser extent, coronary artery disease.

The cardiovascular risks associated with a given blood pressure are dependent upon the combination of the risk factors in the specific individual.

These include age, gender, weight, physical inactivity, smoking, family history, blood cholesterol, diabetes mellitus and pre existing vascular disease.

Effective management of hypertension therefore requires a holistic approach that is based on the identification of those at highest cardiovascular risk and the adoption of multifactorial interventions, targeting not only blood pressure but also all modifiable risk factors.

In light of the observations a useful and practical definition of hypertension is the level of blood pressure at which the benefit of treatment outweigh the cost and hazards'.

American joint National committee on prevention, detection, evaluation and treatment of high blood pressure (JNC 7) introduced a new classification that includes the term "Pre-hypertension' those with Blood pressure ranging from 120 to 139 mmHg systolic and/or 80 to 89 mmHg diastolic blood pressure (DBP).

This new designation is intended to identify those individuals in those early intervention by adoption of healthy life styles could reduce Blood Pressure, decrease the progression of BP to hypertensive levels with age or prevent hypertension entirely.

Magnitude of The Problem:
Hypertension is an important cause of death It is observed by Framingham study that 37 per cent men and 51 per cent women who die of cardiovascular disease had arterial blood pressure over 140/90 mmHg on at least 3 previous occasions.

In USA 30 per cent of the total population suffer from hypertension. It is the most contributing factor of morbidity and mortality due to stroke, heart failure, coronary heart disease and kidney disease. Twenty percent of the Japanese are hypertensive.

Hypertension is more common in men than women up to the age of 50 years; after that time, hypertension is commoner in female and prevalence of the disease increases with age in both the sexes. Life span in untreated hypertensives was seen to be shortened by 15-20 years on average.

Probability of developing a morbid cardiovascular event with a given arterial pressure may vary by as much as twenty fold depending on presence of associated risk factors.

Another study among the government servants showed a prevalence of 13.3 per cent (diastolic BP £ 90 mm Hg), vast majority of whom (71.6 per cent) were not previously diagnosed. Frequency of the disease among University students was 13 per cent (diastolic BP £ 90 rnmHg).

Prevalence of hypertension appears to be lower than that in the industrialised countries but a good number of cases remain undetected and untreated.

Extensive surveillance for detection and treatment of hypertension would go a long way in prevention of its complications.

Rationale for Reducing Elevated Blood Pressure:
It is found by considerable experimental, epidemiological and clinical evidence that reducing elevated blood pressure is beneficial, particularly in high risk patients (Mac Mohon et al., 1997).

The reduction in cardiovascular disease and death can be measured to determine the blood pressure level at which a benefit is derived from antihypertensive therapy.

That level can be as part of the operational definition of hypertension. Expert committees do not agree about the minimal level of blood pressure that should be treated with drugs. The consideration of other risk factors, target organ damage and symptomatic cardiovascular disease puts the decision to treat on a rational basis.

Operational Definition Based on Risk and Benefit:
The diagnosis of hypertension does not automatically mean that the drug treatment should be given to all the people with the elevated blood pressure levels. Moreover, in people highly susceptible to premature cardiovascular disease because of concomitant risk factors or target organ damage, antihypertensive therapy may be needed for level even below 140/90 mmHg.

In addition, patients those blood pressure is not high enough to mandate drug therapy may benefit from being diagnosed as hypertensive if, thereby, they are more willing to modify unhealthy life habits. Such lifestyle modifications may reverse the trend towards progressively higher blood pressure and reduce the level of other cardiovascular risk factors.

Non-Drug Therapy (Primary prevention):
Appropriate life style measures may obviate the need for drug therapy in patients with borderline hypertension, reduce the dose and/or the number of drugs required in patients with established hypertension, and directly reduce cardiovascular risk.

Correcting obesity, reducing alcohol intake, restricting salt intake, taking regular physical exercise and increasing consumption of fruits and vegetables can all lower blood pressure. Moreover, quitting smoking, eating oily fish and adopting a diet that is low in saturated fat may produce further reductions in cardiovascular risk.

Detection and Control of Hypertension in The Population:
Adequate management of the large hypertensive population has proved to be difficult. This difficulty arises from multiple causes. Perhaps the most pervasive is the inherent nature of hypertension: a long life condition that is usually asymptomatic formally years but that requires daily therapy that may itself induce symptoms.

The continued difficulties in maintaining adequate follow up and treatment of the poor are not by any means unique to the United States and in England. In less developed countries, even greater problems, including inadequate funds for medications, continue to impede attempts to control hypertension.

Contribution of Hypertension Control:
The explanation for the reduced mortality rate of the cardiovascular disease in the United States remains uncertain. However, the total contribution from all improvements in risk factors, including the control of hypertension, appears to explain about half of the decline.

In the Framingham Heart Study, the decline in cardiovascular disease mortality noted in groups of subjects who were 50-59 years old in 1950, 1960 or 1970 over the subsequent 20-year intervals was 59 per cent between the female cohorts and 53 per cent between the male cohorts.

More than half of the decline in coronary heart disease mortality in women and from one third to one half of the decline in men could be attributed to improvements in the risk factors, including reductions in obesity, hypercholesterolemia, smoking and hypertension.

The effect of treatment of hypertension was an important part of the overall reduction in risk, with a 60 per cent reduction in the 10-year risk, of mortality from cardiovascular diseases from patients with hypertension who were treated compared to those who were not treated.

If systolic and diastolic categories are different. follow recommendations for shorter time follow-up (e.g., 160/86 mm Hg should be evaluated or referred to source of care within 1 month).

Modify the scheduling of follow-up according to reliable information about past BP measurements, other cardiovascular risk factors or target organ disease. Provide advice about lifestyle modifications.

Hypertensive Heart Disease:
Hypertension more than doubles the risk for symptomatic coronary disease, including acute myocardial infarction and sudden death, and more than triple the risk for congestive heart failure.

The consequences reflect an admixture of effects directly induced by the hypertrophied response of the left ventricle to the increased after load imposed by hypertension, i.e., left ventricular hypertrophy (LVF), and the acceleration of atherosclerosis through various paths.

Hypertensives have more hypertrophy and coronary disease than normotensives. The cardiovascular risk from hypertension reflects vascular overload, more logically related to systolic BP in the young and middle aged and to pulse pressure in the elderly.

Causes of Death:

Untreated Hypertension:
Death may result when the arterial lesions either rupture or become occluded enough to cause ischemia or infarction of the tissues they supply. Cardiovascular diseases are responsible for a higher proportion of deaths as the severity of the hypertension worsens.

In general, patients with severe, resistant disease die of strokes; those presenting with advanced retinopathy and renal damage die of renal failure; the majority, with moderately high pressure, die of complication of ischemic heart disease. Heart disease remains the leading cause of death.

Treated Hypertension:
Initial trials of antihypertesive therapy suggested that the nature of heart disease was changed from congestive heart failure to coronary artery disease.

Antihypertensive treatment has greatly reduced the incidence of complications of hypertension that are directly due to raised BP, most notably congestive heart failure.

Prevention of Hypertension:

Public Health Challenges:
The prevention and management of hypertension are major public health challenges for the developing as well as for the developed countries. If the rise in BP with age could be prevented or diminished, much of hypertension, cardiovascular and renal disease and stroke might be prevented.

A number of important causal factors for hypertension, have been identified, including excess body weight; excess dietary sodium intake; reduced physical activity; inadequate intake of fruits, vegetables and potassium; and excess alcohol intake. The characteristics of these prevalence are high.

Because of the life time risk of developing hypertension is very high, a public health strategy that complement the hypertension treatment strategy is warranted. In order to prevent BP levels from rising, primary prevention measures should be introduced to reduce or minimise these causal factors in the population, particularly in the individuals prehypertension.

A population approach that decreases the BP level in the general population by even modest amount has the potential to substantially reduce morbidity and mortality or at least delay the onset of hypertension.

For example, it has been estimated that a 5 mm Hg reduction of SBP in the population would result in a 14 per cent overall reduction in mortality due to stroke, a 9 per cent reduction in mortality due to CHID, and a 7 per cent decrease in a11-case mortality. Barriers to prevention include cultural norms; insufficient attention to health education by the health care practitioners; lack of reimbursement for health education services; lack of access to places to engage in physical activity; larger serving of food in restaurants; lake of availability of healthy food choices in many school, worksites, and restaurants; lack of exercise programmes in schools; large amount of sodium added to food by the food industry and restaurants.

Overcoming the barriers will require a multi-prolonged approach directed not only to high-risk populations but also to communities, schools, worksites and the food industry.

Community service organisations can promote the prevention of hypertension by providing culturally sensitive educational messages and life style support services and by establishing cardiovascular risk factor screening and referral programmes.

Dr M Shahidullah
The Author is an Assistant Professor, Department of Epidemiology.

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