Coronary Heart Disease





Coronary Heart Disease :

Coronary heart disease (syn: ischaemic heart disease) has been defined  as " impairment of heart function due to inadequate blood flow to the heart compared to its needs, caused by obstructive changes in  the coronary  circulation to the heart". It is the cause of 25_ 30  per cent of deaths in most industrialized countries. CHD may manifest  itself in many presentations: 

(a) Angina pectoris  of effort 

(b) Myocardial  infarction 

(c) irregularities of the heart 

(d) cardiac failure 

(e) sudden death. 


The coronary arteries, supply blood to the muscles of the heart.They supply oxygen and nutrients to the heart and carry carbon dioxide and other metabolic wastes from the walk  of the  heart. Coronary  heart  diseases include angina pectoris  and coronary  thrombosis. 

(a) Angina Pectoris:Sclerosis of the coronary arteries can cause " pain in the chest". This anginal pain usually  starts in the centre of the chest and spreads down the left arm. 

(b) Coronary Thrombosis or Myocardial Infarction (MI) : A clot may form in  the lumen of a  coronary artery,  it is called coronary thrombosis. Therefore, a large portion  of the heart muscle is deprived  of blood and the patient develops a " heart attack ". Anticoagulant treatment helps to prevent the formation  and extension of blood clots.

Rheumatic Heart  disease (RHD):

This  is more frequent  cardiovascular disease in India below the age of 20 years. Thus childhood  throat infection should be taken seriously. The patient may have an acute rheumatic fever, joint pains and infection of throat. Rheumatic fever may cause permanent damage of one or more values ( mitral or aortic semilunar  valves), pericarditis and myocarditis. Streptococcus (bacteria) causes RHO. Coxsackie B_ 4 _ virus has been suggested as a conditioning agent.The  risk of acute Rheumatic fever is greatest  where there is bad housing,  overcrowding  and inadequate conditions of hygiene. 





Risk factors  

The aetiology  of CHD is multifactorial.  Apart from the obvious  ones such as increasing  age and  male sex, studies have identified  several important  " risk" factors (i.e., factors that make the occurrence of the disease more probable). Some of the risk factors are modifiable, others  immutable. Presence of any one of the risk factors places an individual in a high_ risk category  for developing  CHD. The greater the  number of risk factors present, the more likely one is to develop CHD. The principal risk factors are discussed  below :









1. Smoking

Some people commit suicide by drowning, but many by smoking . A uniquely human habit, smoking  has been identified as a major CHD risk factor with several  possible  mechanisms _ carbon monoxide induced atherogenesis;  nicotine  stimulation of adrenergic drive raising  both blood pressure and myocardial oxygen  demand; lipid metabolism with fall in " protective" high_ density  lipoproteins, etc.

 The risk of death  from CHD decreases substantially  within one year of stopping  smoking  and more gradually  thereafter  until, after 10_ 20 years, it is same as that of non_ smokers.



2. Hypertension 

The blood pressure  is the single most useful  test for identifying individuals at a high risk of developing  CHD. Hypertension  accelerates  the atherosclerotic  process especially  if hyperlipidemia is also present  and contributes  importantly  to CHD.



3. Serum Cholesterol  

  It is nearly three decades since it became clear that elevation of serum cholesterol  was one of the factors  which carried  an increased  risk for the development  of myocardial  infarction. Today, there is a vast body of evidence  showing  a triangular relationship  between  habitual diet, blood cholesterol  _ lipoproteins levels and CHD.

 When we look at the various  types of lipoproteins, it is the level of low_ density  lipoproteins (LDL) cholesterol  that is most directly  associated  with CHD. While very low_ density  lipoproteins  ( VLDL)  has also been shown to be associated  with premature atherosclerosis, it is more strongly  associated with peripheral  vascular  disease  (e.g., intermittent claudication) than with CHD. High _ density  lipoproteins (HDL) cholesterol  is protective against  the development  of CHD. 


4) Other  risk factors 

(i) Diabetes  : The  risk of CHD is 2_ 3 times higher in diabetics  than in non_ diabtics. CHD is responsible  for 30 to 50 per cent  of death in diabetics over the age of 40 years in industrialized  countries. 


(ii) Genetic Factors   : A family history of CHD is known to increase  the risk of premature  death. Genetic  factors are probably  most important  determinants of a  given individual's  total cholesterol  and LDL levels. However , the important of genetic factors in the majority  of cases is largely unknown. 

(iii) Physical  Activity: Sedentary  life_ style is associated  with a greater risk of the development  of early CHD. There is evidence  that regular physical activity  exercise increases  the concentration  of HDL and decreases both body weight  and blood pressure  which are beneficial to cardiovascular health. 


(iv) Hormones : The  pronounced difference in the mortality  rates for CHD between  male and female  subjects  suggests that the underlying  basis. It has been hypertensized that hyperoestrogenemia may be the common underlying  factor that leads both to  atherosclerosis and its complications such as CHD, stroke and peripheral  vascular  disease. 

(v) Type_ A  Personality  :  Type_ A behaviour  is associated  with competitive  drive, restlessness, hostility  and a sense of urgency or impatience. Type_ A individuals are more  coronary  prone to CHD than the calmer, more philosophical  Type _ B individuals.

(vi) Alcohol : High alcohol intake,  defined  as 75 gram or more per day, is an independent  risk factor for CHD, hypertension  and all cardiovascular  diseases. The evidence that moderate alcohol  intake leads to a reduction in the risk CHD is un_ substantiated. 

(vii) Oral Contraceptives: Women using oral contraceptives have higher systolic and diastolic  blood pressure. The  risk of myocardial infarction  in women seems to be increased by oral contraceptives, and the risk is compounded by cigarette  smoking. 

(viii) Miscellaneous: The possible role of dietary  fibre, sucrose and soft water have been debated. Dyspnoea on extortion and low vital capacity have also been cited as possible risk factors. 





Prevention of CHD

  For prevention  of  CHO, following  strategies  are recommended. 

(a) Population strategy 

(i) Prevention  in whole populations 

(ii) Primordial prevention  in whole populations 

(b) Hugh _ risk strategy 

(c) Secondary  prevention 

a. Population  strategy 

Specific  interventions 

  The population  strategy  centers around  the following  key areas: 

1. Dietary  changes : Dietary  modification  is the principle  preventive strategy  in the prevention  of CHD. The WHO  Expert Committee considered the following  dietary changes to be appropriate  for high incidence  populations: 

_ reduction of fat intake to 20 _ 30 per cent of total energy intake.


_ Consumption  of saturated  fats must be limited to less than 10 per cent of total energy intake; some of the reduction in saturated  fat may be made _ up by mono and poly_ unsaturated  fats. 

_ a reduction of dietary  cholesterol  to below 100 mg per 1000 kcal per day 

_ an increase in complex carbohydrate consumption  (i.e., vegetables, fruits, whole grains and legumes) 

_ avoidance  of alcohol  consumption ; reduction of salt intake to 5 grams daily or less


2. Smoking :  To achieve the goal of a smoke_ free society , a comprehensive health programme would  be  required  which includes effective information  and education activities , legislative  restriction, fiscal measures  and smoking cessation  programmes.

3. Blood pressure: This involves a multifactorial approach based on a " prudent  diet" (reduced salt intake and avoidance of a high alcohol intake), regular physical  activity  and weight control. The potential  benefits  and the safety and low cost of this advice would justify  its implementation. 

4. Physical activity : Regular  physical  activity should be a part of normal daily life. It is particularly important  to encourage  children to take up physical  activities  that they can continue   throughout  their lives. 


PRIMORDIAL PREVENTION 

     A novel approach  to primary  prevention  of CHD is primordial  prevention .It involves  preventing  the emergence and spread of CHD risk factors and life style that have not yet appeared  or become endemic. This applies to developing  countries  by preserving their traditional  eating patterns  and life _ styles associated  with low levels of CHD risk factors. 




b. High _ risk strategy  

(i) Identifying  risk : High_ risk intervention can only start once those at high_ risk have been identified .By means of simple tests such  as blood pressure  and serum cholesterol measurement, it is  possible  to identify individuals  at special risk, Individuals  at special  risk also include those who smoke, those with a strong family  history  of CHD, diabetes  and obesity , and young women using oral contraceptives. 

(ii) Specific  advice : Having  identified  those at high risk, the next step will be to bring them under preventive care and motivate them to take positive action against all the identified  risk factors, e.g., an elevated  blood pressure  should be treated; the patient  should be helped to break the smoking  habit permanently  _ nicotine chewing  gum can be tried to wean patients  from smoking; serum cholesterol concentration should be reduced  in those in whom it is raised, etc. 

c. Secondary  Prevention 

    The principles governing  secondary  prevention  are the same as those already  set out in the above section,  e.g., cessation  of smoking, control of hypertension and diabetes,  healthy  nutrition,  exercise  promotion, etc.





























































Comments

Popular posts from this blog

Proteins

Cytoplasm

Nucleic Acids