EPIDEMIOLOGY OF CORONARY HEART DISEASES(CHD)

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EPIDEMIOLOGY OF CORONARY HEART DISEASES(CHD)
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The salient epidemiological observations about
CHDs are

• Large population differences in CHD incidence and
  mortality rates
• Strong correlation between population differences
  In CHD rate and population differences in mean
  level and distribution of RFs especially lipids.
• Within population , a strong and continuous
  correlation between several RFs (S.Ch, BP,
  Smoking) and future risk of CHD

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• Tracking of CHD RFs among children into adulthood
• Incidence and RFs of CHD in migrants rapidly
  approached level of adopted population
• Trends in CHD mortality rate , case fatality
  rate, and incidence occur over very short period
  (5-10 years)

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• The decline in CHD mortality rate seen in
  industrial countries include all ages, both
  sexes, and all races
• The above decline is associated with decline in
  death rate , from stroke, all CVDs, and non-CVDs

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• RCTs found direct effect of decrease in RFs on
  subsequent disease rate. Prospective studies
  found that established RFs and associated health
  behavior can be safely modified
• Epidemiological evidences are consistent with
  clinical and laboratory findings about causes and
  mechanism of atherosclerosis , which underlies
  the manifestation of CHDs

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Risk Factors of CHDsDyslipidemia

• Hypercholesterolemia is the most specific and the
  most essential factor
• There is a strong correlation between amount and
  duration of lowering S.Ch with decreased risk of
  CHD
• Lowering S.Ch is not associated with increase in
  mortality from non-CHDs

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Dyslipidemia

• LDL-c is a major component of T.Ch, and
  positively associated with CHD risk. It is
  affected by changes in diet and weight
• HDL-C is negatively associated with CHD risk. It
  is affected by exercise, weight, and smoking. It
  is higher in women
• The role of TG is less consistent. It is
  positively associated with T.Ch, and negatively
  with HDL-C level.

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Hypertension

• It is a strong RF especially in populations with
  high prevalence of CHDs
• SBP is better predictor of CHD events than DBP
• Life-style measures are more effective than mass
  medication in management of mild HT

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Cigarette Smoking

• RR is about 2 , higher in young and in population
  with high prevalence of CHD
• Cessation of smoking is important in primary and
  secondary prevention of CHDs
• Positive association between CHD risk and amount
  (but not duration) of smoking
• Passive smoking also increases CHD risk
• The risk is mediated mainly through increased
  plasma fibrinogen

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Smoking Cessation Measures

• Personal advice, smoking cessation clinic, and
  nicotine withdrawal therapy were tried for
  smoking cessation with poor results.
• The following were tried for smoking cessation
  with strong effects
• Social pressure, prohibition of smoking in public
  places and work, restricted advertisement, and
  heavily taxed cigarette trade.

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Diabetes Mellitus

• Diabetics have very high risk which is equal in
  men and women
• It removes the relative protection of
  premenapausal women
• Insulin resistance is associated with HTG, low
  HDL-C, and high BP

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Obesity

• It increases risk of CHD, stroke, and other CVDs
• It is associated with DM, HT, high TG, high TCh,
  and low HDL-C
• Central obesity is particularly more dangerous

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Physical Inactivity

• CHD epidemic is associated with decreased
  physical activity at work and home
• Physical activity is difficult to be measured
• Exercise can decrease BP, weight , and improves
  lipid profile
• Even light exercise as walking is beneficial

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Other Risk Factors

• Male Sex CHD are 2 times more frequent in males
• Positive family history aggregation of CRFs or
  increased susceptibility to a particular RF
• Dietary factors the amount of fat, saturated
  fat, and cholesterol in the diet increases CHD
  risk. High consumption of fish and plant food
  offer protection

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• Natural antioxidants lipid soluble (vitamin E,
  B-carotene) and water soluble (vitamin C,
  flavonides) decreases CHD risk
• Haemostatic factors
• Hyperfibriniginemia
  
• High coagulation factor VII
  
• Impaired fibrinolytic activity
• High PAI-1

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• Oral Contraceptives through
• Increases body weight, BP and PAI-1
• Decreases HDL-C level
• Altering blood coagulability , platelet
  function, fibrinolytic activity, and integrity of
  vascular endothelium
• Alcohol intake takes J shape curve with CHD risk

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• Stress and type a personality Increased
  sympathetic activity lead to increase
  catecholamine release, which will increase BP,
  PR, FFA, increases myocardial O2 demand, deceases
  O2 supply and alter platelet function
• Socioeconomic status in developed countries, the
  association is inverse
• In developing countries the association is
  positive
• Job characteristics perceived job stress, role
  ambiguity, job change, unemployment, and
  retirement

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• Hyperuricemia not established
• Hyperhomocystenemia easily corrected by folic
  acid
• Hypercalcemia
• Role of trace elements exposure to antimony,
  cobalt, and lead

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• Inhalant occupational exposure carbon
  disulphide, glyceryl nitric esters
• Water hardness negative association with CHD
  risk
• Antiphospholipid antibodies anticardiolipin, and
  anticephalothin antibodies
• Infection Chlamydial pneumonia, dental
  infection, severe viral illnesses

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Manifestations of CHDsAngina Pectoris

• A major cause of disability from 4th decade
  onward
• Subjective diagnosis, with no gold standard
• Rose questionnaire, low sensitivity ,
  specificity, and positive predictive value
• Resting ECG not sensitive
• Ambulatory and exercise ECG expensive
• Radioisotope scan not practical
• Coronary angiography not practical

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• The more severe and persistent symptoms, the
  greater the risk of major coronary events
• The greater the number of indicators of
  myocardial ischemia, the more advanced the
  disease and the worse prognosis
• Various treatment procedures are palliative
  rather than curative
• PTCA is cheaper and more palliative than CABG.
  Both are not better than medical treatment
  regarding survival

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Myocardial Infarction

• 50 of MI cases are either atypical, missed, or
  misdiagnosed as seen by ECG surveys looking for Q
  or QS waves
• The following factors were found to improve
  survival
• Prevention of VF early in the attack
• Initial treatment with aspirin or thrombolytic
  agents
• Long-term treatment with aspirin, B-blockers, and
  ACE inhibiters
• Avoidance of smoking
• Rehabilitation programs
• Cholesterol lowering treatment

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Sudden death

• Definitions are variable from instantaneous death
  to death within 5 minutes, 1 hour, 3 hour, 12
  hour, 24 hour.
• 70 of coronary deaths occurred outside the
  hospital. This led to
• development of mobile CCU
• Para-medical services
• population training programs in resuscitation

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• 20-40 of potential coronary deaths had no
  history, symptoms, or autopsy findings of any
  diagnosis
• Autopsy studies found that sudden death could
  also be due to pneumonia, valvular heart disease,
  or alcohol overdose
• 50 of all deaths occurring within 28 days of
  severe chest pain occur within 2 hours of onset
  and mostly within very few minutes

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Chronic Heart Failure

• It account for small proportion of deaths, but
  increasing
• Its prevalence is increasing because of increase
  aging and increase in survival from CHD
• It follows history of MI or myocardial ischemia
  at many occasions

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• Admission for HF increases with increased age,
  increased number of admissions for other coronary
  events and with DM
• It is a significant contributor to hospital cost
• ACE inhibiters are beneficial in increasing
  survival

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Inter-relationship of various CHD manifestations

• One type of CHD increases risk of other
  manifestations
• 20 of CHD victims have sudden death as a first
  manifestation
• More than 50 of coronary deaths and MI have
  history of AP or MI
• MI may terminate or initiate AP
• Myocardial ischemia on exercise test after MI
  indicate high risk of death or re-infarction

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• Women have lower rates of sudden death and MI
  than men, but have almost similar rates of AP
• Women have lower rates of CHD mortality than men
• A PARADOX those admitted for coronary emergency
  without previous history have worse prognosis
  than those who have positive history

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Prevention of CHDsPrimordial Prevention

• 1. National policies and programs on food and
  nutrition
• 2. Comprehensive policies to discourage smoking
• 3. Programs for prevention of HT
• 4. Programs to promote regular physical activity

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• The strategy is to introduce population wide
  interventions to lower population levels of
  smoking, obesity, saturated fat consumption, and
  salt intake.
• The strategy is to maintain health promoting
  diet, social and economic conditions which
  support non-smoking and physically active
  life-style

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Specific actions1. Tobacco control

• Political commitment and support
• Special emphasis on the control among women,
  children, and adolescents.
• Effective health education
• Legislations and implementation of these
  legislations
• Role model by health professionals and school
  teachers
• Strengthening of cultural and religious values
  against smoking

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Examples of Legislations

• Banning smoking in public places, schools, and
  health care facilities
• Banning vending machines and selling cigarettes
  to children
• Banning of tobacco advertisement and promotion
• Preventing new investment in the development of
  tobacco industry
• Increasing taxation on tobacco product
• Appropriate warning labels

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2. Physical Activity

• Activities should be feasible and able to be
  incorporated into daily life
• Encouraging sports activities at schools and
  workplace
• Formulation and use of guidelines on physical
  exercises
• Changing the misconception of both women and
  community about obesity through health education

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3. Nutrition and dietary modification

• It should cover all aspects of food chain from
  production to consumption
• Multi-sectoral collaboration is essential
  (agricultural, trade, industry, education,
  health)
• Health education and specific legislations are
  basic components

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Dietary Guidelines

• A balanced intake of calories
• A reduced salt content of the diet
• A reduced total saturated fat intake
• A rise in the consumption of fruits and
  vegetables
• Prevention of unhealthy dietary habits and
  stopping the cultural invasion of fast food
• It is necessary to strengthen the role of the
  school health curriculum which should cover the
  knowledge and attitudes needed for CVD prevention