Epidemiology of Cardiovascular Diseases Flashcards
CHD Pathology: Atherosclerosis
Atheroma plaque made, mainly of lipids starts to occlude the lumen of an artery
Atheroma plaque ruptures and triggers clotting
Results in a thrombus: CHD IS CAUSED BY ATHEROMA AND THROMBOSIS
What causes an acute MI?
If not reopened, the portion of myocardium supplied by that artery will die, causing an infarction.
Depending on the size and other phenomena, the patient may die suddenly or suffer a heart attack, we call it an acute myocardial infarction.
CHD: Typical pattern of disease progression
Childhood= coronary atheroma develops silently from childhood
Middle age= manifests as adult disease or death
CHD: Clinical presentations
Sudden cardiac death
Heart attack/myocardial infarction
Angina- chest pain on exertion or stress (~70% occlusion)
Progressive heart failure- shortness of breath, ankle oedema, fatigue
CHD epidemiology
CHD descriptive epidemiology:
Time, Place, Person
Time: risk increases with age
Place: CHD most prevalent in eastern European countries, low in Mediterranean countries and Japan
Person: more prevalent in men & lower economic backgrounds
- oestrogen seems to protect against CHD but effects stop after menopause
What is a risk factor?
any characteristic which identifies a group at increased/decreased risk of disease
- doesn’t need to be independent, causal, modifiable
- e.g. age
What is a cause?
factor which itself increases risk of disease (prevalence, incidence, mortality)
Cause = biological, not sociocultural phenomenon
Low Quality of Life in CHD patients
We measure quality of life with a validated questionnaire like SF36, we can see that for all domains on which we can measure quality of life , coronary heart failure substantially decrease the scores. It measures:
Social function
Physical role limitation
Emotional role limitation
Physical function
Mental health
General health
Energy and vitality
Bodily pain
Survival following Acute MI
By 10 years only <25% will survive
Immediately only 50% survive
Half of the deaths will occur without have any chance of reaching hospital, and life saving treatment.
Survival following first admission with CHD
Survival is greatly affected by developing any form of chd. But here is shown that substantial differences in prognosis exist.
By far, heart failure has a huge impact on survival probability, greater than that observed with myocardial infarction.
Prognosis is poor in both
Five Year survival after hospital admission- Heart failure worse than common cancers
Heart failure is a common occurrence after developing clinical coronary heart disease
And we can see here that 5 year survival of patients in heart failure is actually worse than many very lethal cancers.
It is only beat by lung cancer, as the big killer.
Cardiovascular Diseases
Cardiovascular diseases count for about 26% of all UK deaths
The largest single cause is CHD, followed by stroke
Estimated 7+ million people in the UK living with CVD
Estimated 42,245 die under the age of 75 every year
CHD is a big problem for the UK
70,000 deaths UK annually, 23,000 premature (<75 years)
CHD accounts for 16% of all male and 10% female deaths
2.3 million living with CHD
relatively high mortality rates internationally
2.5 million years of life lost annually
£6.8 billion costs NHS costs
CHD is a big problem for the NHS (REFERENCE)
200,000 Myocardial Infarctions (MIs) per year
30,000 out of hospital cardiac arrests (survival <1 in 10)
Almost 1 million have survived a heart attack
CHD PREVALENCE ~ affects 2.3 million people in UK
(about 1/3 middle-aged & elderly people)
NHS ACTIVITY ANNUALLY (approximate figures)
GPs see 1million individuals
Hospitals admit half a million CHD patients
3.5% NHS admissions UK men, 1.5% UK women
97,000 get angioplasty, & 16,000 CABG (bypass graft)
Describe the iceberg effect
People mostly see the visible part of the problem, like MI admissions, incredible attractive stories of life saved by the latest and costlier gadget, or the misery of people mistreated by the overstretched health system.
But a really bigger monster lurk in the darkness, the huge amount of disease not known to the health system, and those healthy people but with risk factors, slowly building up their plaques, waiting for clinical chd to appear.
A huge amount of disease is hidden, but contributing to maintain CHD as the first killer in our society.
Five year CHD death rates in British men aged 35-64 (BRHS)
British regional heart study found three main risk factors of CHD in men:
Found that most of the variation in CHD mortality can be explained by:
Smoking status
BP
High or low cholesterol
Main factor for acute MI is
DIET
Prevention
PRIMARY PREVENTION = (before disease presents)
SECONDARY PREVENTION = (reduce complications) – if already have symptoms
TERTIARY PREVENTION = (rehabilitation)
CHD characteristics
CHD has a long asymptomatic phase and the a shorter clinical phase
When we start with symptoms, we know that death is ahead.
This tends to occur at middle age when the symptom threshold has been crossed
But remember that many will experience just death as their first symptom.
What we can do with secondary prevention is improve things, and we can postpone death and control symptoms. But again, peoples dying suddenly will not benefit at all.
Primary Prevention
Prevention in people who are free from CHD.
2 Methods:
Identify high risk subjects
Reduce risk in entire population
High Risk approach:
High Risk Approach
We can estimate the risk of developing chd at the individual level with good enough accuracy to recommend its use. By assesing the presence or absence of several patients characteristics, we can estimate the probability of a major event within a certain period.
Categorise patient by key risk factors e.g. sex, age, diabetes status, smoker, BP and cholesterol
QRISK2 score is used to identify subjects with 10 year CVD risk of 10% or more, it uses:
-age and sex
-ethnicity
-deprivation
-systolic BP
-BMI
-BP treatment
-ratio total : HDL cholesterol
-cigarette smoking
-CKD / RA / AF
-diabetes
Population Approach
rather than focusing on specific high risk individuals:
Try to create a healthier environment for: Deprived, unemplyed, smokers, poor housing, diet.
You try to reduce risk factors in the entire population.
Eg you try and reduce the blood cholesterol level for the entire population.
Blood Pressure and CHD risk
Risk of CHD is highest for those with high systolic BP
But very few people in the population have BP that high:
Most people have much lower BP
But if we plot the distribution of blood pressure values we see that most of the population lies in the are of lower risk, and the number of deaths is higher as well at lower blood pressure values.
So more CHD occurs in people with only slightly elevated BP, this is because this is where most of the population are.
This shows the importance of a population level approach as a high risk level approach wont help the majority of people
NICE Guidance
Prevention of cardiovascular disease at population level
Main messages are:
Evidence base for population prevention is surprisingly strong:
meta-analyses & natural experiments
Potentially big disease reductions in diease resulting in
COST SAVING, RAPID, EQUITABLE, ACCEPTABLE
This is done by altering any upstream determinant that affects the downstream causes of disease eg:
Food ⇒ Salt ⇒ Blood Pressure
Food ⇒ Sat Fats ⇒ Cholesterol
Food ⇒ Trans Fats ⇒ Cholesterol
Soft drinks sugar tax
Positive results in Mexico
Challenges
We know the major factors which cause CHD in practice
Need to understand reasons for social and ethnic differences
Implementing prevention in clinical practice
Implementing population-based strategies for reducing CHD risk
Controlling epidemic in developing world
