Coronary restenosis refers to the re-narrowing or reoccurrence of blockage in a coronary artery that has previously been treated with a procedure such as angioplasty and stent placement. Angioplasty is a procedure used to open narrowed or blocked arteries by inflating a balloon-like device to widen the artery, and a stent may be placed to help keep the artery open.
Restenosis can occur when the artery becomes narrowed again due to various factors, including the growth of scar tissue inside the artery, inflammation, or the formation of new plaque. Restenosis can lead to recurrent symptoms of chest pain (angina) or other complications.
To help prevent restenosis, doctors may recommend lifestyle changes such as quitting smoking, adopting a heart-healthy diet, exercising regularly, and taking medications to manage risk factors such as high cholesterol, high blood pressure, and diabetes. In some cases, additional treatments or procedures may be necessary to address restenosis, such as repeat angioplasty, stent placement, or bypass surgery. It's essential for individuals who have undergone coronary artery procedures to follow their healthcare provider's recommendations for monitoring and managing their heart health to reduce the risk of restenosis.
Arrhythmias are abnormal heart rhythms that can occur when the electrical impulses that coordinate the heartbeats are disrupted. There are different types of arrhythmias, including:
1. Atrial Fibrillation (AFib): This is the most common type of arrhythmia and occurs when the heart's upper chambers (atria) beat irregularly and out of sync with the lower chambers (ventricles).
2. Supraventricular Tachycardia (SVT): SVT is a fast heart rate originating above the ventricles, often in the atria.
3. Ventricular Tachycardia (VT): VT is a fast heart rate that starts in the heart's lower chambers (ventricles).
4. Ventricular Fibrillation (VFib): VFib is a life-threatening arrhythmia where the ventricles quiver instead of pumping blood effectively.
5. Bradycardia: This is a slow heart rate, usually below 60 beats per minute.
Arrhythmias can be caused by various factors, including heart disease, high blood pressure, diabetes, smoking, excessive alcohol consumption, stress, certain medications, and structural abnormalities in the heart. Some arrhythmias may not cause any symptoms, while others can lead to symptoms such as palpitations, dizziness, chest pain, shortness of breath, and fainting.
Treatment for arrhythmias depends on the type and severity of the condition. It may include lifestyle modifications, medications, medical procedures like cardioversion or ablation, or implantation of devices like pacemakers or implantable cardioverter-defibrillators (ICDs) to help regulate the heart's rhythm.
If you experience symptoms of an arrhythmia or have been diagnosed with one, it's important to work closely with your healthcare provider to determine the best treatment plan and management strategies to help control
2. Objective of the course
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Introduction to study design
Describe the basic concepts of descriptive studies
Describe when and how to carry out common descriptive studies
Describe the limitations and strength of Descriptive studies
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There are ample of health problem in the community which need
evidence based answer
Planners and decision makers also need evidence as a resource based
on magnitude and factors causing disease for prevention and control
Health professionals and researchers need evidence to answer why
and how the disease occurs
Thus, all need research . . . appropriate study design
Introduction
4. Introduction
Research design is the overall plan which connect the conceptual
research problems to the pertinent research outcome
Study design is action plan which portray the strategies and tool
to answer the research question
Study Design articulates what data is required, what methods are
going to be used to collect & analyze data, & how all of these are
going to answer your research question
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5. Introduction …
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Epidemiology is broadly categorized into descriptive and analytical
=> Corresponding action plan /design/ exist
Broad categories of epidemiological studies: according to their
focus of investigation
1. Descriptive studies: focus on the distribution of disease /person,
time and place/
2. Analytic studies: focus in elucidating (ማብራራት) the
determinants of disease /analyze cause effect relationships/
6. Introduction . . .
Purpose of Epidemiological Studies
Descriptive study Analytic Study
Characterize disease occurrence
by person, time and place
Generate hypothesis
Dealing with population
- Correlational or ecological
Dealing with individuals
- Case report
- Case series
- Cross sectional
survey/Prevalence study
Concerned with the search for
causes and effects relationships
Test hypothesis about association
between exposure and outcome
Observational studies
- Case-control
- Cohort
Intervention studies
- RCT
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8. Descriptive Epidemiology
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Description of disease occurrence by person, place and time
Not intended to asses causality
The Purpose of descriptive epidemiology is to quantify amount
and characterize the distribution of disease within a population.
Thus, in other words to identify health problems and patterns of
disease occurrence
9. Summary on Purpose of Descriptive Epidemiology
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Trend analysis
Basic to health policy
- Measuring health status
- Assessing needs
- Identification of priorities
- Health planning and evaluation
Cue about cause
10. Descriptive study designs …
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Describe the person, time and place of health event occurrence
Descriptive studies generally precede analytic studies,
Descriptive information is important to generate hypothesis that
should be tested by analytical study designs
Thus, descriptive studies often help to generate hypotheses about
cause and effect relationship
11. Descriptive study designs …
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Person
Since disease does not occur at random:
What kinds of people tend to develop a particular disease, and who tends
to be spared?
What’s unusual about those people?
-Age,
-Sex,
-Race/Ethnicity,
-Social class,
12. Person…
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Age
the most fundamental factor to consider when describing disease
occurrence
The incidence of most chronic diseases increases with age
However, the incidence of many infectious diseases is highest in
childhood
13. Person…
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Sex:-biological and non-biological factors related to sex have disease risk.
In all developed countries, life expectancy is higher in females than males
– principally due to lower heart disease mortality
However, many chronic diseases occur more frequently in women
(depression, lupus, etc.)
As lifestyles continue to become more similar, a question is whether
mortality rates will become more similar? (i.e. environmental vs biology)
14. Person…
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Race/Ethnicity – difficult to define, and to identify which characteristics
may relate to disease occurrence
- Remarkable variation exists in rates of disease occurrence across racial and
ethnic groups
- Genetics?
- Socioeconomic status(SES)?
- Environmental exposures?
- Access to health care?
- Lifestyle factors, nutrition, …. ?
15. Person…
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Social class –Despite its unreliability, SES is consistently
associated with mortality in a gradient fashion
Example:
Occupation
Education
Area of residence
Income
Lifestyle
16. Place
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Investigation by place includes:
Across countries (international)
Within country variation
Urban/rural differences
Localized areas
17. Place…
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Infectious and chronic diseases show great variation from one
country to another
Some differences may be attributed to:
- Climate
- Cultural factors
- Diet
- Genetics
18. Place…
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Some differences in disease occurrence between urban and rural
locations may be attributed to:
Diet
Physical activity
Housing conditions (i.e. lead paint)
Crowding (i.e. spread of infection)
Pollution
19. Time
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Since disease does not occur at random:
How does disease frequency change over time, and what other
factors are temporally associated with those changes?
The occurrence of health-relate events can vary by time:
Secular trends
Cyclic fluctuations (periodic)
Point epidemics
20. Time…
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Secular trends
refer to gradual changes in disease occurrence over long periods of
calendar time.
Example: Death from communicable diseases has been declining
where as deaths from non-communicable diseases has been
raising in some developing countries
Cyclic fluctuations /periodic/
refer to shorter-term increases and decreases in disease occurrence
over a period of years, or within a year
21. Descriptive Study Designs
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Studies based on individual level information
Case reports
Case series
Cross sectional surveys
Studies based on population level information
Ecologic/correlational (aggregate) studies
22. 1. Case Reports
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Careful and detailed report by one or more clinicians about the profile
of a single patient
Purpose of case report
- Document unusual medical occurrences
- Can provide clues in identification of a new disease or adverse effects of
exposures (i.e. case report gave the clue OC use increases the risk of venous
thromboembolism)
Case report is compiled from patient history, physical examination
and Laboratory investigation, radiology investigation, Treatment,
Outcome, etc.
23. Case report…
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A group of physicians present a careful and detailed profile of a
single case which has not been seen before or change in natural
history of disease
This may provide a clue as there is
An emergence of new disease
A change in the natural history of a disease
A change in the agent character
Emergence of new strain
24. Case report…
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Limitations of Case report
No appropriate comparison group
Cannot be used to test for presence of a valid statistical association
Since based on the experience of one person:
-presence of any risk factor may be purely coincidental
-not a true epidemiologic design
25. 2. Case Series
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Description of clinical/epidemiologic characteristics of a number
of patients (usually 5-12) with a given disease
Collection of individual case reports occurring within a fairly
short period of time
Purpose of case rseries
Similar to case report
Document unusual medical occurrences
Can provide clues in identification of a new disease or adverse
effects of exposures
Upcoming of epidemic
26. Case series…
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Strengths of case series:
Used as an early means to identify the beginning or presence of an
epidemic
Can suggest the emergence of a new disease (i.e. AIDS)
27. Case series…
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Limitations of case series:
Lack of an appropriate comparison group
Cannot be used to test for presence of a valid statistical association
Not a true epidemiologic design
Studies are prone to atomistic fallacy (opposite of ecological
fallacy) –impossible to generalize the result to population
Example: At individual level a high income may be associated with
lower rate of suicide but this does not mean that rich societies have a
lower rate of suicide
representativeness of cases???
28. 3. Cross-Sectional Studies
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Purpose of cross-sectional study
Snapshot of the health status of population at a certain
point/cross section/ in time
For each subject, exposure and disease outcome are assessed
simultaneously at cross section of time (hence, called a
“prevalence study/survey”)
Can also used to compare prevalence of outcomes among
exposed and non-exposed => Analytic characteristics
29. Cross-Sectional study …
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Strengths:
Provides prevalence estimates of exposure and disease for a well-defined
population such as burden of disease, risk factors, coverage of
interventions, health service utilization, knowledge, attitude and
practice
Easier to perform than studies that require follow-up (hence relatively
inexpensive)
Can evaluate multiple risk (and protective) factors and health outcomes at
the same point in time
30. Cross-Sectional study …
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Strengths:
May identify groups of persons at high or low risk of disease
Can be used to generate hypotheses about associations between
predictive factors or exposures and disease outcomes
31. Cross-Sectional study …
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Limitations of cross-sectional study:
Prevalent rather than incident (new) cases are used
Can not show strong cause and effect relationship
- Statistical significance
- Temporal sequence b/n exposure and disease cannot be
established
* i.e. Which came first, chicken or the egg?
Cross-sectional study will over represent cases with long duration &
under represent with short duration of illness
People who died of the disease are missed in cross-sectional study
32. Cross-Sectional Studies…
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Example:
Respiratory problems
Yes No Total
Smoking Yes 70 50 120
No 30 70 100
Total 100 120 220
Prevalence of smokers among respiratory problems
/prevalence of exposure/
=70 x100=70%
100
Prevalence of respiratory problems among smokers
/prevalence of outcome/
=70 x100=58.3%
120
33. Analysis in Cross sectional study
Descriptive statistics , chi-square, regression (linear, logistic)
Measure of association like Odds ratio/prevalence ratio…the
prevalence of the disease is higher among those exposed
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34. 4. Correlational/ecological studies
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Purpose of correlational or ecological studies
Uses data from entire population to compare disease frequencies
- between different groups during the same period of time, or
- in the same population at different points in time
Does not provide individual data, rather presents average exposure
and outcome in the community level
Cause could not be ascertained or measured
Correlation coefficient (r) is the measure of association in
correlational or ecological studies
35. 4. Correlational/ecological studies…
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Example:
- Average per capita fat consumption and breast cancer rates
compared between countries.
- Comparing incidence of dental carries in relation to fluoride content
of the water among towns in the rift valley.
- Mortality from CHD in relation to per capita cigarette sales among
the regions of Ethiopia.
37. Forecast of Cancer Deaths
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Forecast of cancer deaths if present trends continue
(Data from the American Cancer Society)
38. Possible Reasons for Changes in Trends
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Artefactual
Errors in numerator due to
Changes in the recognition of disease
Changes in the rules & procedures for classification of causes
of death
Changes in the classification code of causes of death
Changes in accuracy of reporting age at death
Errors in the denominator due to
Error in the enumeration of the population
39. Possible Reasons for Changes in Trends …
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Real
Changes in age distribution of the population
Changes in survivorship
Changes in incidence of disease resulting from
Genetic factors
Environmental factors
40. Correlational/ecological studies …
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Strength of correlational/ecological study
can be done quickly,
inexpensively, and
often using available data (routine records and reports– e.g.
death rates, per capita income, national food consumption…)
41. Correlational/ecological studies …
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Limitation of correlational/ecological study
Inability to link exposure with disease
- Data on exposure and outcome are not linked at the individual level; association
found with aggregate data (average values) may not apply to individuals (Prone to
ecological fallacy)
Lack ability to control effects of potential confounding factors.
It may mask a non-linear relationship between exposure and
disease.
E.g. non-linear relationship in alcohol consumption and mortality from
Congestive Heart Disease
42. Assignment
1. Search research article on each design and explain
how appropriate for the research question, how is the
design outlines the strategies and tools to answer the
question?
2. Write tree research titles which need each study
design
Present to class next session !!! (5 minute for each student)
Do not copy from each other
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