Hypertension Flashcards
High blood pressure is a classic example of a QUANTITATIVE rather than a QUALITATIVE health problem. Explain
Not a yes/no problem but a `how much’ problem
Name 6 factors that can affect a BP reading:
- Patient Anxiety (SNS - Higher)
- Physician attitude and technique (Either)
- Instrument Bias
- Cuff Size (Smaller = Lower, Larger = Higher)
- Environment (eg. Cold, Noisy) (Higher)
- “Regression to the Mean”
True or False, in a 2012 study in the The Lancet Hypertension was found to carry the greatest global burden of disease.
True
Give a brief overview of the results of a Cohort (Longitudinal) study, and how it indicates a link between Hypertension and various CVD/related conditions.
What is meant by an observational study?
Full list of related pathologies:
- Coronary (ischaemic) heart disease
- Stroke (all types)
- Ischaemic stroke
- Haemorrhagic stroke
- Subarachnoid haemorrhage
- Heart failure
- Hypertensive heart disease
- Sudden death
- Renal (kidney) failure
- All-cause mortality
What is relative risk?
Why is it useful?
How should we word the formula when used in the context of HTN?
Relative Risk of x:
Risk of disease outcome in patients with x /
Risk of disease outcome in patients without x
Relative risk provides a good summary of the influence which high blood pressure has on cardiovascular risk across the population
Formula for RR of HTN
Cardiovascular risk in people with** **a higher BP Cardiovascular risk in people with a lower BP
Example
= 1.0 Exposure has no effect on risk
= 2.0 Exposure associated with doubling of risk
(`twice as likely’)
= 0.5 Exposure associated with halving of risk
(half as likely’) (protective’)
In practice, relative risk estimates always have associated error, which needs to be considered in interpretation
Name three common complications of HTN that will greatly enlarge the R.R.
Left ventricular hypertrophy
Proteinuria or renal impairment
Hypertensive retinopathy
Why do we sometimes consider Systolic readings to be more important in HTN measurements?
In older people, high’ systolic BP can occur with normal’ diastolic pressure (isolated systolic hypertension), and is still associated with increased CV risk
What is attributable risk?
Why is it useful?
How should we word the formula when used in the context of HTN?
Attributable risk
Cardiovascular risk in people with a higher/lower BP MINUS
Cardiovascular risk in people with a normal BP
This provides a measure of the impact of high blood pressure on the absolute risk of disease, though it is important to remember that this measure of risk varies between individuals
NB* Also known as excess risk’, risk difference’
(can also considered in the context of `attributable benefit’ of treatment)
Draw the diagram explaining how attributable risk can lead to vastly larger differences in disease risk, depending on the starting point of measurement.
e.g.
Starting CVD risk of 3 (/1000/yr) x R.R. of 2 = 6.
Attributable risk = 6 - 3 = 3 (/1000/yr)
Starting CVD risk of 20 (/1000/yr) x R.R. of 2 = 40.
Attributable risk = 40 - 20 = 20 (/1000/yr)
What conclusions can we draw from these results?
- For a given increase in blood pressure, the proportional effects on CVD risk will be similar in all patients.
- The effect of HTN on CVD risk in individual patients will be much larger if the patient is already at high CVD risk irrespective of their blood pressure (e.g older patient, with CVD already, several key risk factors etc)
- Similarly, the benefits of blood pressure treatment will be much greater in a patient who is already at high CVD risk
Given the continuing, quantitative nature of HTN, How can we most usefully delineate high blood pressure from normal blood pressure?
4 Possibilities:
1 – Symptoms?
NO - Symptoms are often generated after the damage of HTN has already taken place.
2 – Blood pressure distribution: Do people with high BP have a separate BP distribution?
NO - BLOOD PRESSURE IS CONTINUOUSLY DISTRIBUTED IN THE POPULATION: THERE IS NO CLEAR SEPARATION BETWEEN NORMAL’ AND HIGH’
3 - Relation of blood pressure to cardiovascular risk, is there a clear cutoff?
NO- THERE IS NO OBVIOUS CUT POINT IN THE ASSOCIATION BETWEEN BLOOD PRESSURE AND CVD RISK
4 – Benefits of treatment?
YES - CLINICALLY BENEFICIAL - This is the definition generally used
NB: It is an arbitrary definition, which has changed over time with growing evidence of BP lowering benefits
What are the key modifiable risk factors for HTN in the general population?
NB. Should include Alcohol and Smoking
What evidence is there to point toward a strong adult environmental impact on HTN?
- Age does not naturally correlate with higher BP in ALL cultures (notable indigenous - Yanomamo Indians)
- In migratory studies in which people are moving from low blood pressure (origin) to higher blood pressure (adoption) populations, it is shown how blood pressure patterns change (increase) to match those of the adopted population
Change generally occurs within 6 months of migration
How large are the benefits of BP reduction at 70-79 years of age?
Give an overview of the Traditional, New and Balanced view of which patient population should be the focus of lowering HTN
What are some of the main medical causes of secondary hypertension?
Coarctation of aorta
Renal and renal vascular disease
Adrenal disease
- Cortex Primary hyperaldosteronism,
Cushing’s syndrome
- medulla phaeochromocytoma
Pregnancy
Drugs especially Oral Contraceptive Pill, Hormone Replacement Therapy
