Blood Pressure and CVD Risk

Blood Pressure and Absolute Cardiovascular Disease Risk

In Australia the risk of an adverse cardiovascular disease (CVD) event in the coming 5 years is assessed using the FRE (Framingham Risk Equation; Anderson and colleagues 1991). This is a predictive equation borne out of the Framingham Heart Study, which started in 1948. You can read about the Framingham Heart Study by clicking here.

The National Vascular Disease Prevention Alliance recommend completing a Framingham risk assessment for anyone aged 45 to 74 years of age (or from the age 35 if your patient is of Aboriginal or Torres Strait Islander background).

Blood Pressure is just a small part of CVD risk but my plan is to focus on one aspect at a time. Remember that in real life patients develop clusters of risk factors which may be additive. Moderate reduction in a range of modifiable risk factors (see below) may be more effective than just focussing on BP for example. 

But First--Back To Basics!

Blood pressure is the force of circulating blood against the arterial walls. The components to a heart beat include--systole when the heart contracts--and diastole when it relaxes and fills with blood. During systole the blood pressure is at its highest (the systolic reading) and during diastole it is at its lowest (the diastolic blood pressure). When we attach a cuff to a patient's arm we are recording the pressure in mm of Hg that their blood exerts against the brachial artery walls.

For elderly or diabetic patients BP must be recorded in both the sitting and standing position to detect autonomic dysfunction/ orthostatic hypotension.

Individual cardiovascular risk for each patient determines management--not just the blood pressure reading.

Classification and follow up of BP levels in adults:

normal <120/ <80 (recheck in 2 years)

...from here on the grades jump by 20 mm Hg systolic and by 10 mm Hg diastolic...so if you remember the first one, you can recall the others in an exam...

• high normal       120-139 / 80 - 89             (recheck in 1 year)
• Grade 1             140- 159/ 90 - 99             (recheck in 2 months)
• Grade 2             160- 179/ 100-109           (recheck in 1 month)
• Grade 3            ≥180 / ≥ 110                      (reassess or refer in 1 to 7 days)

and isolated systolic hypertension  >140 / < 90
and isolated systolic with widened pulse > 160 / < 70

When your patient's systolic and diastolic fall into two different categories, use the HIGHER of the two to determine your treatment.

Always consider the ubiquitous SNAP (smoking, nutrition, alcohol, physical activity)

Only start anti-hypertensive treatment straight away if the patient is at high risk of CVD.
Below is a poem to help you remember what factors put your patient in the “high risk” group (and the blue table below contains the actual details):

Start with SNAP at the beginning
And you’re already winning

BUT

Diabetics who are aged

with ACR above the range
need antihypertensives
as a main counteroffensive.
If GFR be 45
with proteinuria too high
treatment will be a breeze
with  ACE or ARB to slow disease.
Total fat over 7.5 ought to be treated to survive
and if high lipids are a mystery
don’t forget the family history!

increased cardiovascular risk

 
*Taken from page 7 "Guidelines for the Management of Absolute Cardiovascular Disease Risk." National Vascular Disease Prevention Alliance 2012)

The presence of any of these factors, or having BP persistently over 180 systolic or 110 diastolic, means you don’t do the Framingham calculation, but go straight ahead and consider modifiable risk factors and while initiating pharmacotherapy.

Summary of blood pressure recommendations

Ø  Consider treating any BP over 160/100 regardless of risk

Ø  Treat ant BP in a person with moderate risk if they have

o   A positive family history of premature CVD

o   “at risk” ethnic background (ie Sth Asian, Middle Eastern, Pacific or SE Islander, or ATSI)

Ø  Treat any BP in a person at high risk (see the blue table above*)

The Framingham Risk Equation underestimates risk in:

Ø  Aboriginal and Torres Strait Islanders

Ø  Adults with diabetes (under age 60)

Ø  Adults over age 74

The usefulness of the FRE in obese adults is uncertain

BP targets for specific populations

Ø  Diabetics ≤ 130/80

Ø  Albuminuria (urine ACR > 2.5 male or 3.5 female)  ≤130/80

Ø  Chronic kidney disease (CKD) < 140/90 (Note that this target as recommended by the Stroke Foundation and Kidney Health Australia is higher than that recommended by the Heart Foundation who suggest that a target of < 130/80 should be achieved in patients with CKD)

Here is a very basic way to remember these targets...

The 13 of 130/80 is hidden in the word diabetes and albuminuria:

The 140 of 140/90 is hidden in the initials CKD: 

 

Modifiable risk factors:

(Important part of assessment of CVD risk)

Remember “SNAP BBL”

Smoking, Nutrition, Alcohol, Physical activity, BMI & waist circumference (the two always go together), Blood Pressure and serum Lipids.

Non-modifiable risk factors

Remember "NAFS"

Non modifiable factors=Age & sex, Family Hx of premature CVD and Social history including ethnicity and socioeconomic status.

To calculate CVD riak use the online calculator www.cvdcheck.org.au or from www.heartfoundation.org.au

The following blogs will address evaluation of patients with confirmed hypertension, followed by management, and aspects of anti-hypertensives, including case studies and questions.