25. General pathophysiology and classification of systemic hypertension – age and blood pressure

Page created on October 6, 2018. Last updated on May 24, 2019 at 18:42

Systemic hypertension is defined as the state where the resting blood pressure is higher than 140/90 mmHg, although anything above 135/85 is a “high normal”. Hypertension is a very common disease and often presents without symptoms, which means many cases go undiagnosed for a long time. It is still a dangerous disease, which is why it’s often called “the silent killer”. A small increase in blood pressure gives a rapid increase in cardiovascular mortality.

A hypertensive crisis is an umbrella term for medical emergencies where the blood pressure is above 180 mmHg systolic or 120 mmHg diastolic. There are two subtypes: hypertensive emergency, where there is ongoing organ damage and the BP must be lowered immediately, and hypertensive urgency where there is no ongoing organ damage. In hypertensive urgencies is it not necessary to decrease the blood pressure immediately but rather within 24 – 48 hours.

There can be isolated systolic or diastolic hypertension, where only the systolic or diastolic pressure is increased, but it’s most common to have both increased.

It’s important to keep in mind that “white coat hypertension” also exists, which is an increase in blood pressure that only occurs when the patient is in the hospital or around a doctor.

Recall that the pulse pressure is the difference between the systolic and diastolic blood pressure. Therefore, can isolated systolic hypertension be referred to as “hypertension with increased pulse pressure”.

We usually see an isolated systolic hypertension in cases where the blood volume is increased, like:

  • Decreased elasticity of the arteries (in aging)
  • Increased cardiac output
    • Hyperthyroidism
    • Fever
    • Arterio-venous fistula

We usually see an isolated diastolic hypertension in hypothyroidism only.

Systolic and diastolic hypertension together is seen in cases where the arterial resistance is increased, like in arteriosclerosis due to atherosclerosis.

Blood pressure usually follows a day and night cycle. In healthy people the blood pressure “dips” more than 10% during the night. These people are called “dippers”. In people where this dip doesn’t happen, the “non-dippers”, the risk for cardiovascular disorders is increased, even if their blood pressure isn’t elevated in rest.

Hypertension can either be primary (also called essential) or secondary. Primary hypertension accounts for 95% of cases and involves those cases where there is no clear etiology. Secondary hypertension occurs due to a well-defined underlying cause but accounts for only 5% of cases. We’ll look at them in their own topics.

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