Hypertension: Causes and Health Effects of High Blood Pressure [Biology, MCAT, USMLE]

In this quick, easy lesson, we learn about hypertension, also known as high blood pressure, for USMLE and medicine. Hypertension is defined numerically as >140/90 and more recently as >130/80.

Primary Hypertension vs Secondary Hypertension

90% cases of hypertension is primary. Primary hypertension means that the cause of hypertension is not clear.

10% cases of hypertension is secondary, meaning that hypertension is a result of another underlying condition or medical problem, like chronic kidney disease.

Risk Factors of Hypertension

Risk factors of hypertension include a family history of hypertension, high salt intake, obesity, alcohol, and physical inactivity. African Americans also have a higher risk for hypertension due to genetics.

Risk of Hypertension By Race: African Americans > Hispanics > Caucasians/Whites > Asians

Sodium and Hypertension: Why is too much salt bad for you?

Too much salt is bad for our health, but why? Let’s learn about the role high sodium plays on hypertension.

Salt and Hypertension Mechanism

High sodium intake –> Higher P osmolarity –> Increases ADH –> Increases Water retention –> [Na] Sodium concentration in blood stabilizes at 140 meq/L

When water retention increases –> Higher ECV (Effective Circulating Volume) –> Increases Blood Pressure

Hypertension Effects

Atherosclerosis: lipid plaques develop in blood vessels

‘athero’ and ‘sclerosis’ –> vessels harden because of plaque buildup

Remember, that sclerosis means hardening of the walls, athero refers to arterial or vessels, and arterio refers to arteries directly.

Arteriosclerosis: Thickening of the arteries’ walls

‘aterio’ and ‘sclerosis” –> artery hardens because the walls thicken

1. Hyaline arteriosclerosis

Glassy appearing

Thickening of small arteries because of protein leakage of vessel wall because of hypertension.

Seen with aging, common with diabetes

2. Hyperplastic arteriosclerosis

Onion skin

Occurs when hypertension = severe (>120 DBP)

Malignant hypertension; blood pressure is so high that basement membranes replicate, which is hyperplasia

Can cause problems like retinal hemorrahges, exudates, or papilledema. Blood vessels can lead to ischemia.

3. Arteriolar Rarefaction

Lose arterioles. Because of hypertension, arterioles close off and get resorbed (gradual breakdown).

Hypertension Increases Pulse Pressure and Afterload.

Pulse Pressure and Hypertension

Pulse pressure increases with hypertension. Both systolic and diastolic pressure can increase. Difference between the two numbers increases because the arteries’ compliance decreases. Arteries become more stiff.

If arteries are distensible, that means the vessels are more flexible and can stretch. Blood is not as tightly packed together, so blood pressure is not as high. However, for stiff vessels, blood is tightly packed together, leading to hypertension.

Afterload and Hypertension

Afterload also increases because of hypertension. Lots of pressure on left ventricle, so left ventricle hypertrophies. On the EKG, you can see a large voltage in QRS segment.

Hypertensive Urgency vs Hypertensive Emergency

Difference between Hypertensive Urgency and Hypertensive Emergency

Hypertensive Urgency = severe hypertension but NO damage on organs yet >180/120

Hypertensive Emergency = severe hypertension WITH end-organ damage. That’s why it’s an emergency. Damaged organs include kidneys and brain, including renal impairment and neurological impairment. Cardiac ischemia can also develop. Rarely, microangiopathic hemolyic anemia MAHA is associated with hypertensive emergency. This is caused by endothelial injury leading to thrombus formation.

Malignant Hypertension is a rare, fatal form of hypertension. Blood pressure is severely elevated (>120 mmHg for distolic). Patients typically die because of rapid deterioration, renal failure, retinal hemorrhage, and ischemia.

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