Cardiovascular 2 Flashcards
Hypertension:
Chronically elevated arterial BP
How are HTN and atherosclerosis related?
HTN contributes to atherosclerosis, which interferes with endothelia, worsening HTN.
Primary HTN:
- Etiology unknown
- 90~95% cases
- Tx aimed at directly lowering BP
Secondary HTN:
Results from identifiable underlying causes (3~5% renal, 2~5% endocrine, congenital aortic narrowing), permanent cures targeting underlying cause are more effective.
Normal BP
Systolic < 120 AND
Diastolic < 80
Elevated BP
Systolic 120-129 AND
Diastolic <80
Stage 1 HTN
Systolic 130-139 OR
Diastolic 80-89
Most common, therefore most deaths occur in this category
Stage 2 HTN
Systolic > 140 OR
Diastolic > 90
Hypertensive crisis
Systolic > 180 AND/OR
Diastolic > 120
How do the heart & vasculature contribute to HTN?
(1) Excessive responsiveness to catecholamines (i.e. SNS) generally increases vasoconstriction, leading to increased HR, SV & TPR.
(2) Loss of local vasodilators such as NO (occurs w/ atherosclerosis)
(3) Excessive production of vasoconstrictors (eg: endothelin-1). Associated with injury and blood clotting (so likely to be common in vessels that are affected by atherosclerosis.
(4) Ion channel defects affecting both vasoconstriction and cardiac function
(5) Structural defects in heart or blood vessels
How does the SNS activation measured?
Plasma epinephrine levels
How does the nervous system contribute to HTN?
- Increased SNS activity
- Desensitized baroreceptors and volume receptors (esp. w/long-term high BP) or abnormal response to their signals.
How does the SNS contribute to HTN?
- Increased baseline SNS activity
- Abnormally high stress response
Pressure diuresis
In a normally functioning kidney, increased blood pressure (like from high fluid consumption) should increase urine production.
From an evolutionary perspective, the kidney is designed for…
Our Paleozoic ancestors who ate less Na+ and more K+
When excess salt is consumed…
Plasma osmolarity increases, triggering ADH release and causing water retention and more concentrated urine. In the absence of aldosterone, there is a net Na+ loss. This is usually enough to prevent changes in BP.
Pressure natriuresis kicks in when…
ADH response is not enough to prevent increased blood pressure. Elevations in renal perfusion pressure (RPP) inhibits Na+ reabsorption in the tubule, increasing sodium excretion.
Pressure natriuresis is __________ on neural or endocrine factors.
not dependent
*however, neural and endocrine factors (e.g. renin and ANP) can MAGNIFY it
Angiotensin _____ pressure natriuresis,
inhibits
ANP _____ pressure natriuresis.
augments
Pressure natriuresis
When BP rises, Na+ and H2O are excreted until blood volume is lowered enough to reduce BP intake to normal.
