Balance Wk3 CBL Hypertension

What is essential hypertension?

Answer: Chronic hypertension without a single identifiable secondary cause.

Extra Information:

• Essential hypertension is also called primary hypertension.

• It results from interacting genetic, environmental, renal, neural, hormonal, vascular, and immune mechanisms.

What equation provides the basic hemodynamic framework for essential hypertension?

Answer: Blood pressure = cardiac output × total peripheral resistance.

Extra Information:

• Sustained hypertension requires increased cardiac output, increased total peripheral resistance, or both.

Why are the kidneys especially important for long-term blood-pressure regulation?

Answer: They regulate long-term sodium and extracellular-fluid balance.

Extra Information:

• Renal sodium handling determines how much arterial pressure is required to maintain sodium balance.

What is pressure natriuresis?

Answer: Increased arterial pressure causes increased renal sodium excretion.

Extra Information:

• Water follows sodium, decreasing extracellular-fluid volume.
• The resulting fall in venous return and cardiac output helps lower blood pressure.

How is pressure natriuresis altered in many forms of essential hypertension?

Answer: The pressure-natriuresis relationship is shifted to a higher arterial pressure.

Extra Information:

• The kidneys require a higher BP to excrete enough sodium to maintain sodium balance.

Trace how impaired renal sodium excretion can raise blood pressure.

Answer: Na⁺ retention → H₂O retention → ↑ ECF volume → ↑ blood volume → ↑ Pms → ↑ venous return → ↑ preload → ↑ cardiac output → ↑ BP.

Extra Information:

• This connects renal sodium handling directly to the Guyton venous-return framework.

How does increased blood volume affect the venous-return curve?

Answer: It increases mean systemic filling pressure and shifts the venous-return curve right and upward.

Extra Information:

• Venous return and cardiac output consequently increase.

Why can hypertension persist even if cardiac output later becomes relatively normal?

Answer: Vascular autoregulation and remodeling can increase total peripheral resistance.

Extra Information:

• Long-term hypertension therefore may become increasingly resistance-dependent.

What type of genetic disorder is essential hypertension?

Answer: It is polygenic.

Extra Information:

• Many genetic variants each contribute relatively small effects.
• There is not one single hypertension gene responsible for most essential hypertension.

What physiologic systems can genetic variation alter in essential hypertension?

Answer: Renal sodium transport, sympathetic activity, RAAS, vascular tone, and endothelial function.

Extra Information:

• Genetic susceptibility interacts strongly with environmental exposures.

How does β₁ sympathetic stimulation of the heart increase blood pressure?

Answer: It increases heart rate and contractility, increasing cardiac output.

Extra Information:

• Increased cardiac output raises BP when other variables are unchanged.

How does α₁ stimulation of arterioles increase blood pressure?

Answer: It causes arteriolar vasoconstriction and increases total peripheral resistance.

Extra Information:

• This acts on the resistance side of BP = CO × TPR.

How does α₁ stimulation of veins increase blood pressure?

Answer: Venoconstriction decreases venous capacitance and increases mean systemic filling pressure and venous return.

Extra Information:

• Increased venous return increases preload and can increase cardiac output.

How does sympathetic stimulation activate RAAS?

Answer: β₁ stimulation of juxtaglomerular cells increases renin release.

Extra Information:

• Renal sympathetic nerves also promote renal vasoconstriction and tubular sodium reabsorption.

How can excessive angiotensin II contribute to essential hypertension?

Answer: AT₁ activation causes arteriolar vasoconstriction and increases total peripheral resistance.

Extra Information:

• Angiotensin II also promotes sympathetic activity and vascular remodeling.

How does excessive RAAS activity increase blood volume?

Answer: Angiotensin II increases aldosterone, increasing distal Na⁺ reabsorption and water retention.

Extra Information:

• Increased blood volume can increase cardiac output.

Does essential hypertension always cause a high plasma renin level?

Answer: No.

Extra Information:

• Essential hypertension is heterogeneous.
• Salt-sensitive and volume-dependent hypertension can occur with suppressed circulating renin.

How can obesity contribute to essential hypertension?

Answer: Through sympathetic activation, altered renal Na⁺ handling, RAAS or mineralocorticoid activity, and metabolic and vascular abnormalities.

Extra Information:

• Obesity-associated sodium retention can shift pressure natriuresis toward higher pressures.

How can obstructive sleep apnea contribute to hypertension?

Answer: It can increase sympathetic activation.

Extra Information:

• Obstructive sleep apnea is frequently associated with obesity.

How does endothelial dysfunction increase blood pressure?

Answer: Reduced nitric-oxide bioavailability decreases vasodilation and increases relative vasoconstrictor tone.

Extra Information:

• The result is increased systemic vascular resistance.
• Oxidative stress and inflammation can worsen endothelial dysfunction.

How does vascular remodeling contribute to hypertension?

Answer: Arteriolar wall thickening and luminal narrowing increase vascular resistance.

Extra Information:

• Chronic pressure and neurohormonal signaling promote remodeling.

What relationship explains why small decreases in arteriolar radius greatly increase resistance?

Answer: Resistance is proportional to 1 divided by radius to the fourth power.

Extra Information:

• Small reductions in radius can therefore markedly increase resistance.

How does large-artery stiffness affect blood pressure?

Answer: It particularly increases systolic blood pressure and pulse pressure.

Extra Information:

• Arterial stiffness becomes increasingly important with aging.

What major lifestyle factors contribute to essential hypertension?

Answer: High sodium intake, excess body weight, physical inactivity, excessive alcohol, and unhealthy dietary patterns.

Extra Information:

• These factors interact with underlying genetic and physiologic susceptibility.

Trace the integrated pathogenesis of essential hypertension.

Answer: Genetic and environmental factors → renal, sympathetic, RAAS, and vascular abnormalities → volume retention and vasoconstriction → ↑ CO and/or TPR → hypertension.

Extra Information:

• Vascular remodeling and renal adaptation then help sustain hypertension.

What is uncontrolled hypertension?

Answer: Blood pressure that remains above the patient's treatment goal.

Extra Information:

• Uncontrolled hypertension does not automatically mean resistant hypertension.

What is apparent resistant hypertension?

Answer: Hypertension that appears resistant before nonadherence and white-coat effect have been adequately excluded.

Extra Information:

• True resistance cannot be established until pseudoresistance is addressed.

What is resistant hypertension?

Answer: BP above goal despite at least 3 antihypertensive classes at maximally tolerated doses, generally including a diuretic.

Extra Information:

• The traditional American Heart Association definition also includes controlled BP requiring at least 4 medications.

What is secondary hypertension?

Answer: Hypertension caused by an identifiable underlying disease or process.

Extra Information:

• Renovascular hypertension is one form of secondary hypertension.

What is renovascular hypertension?

Answer: Secondary hypertension caused by reduced renal arterial perfusion activating pressor mechanisms, especially RAAS.

Extra Information:

• It describes a physiologic consequence rather than merely an anatomic stenosis.

What causes of pseudoresistance should be excluded before diagnosing resistant hypertension?

Answer: Incorrect BP measurement, medication nonadherence, white-coat effect, and inadequate doses or regimen.

Extra Information:

• Excess sodium, obesity, interfering medications, and secondary hypertension should also be investigated.

How does resistant hypertension differ from uncontrolled hypertension?

Answer: Uncontrolled hypertension simply means BP is above goal, while resistant hypertension persists despite an adequate multidrug regimen after excluding pseudoresistance.

Extra Information:

• Therefore, not every patient with uncontrolled BP has resistant hypertension.

What does the Cockcroft-Gault equation estimate?

Answer: Creatinine clearance, not true GFR.

Extra Information:

• It remains commonly encountered for medication dosing.

What is the Cockcroft-Gault equation for serum creatinine in mg/dL?

Answer: CrCl = [(140 − age) × weight in kg] ÷ [72 × serum creatinine].

Extra Information:

• The resulting units are mL/min.

What historical sex adjustment is applied to Cockcroft-Gault?

Answer: Multiply the calculated value by 0.85 for females.

Extra Information:

• This is the historical Cockcroft-Gault adjustment used in the provided material.

What are important limitations of Cockcroft-Gault?

Answer: It was derived from a small, predominantly White male population and estimates creatinine clearance rather than true GFR.

Extra Information:

• Modern race-free eGFR equations are generally preferred for GFR assessment.

Why is Cockcroft-Gault still clinically encountered?

Answer: It is commonly used for drug dosing when medication labeling or trials used creatinine clearance.

Extra Information:

• Its clinical role differs from modern equations used to assess GFR.

What equation calculates measured creatinine clearance?

Answer: CrCl = urine creatinine concentration × urine flow rate ÷ plasma creatinine concentration.

Extra Information:

• Urine flow rate must be expressed in mL/min.

How is urine flow rate calculated from a 24-hour urine collection?

Answer: Twenty-four-hour urine volume in mL divided by 1440 minutes.

Extra Information:

• This converts total daily urine volume into mL/min.

Why does creatinine clearance slightly overestimate true GFR?

Answer: Creatinine is freely filtered and also slightly secreted by proximal tubules.

Extra Information:

• Creatinine is not significantly reabsorbed.

What can a properly collected 24-hour urine be used to measure?

Answer: Creatinine clearance and total urinary excretion of protein, albumin, or other solutes.

Extra Information:

• It can also help when serum-based kidney-function estimates are unreliable.

What is a major limitation of a 24-hour urine collection?

Answer: Collection error.

Extra Information:

• Missing urine makes measured excretion and clearance inaccurate.

Differentiate Cockcroft-Gault from 24-hour measured creatinine clearance.

Answer: Cockcroft-Gault estimates CrCl, while urine creatinine plus serum creatinine and urine flow calculate measured CrCl.

Extra Information:

• Neither method literally provides a direct measurement of GFR.

Why does increased dietary sodium have the potential to increase blood pressure?

Answer: Sodium retention causes water retention, expanding extracellular-fluid and blood volume.

Extra Information:

• The effect is strongest when renal Na⁺ excretion does not appropriately match intake.

Trace the hemodynamic effect of sodium retention on blood pressure.

Answer: Na⁺ retention → H₂O retention → ↑ ECF → ↑ blood volume → ↑ Pms → ↑ venous return → ↑ preload → ↑ cardiac output → ↑ BP.

Extra Information:

• This links sodium balance directly to the venous-return framework.

What is salt-sensitive hypertension?

Answer: Hypertension in which blood pressure responds particularly strongly to changes in sodium intake.

Extra Information:

• Salt sensitivity reflects differences in how the body handles sodium and volume.

Why can peripheral resistance become important after initial volume expansion?

Answer: Chronic hypertension can produce vascular adaptation and increased resistance that helps maintain elevated BP.

Extra Information:

• Hypertension can therefore persist even if cardiac output is no longer markedly elevated.

What major nonpharmacologic interventions lower blood pressure?

Answer: Weight reduction, DASH-style diet, sodium reduction, physical activity, adequate potassium when safe, and limiting excessive alcohol.

Extra Information:

• These strategies address modifiable contributors to hypertension.

When is increasing dietary potassium appropriate for BP reduction?

Answer: When it is safe given the patient's renal function and medications.

Extra Information:

• Potassium recommendations should account for hyperkalemia risk.

What is the role of smoking cessation in hypertension management?

Answer: It primarily reduces overall cardiovascular risk rather than producing a major chronic BP-lowering effect.

Extra Information:

• It remains an important nonpharmacologic cardiovascular intervention.

How does dietary sodium reduction shift the Guyton venous-return relationship?

Answer: Lower volume decreases Pms and shifts the venous-return curve left.

Extra Information:

• Venous return, preload, cardiac output, and BP subsequently decrease.

What RAAS laboratory pattern may occur in renovascular hypertension?

Answer: Increased renin and increased aldosterone.

Extra Information:

• Reduced renal perfusion stimulates renin, which activates angiotensin II and aldosterone.

Why is hyperaldosteronism from renal artery stenosis considered secondary hyperaldosteronism?

Answer: Aldosterone rises in response to increased renin and angiotensin II.

Extra Information:

• The adrenal gland is responding appropriately to an upstream stimulus.

How do renin levels distinguish primary hyperaldosteronism from renovascular hypertension?

Answer: Primary hyperaldosteronism has high aldosterone with low renin, while renovascular hypertension can have high renin and high aldosterone.

Extra Information:

• Renin suppression is a key distinction in primary hyperaldosteronism.

What electrolyte abnormality can aldosterone excess cause in renovascular hypertension?

Answer: Hypokalemia.

Extra Information:

• Aldosterone increases renal K⁺ secretion.
• Normal potassium does not exclude renovascular hypertension.

What acid-base disturbance can aldosterone excess cause in renovascular hypertension?

Answer: Metabolic alkalosis.

Extra Information:

• Aldosterone promotes H⁺ secretion in addition to K⁺ secretion.

What renal-function abnormalities can reduced renal perfusion produce?

Answer: Increased serum creatinine and decreased estimated GFR.

Extra Information:

• Persistent renal ischemia can impair renal function.

What BUN-to-creatinine ratio may support acute prerenal physiology?

Answer: Greater than 20 to 1.

Extra Information:

• This finding is not specific for renal artery stenosis.

What fractional excretion of sodium may support acute prerenal physiology?

Answer: Less than 1%.

Extra Information:

• This finding can support reduced renal perfusion but is not specific for renal artery stenosis.

Why can ACE inhibitors or ARBs reveal clinically important renal artery stenosis?

Answer: Blocking angiotensin II dilates the efferent arteriole and can substantially decrease GFR when renal perfusion is compromised.

Extra Information:

• This is particularly concerning with bilateral stenosis or stenosis to a solitary functioning kidney.

Why does angiotensin II help maintain GFR during renal artery stenosis?

Answer: It constricts the efferent arteriole and helps preserve glomerular hydrostatic pressure.

Extra Information:

• This compensatory mechanism becomes important when afferent perfusion is reduced.

What change after starting or increasing RAAS blockade should prompt evaluation for causes of declining renal perfusion?

Answer: A greater than 30% decline in GFR.

Extra Information:

• Evaluate volume depletion, NSAIDs, low-output states, and possible bilateral renal artery stenosis.

What are the three major physiologic triggers of renin release?

Answer: Decreased renal perfusion pressure, decreased macula-densa NaCl delivery, and increased β₁ sympathetic stimulation.

Extra Information:

• These signals indicate a need to preserve pressure or circulating volume.

How does decreased renal perfusion pressure stimulate renin?

Answer: Reduced pressure is detected by the juxtaglomerular apparatus and promotes renin secretion.

Extra Information:

• Renal artery stenosis is a classic example.

How does the macula densa regulate renin release?

Answer: Decreased tubular NaCl delivery to the macula densa increases renin.

Extra Information:

• Macula-densa NaCl delivery reflects upstream tubular flow and filtration.

How does the sympathetic nervous system stimulate renin release?

Answer: β₁ stimulation of juxtaglomerular cells increases renin secretion.

Extra Information:

• This links sympathetic activation directly to RAAS.

Trace the RAAS pathway beginning with renin.

Answer: Renin → angiotensinogen to angiotensin I → ACE → angiotensin II → AT₁ receptors.

Extra Information:

• AT₁ activation produces vasoconstriction and promotes aldosterone effects.

What are the major blood-pressure effects of angiotensin II in the RAAS pathway?

Answer: Vasoconstriction and increased aldosterone-mediated sodium retention.

Extra Information:

• These increase total peripheral resistance and blood volume.

How does renal artery stenosis initiate renovascular hypertension?

Answer: Renal artery narrowing decreases renal perfusion pressure, stimulating juxtaglomerular renin release.

Extra Information:

• Renin then activates the RAAS cascade.

Trace RAAS activation from renal artery narrowing to angiotensin II.

Answer: Renal artery narrowing → ↓ renal perfusion → ↑ renin → ↑ angiotensin I → ACE → ↑ angiotensin II → AT₁ activation.

Extra Information:

• This is the central pathway connecting renovascular disease to hypertension.

How does angiotensin II increase total peripheral resistance in renovascular hypertension?

Answer: AT₁-receptor activation causes arteriolar vasoconstriction.

Extra Information:

• Increased TPR directly increases BP.

How does RAAS activation increase cardiac output in renovascular hypertension?

Answer: Aldosterone increases Na⁺ and water retention, increasing blood volume, Pms, venous return, and preload.

Extra Information:

• Increased preload can increase cardiac output.

How can renovascular hypertension increase both components of the BP equation?

Answer: Angiotensin II increases TPR while aldosterone-mediated volume retention can increase cardiac output.

Extra Information:

• Therefore both CO and TPR can contribute to the elevated BP.

Why are ACE inhibitors useful in renovascular hypertension?

Answer: They decrease angiotensin II generation, reducing vasoconstriction and aldosterone-mediated volume retention.

Extra Information:

• This lowers both vascular resistance and volume-related pressure effects.

Why are ARBs useful in renovascular hypertension?

Answer: They block AT₁ receptors, reducing angiotensin II-mediated vasoconstriction and aldosterone effects.

Extra Information:

• Their downstream hemodynamic goal resembles ACE inhibition.

Why must kidney function be monitored during ACE-inhibitor or ARB therapy in renal artery stenosis?

Answer: Efferent dilation can lower intraglomerular pressure and GFR.

Extra Information:

• Risk is particularly important with bilateral stenosis or a solitary functioning kidney.

What laboratory values should be monitored during RAAS blockade in renovascular disease?

Answer: Serum creatinine and potassium.

Extra Information:

• RAAS blockade can reduce GFR and alter potassium handling.

What are the two major causes of renal artery stenosis?

Answer: Atherosclerotic renal artery stenosis and fibromuscular dysplasia.

Extra Information:

• They differ in typical patient population, vascular location, and imaging appearance.

Where does atherosclerotic renal artery stenosis usually occur?

Answer: At the ostium or proximal renal artery.

Extra Information:

• It is typically associated with older patients and generalized atherosclerotic risk factors.

How does atherosclerotic renal artery stenosis cause hypertension?

Answer: Plaque narrows the renal artery, reducing renal perfusion and activating renin and RAAS.

Extra Information:

• The resulting hypertension is secondary hypertension.

What can persistent renal ischemia from renal artery stenosis cause?

Answer: Ischemic nephropathy, renal atrophy, and declining renal function.

Extra Information:

• Persistent hypoperfusion can therefore damage the affected kidney.

What is fibromuscular dysplasia?

Answer: A nonatherosclerotic, noninflammatory arterial disease.

Extra Information:

• It can narrow renal arteries and activate RAAS.

Where does renal fibromuscular dysplasia classically occur?

Answer: In the middle or distal renal artery segments.

Extra Information:

• This contrasts with the ostial or proximal location typical of atherosclerosis.

What angiographic appearance is characteristic of fibromuscular dysplasia?

Answer: A string-of-beads appearance.

Extra Information:

• It reflects alternating areas of arterial narrowing and dilation.

What is the difference between renal artery stenosis and renovascular hypertension?

Answer: Renal artery stenosis is an anatomic lesion, while renovascular hypertension is hypertension physiologically caused by impaired renal perfusion.

Extra Information:

• Imaging evidence of stenosis does not prove that the lesion is driving the hypertension.

What does duplex Doppler ultrasonography evaluate in suspected renal artery stenosis?

Answer: Renal arterial blood-flow velocities.

Extra Information:

• Increased peak systolic velocity across a stenosis supports significant narrowing.

What peak systolic velocity commonly suggests significant renal artery stenosis on Doppler?

Answer: Approximately 180 to 200 cm/s.

Extra Information:

• Exact thresholds vary by laboratory and technique.

What are advantages of duplex Doppler ultrasonography for renal artery stenosis?

Answer: It is noninvasive and uses neither iodinated contrast nor radiation.

Extra Information:

• It can also assess the renal-to-aortic velocity relationship.

What are important limitations of renal duplex Doppler ultrasonography?

Answer: It is operator dependent and can be limited by obesity, bowel gas, and difficulty visualizing accessory vessels.

Extra Information:

• Technical quality therefore affects diagnostic usefulness.

What does CT angiography provide in suspected renal artery stenosis?

Answer: Detailed visualization of the renal arteries, aorta, and location and severity of stenosis.

Extra Information:

• Important disadvantages are ionizing radiation and iodinated contrast.

What does MR angiography provide in suspected renovascular disease?

Answer: Detailed vascular anatomy without ionizing radiation.

Extra Information:

• Contrast-enhanced studies require consideration of renal function and the gadolinium agent used.

When is catheter angiography particularly useful for renal artery stenosis?

Answer: When noninvasive testing is inconclusive or intervention is being considered.

Extra Information:

• It provides high-resolution anatomy and can measure pressure gradients.

• It is invasive and is generally not used merely for screening.

How do imaging patterns distinguish atherosclerotic RAS from fibromuscular dysplasia?

Answer: Atherosclerosis usually causes ostial or proximal narrowing, while FMD causes mid-distal irregularity with a string-of-beads appearance.

Extra Information:

• Location and morphology can therefore suggest the underlying etiology.

What is the usual first-line approach to stable atherosclerotic renal artery stenosis?

Answer: Medical therapy.

Extra Information:

• Finding renal artery stenosis on imaging does not automatically mean the lesion should be stented.

What did the CORAL trial show about routine stenting of atherosclerotic renal artery stenosis?

Answer: Adding stenting to medical therapy did not significantly reduce cardiovascular or renal clinical events.

Extra Information:

• The systolic BP difference was modest.
• The study included 947 patients.

When can revascularization be considered in atherosclerotic renal artery stenosis?

Answer: When clinically consequential disease persists despite medical treatment.

Extra Information:

• Important scenarios include refractory hypertension, worsening renal function, and acute or intractable heart failure.

What pulmonary complication can support consideration of renal revascularization?

Answer: Clinically important recurrent pulmonary edema.

Extra Information:

• This suggests hemodynamically consequential renovascular disease.

How is renal-artery fibromuscular dysplasia commonly revascularized?

Answer: Percutaneous balloon angioplasty.

Extra Information:

• It may markedly improve or sometimes resolve hypertension.

Is a stent automatically required when treating renal fibromuscular dysplasia?

Answer: No.

Extra Information:

• Balloon angioplasty can be effective without routine stenting.

What high-yield rule distinguishes revascularization strategies for stable atherosclerotic RAS and FMD?

Answer: Stable atherosclerotic RAS is treated medically first, while FMD-related hypertension may respond particularly well to angioplasty.

Extra Information:

• Revascularization for atherosclerotic disease is reserved for selected clinically consequential cases.