Understanding Blood Flow, Cardiac Output, and Regulation
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Questions and Answers

In a healthy individual at rest, which of the following statements best describes the distribution of blood within the circulatory system?

  • The majority of blood volume is found in the systemic circulation, supporting the metabolic demands of various tissues and organs. (correct)
  • The majority of blood volume is equally distributed between the pulmonary and systemic circulations to ensure efficient gas exchange.
  • The majority of blood volume resides within the heart chambers to maintain adequate preload for subsequent contractions.
  • The pulmonary circulation contains the highest percentage of blood, ensuring maximum oxygenation before distribution to the body.

A patient's blood pressure is consistently lower than normal, and their tissues show signs of inadequate perfusion. According to the principles of blood flow, which factor is most likely contributing to this patient's condition?

  • The resistance to blood flow is significantly lower than the force driving it.
  • The force driving blood flow is approximately equal to the resistance.
  • The resistance to blood flow is significantly greater than the force driving it. (correct)
  • The force driving blood flow is significantly greater than the resistance.

Deoxygenated blood needs to return to the heart from the lower extremities. Which mechanism plays the most significant role in facilitating this return?

  • Gravity, which assists the flow of blood towards the heart.
  • The pumping action of skeletal muscles during movement, compressing veins and propelling blood. (correct)
  • The negative pressure within the pericardial sac, which actively sucks blood into the heart.
  • Arterial vasodilation creating a pressure gradient that favors upward flow.

After a severe hemorrhage, the body attempts to compensate to maintain blood flow. Which of the following compensatory mechanisms would least contribute to restoring adequate circulation?

<p>Vasodilation of major arteries to reduce afterload on the heart. (A)</p> Signup and view all the answers

A researcher is studying the impact of a new drug on blood distribution in animals. After administering the drug, they observe a significant increase in blood volume within the pulmonary circulation. What is the most likely direct consequence of this change?

<p>Increased risk of pulmonary edema due to fluid overload. (A)</p> Signup and view all the answers

A patient's cardiac output is 4.8 L/min and their heart rate is 60 bpm. According to this data, what is the patient's stroke volume?

<p>80 mL (D)</p> Signup and view all the answers

Which adaptation does the body employ to counteract hypotension and maintain blood pressure?

<p>Activation of the baroreceptor refleX (A)</p> Signup and view all the answers

The greatest diuresis results from diuretics that act on which part of the nephron?

<p>Proximal tubule (A)</p> Signup and view all the answers

A patient taking furosemide (Lasix) is noted to have muscle weakness and cardiac dysrhythmias. Which electrolyte imbalance is the MOST likely cause?

<p>Hypokalemia (B)</p> Signup and view all the answers

Spironolactone is classified as what kind of diuretic?

<p>Potassium-sparing diuretic (A)</p> Signup and view all the answers

Which of the following is the primary mechanism by which ACE inhibitors lower blood pressure?

<p>Blocking the conversion of angiotensin I to angiotensin II (A)</p> Signup and view all the answers

What is a significant adverse effect associated with ACE inhibitors that necessitates cautious prescribing?

<p>Increased potassium levels (D)</p> Signup and view all the answers

Dihydropyridines primarily affect which of the following?

<p>Vascular smooth muscle (D)</p> Signup and view all the answers

Medications that cause vasodilation of veins primarily reduce:

<p>Preload (D)</p> Signup and view all the answers

The primary difference between essential hypertension and secondary hypertension is that secondary hypertension:

<p>Has an identifiable underlying cause (D)</p> Signup and view all the answers

Drugs that inhibit RAAS, such as ACE inhibitors, are frequently used in heart failure to:

<p>Reduce cardiac remodeling (C)</p> Signup and view all the answers

Class I antidysrhythmic drugs affect the heart by:

<p>Blocking sodium channels and slowing impulse conduction (D)</p> Signup and view all the answers

A patient with angina is prescribed nitroglycerin. What is its primary mechanism of action for relieving anginal pain?

<p>Reducing preload and myocardial oxygen demand (C)</p> Signup and view all the answers

Which class of medications is designed to prevent the formation of blood clots by inhibiting platelet aggregation?

<p>Antiplatelets (D)</p> Signup and view all the answers

Aplastic anemia, characterized by a deficiency in erythrocytes, can be caused by:

<p>Dysfunction in the bone marrow (C)</p> Signup and view all the answers

Which of the following best describes the primary factor determining blood flow through a vessel?

<p>A pressure gradient that overcomes vascular resistance. (A)</p> Signup and view all the answers

During vigorous exercise, the skeletal muscles receive a higher percentage of blood flow. Which mechanism primarily facilitates this redistribution of blood?

<p>Selective vasodilation in skeletal muscles and vasoconstriction in less active tissues. (D)</p> Signup and view all the answers

If the resistance in a blood vessel increases while the pressure gradient remains constant, what immediate change would be expected in blood flow through that vessel?

<p>Blood flow will decrease proportionally to the resistance. (D)</p> Signup and view all the answers

Considering the distribution of blood volume in the body, what percentage of the total blood volume is typically found within the systemic circulation?

<p>84% (B)</p> Signup and view all the answers

Which of the following scenarios would most likely result in decreased venous return to the heart?

<p>Standing still for an extended period. (C)</p> Signup and view all the answers

Which of the following physiological responses would be expected in an individual experiencing hypotension?

<p>Activation of the baroreceptor reflex, leading to increased sympathetic outflow. (D)</p> Signup and view all the answers

A patient is prescribed furosemide. The healthcare provider should educate the patient about which potential adverse effect?

<p>Possible hearing loss (ototoxicity). (D)</p> Signup and view all the answers

A patient with heart failure is prescribed spironolactone. The medication's mechanism of action primarily addresses which aspect of the disease?

<p>Blocking aldosterone receptors, leading to reduced sodium reabsorption and potassium retention. (A)</p> Signup and view all the answers

A patient is started on an ACE inhibitor for hypertension. After a week, they complain of a persistent dry cough. What is the most likely mechanism causing this side effect?

<p>Increased levels of bradykinin due to ACE inhibition. (D)</p> Signup and view all the answers

Which of the following best describes the primary mechanism by which calcium channel blockers reduce blood pressure?

<p>By promoting vasodilation of arterioles, reducing peripheral vascular resistance. (A)</p> Signup and view all the answers

A patient with hypertension is prescribed a vasodilator that primarily affects veins. What is the expected outcome of this treatment?

<p>Reduced preload, decreasing the volume of blood returning to the heart. (D)</p> Signup and view all the answers

A young adult is diagnosed with secondary hypertension. Which of the following conditions is most likely to be the underlying cause?

<p>Renal artery stenosis. (B)</p> Signup and view all the answers

How do ACE inhibitors help manage heart failure?

<p>By reducing afterload and preload, decreasing the heart’s workload and improving cardiac output. (B)</p> Signup and view all the answers

The underlying cause of most dysrhythmias is:

<p>Abnormality in impulse formation or conduction. (A)</p> Signup and view all the answers

A patient with angina pectoris is prescribed nitroglycerin. What should the patient be taught regarding storage of the medication to maintain its efficacy?

<p>Keep the medication in its original dark glass container, away from light and moisture. (B)</p> Signup and view all the answers

Which of the following classes of medications is primarily used to prevent arterial thrombus formation?

<p>Antiplatelets. (C)</p> Signup and view all the answers

A patient with a known history of Afib presents to the clinic, what is the best type of medication to prevent a stroke?

<p>Anticoagulant (C)</p> Signup and view all the answers

A patient receiving furosemide is also prescribed an ACE inhibitor. What adjustment to the furosemide dosage may be necessary and why?

<p>Decrease the furosemide dose to prevent excessive diuresis and hypotension. (B)</p> Signup and view all the answers

What is the physiological rationale behind combining an ACE inhibitor with hydrochlorothiazide (HCTZ)?

<p>To enhance the antihypertensive effect through complementary mechanisms. (C)</p> Signup and view all the answers

A patient with significant blood loss is being treated for anemia. Apart from addressing the cause of blood loss, which intervention directly supports red blood cell production?

<p>Supplying substances essential for RBC formation, such as iron and vitamin B12. (C)</p> Signup and view all the answers

Considering the distribution of blood volume, what percentage is primarily located within the systemic circulation?

<p>84% (D)</p> Signup and view all the answers

If the force driving blood flow is significantly less than the resistance within the circulatory system, what is the most likely immediate consequence?

<p>A significant reduction in blood flow. (A)</p> Signup and view all the answers

Which of the following statements best describes the relationship between blood flow, driving force, and resistance?

<p>Blood flow occurs when the driving force exceeds resistance. (C)</p> Signup and view all the answers

What percentage of the total blood volume is typically found within the heart?

<p>7% (D)</p> Signup and view all the answers

Which of the following best describes the primary challenge the body faces in returning blood from the lower extremities to the heart?

<p>Counteracting the effects of gravity. (A)</p> Signup and view all the answers

Which of the following factors directly affects stroke volume?

<p>Preload (D)</p> Signup and view all the answers

According to the Frank-Starling law of the heart, what is the relationship between venous return and stroke volume?

<p>Increased venous return leads to increased stroke volume. (D)</p> Signup and view all the answers

Which of the following is the initial compensatory response of the body to a sudden drop in blood pressure?

<p>Baroreceptor reflex activation. (D)</p> Signup and view all the answers

How does the renin-angiotensin-aldosterone system (RAAS) contribute to regulating blood pressure?

<p>By increasing blood volume and vasoconstriction (C)</p> Signup and view all the answers

Which of the following direct effects would be expected from taking a medication that inhibits aldosterone?

<p>Decreased sodium reabsorption (D)</p> Signup and view all the answers

Furosemide causes a profound diuresis because it primarily acts on which part of the nephron?

<p>Thick ascending limb of the loop of Henle (A)</p> Signup and view all the answers

A patient taking a loop diuretic is at risk for developing which electrolyte imbalance?

<p>Hyponatremia (A)</p> Signup and view all the answers

Spironolactone is classified as a potassium-sparing diuretic because it directly:

<p>Antagonizes the effects of aldosterone in the distal tubule (C)</p> Signup and view all the answers

Which of the following represents the primary mechanism by which ACE inhibitors lower blood pressure?

<p>Inhibiting the conversion of angiotensin I to angiotensin II (C)</p> Signup and view all the answers

Which of the following best describes the action of calcium channel blockers on vascular smooth muscle?

<p>Block calcium influx, leading to vasodilation. (D)</p> Signup and view all the answers

How do drugs that dilate veins primarily affect cardiac function?

<p>By reducing preload (D)</p> Signup and view all the answers

A patient has primary (essential) hypertension. What does this diagnosis mean?

<p>The hypertension has no known cause. (B)</p> Signup and view all the answers

Which of the following best describes how ACE inhibitors improve outcomes in heart failure?

<p>By reducing cardiac remodeling and fluid retention (B)</p> Signup and view all the answers

Which of the following is a common mechanism by which antidysrhythmic drugs work?

<p>All of the above (D)</p> Signup and view all the answers

How do antiplatelet medications prevent arterial thrombus formation in coronary heart disease?

<p>By inhibiting the aggregation of platelets (B)</p> Signup and view all the answers

Flashcards

Circulatory System Components

Heart, blood vessels, and blood

Blood Distribution in the Body

Lungs (9%), Heart (7%), Body (84%)

What Drives Blood Flow?

Pressure difference overcomes resistance.

Blood Pressure

The force that drives blood through the body's vessels.

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How Blood Returns to Heart

Skeletal muscle contraction, valves in veins prevent backflow, and breathing creates pressure changes.

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Cardiac Output

Volume of blood pumped by the heart per minute; calculated as heart rate multiplied by stroke volume.

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Preload

The amount of stretch (volume) in the ventricles before contraction. It affects stroke volume.

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Afterload

The resistance the heart must overcome to eject blood. Increased afterload decreases stroke volume.

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Baroreceptor Reflex

Compensatory response to hypotension; involves baroreceptors, the autonomic nervous system, and hormonal mechanisms to increase blood pressure.

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RAAS

Hormonal system (Renin-Angiotensin-Aldosterone System) that regulates blood pressure, fluid, and electrolyte balance.

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Diuretics

Drugs that increase urine production by blocking sodium and chloride reabsorption in the kidneys.

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Hypovolemia

Reduced blood volume often caused by excessive diuresis, leading to dehydration and electrolyte imbalances.

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Loop Diuretics

Diuretics that block sodium and chloride reabsorption in the loop of Henle, causing significant diuresis.

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Thiazide Diuretics

Diuretics that inhibit sodium reabsorption in the distal tubule, leading to moderate diuresis.

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Osmotic Diuretics

Diuretics that increase osmolality of the filtrate, drawing water into the renal tubules and increasing urine output.

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Potassium-Sparing Diuretics

Diuretics that block the action of aldosterone or directly inhibit sodium reabsorption, reducing potassium loss in the urine.

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ACE (Angiotensin-Converting Enzyme)

Enzyme that converts angiotensin I to angiotensin II.

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Calcium Channel Blockers

Drugs that block calcium channels in blood vessels and the heart, leading to vasodilation and reduced heart rate. Used for hypertension and angina.

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Vasodilation

Widening of blood vessels, reducing blood pressure and increasing blood flow.

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Angina Pectoris

Sudden chest pain caused by reduced blood flow to the heart muscle.

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Circulatory system

Heart, blood vessels, and blood circulating together.

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Blood distribution

9% in lungs, 7% in heart, 84% in body

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Blood flow driver

Force pushing blood must be stronger than resistance of vessels.

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Venous return mechanisms

Combination of skeletal muscle pumps, venous valves, and respiratory pressure changes

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Heart Rate

Number of heartbeats per minute.

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Stroke Volume

The amount of blood ejected by the heart with each beat.

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Starling Law of the Heart

Force of ventricular contraction is proportional to muscle fiber length (to a point).

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Hypotension

Low blood pressure; can be caused by various factors, including medications and dehydration.

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Natriuretic Peptides

Hormones secreted by the heart that promote sodium and water excretion, lowering blood pressure

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Diuretic Site of Action

The site in the kidney where a diuretic exerts its effects, influencing sodium and water reabsorption.

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Diuretics: Adverse Effects

The primary effect of diuretics; disrupts normal fluid and electrolyte balance

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Acid-Base Imbalance

A reversible imbalance that occurs when the acidity or alkalinity of blood shifts, causing the body to compensate.

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Primary vs. Secondary Hypertension

Primary hypertension has no known cause, while secondary hypertension results from an identifiable underlying disorder.

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Heart Failure

A chronic condition where the heart can't pump enough blood to meet the body's needs.

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Dysrhythmia

An abnormality in the heart's rhythm caused by issues with electrical impulse formation or conduction.

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Plasma lipoproteins

Plasma proteins that transport lipids (e.g., cholesterol) in the blood; includes LDL, HDL, and VLDL.

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Anticoagulants

Group of drugs that limit the synthesis of clotting factors.

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Anemia

A condition characterized by a deficiency of red blood cells, hemoglobin, or both.

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Driving Blood Flow

For blood to circulate, the force propelling it must exceed the resistance within the blood vessels.

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Venous Return

Skeletal muscle contraction, one-way valves in veins, and pressure changes during breathing facilitates blood return to the heart

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Cardiac Output Equation

Output is equal to the heart rate multiplied by the stroke volume.

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Diuretics MOA

Inhibits sodium and chloride reabsorption in the kidney, leading to increased urine production.

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Diuretic Classes

Loop, thiazide, osmotic, and potassium-sparing diuretics.

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Loop Diuretics MOA

Blocks sodium and chloride reabsorption in the ascending loop of Henle.

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Thiazide Diuretics MOA

Inhibits sodium reabsorption in the distal convoluted tubule.

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Spironolactone MOA

Blocks aldosterone receptors, promoting sodium and water excretion and potassium retention.

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ACE Function

Enzyme that converts angiotensin I to angiotensin II, a potent vasoconstrictor.

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Balanced Vasodilators

Dilates arterioles, reducing afterload AND dilates veins, reducing preload.

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Anti-dysrhythmics

Drugs that prevent/treat abnormal heart rhythms.

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Lipid-Lowering Drugs

Reduce LDL cholesterol, increase HDL cholesterol, and lower triglycerides.

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Anti-Anginal Drugs

Medications that dilate coronary arteries, increasing the oxygen supply to the heart.

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Antiplatelet Drugs

Inhibit platelet aggregation, preventing clot formation.

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Thrombolytics

Dissolve existing clots by promoting the breakdown of fibrin.

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Anticoagulant Function

Prevents new clots from forming, by disrupting the coagulation cascade and suppressing fibrin production.

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Anemia causes

Blood loss, hemolysis, and bone marrow dysfunction

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Study Notes

Components of the Circulatory System

  • The force driving blood flow needs to be greater than the resistance for blood to flow.
  • Blood returns to the heart via mechanisms not specified.

Distribution of Blood

  • Pulmonary circulation contains 9% of blood.
  • The Heart contains 7% of blood.
  • Systemic circulation holds the majority of blood, at 84%.

Determinants of Cardiac Output

  • Cardiac output equals heart rate multiplied by stroke volume.
  • Heart rate and stroke volume are key determinants.
  • Preload and afterload also affect cardiac output.
  • The Frank-Starling law of the hear is also a another key determinant.

Regulatory Systems

  • The baroreceptor reflex, RAAS (renin-angiotensin-aldosterone system), and natriuretic peptides influence blood pressure.

Hypotension

  • Hypotension and its management are significant clinical considerations.

Diuretics

  • Diuretics work by blocking sodium and chloride reabsorption in the kidney.
  • The proximal tubule produces the greatest diuresis due to its high reabsorption capacity.
  • Adverse effects of diuretics include hypovolemia, acid-base imbalance, and electrolyte imbalances.

Classification of Diuretics

  • Loop diuretics (e.g., Furosemide).
  • Thiazide diuretics (e.g., Hydrochlorothiazide).
  • Osmotic diuretics (e.g., Mannitol).
  • Potassium-sparing diuretics, including aldosterone antagonists (e.g., Spironolactone) and nonaldosterone antagonists (e.g., Triamterene).
  • A fifth group includes carbonic anhydrase inhibitors.
  • Loop diuretics include drugs like furosemide (Lasix), ethacrynic (Edecrin), bumetadine (Burinex), and torsemide (Demadex).
  • A common thiazide diuretic is hydrochlorothiazide.
  • Potassium-sparing diuretics include spironolactone and amiloride.

Renin-Angiotensin-Aldosterone System (RAAS)

  • Angiotensin I, Angiotensin II, and Angiotensin III are types of angiotensin.
  • Renin and angiotensin-converting enzyme (ACE) facilitate the formation of angiotensin II.
  • The renin-angiotensin-aldosterone system regulates blood pressure.
  • Angiotensin II can also be produced locally in tissues.

ACE Inhibitors

  • ACE inhibitors include benazepril, captopril, and enalapril.
  • Some ACE inhibitors are combined with hydrochlorothiazide (HCTZ).
  • Drug interactions with ACE inhibitors include diuretics, antihypertensive agents, drugs that raise potassium levels, lithium, and nonsteroidal anti-inflammatory drugs (NSAIDs).

Calcium Channel Blockers

  • Prevent calcium ions from entering cells, especially in the heart and blood vessels.
  • Treat hypertension, angina pectoris, and cardiac dysrhythmias.
  • Also known as calcium antagonists and slow channel blockers.
  • Verapamil and diltiazem act on vascular smooth muscle and the heart.
  • Dihydropyridines mainly affect vascular smooth muscle.
  • There is safety concern when using in patients with hypertension and diabetes.

Vasodilation

  • Vasodilation can be achieved using various drugs that act on veins, arterioles, or both.
  • Drugs that dilate arterioles decrease cardiac afterload.
  • Drugs that dilate veins reduce preload by decreasing the force of blood returning to the heart.

Types of Hypertension

  • Primary (essential) hypertension has no identifiable cause, is chronic and progressive, and is more common in older adults, African Americans, and postmenopausal women; it can only be treated, not cured.
  • Secondary hypertension has an identifiable primary cause that can be treated directly, potentially leading to a cure.

Heart Failure (HF)

  • Heart failure with left ventricular (LV) systolic dysfunction
  • Diastolic heart failure, also known as heart failure with preserved LV ejection fraction

Heart Failure Characteristics

  • Heart failure is a progressive and often fatal disorder.
  • Characterized by left ventricular dysfunction, reduced cardiac output, insufficient tissue perfusion, and signs of fluid retention.

Drugs for Heart Failure

  • Diuretics
  • RAAS inhibitors, including angiotensin-converting enzyme inhibitors, angiotensin II receptor blockers, aldosterone antagonists, and direct renin inhibitors.
  • Beta blockers
  • Digoxin
  • Dopamine
  • Hydralazine

Dysrhythmia

  • Dysrhythmia is an abnormality in the rhythm of the heartbeat, also known as arrhythmia.
  • Tachydysrhythmias (supraventricular and ventricular) and bradydysrhythmias arise from disturbances in impulse formation.
  • Virtually all drugs that treat dysrhythmias can also cause dysrhythmias.

Prophylaxis of Coronary Heart Disease (CHD)

  • Cholesterol and plasma lipoproteins are key factors.
  • LDL cholesterol contributes to atherosclerosis.
  • ATP III guidelines provide recommendations for detection, evaluation, and treatment of high cholesterol.

Drugs for Angina Pectoris

  • Angina pectoris is sudden pain beneath the sternum, often radiating to the left shoulder and arm, due to insufficient oxygen supply to the heart.
  • Two main goals of drug therapy are the prevention of myocardial infarction and death, and the prevention of myocardial ischemia and anginal pain.
  • Therapeutic agents for symptomatic relief include organic nitrates, beta blockers, calcium channel blockers, and ranolazine.
  • Nondrug therapy includes avoiding factors that can precipitate angina and decreasing risk factors.

Thromboembolic Disorders

  • Anticoagulants disrupt the coagulation cascade.
  • Antiplatelets inhibit platelet aggregation.
  • Thrombolytics promote lysis of fibrin.

Medications

  • Enoxaparin, dalteparin, and tinzaparin are available LMW heparins in the US.
  • Warfarin, dabigatran etexilate, bivalirudin, desirudin, argatroban, rivaroxaban are other key medications.

Anemias

  • Anemias involve a decrease in erythrocytes (RBCs) in number, size, or hemoglobin content.
  • Causes include blood loss, hemolysis, and bone marrow dysfunction.
  • It can also result from a deficiency of substances essential for RBC formation and maturation.

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Description

Explore the dynamics of blood flow, cardiac output determinants such as heart rate and stroke volume, preload, afterload and the Frank-Starling law. Learn about regulatory systems like the baroreceptor reflex and RAAS and their influence on blood pressure, including hypotension. Also learn about diuretics and how they work.

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