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3.23 > Lecture 18: Physiology/ Pharmacology/ Management of heart failure > Flashcards

Lecture 18: Physiology/ Pharmacology/ Management of heart failure Flashcards

1
Q

What is heart failure characterized by?

A

Impaired cardiac pumping such as the heart is unable to pump adequate amount of blood to meet metabolic needs.

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2
Q

What can heart failure result from?

A

Any structural or functional cardiac disorder that impairs the ability of the ventricle to eject blood or to fill with blood.

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3
Q

What are other words for heart failure?

A
  • Chronic heart failure
  • Congestive cardiac failure
  • Congestive heart failure
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4
Q

What are the signs and symptoms of heart failure?

A
  • Shortness of breath
  • Excessive tiredness
  • Leg swelling
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5
Q

What are the underlying causes and risk factors for heart failure?

A
  • Ischemic heart disease
  • Hypertension
  • Myocardial infarction
  • Valvular heart disease
  • Congenital heart disease
  • Dilated cardiomyopathy
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6
Q

What is congestive heart failure?

A

Left sided failure
- its the most common form
- Blood backs up through the left atrium into the pulmonary veins

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7
Q

How is cardiac output calculated?

A

heart rate x stroke volume

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8
Q

What is stroke volume?

A

The volume of blood pumped from each ventricle

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9
Q

What is stroke volume affected by?

A
  • Preload
  • Afterload
  • Ventricular contractility
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10
Q

What happens when preload increases?

A
  • End diastolic volume increases
  • Resulting in an increase stroke volume
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11
Q

What happens when afterload increases?

A
  • End systolic volume increaeses
  • Resulting in a decreased stroke volume
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12
Q

What happens if contractility is increased?

A
  • End systolic volume is reduced, resulting in an increse in stroke volume
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13
Q

How does heart rate affect cardiac output?

A

The higher the heart rate, the higher the cardiac output

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14
Q

How does excessivly high heart rate affect cardiac output?

A

Diastolic filling time begins to fall, causing stroke volume and cardiac output falls

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15
Q

What is preload?

A

The amount of fibre stretch in the ventricles at the end of diastole (so before the next contraction)

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16
Q

What is preload directly related to?

A

Ventricular filling

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17
Q

What does a higher end diastolic volume imply?

A

Higher preload

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18
Q

What does preload increase with?

A
  • increase in blood volume
  • Vasodilation
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19
Q

What does preload decrease with?

A
  • Loss in blood volume
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20
Q

What is starlings law?

A

Describes the relationship between preload and cardiac output

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21
Q

How does the stretch of the cardiac muscle fibers affect the force of contraction?

A

The greater the stretch, the greater the force of contraction

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22
Q

What does excessive preload result in?

A

Excessive stretch, reduced contraction, reduced systolic volume/ cardiac output

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23
Q

What is afterload?

A

The resistance against which the ventricle must pump

24
Q

What is the effect of excessive afterload?

A

Difficult to pump blood so reduced systolic volume and cardiac output

25
Q

What causes an increase in afterload?

A
  • Hypertension
  • Vasoconstriction
26
Q

What causes a decrease in afterload?

A

Vasodilation

27
Q

What is contractility of the heart?

A

Ability of the heart muscles to contract

28
Q

What causes a decrease in heart contractility?

A
  • Infarcted tissue: no contractile strength
  • Ischemic tissue: reduced contractile strength
29
Q

What causes an increase in heart contractility?

A

Positive inotropes (medications that increase contractility, such as digoxin, sympathiomimetics

30
Q

What are the mechanisms that attempt to increase cardiac output when the heart pump fails?

A
  • Sympathetic nerve stimulation
  • Myocardial hypertrophy
  • Hormonal response
31
Q

What is sympathetic nerve stimulation?

A
  • Release of epinephrine/ norepinephrine
32
Q

What does release or epinephrine/ norepinephrine result in?

A
  • Increased heart rate
  • Increased contractility
  • Peripheral vasoconstriction (incraeses afterload)
33
Q

What is myocardial hypertrophy?

A

Walls of the heart thicken to provide more muscle mass so stronger contraction

34
Q

What is the hormonal response to increase cardiac output?

A
  • Reduced cardiac output decreased renal perfusion which is interpretated by juxtaglomerular apparatus as hypovolemia
  • Kidneys release renin - this stimulates conversion of angiotensin I to angiotensin II
  • Angiotensin II causes aldosterone release, resulting in Na and water retention (via antidiuretic hormone secretion) and increasing fluid volume in the venous return to the atria
  • Angiotensin II also causes peripheral vasoconstriction
35
Q

How can excess compensatory mechanisms worsen heart failure?

A
  • Vasoconstriction increases the resistance against which the heart has to pump (increases afterload), so may decrease cardiac output
  • Na and water retention increase fluid volume, this increases preload. Too much stretch means a decreased strength of contraction and decreased cardiac output
  • Excessive tachycardia means a decreased diastolic filling time so decreased ventricular filling so a decrease SV and cardiac output
36
Q

What is the cycle of heart failure?

A
  • Decreased blood pressure and decreased renal perfusion
  • Stimulates the release of renin, allows the conversion of angiotensin I to angiotensin II. Angiotensin II stimulates aldosterone secretion which causes retention of Na and water, increasing filling pressure
  • LV dysfunction causes decreased cardiac output
37
Q

What is acute heart failure?

A

An emergancy situation in which a patient was stable before the onset of heart failure; seen in acute heart injury such as MI

38
Q

What is chronic heart failure?

A

Long term syndrome in which a patient exhibits syndromes over a long period of time, usually as a result of a preexisting cardiac condition

39
Q

What drugs are used in chronic congestive heart failure?

A
  • ACE inhibitor
  • Aldosterone antagonist
  • Beta blocker
  • Diuretics
  • Vasodilators
  • New drugs eg Neprilysin antagonist
40
Q

What is at the core of the pathophysiology of heart failure?

A

RAAS
- Its modulation is central to altering the disease in patients with reduced ejection fraction

41
Q

How do ACE inhibitors work in heart failure patients?

A
  • ACE inhibitors block the conversion of angiotensin I to angiotensin II
  • Relax block vessels, lower arteriolar resistance and increase venous capacity, decrease cardiac output, stroke work and volume
  • Lowers resistance in blood vessels in the kidneys; and leads to increased natriuresis
  • Reduces secretion of aldosterone, reducing reabsorption of sodium
42
Q

What is natriuresis?

A

Excretion of sodium in the urine

43
Q

How do beta blockers work in heart failure patients?

A
  • Metoprolol, bisopralol, carvedilol
  • Reduce excessive sympathetic stimulation which causes : -
    ↳ Tachycardia increase myocardial oxygen demand
    ↳ Cardiac effects caused catecholamines remodeling by catecholamines
  • Reduce heart rate decrease force of contraction
44
Q

What is aldosterone?

A

A steroid hormone produced by adrenal cortex is essential for sodium conservation mainly via mineralocorticoid receptors in the distal tubules and
collecting ducts of the nephron .

45
Q

What do aldosterone antagonist do?

A

Reduce sodium and water retention which decreases intravascular volume by releasing fluid from the body.

45
Q

What are the pharmacological effects of aldosterone antagonists?

A

↳ Reduce preload
↳ Reduce afterload
↳ Relieve symptoms of congestion

46
Q

What diuretics are used in heart failure patients?

A

Loop diuretics (furosemide, bumetanide)

47
Q

Where do loop diuretics act?

A

Ascending limb of the loop of Henle in the kidney

48
Q

What do loop diuretics do?

A

inhibit sodium, chloride and potassium reabsorption , so that there is less osmotic driving force for water has to leave the collecting duct system.

49
Q

What does a decrease in intravascular volume lead to?

A
  • Reduces preload
  • Improves LV function by reducing venous return
50
Q

What are vasodilators used in heart failure?

A

Hydralazine combined with isosorbide dinitrate - smooth muscle relaxants

51
Q

What are natriuretic peptides?

A

Peptides released by the heart in response to elevated wall strength from increased preload and afterload

52
Q

What is the effect of netriuretic peptide release?

A

Promote vasodilation and natriuresis

53
Q

What is neprilysin?

A

An enzyme that cleaves natriuretic peptides reducing their beneficial effects in a failing heart

54
Q

What are neprilysisn inhibitors?

A

Used to prevent the breakdown of natriuretic peptides maintaining their ability to decrease intravascular volume and vasodilation

3.23 (26 decks)

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