Lecture 10: Heart Failure

Question 1

Define heart failure

Answer 1

• Failure of the heart to pump enough blood to satisfy the body’s requirements.
  
  • Acute or chronic
• Characterized by a clinical syndrome involving a characteristic pattern of hemodynamic, renal, neural, and hormonal responses. Heart failure is considered a multisystem disorder.

Question 2

Causes of heart failure

Answer 2

• Diminished coronary blood flow (ischemic heart disease)
• Damaged heart valves
• thyrotoxicosis
• Vitamin B deficiency
• Cardiac muscle disease

Question 3

What are the acute effects of moderate heart failure?

Answer 3

• Sudden damage (MI)
• Reduced cardiac output → fatigue
• Fall in arterial pressure
• Damming of blood in veins → congestion
• RESULT: compensation

Question 4

What is the role of sympathetic reflexes in heart failure compensation?

Answer 4

• Baroreceptor that measure arterial pressure
  
  • Detect fall in BP
  • NET EFFECT
    
    • Sympathetic nervous system activated
    • Parasympathetic nervous system inhibited
  • TLDR: fall in CO, body compensates by increase CO n BP
• Direct effect on the heart
  
  • SNS speeds up the heart n contractility of the heart (positive ionotropic effect)
  • Positive ionotropic n chronotropic
• Increases venous return [causes blood vessel constriction] → more blood cmng to the heart → increases cardiac output → raises filling pressure

Question 5

What is the effect of heart failure on the Starling curve?

Answer 5

• Increase filling pressure → bigger CO
  
  • Stretching the muscles fibers of the myocardium
  • When they contract, they push out more blood
  • More preload (blood cmng back to the heart in the vein) → shift along the curve
• Sudden fall in BP [lack of CO] → curve shift to the right [more filling pressure bc constricting the vein]
• Sympathetic nervous system increases contractility → efficiency of pumping increased
  
  • For given pressure, more CO
  • Direct effect of sympathetic nervous system by beta receptors
  • Pushes the curve upwards
• Fall in CO → body compensates in short term by shifting along the curve n shifting curve up
  
  • Result net increase in CO for increase filling pressure

Question 6

How does the baroreceptor reflex compensate for a decrease in BP?

Answer 6

• Decrease in BP [fall in CO] detected by baroreceptors in carotid sinus n aortic arch
• Reduces number of nerve impulses in vasomotor centers in medulla
• Inhibits parasympathetic nervous system
• Activates SNS
• Increase heart rate n contractility
• Increase vasomotor tone (constricts blood vessels) -> increases TPR n venous return
  
  • More pressure for the heart to push against can help compensate in short term but may be damaging in the long term
• When the heart fails, makes the heart work harder -> can be damaging

Question 7

What is the role of fluid retention in heart failure compensation?

Answer 7

• Long term try n increase fluid retention
• Retention of fluid by kidneys -> reduced urine output via release of aldosterone n ADH
• Effects of aldosterone n ADH
• Increased blood volume -> increased venous return ->

increased systemic filling pressure

• Reduces venous resistance which eases flow of blood to the heart
• Moderate fluid retention is beneficial
• Large amt of fluid retention is not beneficial

Question 8

What are the causes of reduced renal urine output?

Answer 8

• Decreased glomerular filtration
  
  • Caused by a fall in arterial pressure
• Renin-angiotensin system
• Aldosterone secretion

Question 9

What are the aims of treating CHF?

Answer 9

• Relieve symptoms
• Improvise exercise tolerance
• Reduce acute exacerbations
• Reduce mortality

Question 10

What are some first line treatments of chronic CHF?

Answer 10

• ACE inhibitors
• Angiotensin II receptor antagonists
• β-adrenoreceptor blockers

Question 11

What are some second line treatments of chronic CHF?

Answer 11

• Aldosterone antagonist (spironolactone)
• Cardiac glycosides (digoxin)
  
  • Increase heart contractility

Question 12

What do ACE inhibitors and angiotensin II receptor antagonists do and what are some examples?

Answer 12

• ACE inhibitor: enalapril
• Angiotensin II receptor antagonists: candersarta
• FUNCTION
  
  • Reduce peripheral resistance (afterload)
    
    • Stop angiotensin II vasoconstriction
  • Reduce blood volume (preload) via reducing aldosterone release
  • Increase K+ concentration counteracting loss via diuretics
  • Helps to prevent cardiac remodeling
    
    • Increase in size
  • Strong evidence that they increase survival

Question 13

What do β-adrenoreceptor blockers do and what are some examples?

Answer 13

• EXAMPLES: bisoprolol n carvedilol
• Reduce the work of the heart n slow disease progression
• Reduce renin-angiotension-aldosterone
• Some also block α receptors on blood vessels leading to vasodilation
• Start at low dose n slowly titrate
• Only use in stable heart failure
  
  • Can shift along the curve w/o changing CO
  • Reducing work of the heart

Question 14

What do cardiac glycosides do?

Answer 14

• Block Na+/K+ exchange → greater Ca2+ influx via Na+/Ca2+ exchanger → increases myocardium contractility
• Suitable for patients w CHF n atrial fibrillation
• Worsening or severe heart failure due to left ventricular systolic dysfunction despite ACE inhibitor, β-blocker n diuretic therapy

Question 15

What is ivabradine?

Answer 15

• Used to treat angina
• Slows heart by direct action on SA node
• Probably blocks pacemaker current (If)
• Increases filling time n CO

Question 16

How to treat intractable heart failure?

Answer 16

• Transplantation
• Ventricular assist device (VAD)
  
  • Mechanical pump that pumps blood thru the body