STAGING OF HEART DISEASE AND PATHOPHYSIOLOGY OF HEART FAILURE

Question 1

Definition of Heart Failure

Answer 1

• Progressive, usually fatal, syndrome that represents a final common pathway by which a variety of disease processes impair cardiac function
• A state in which the heart fails to meet the metabolic demands of the body
• A clinical syndrome in which heart disease reduces cardiac output, increases venous pressures, and generally causes a progressive deterioration of heart muscle

Question 2

backward heart failure signs

Answer 2

Signs of venous congestion
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Right sided:
* Jugular pulsation
* Pleural effusion
* Hepatomegaly
* ascites
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Left sided:
* Pulmonary venous distension
* Pulmonary edema

Question 3

forward heart failure signs

Answer 3

Signs of poor cardiac output
* Lethargy
* Weakness
* Hypotension
* Exercise intolerance
* Cold extremities
* Syncope
* Azotemia

Question 4

Heart failure: Common Theme (whether primary problem is ejection, filling, or both)

Answer 4

• increased ventricular end-diastolic pressure
• increased atrial pressure
• increased venous pressure (central or pulmonary)
• increased capillary pressure
• edema/effusion

Question 5

Neurohormonal Response to HF: Simplified Overview

Answer 5

reduction in cardiac output for some reason:
- compensatory mechanisms:
> SNS and Renin Angiotensin Aldosterone system upregulate
- excessive vasoconstriction
- blood volume increase (retain fluid)
- vascular resistance increase
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- increased vascular resistance will actually further decrease cardiac output :(
- these systems are designed to compensate in acute cases, but problems arise in chronic cases

Question 6

Sympathetic nervous system
- what does beta1 stimulation result in?
- what does alpha stimulation result in?
- other things stimulated, relevant to heart failure?

Answer 6

beta1:
* Increased heart rate
* Increased contractility
* Improved relaxation
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alpha:
* Vasoconstriction > Increased afterload
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* Stimulates RAAS and ADH

Question 7

Renin Angiotensin Aldosterone System (RAAS)
* Renin release stimulated by:
* how does this system work?
* what does angiotensin2 do?
* aldosterone and ADH?

Answer 7

Renin release stimulated by
* Decreased CO
* SNS
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- Renin converts angiotensinogen > angiotensin 1
- Angiotensin Converting Enzyme converts angiotensin 1 > angiotensin 2, which is a potent vasoconstrictor
- increased angiotensin2 results in:
> increased aldosterone > Na & water retention, myocardial remodelling / fibrosis
> increased Argenine Vasopressin (ADH) > vasoconstrictor, water retention

Question 8

Effect of Neurohormonal Response on heart

Answer 8

• increased preload (due to volume retention)
• increased afterload (due to vasoconstriction)

Question 9

Determinants of Cardiac Performance

Answer 9

• Preload
• Afterload
• Contractility
• Distensibility
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• Heart rate
• Synergy of contraction

Question 10

Preload - what is it? how is it measured?

Answer 10

• What the pump is “primed” with just before contraction
• Measured as end- diastolic volume or pressure

Question 11

How do changes in preload affect cardiac performance?
what about in a failing heart

Answer 11

• Stroke volume (volume ejected with each heart beat) increased with increase in preload
  > at some point, there can be too much preload (volume), such that congestion can happen, even in a normal heart
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• in a failing heart, increased preload still means increased stroke volume, but not to the same extent ( stroke volume will not substantially increase with increased preload, especially after a certain point)
  > we reach congestion sooner in a failing heart

Question 12

Afterload - what is this? when does it increase?

Answer 12

• The resistance the heart encounters in ejecting blood
• Conceptual and cannot be measured directly
• Is increased by increased ventricular volume and increased arterial resistance

Question 13

How do changes in afterload affect cardiac performance?
how does heart failure affect this?

Answer 13

• Stroke volume (volume ejected with each heart beat) decreases with increases in afterload
• in heart failure, stroke volume will be greatly decreased for a given afterload vs normal

Question 14

Contractility - what is this?

Answer 14

• Strength of the myocardium’s contraction (myocytes’ ability to shorten)

Question 15

How do changes in contractility affect cardiac performance?

Answer 15

• Stroke volume (volume ejected with each heart beat) will increase with increases in contractility, and
• Stroke volume will decrease with decreases contractility

Question 16

Distensibility - what is this?

Answer 16

• Ease of ventricular filling
  during diastole
• Heart’s ability to be stretched during diastole

Question 17

How do changes in distensibility affect cardiac performance?
how does heart failure affect this?

Answer 17

• With decreased distensibility, there is increased ventricular pressure for the same ventricular volume
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• as left ventricular end diastolic volume (preload) increases, left ventricular pressure increases exponentially (it takes a while for pressures to start to rise, but then they take off)
  > in heart failure, the pressure increases more at lower preload values (with only a small increase in volume, pressure increase quickly > higher risk of congestion)