SACCM 41: Mechanisms of Heart Failure Flashcards

1
Q

What are the neurohormonal pathways implicated in the development of heart failure?

A
  • RAAS
  • sympathetic nervous system
  • natriuretic peptides
  • endothelin-1 system
  • vasopressin system
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

List the pathways of RAAS

A

renal perfusion decreased –> macula densa in the ascending thick limb of the loop of Henle senses decreased tubular flow (specifically Cl-) –> sends signal to the juxtaglomerular apparatus of the same nephron –> renin-secreting cells release renin

renin –> converts angiotensinogen to angiotensin I
ACE (produced by endothelial cells, predominantly in the lungs) –> converts angiotensin I to angiotensin II

Angiotensin II –> increases production and release of aldosterone

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Explain how the RAAS system contributes to the development of heart failure

A

Angiotensin II and Aldosterone lead to:
* sodium and water retention
* myocardial apoptosis
* cardiac and vascular remodeling and fibrosis
* increased thirst
* vasoconstriciton

–> fluid retention (CHF) and maladaptive myocardial and vascular remodeling –> further cardiac injury and depressed cardiac function

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What are the adverse effects of chronic sympathetic nervous system activation in patients heart disease?

A
  • downregulation of adrenergic receptors
  • persistent tachycardia
  • increased myocardial oxygen demand
  • myocyte necrosis
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What are the two natriuretic peptides, what are their effects and how are they implicated to play into the development of heart failure?

A

atrial natriuretic peptide (ANP) and B-type natriuretic peptide (BNP)

produced in response to stretch or stress of myocardial tissue –> lead to natriuresis, diuresis, and vasodilation

help counteract RAAS activation, but becomes ultimately insufficient because of:
* receptor downregulation
* inadequate production and processing
* increased clearance/degradation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is the stimulus for Ebndothelin 1 production, what are its effects?

A

stimuli for production:
* sheer stress
* angiotensin II
* various cytokines

effects:
* vasoconstriction –> increased cardiac afterload
* alters normal Ca++ cycling within myocytes –> toxic to myocardiocytes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What causes dilutional hyponatremia in patients with heart failure?

A

decreased CO –> decreased intravascular pressure –> stimulates baroreceptors in the carotid arteries and aortic arch –> release of vasopressin/ADH –> water retention in the distal collecting ducts –> water retained in excess of Na –> dilutes Na

BUT total body sodium is actually high from excessive RAAS activation

poor prognostic indicator

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Describe the different complications associated with eccentric versus concentric hypertrophy of the cardiac myocytes

A

concentration - increased pressure –> sarcomeres replicate in parallel –> thickness increase
* increased myocardial oxygen demand
* endocardial ischemia
* fibrosis
* collagen disruption
* injury to small coronary vessels

eccentric - increased volume –> sarcomeres replicate in series –> elongation of myocytes
* increased myocardial wall stress
* myocyte injury or necrosis
* myocyte slippage

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Explain the Ca++ movement during cardiac muscle contraction

A

CONTRACTION
Ca++ enters the myocardial cell –> triggers the release of additional Ca++ from the sarcoplasmic reticulum (SR) –> Ca++ flows through the ryanodine channel –> binds to troponin C located on the actin and myosin complex –> sarcomere contraction

RELAXATION
Ca++ released from troponin C –> Ca++ sequestered back into the SR via the sarcoplasmic/endoplasmic reticulum Ca++-ATPase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What are the heart’s main substances for energy production and how does heart failure affect the preferred substance?

A
  • free fatty acids or glucose
  • in heart failures the heart prefers glucose –. requires less oxygen to metabolize than fatty acids
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is the function of Phospholamban?

A

cardiac myocyte intracellular Ca++ regulator –> inhibits reuptake by SERCA2a

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Above what venous pulmonary venous pressure is pulmonary edema likely to occur?

A

> 25 mm Hg

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

At what systemic venous pressures is right-sided congestion likely to occur?

A

> 20 mm Hg

How well did you know this?
1
Not at all
2
3
4
5
Perfectly