Pathophysiology of cardiac failure

Question 1

Cardiac Output =

Answer 1

SV x HR

Question 2

What determines preload?

Answer 2

venous return

Question 3

What is afterload?

Answer 3

Force the contracting heart muscle must generate to eject blood from the heart

Question 4

What are the main components of afterload?

Answer 4

• Vascular resistance
• Ventricular wall tension

Question 5

What determines myocardial contractility?

Answer 5

Sympathetic nervous system

Question 6

What does an increase in contractility generate?

Answer 6

increases CO independent of preload and afterload

Question 7

Classify stage 1 heart failure

Answer 7

No limitation on physical activity

Question 8

Classify stage 2 heart failure

Answer 8

Slight limitation on physical activity

Physical activity results in fatigue, palpitation, dyspnoea

Question 9

Classify stage 3 heart failure

Answer 9

Marked limitation of physical activity

Question 10

Classify stage 4 heart failure

Answer 10

Unable to carry on any physical activity without discomfort. Will experience symptoms of heart failure at rest

Question 11

What is systolic ventricular dysfunction?

Answer 11

Impaired cardiac contractility therefore a decreased ejection fraction

Question 12

What is diastolic ventricular dysfunction?

Answer 12

Normal ejection fraction but impaired diastolic ventricular relaxation and decreased filling. Heart is pumping less volume than normal

Question 13

What are the 3 factors that cause systolic dysfunction when affected?

Answer 13

• Contractility
• Volume overload
• Pressure overload - valvular stenosis

Question 14

What are the results of systolic dysfunction?

Answer 14

• Increased EDV
• ventricular dilation
• Increased ventricular wall tension (leads to long term remodelling)

Question 15

What is more common; systolic or diastolic dysfunction?

Answer 15

systolic dysfunction

Question 16

What are the causes of diastolic dysfunction?

Answer 16

• Impedance of ventricular expansion - constrictive pericarditis
• Increased wall thickness; hypertrophy
• Delayed diastolic relaxation; aging, ischaemia
• Increase HR; less opportunity for the heart to relax

Question 17

What does cardiac tamponade cause in the pericardium?

Answer 17

reduces the space that the heart occupies

Question 18

What conditions cause impaired diastolic filling?

Answer 18

• Left ventricular hypertrophy
• Restrictive cardiomyopathy
• Myocardial fibrosis
• Transient myocardial ischaemia
• Pericardial constriction or tamponade

Question 19

What causes impaired contractility in systolic dysfunction?

Answer 19

• Coronary artery disease
  
  • Myocardial Infarction
  • Transient myocardial ischaemia
• Chronic volume overload
  
  • Mitral regurgitation
  • Aortia regurgitation
• Dilated cardiomyopathies

Question 20

What causes increase afterload (chronic pressure overload) in systolic dysfunction?

Answer 20

• Advanced aortic stenosis
• Uncontrolled severe hypertension

Question 21

What is LHS HF most likely to cause?

Answer 21

RHS heart failure

Question 22

What occurs in RHS heart failure?

Answer 22

Congestion of peripheral tissues:

• Oedema and ascites
• Liver congestion; impaired liver function
• GI tract congestion; anorexia, GI distress, weight loss

Question 23

What is an ascites?

Answer 23

swelling of abdominal region due to back up of fluid in the portal system

Question 24

What occurs in LHS heart failure?

Answer 24

• Decreased cardiac output
  
  • Activity intolerence and signs of decreased tissue perfusion; cyanosis and hypoxia
• Pulmonary congestion
  
  • Othopnea
  • Parxysmal nocturnal dyspnoea
  • Cough with frothy sputum

Question 25

What conditions mpede flow into the lungs in RV dysfunction?

Answer 25

* Pulmonary hypertension * Valve damage/stenosis/incompetence

Question 26

What conditions affect the pumping ability of the RV?

Answer 26

* Cardiomyopathy * Infarction

Question 27

What are the causes of Left ventricular dysfunction?

Answer 27

* Hypertension (increase TPR) * Acute MI * Aortic or mitral valve stenosis or regurgitation * Increase in pulmonary pressure can lead to RV failure if you have LV failure

Question 28

What are the main compensatory mechanisms that ultimately contribute to heart failure?

Answer 28

* Sympathetic nerve activity * Renin-angiotensin-aldosterone * Frank-Starling (length-tension) mechanism * Fluid movements

Question 29

What is the problem with the frank-starling mechanisms in systolic dysfunction

Answer 29

* Increased vascular volume --\> increased EDV * Increase in muscle stretch and O₂ consumption * Walls of the ventricles are stretch beyond the optimal length resulting in an decreased force of contraction * Increasing HR has very little impact on SV

Question 30

What are the problems with sympathetic activity in systolic dysfunction?

Answer 30

* Tachycardia, vasoconstriction, decreased perufsion, cardiac arrhythmias, renin release * Increase the workload of the heart - causes ischaemia, damage to myoctes and decreased contractility * Desensitisation of beta but not alpha receptors \*\*Numb to the effect of adrenaline

Question 31

What are the problems with Renin-Angiotensin system in systolic dysfunction?

Answer 31

* Decrease in renal blood flow stimulate renin * Renin --\> Angiotensin II (constriction and remodelling) * Angiotensin II = vasocontrictor and stimulates aldosterone release * Sodium and water retention increase

Question 32

What are the other functions of angiotensin and aldosterone and what are the results of this on the heart?

Answer 32

* Angiotensin II and aldosterone are involved in inflammatory responses leading to the deposition of fibroblasts and collagen in the ventricles * Increase in stiffness and decrease contractility of the heart leading to remodelling and progressing dysfunction

Question 33

Strategies for the treatment of heart failure

Answer 33

* Increase cardiac contractility * Decrease proload or afterload * By relaxing vascular smooth muscle * Reducing blood volume * Inhibit RAAS * Prevent inappropriate increase in HR