Session 9-Pathophysiology Of Heart Failure Flashcards
What is the definition of heart failure relating to its pathophysiological state?
Pathophysiological state in which an abnormality of cardiac function is responsible for the failure of the heart to pump blood at a rate commensurate with requirements of the metabolising tissues
What is the definition of heart failure relating to it being a clinical syndrome?
Clinical syndrome caused by an abnormality of the heart and recognised by characteristic pattern of haemodynamic, renal, neural and hormonal responses
What is the other definition of heart failure?
State in which heart fails to maintain an adequate circulation for the needs of the body despite an adequate filling pressure
What is the primary cause of systolic heart failure?
Ischaemic heart disease
What is the approximate cardiac output of the heart?
~5 litres/min
What is the approximate ejection fraction of the heart?
50-60%
Which factors influence the cardiac output of the heart?
1) heart rate
2) venous capacity (LV preload)
3) aortic and peripheral impedance (after load)
4) myocardial contractility
What does Starling’s Law of the heart say?
The force developed in a muscle fibre depends on the degree to which the fibre is stretched
What is the most common cause of heart failure?
Left ventricular systolic dysfunction
What happens to the myocardial wall in left ventricular systolic dysfunction?
Thins due to:
- fibrosis and necrosis of myocardium
- activity of matrix proteinases
Why does left ventricular systolic dysfunction lead to mitral valve incompetence?
Gap forms between the cusps due to dilatation of the ventricle
What structural heart changes occur in left ventricular systolic dysfunction?
1) loss of muscle
2) uncoordinated or abnormal myocardial contraction
3) changes to extra cellular matrix: increase in collagen
4) change of cellular structure and function:
- sarcoplasmic reticulum dysfunction
- changes to calcium availability
- myocyte hypertrophy
What are the long-term deleterious effects of an increased level of noradrenaline after heart failure?
1) beta-adrenergic receptors are down-regulated
2) noradrenaline induces cardiac hypertrophy/myocyte apoptosis and necrosis via alpha receptors
3) noradrenaline induces up-regulation of RAAS
4) reduction in heart rate variability (reduced parasympathetic and increased sympathetic nervous system)
How does sympathetic activation in heart failure lead to myocardial hypertrophy?
1) myocardial damage
2) activation of sympathetic nervous system
3) RAAS -> fluid retention -> increased wall stress -> myocardial hypertrophy
OR
3) vasoconstriction -> increased wall stress -> myocardial hypertrophy
How does sympathetic activation in heart failure lead to decreased contractility?
1) myocardial damage
2) activation of sympathetic nervous system
3) vasoconstriction -> increased wall stress -> increased myocardial oxygen demand -> decreased contractility
OR
3) increased heart rate and contractility -> increased myocardial oxygen demand -> decreased contractility
How does sympathetic activation in heart failure lead to myocyte damage?
1) myocardial damage
2) activation of sympathetic nervous system
3) direct cardiotoxicity -> myocyte damage
What effects does elevated angiotensin II have?
- potent vasoconstrictor
- promotes left ventricular hypertrophy and myocyte dysfunction
- promotes aldosterone release
- promotes Na+/H20 retention
- stimulates thirst by central action
True or false: natriuretic hormones work in the same way as angiotensin
FALSE - opposite way
What effect does atrial natriuretic hormone have on arterioles?
Constricts afferent and vasodilates efferent arterioles
What effect does atrial natriuretic hormone have on Na+ reabsorption?
Decreases Na+ reabsorption in collecting duct
What causes the release of natriuretic peptides?
Stretch or increase in cardiac chamber volume
What can cause hypo-natraemia?
- increased water intake
- action of anti-diuretic hormone on V2 receptors in collecting duct
True or false: normally, hypo-natraemia/hypo-osmolality inhibits anti-diuretic hormone release but its levels are increased in heart failure
TRUE
Which cells secrete endothelin?
Vascular endothelial cells
What is endothelin?
Potent system and renal vasoconstrictor acting via autocrine activity thus activating RAAS
What happens to the level of endothelin in patients with heart failure?
Increases
What stimulates prostaglandins E2 and I2?
Noradrenaline and RAAS
What do prostaglandins E2 and I2 act as?
Vasodilators on afferent renal arterioles to attenuate effects of noradrenaline/RAAS
Which cells produce nitric oxide?
Endothelial cells via nitric oxide synthase
What does bradykinin promote?
Natriuresis and vasodilation
Production of prostaglandins
What happens to the level of tumour necrosis factor in heart failure?
Increases
What is net filtration pressure equal to?
Hydrostatic pressure - osmotic pressure
How does heart failure affect capillary hydrostatic pressure?
Increases pressure
What changes in skeletal muscle can alterations in vascular tone lead to?
- reduced skeletal muscle blood flow
- reduction in skeletal muscle mass (cachexia)
- abnormalities of structure and function
- contribute to fatigue and exercise intolerance
What renal changes can alterations in vascular tone lead to?
-increased Na+/water retention due to neuro–hormonal activation
What are the cardiomyocytes like in heart failure with preserved ejection fraction (HFpEF)?
Thicker and shorter
What can heart failure be divided into in clinical practice?
- left sided heart failure
- right sided heart failure
- biventricular (congestive) cardiac failure
- LVSD (pump failure)
- HFpEF (failure of LV relaxation)
What are the signs/symptoms of left heart failure?
- fatigue
- exertional dyspnoea
- Orthopnoea
- paroxysmal nocturnal dyspnoea (PND)
- tachycardia
- cardiomegaly
- 3rd or 4th heart sound
- functional murmur of mitral regurgitation
- basal pulmonary crackles
- peripheral oedema
What can cause right heart failure?
- chronic lung disease
- pulmonary embolism/pulmonary hypertension
- left-to-right shunts
- isolated right ventricular cardiomyopathy
- pulmonary/tricuspid valvular disease
What are the signs/symptoms of right heart failure?
- fatigue
- dyspnoea
- anorexia
- nausea
- increased jugular venous pressure
- tender, smooth hepatic enlargement
- dependent pitting oedema
- ascites
- pleural effusion
What is left ventricular systolic dysfunction?
Increased LV capacity but reduced LV cardiac output
What is heart failure with preserved ejection fraction?
Ejection fraction is normal, LV relaxation decreases, leading to impaired LV filling
What are the risk factors for HFpEF?
Obesity Elderly Female Hypertension Diabetes
Why is peripheral oedema seen in left heart failure?
Increased hydrostatic pressure in vessels
