CVS Heart Failure Flashcards
Normal cardiac output
5L/min
Normal stroke volume
75ml/beat
Normal LV end diastolic volume
150ml
Normal LV end systolic volume
75ml
Give some causes of heart failure.
Any condition that reduces myocardial efficiency through damage or overload. Ischaemic heart disease Hypertension Pregnancy Congenital heart disease Pericardial disease
What happens when the heart is overloaded.
Myocardium is overstretched and according to Starling’s law, contraction becomes less efficient at very high end diastolic volumes.
How is stroke volume affected in heart failure?
Increased end systolic volume due to reduced contractility
What falls in heart failure!
Inotropy - overload
Stroke volume
Spare capacity
What rises in heart failure
Heart rate
Hypertrophy
Ventricular volume - mechanical inefficiency
What does reduced CO cause?
Arterial pressure falls This activates Baroreceptors Increased sympathetic activity Vasoconstriction, increased TPR, increased after load Increased intropy
Why does oedema occur?
Vasoconstriction and fluid retention results in increased capillary hydrostatic pressure so there is net outflow of fluid from the capillaries forming tissue fluid.
What is systolic dysfunction?
Failure of the heart to pump.
Strength of contraction is not sufficient.
Increased end systolic volume due to inadequate emptying.
Pressure transmitted to venous systems.
Where is led a found in right heart failure
Peripheral oedema as pressure is transmitted to systemic venous circulation
Where is oedema found on left heart failure? How does this affect the right heart.
Pulmonary oedema as pressure is transmitted to the pulmonary venous system.
As this is a low resistance system, the pressure is transmitted to the pulmonary arteries resulting in right ventricular hypertrophy.
What is systolic dysfunction caused by?
Thinning of myocardial wall
Mitral valve incompetence
Arrhythmias
What is diastolic dysfunction?
Failure of heart to relax.
Inadequate filling so inadequate stroke volume.
Reduced cardiac output.
What structural heart changes occur in heart failure
Loss of muscle Increased collagen Myocyte hypertrophy SER dysfunction Dilated heart is systolic dysfunction Hypertrophied heart is diastolic dysfunction
How does the starling curve change
Heart can no longer produce same amount of force for a given filling
Less CO for a given venous pressure
Describe classes of heart failure
1 no symptoms
2 no limitation of physical activity. Fine at rest.
3 marked limitation of physical activity. Fine at rest.
4 inability to carry out physical activity without symptoms. Symptoms at rest
What is congestive heart failure
Both ventricles affected
Symptoms of left heart failure
Pulmonary oedema Tachycardia Cardiomegaly Fatigue Extra heart sounds Mitral regurgitation
Symptoms signs of right heart failure
Peripheral oedema Raised JVP Fatigue Pitting oedema Ascites Hepatomegaly
What causes right heart failure?
Lung disease
Pulmonary embolism or hypertension
Valve disease
Describe the RAAS
Reduced kidney perfusion and stimulation of beta adrenergic receptors in the kidey causes renin release.
This converts angiotensin oven to angiotensin I.
ACE then converts angiotensin I to angiotensin II.
Angiotensin II acts on zona glomerulus to increase aldosterone which promotes reap take of sodium and water from the kidney tubules, which results in increased blood volume.
It also causes vasoconstriction.
Together these raise blood pressure, increaseing preload and after load.
ACE also fragments bradykinin.
Angiotensin can cause direct damage to heart myocytes
