Heart failure Flashcards
Definition of heart failure
Physiological control of cardiac output
Response to increased demand on the heart in physiological state vs heart failure
Significance of the circulatory system . being a closed loop
Because the circulatory system is a closed loop, heart failure on either side would eventually lead to biventricular failure
Overview of causes of heart failure
Common causes of heart failure
- Ischaemic heart disease
- hypertension
- valvular disease- mitral and aortic
- shock
Molecular changes that occur in heart failure
- induction of foetal genes: alpha myosin to beta myosin, which is less efficienct at contracting
- abnormal protein synthesis: ion channels, contractile proteins. abnormal excitation/contraction coupling.
- production of cytokines, growth factors and neurohormones: eg noradrenaline, angiotensin by myocytes or stromal cells. results in autocrine/paracrine loops causing local myocyte damage–once initiated they may result in ongoing myocardial damage
Myocardial Remodelling in heart failure
(debate as to whether it’s a cause or effect of heart failure)
Myocardial cells
- hypertrophy: thickening by increasing the number of sarcomeres eg left ventricular wall
- lengthening: sarcomeres overlap. associated with ventriuclar dilatation and more advanced disease
Changes in ECM
-fibrosis triggered by Ang2 and aldosterone. Alter the way forces are transmitted through the myocardium
Myocardial death
Apoptosis triggered by SNS, Ang2 and other local factors
Changes in heart shape
- heart becomes more globular and spherical
- this is a macroscopic change
- poor mechanics- increases end-diastolic wall stress
- pulls apart papillary muscles of mitral/tricuspid valves
Macroscopic appearance of heart in heart failure
- ventricular dilatation
- compensatory hypertrophy: weight and thickness
General rule of thumb:
a) Pressure overload–>hypertorphy
b) Volume overload–>hypertrophy AND dialtation
- might detect underlying cause: amyloid, HOCM, infarction etc
Microscopic appearance of heart in heart failure
What are the broad categories of intrinsic diseases of the heart?
Ones affecting the:
myocardium
endocardium
pericardium
valves
(but main cause of HF is obviously IHD)
3 patterns of myocardial disease (Cardiomyopathies)
- dilated cardiomyopathy
- hypertorphic cardiomyopathy
- restrictive cardiomyopathy
Most common cardiomyopathy
Dilated cardiomyopathy
What happens in Dilated cardiomyopathy?
- increased mass- slight, due to hypertrophy
- but most importantly- THINNED walls as CHAMBER DILATES
- macro: globular heart
- micro: (non-specific) hypertrophy and fibrosis
Patohgenesis of DCM
Inflammatory causes of dilated cardiomyopathy (i.e. myocarditis)
Infection: viral, bacterial (less common), protozoal (trypanosome)
Drug: hypersensitivity reaction to a drug
Systemic: SLE, amyloid
Idiopathic: giant cell myocarditis
Familial hypertrophic cardiomyopathy
A cause of hypertrophic cardiomyopathy
Microscopic changes in Familial HOCM
Myocyte disarray (not aligned) and fibrosis.
This leads to arrythmias.
Pathogenesis of HOCM
What is restrictive cardiomyopathy?
Heart muscle is unable to relax so ventricles can’t fill properly.
This could be because of abnormalities in the heart MUSCLE itself (myocardium) or because of abnormalities in the PERICARDIUM/ENDOCARDIUM.
Myocardial: amyloid
Pericardial fibrosis
Endocardial fibrosis
2 broad categories of cardiac amyloid (a cause of restrictive cardiomyopathy)
-
senile atrial amyloid
- amyloid is derived from ANP
- normal ageing change -
systemic
- AL amyloid: produced in myeloma
- AA amyloid: produced in autoimmune diseases like RA
- can be hereditary
Essentially amyloid protein deposits in the myocardium and impairs normal function of muscle
Causes of endomyocardial fibrosis
How can disease of pericardium cause heart failure?
Constrictive pericarditis
Can happen following bacterial or viral pericarditis, for eg
Which valve diseases can cause heart failure and how?
Mitral
Mitral regurgitation- leads to volume overload
Aortic
Aortic stenosis- leads to pressure overload
Aortic regurgitation- leads to volume overload
Macro changes in valvular heart failure
How does congenital heart disease cause heart failure?
Ventricular septal defect
Causes right ventricular hypertrophy as blood flows from left ventricle into the right ventricle upon systole.
Pressure in thin walled right ventricle rises, causing right heart failure
Extrinsic causes of heart failure
- Pulmonary hypertension–>right heart failure
- Systemic hypertension–>right heart failure
Causes of pulmonary hypertension
obstruction or destruction of pulmonary vessels
- pulmonary fibrosis
- pulmonary thromboembolic disease eg DVT
chronic hypoxia- this will cause pulmonary vessels to vasoconstrict (to shunt blood away from poorly ventilated areas)
- COPD
- lung fibrosis
- cystic fibrosis
Complications of heart failure
Local
- arrythmias, sudden cardiac death
- further ischaemic myocardial damage
Systemic
- Left sided HF
a) Forward failure: hypoperfusion of Kidneys, GI tract and brain
b) Backward failure: pulmonary congestion and oedema - Right sided HF
a) Forward failure: not that important
b) Backward failure: systemic oedema and organ congestion (nutmeg liver- impaired liver function)
Schematic of systemic hypoperfusion of kidneys
