Heart failure
Condition caused by impairment of heart’s function as pump
Clinical manifestations of heart failure
Fluid congestion (backward failure) Inadequate blood flow to tissues (forward failure)
Compare acute and chronic heart failure
In acute failure, events are rapid and consequence is forward failure (shock)
In chronic, compensatory mechanisms are brought into play and backward failure dominates (congestion)
Compensatory mechanisms in chronic heart failure
Ventricular chamber enlargement - increases amount of blood in ventricle, so more is ejected at cost of fluid retetion
Muscle mass increase - Can eject more but more O2 required for larger muscle
Sympathetic stimulation - Increase in heart rate and contractility, redistribution and retention of fluid
Cardiac remodelling that occurs in heart failure
Hypertrophy in response to greater demand
Adrenergic stimuli, cytokines & angiotensin II mediate effects
These increase cardiac output at cost of adverse effects
Benefit/Harm from adrenergic signals to remodel heart after failure
Benefit
- Contractility
- Hypertrophy
Harm
- Myocyte apoptosis
- Myocyte toxicity
Benefit/Harm from angiotensin II to remodel heart after failure
Benefit
- Hypertrophy
Harm
- Changed expression of contractile proteins
Benefit/Harm from Cytokines (TNFa) to remodel heart after failure
Benefit
- Hypertrophy
Harm
- Remodelling of matrix
- Dilatation
What does a dilating chamber indicate
A dilating chamber is a failing chamber
Main 3 Types of heart failure
Left Ventricular Failure
Right Ventricular Failure
Congestive cardiac failure
Consequences of LV failure
Raised end diastolic pressure –> raised LA pressure –> Raised pulmonary capillary pressure –>
Increased diffusion barrier for gas exchange & pulmonary oedema leading to breathlessness
NY heart association - classification of heart failure
Class I No limitation of physical activity
Class II Slight limitation of activity (breathlessness/fatigue with moderate exercise)
Class III Marked limitation of activity (breathlessness with minimal exercise)
Class IV Severe limitation of activity (symptoms at rest)
LVF on CXR
Alveolar oedema kerly B Lines Cardiomegaly Dilated Upper lobe vessels pleural Effusion
(ABCDE)
Causes of LVF
Acute ventricular dysrythmias (VF) MI/Ischaemic heart disease Longstanding hypertension Valve disease (Left side) Cardiomyopathies & Drugs Congenital heart disease
Consequences of RV Failure
Raised end diastolic pressure –> raised RA & jugular venous pressures –> Raised central venous pressures –>
Hepatomegaly (abdominal discomfort) & pulmonary oedema
Causes of RVF
Left Heart Disease Lung disease Thromboemboli Haematopathologies Pulmonary Arterial Hypertension (rare)
RVF due to LV disease
Coronary artery disease causes myocyte damage; LV dilates & fails, increasing backward pressure in RA and pulmonary capillary bed
Pressure increases in pulmonary arteries to compensate leading to further damage to pulmonary arterial wall and greater resistance
Emphysema causing RVF
Destruction of alveolar walls and loss of lung capillaries; failure of lung ventilation so hypoxia constricts pulmonary arteries and causes pulmonary hypertension and RVF
Cor pulmonale
RVF as result of respiratory disease
Congestive heart failure and causes
Combination of both LVF & RVF
Commonest cause of CCF is ischaemic heart disease followed by other causes of LVF
Also cardiomyopathies/drugs
High Output Cardiac Failure
Heart muscle essentially normal but output cannot adequately perfuse tissue
Consequences of High Output Cardiac Failure
Arteriovenous fistula - blood bypasses tissue
Septic shock
Anaemia
Thyrotoxicosis
