heart failure diagnosis, investigation and management Flashcards
what is the commonest cause of heart failure in the west?
coronary artery disease
how does heart failure affect the heart?
impairs the ability of the heart to function as a pump to support physiological circulation
describe the pathophysiology of heart failure?
- changes to heart and peripheral vascular system due to haemodynamic changes associated with heart failure
- these are compensatory to maintain cardiac output and peripheral perfusion
- as disease progresses the mechanisms are overwhelmed and become pathophysiological
- development of pathological peripheral vasoconstriction and sodium retention by activation of RAAS are a loss of beneficial compensatory mechanisms and represent cardiac decompensation
- factors involved in this are venous return, outflow resistance, contractility of myocardium and salt and water retention
what affect does myocardial failure have on venous return (preload)?
- reduction in volume of blood ejected with each heart beat and increase in blood remaining after systole
- Increased diastolic volume stretches myocardial fibres and myocardial contraction is restored (starlings law) yet in failing myocardium it results in depression of ventricular function curve
- In heart failure the proportion of blood ejected with each heart beat is reduced
- Sinus tachycardia ensures that any reduction of stroke volume is compensated for by increased heart rate and cardiac output is maintained
- In severe myocardial dysfunction, the CO can only be maintained by a large increase in venous pressure and/or marked sinus tachycardia. This contributes to dyspnoea due to accumulation of interstitial and alveolar fluid and also to hepatic enlargement, ascites and dependent oedema due to increased systolic venous pressure. A normal increase in CO during exercise cannot be produces
- In severe heart failure CO at rest is depressed despite high venous pressures and CO is redistributes to maintain perfusion of vital organs such as heat, brain, kidneys at expense of skin and muscle
what is after load (outflow resistance) and what is it formed by?
the load or resistance against which the ventricle contracts
formed by
-pulmonary and systemic resistance
-physical characteristics of the vessel walls
-volume of blood that is ejected
- what affect does increased after load have on the heart
2. how can this be expressed?
- decreases cardiac output -> further increase in end-diastolic volume and dilation of ventricle ->exacerbation
- laplace’s law
how is myocardial contractility (ionotropic state) affected in heart failure?
- sympathetic NS-activated via baroreceptors as early compensatory mechanism to give ionotropic support and maintain CO
- chronic sympathetic activation-increase neurohormonal activation leading to myocyte apoptosis. compensated by down regulation of beta receptors. increased contractility can result from increased sympathetic drive and this is a normal part of frank-starling relationship. myocardial depressants (hypoxia) decrease myocardial contractility
what pathophysiological changes are seen in heart failure?
ventricular dilatation myocyte hypertrophy increased collagen synthesis altered myosin gene expression altered sarcoplasmic calcium ATPase density increased ANP secretion salt and water retention sympathetic stimulation peripheral vasoconstriction
what are the main causes of heart failure?
ischaemic heart disease
cardiomyopathy (dilated)
hypertension
name some other causes of heart failure?
- cardiomyopathy (undilated)
- valvular heart disease
- congenital heart disease
- alcohol and drugs
- hyperdynamic circulation (anaemia, thyrotoxicosis, haemochromatosis, Paget’s disease)
- right heart failure
- tricuspid incompetence
- arrythmias
- pericardial disease
- infections (chagas disease)
describe how heart failure causes neuohormonal and sympathetic activation (salt and water retention?
- Increase in venous pressure when ventricles fail leads to retention of salt and water and their accumulation in interstitium
- Reduced cardiac output leads to diminished renal perfusion activating RAAS and enhancing salt and water retention which increases venous pressure. The retention of sodium is partly compensated by circulating atrial natriuretic peptides and antidiuretic hormone
- Increased ventricular wall stress promotes ventricular dilation and further worsens contractile efficiency. Prolonged activation of the sympathetic nervous and RAA systems exerts direct toxic effects on myocardial cells
describe myocardial remodelling in heart failure?
Left ventricular remodelling is a process of progressive alteration of ventricular size, shape and function owing to the influence of mechanical, neurohormonal and genetic factors in clinical conditions such as MI, cardiomyopathy, hypertension, valvular heart disease. Hallmarks include hypertrophy, loss of myocytes and increased interstitial fibrosis. Remodelling continues for months and eventually leads to change in ventricles and impairment of function of the heart as a pump. In cardiomyopathy the process of progressive ventricular dilation or hypertrophy occurs without ischaemic myocardial injury or infarction.
describe changes in myocardial gene expression in heart failure?
Haemodynamic overload of ventricle stimulates change in cardiac contractile protein gene expression. Increases protein synthesis but many proteins also switch to fetal and neonatal isoforms
describe abnormal calcium homeostasis in heart failure?
- Calcium ion flux within myocytes regulates contractile function.
- Excitation of myocyte cell membrane causes rapid entry of calcium from extracellular space and triggers the release of intracellular calcium from sarcoplasmic reticulum and initiates contraction.
- Relaxation results from uptake and storage of calcium by sarcoplasmic reticulum controlled by changes in nitric oxide. In heart failure there is prolongation of calcium current association with prolongation of contraction and relaxation
describe ventricular remodelling after an acute infarction?
- initial infarct
- expansion of infarct (hours to days)
- global remodelling (days to months)
describe ventricular remodelling in diastolic and systolic heart failure?
hypertrophied heart (diastolic heart failure) dilated heart (systolic heart failure)
describe apoptosis of myocytes in heart failure?
Apoptosis of myocytes is associated with irreversible congestive heart failure and the spiral of ventricular dysfunction, characteristic of heart failure, results from initiation of apoptosis by cytokines, free radicals and other triggers
what is ANP?
ANP is released from atrial myocytes in response to stretch. It induces diuresis, natriresis, vasodilation and suppression of RAAS. Levels are increased in congestive heart failure. Renal response to ANP is attenuated in heart failure.
name natriuretic peptides implicated in heart failure?
ANP
BNP
C-type
what is BNP?
BNP is mainly secreted by the ventricles and has similar action to ANP but is of greater diagnostic and prognostic value
what Is C type peptide?
C-type peptide-limited to vascular endothelium and CNS and has similar effects to ANP and BNP
what are the therapeutic benefits of natriuretic peptides?
- BNP (nesritide) has no effect on dysponea and no longer recommended
- NEP involved in degradation of variety of vasoactive peptides.
describe endothelial function in heart failure?
Central role in regulation of vasomotor tone
In patients with heart failure, endothelium-dependent vasodilation in peripheral blood vessels is impaired and one mechanism of exercise limitation
Abnormal endothelial responsiveness is due to abnormal release of nitric oxide and vasoconstrictor substances (endothelin)
Activity of nitric oxide is a potent vasodilator is blunted in heart failure
ET has actions contributing to pathophysiology of heart failure; vasoconstriction, sympathetic stimulation, RAAS activation and left ventricular hypertrophy
describe the role of antidiuretic hormone (vasopressin) in heart failure?
ADH is raised in severe chronic heart failure especially in patients on diuretics.
High ADH conc. Precipitates hyponatraemia which is ominous prognostic indicator
what are the different clinical syndromes of heart failure?
- left ventricular systolic dysfunction
- right ventricular systolic dysfunction
- diastolic heart faiure
what causes left ventricular systolic dysfunction?
caused by ischaemic heart disease but can also occur with valvular heart disease and hypertension
what causes right ventricuar systolic dysfunction?
may be secondary to chronic LVSD but can occur with primary and secondary pulmonary hypertension, right ventricular infarction, arrythmogenic right ventricular cardiomyopathy and adult congenital heart disease
what is diastolic heart failure?
syndrome consisting of symptoms and signs of heart failure with preserved left ventricular ejection fraction above 45-50% and abnormal left ventricular relaxation assessed by echo. There is increased stiffness in ventricular wall and decreased left ventricular compliance leading to impairment of diastolic ventricular filling and decreased cardiac output. It is more common in elderly hypertensive patients but may occur with primary cardiomyopathies
what are the common symptoms of heart failure?
Exertional dyspnoea
Orthopneoa
Paroxysmal nocturnal dyspnoea
Fatigue
what are the common signs seen in a patient with heart failure?
Cardiomyopathy Third and fourth heart sounds Elevated JVP Tachycardia Hypotension Bi-basal crackles Pleural effusion Peripheral ankle oedema Ascites Tender hepatomegaly
describe how a diagnosis of heart failure should be made?
Diagnosis relies on evidence of cardiac dysfunction usually via echo. The underlying cause should be established
what classification system can be used in heart failure?
New York heart association (NYHA) classification of heart failure
describe the features of class I NYHA?
no limitation
normal physical exercise doesn’t cause fatigue, dyspnoea or palpitations
describe the features of class II NYHA?
mild limitation
comfortable at rest but normal physical activity produces fatigue, dyspnoea or palpitations
describe the features of class III NYHA?
marked limitation
comfortable at rest but gentle physical activity produced marked symptoms of heart failure
describe the features of class IV NYHA?
symptoms of heart failure occur at rest and are exacerbated by any physical activity
describe the algorithm for the diagnosis of heart failure?
- signs and symptoms
- ECG, CXR, natriuretic peptides (if normal HF unlikely)
- Echo (if normal HF unlikely)
- assess aetiology, degree, precipitating factors, type of cardiac dysfunction
- choose treatment
what investigations are useful in a patient with suspected heart failure?
- bloods
- CXR
- ECG
- echo
- stress echo
- nuclear cardiology
- cardiac MRI
- cardiac catheterisation
- cardiac biopsy
- cardiopulmonary exercise testing
- ambulatory ECG
what blood tests are useful to perform in a patient with suspected heart failure?
FBC, liver biochem, U&E, cardiac enzymes, BNP or NTproBNP, thyroid function
what may CXR show in a patient with heart failure?
cardiomegaly, pulmonary congestion with upper lobe diversion, fluid in fissures, kerley B lines, pulmonary oedema
what is the purpose of doing an ECG in a patient with heart failure?
for ischaemia, hypertension or arrythmia
what is the purpose of doing echo in patients with heart failure?
cardiac chamber dimension, systolic and diastolic function, regional wall motion abnormalities, valvular heart disease, cardiomyopathies
what is the purpose of doing stress echo in patients with heart failure?
assessment of viability of dysfunctional myocardium-dobutamine identifies reserve in stunned or hibernating myocardium