Pathophysiology of heart failure Flashcards
Physiological definition of heart failure?
Heart fails to deliver enough blood for the needs of the body
Clinical definition of heart failure?
Syndrome with multiple causes. Symptoms including breathlessness, fatigue and oedema
Describe blood flow through the heart?
de-oxygenated blood from the body into the superior and inferior vena cava. Into the right atrium, through tricuspid valve into right ventricle. Through pulmonary valve into pulmonary artery to the lungs..
Oxygenated blood from lungs into pulmonary veins into the left atrium through mitral valve into left ventricle, through aortic valve into aorta
What surrounds the heart?
Myocardium
List the 4 types of heart failure?
Acute or chronic
Right or left sided
How do right and left sided heart failure dffer?
Right = peripheral oedema ad raised jugular venous pressure Left = pulmonary venous pressure raised and pulmonary oedema
What can aggravate chronic heart failure?
Dysfunctional neuro-hormonal regulation
What is a complication of chronic heart failure regarding medical procedures?
Complications of GA
Cardiac causes of heart failure?
Heart itself is damaged or its function is restricted - heart muscle disease (ischaemic heart disease)
Abnormal rhythm
Non-cardiac causes of heart failure syndrome?
Excessive demand in high output heart failure - anaemia
Fluid overload from other causes - renal failure, IV therapy
LIst the 4 most common causes of heart failure
Ischaemic heart disease
Hypertension
Valvular heart disease
Chronic obstructive pulmonary disease
Symptoms of heart failure? and causes
Breathlessness (pulmonary oedema)
Oedema (fluid retention)
Fatigue (poor cardiac output)
Investigations of heart failure?
ECG
Echocardiogram
How does reduced cardiac output resemble dehydration?
Reduced blood pressure = low blood volume. Physiological process (activation of renin-angiotensin-aldosterone system) retain salt and water = dehydration
Reduced cardiac output leads to the activation of the renin-angiotensin-aldosterone system to retain salt and water. What else is activated by renin-angiotensin-aldosterone system?
Activates sympathetic nervous system to vasoconstrict (maintain BP) and stimulate heart (maintain cardiac output)
Why is the activation of the renin-angiotensin-aldosterone system and sympathetic nervous system conflicting in chronic heart failure?
Chronic heart failure - excessive adrenaline (from sympathetic NS) causes overdrive of the heart
and renin-angiotensin-aldosterone system causes fluid retention = symptoms of chronic heart disease
Activation of renin-angiotensin-aldosterone system and sympathetic NS is compensatory in what type of heart disease?
Acute
How do stretch receptors cause a conflicting compensatory response?
Increased intracardiac pressures detected by stretch receptors = signla fluid overload = peptides released to stimulate sodium excretion = opposite tot he other effects = hormones fighting each toher
Result of renin-angiotensin-aldosterone system?
Increased circulatory volume, oedema, vasoconstriction
What hormones activate sympathetic NS?
Adrenaline and noradrenaline
Effects of sympathetic NS?
Stimulate HR and contractility
Vasocontriction
Increase BP
Consequences of sympathetic NS in the long term?
Fluid retention and oedema
Vasoconstriction increases the resistance against which the heart has to work
Continuous sympathetic stimulation damages heart muscle
Mechanism of action of ACE inhibitors?
Stop production fo angiotensin II from angiotensin I - prevents the effects of angiotensin - vasoconstriction, oedema, increased volume, sympathetic NS activation - these are intially compensatory but then exacerbate symptoms of heart failure
What activates renin-angiotensin-aldosterone system?
Renal hypoperfusion
Effects of angiotensin II?
Vasoconstriction and aldosterone secretion = Increase HR and BP, activate sympathetic NS and retain NA and water which raises BP
Mechanism of action of angiotensin II receptor blockers?
Prevents action of angiotensin II = exacerbates symptoms of chronic heart failure
Mechanism of action of aldosterone antagonists?
Prevents action of aldosterone = sympathetic NS, increase BP, HR, retain Na (increase BP 0 = exacerbate symptoms of heart failure
Mechanism of action of beta blockers?
Block the effect of adrenaline and noradrenaline on the heart = decrease HR and contractility = decrease fluid retention = decreased oedema, vasodilation = heart has to work less
What drugs are used when a patient has fluid overload, how do these works?
Loop diuretics - make kidney get rid of salt and water
Mechanism of action of sacubitril valsartan treatment?
Blocks ATI receptor and neprilysin (enzyme that degrades vasoactive peptides)
List 2 non-pharmacological treatments for heart failure?
Cardiac resynchronisation pacemaker Cardiac surgery (valve replacement, repair, transplant)
How does left sided heart failure present?
Pulmonary oedema
How does left sided heart failure cause pulmonary oedema?
As the left ventricle fails, blood dams back in the pulmonary veins where venous pressure rises casuing alveoli in lungs to fill with fluid
What is dyspnoea and orthopneoea?
Laboured breathing on effort and at rest
Caused by pulmonary oedema
Effects of right sided heart failure?
Congestion of the systemic and portal veins = subcutaneous oedema, fatigue, abdominal distension and discomfort
Main difference between effects of right vs left sided heart failure?
Right = systemic symptoms Left = pulmonary
What normally governs the heart rate? where is this found?
Sinoatrial node - right atrium
What causes the left and right atria to contract?
Depolarisation of sino-atrial node
What ensures there is a pause between the contraction of the atria and the ventricles?
Depolarisation fo the atrioventricular node
What causes a coordinated contraction fo the ventricles?
Depolarisation of the His-Purkinje system
ECG composed of P QRS and T wave, what do this signify?
P = atrial contraction QRS = ventricular contraction T = ventricular repolarisation
What is tachycardia?
HR too fast - greater than 100bpm
What is bradycrdia?
HR too slow - less than 60bpm
What triggers sinus tachycardia? How does it look on ECG?
Normal response to exercise or emotion
Hyperthyroidism, heart failure
Normal P waves visible, just more of them
What is atrial fibrillation?
Tachcardia due to uncoordinated and ineffectual atrial contraction = rapid and irregular ventricular rate
Effect of atrial fibrillation?
Reduce efficiency of heart = heart failure
What type of tachycardia is associated with ischaemia hear disease?
Ventricular tachycardia
How does ventricular tachycardia display in ECG?
Complexes are wide since not conducted by His-Purkinje system
What can cause sinus bradycardia?
Athletes
What is extracsystoles?
Single extra beats arising from atria or ventricles
What kind of heart rate disturbance causes cardiac arrest?
Ventricular fibrillation or asystole
Effect of ventricular fibrillation?
Uncoordinated and ineffective electrical activity of ventricles = no cardiac output = cardiac arrest
Common cause of ventricular fibrillation?
Acute coronary ischaemia (MI)
Treatment of arrhythmias?
Anti-arrhythmic drugs
Direct current cardioversion
Pacemakers (bradycardia)
Implantable defibrillators
