16.2 Heart failure therapeutics Flashcards
What is heart failure?
A state in which cardiac output is inadequate for the body’s requirements.
How common is heart failure?
- Extremely common
- Approx. 1% of UK population affected
- 1 in 5 people over 40 have heart failure
- Incidence is increasing, due to ageing population and rise in type 2 diabetes
What is the mortality for heart failure?
- 24% 1-year mortality
- 54% 5-year mortality
Prognosis for hear failure is related to its severity.
How is the severity of heart failure classified?
New York Heart Association classification:
- Grade I = mild symptoms only on extreme exertion
- Grade II = symptoms on walking approx. 250metres
- Grade III = symptoms on minimal exertion
- Grade IV = symptoms present on rest or performing activities of daily living e.g. washing, getting dressed
Grade III and IV have particularly poor prognosis.
Name the aetiologies of heart failure.
- Coronary artery disease (ischameic heart disease)
- Hypertension
- Cardiomyopathies
- Infective causes
- Valvular heart disease
- Drugs and poisons
- Peristent tachycardias
- Infiltrative diseases
- Endocrine causes
- Nutritional disorders
- Exacerbating factors
What drug has decreased the number of patients developing heart failure after an MI?
ACE inhibitors.
Historically, patients who survived an MI were very high risk for developing heart failure.
How can hypertension give rise to heart failure?
- Systemic BP increase
- This increases strain on the heart
- The left ventricle has to work hard against resistance, causes it to hypertrophise and outsrip its blood supply
- Causes ischaemia
- Can give rise to heart failure
What are cardiomyopathies?
- General term to describe diseases of the heart muscle
- Diseases can either make the muscle dilate and saggy (poor contractility) or cause cardiac myocytes to hypertrophy (become bigger)
What infective causes could lead to heart failure?
- COVID
- Coxsackie virus
Why might a patient have valvular heart disease?
- Following an acute coronary syndrome e.g. MI
- Rheumatic fever (more historic)
Causes increased risk of heart failure.
What drugs/poisons can cause heart failure?
- Chronic alcohol exposure
- Chemotherapy drugs e.g. doxorubicin
- Radiation exposure
How does a persistent tachycardia lead to heart failure?
- Raised heart rate for a long period of time means heart muscles have to work harder
- Can cause heart to fail as it struggles to keep up
How do infiltrative diseases cause heart failure?
- Deposition of abnormal substances within the heart
- Can affect both the muscle and connective tissue of the heart
- E.g. haemochromatosis: excess iron accumulation in the heart
- E.g. Wilson’s disease: excess copper accumulation in the heart
Name an endocrine cause of heart failure.
- Chronic excess of growth hormone can lead to acromegalic cardiomyopathy, heart muscle hypertrophy
Name a nutritional disorder that can lead to heart failure.
Beri-Beri disease
- Thiamine deficiency (vit B1)
What factors can exacerbate present heart failure?
- Anaemia
- Thyroid disease
- Vit B1 deficiency
What are the clinical features of left ventricular failure?
- Dyspnoea (shortness of breath)
- Orthopnoea (breathlessness when lying flat, pt requiring 3 or more pillows to sleep on at night)
- PND: paroxysmal nocturnal dyspnoea, sudden onset of breathlessness during the night, wake up in their sleep very breathless
- Fatigue
What are the clinical features of right ventricular failure?
- Peripheral oedema, excessive accumulation of fluid: volume overload in the right circulation which causes an increase in pressure in the venous side thus creating impaired reabsorption of tissue fluid, initially presents in the ankles and can progress until whole leg is swollen
- Ascites, fluid collecting in abdomen
- Hepatic pain and abnormal LFTs
- Facial engorgement in severe cases of fluid accumulation
What are the systemic features of heart failure?
Regardless of left or right ventricle affected, both types of heart failure cause a hypermetabolic state, causing:
- Weight loss
- Muscle wastage
- Fatigue
- Deconditioning
- Breathlessness
Summarise the pathophysiology of heart failure.
An adverse neuro-endocrine response to decreased cardiac output, driven by the sympathetic nervous sytem and renin-angiotensin-aldosterone system.
Explain the pathophysiology of heart failure.
- Cardiac output decreases, this is detected by baroreceptors
- Causes increased activation of the sympathetic NS and renin-angiotensin-aldosterone system
- Increases vasoconstriction and increases retention of water and salt in the kidneys
- If these systems stay activated over long periods of time, they increase pre-load and after-load on the heart
- Heart has to work against greater restistance, causes cardiac ouput to fall further
Viscious cycle.
What investigations are carried out for patients with suspected heart failure?
- 12-lead ECG
- NT-pro BNP (peptide released in response to excessive stretch of the right atrium)
- If higher than 400ng/l an echocardiogram is required
- Echocardiogram helps in the diagnosis of hear failure on the basis of the left ventricle’s function
How is heart failure classified based on the ejection fraction?
- HFrEF: heart failure with reduced ejection fraction (ejection fraction less than 40%)
- HFpEF: heart failure with preserved ejection fraction (ejection fraction greater than 50%)
- Mixed pattern: mild reduction in ejection fraction but elevated NT-pro BNP
What is ejection fraction?
Measurement of the percentage of blood ejected from the left ventricle with each contraction of the heart.
What are the 2 presentations of heart failure?
- Acute (decompensated) heart failure: a medical emergency
- Chronic heart failure: a chronic condition that develops gradually over time
Describe the features of acute (decompensated) heart failure.
- Presents with classic features of heart failure
- Dyspnoea, oedema, fatigue
- Acute heart failure causes can include MI, coronary artery disease, hypertension
What is the emergency management for acute heart failure?
- Oxygen if saturation is below 92%, if they have COPD give oxygen if saturation is below 88%
- Loop diuretics
- Nitrates if patient has angina/hypertensive emergency/aortic regurgitation or mitral valve disease
- Inotropic agents if pt is in cardiogenic shock
- Non-invasive ventilation if pt shows evidence of respiratory failure, hypoxia or dyspnoea
What is the subsequent treatment for a pt with acute heart failure after emerency management?
- Optimise diuretics
- Daily weights/U and Es/urine ouput
- Daily INR if on Warfarin
- After 48 hours: beta blockers used to block sympathetic NS and RAAS systems
What is the drawback of diuretics?
- Cause decrease in BP
- Hypotension
- Can cause a fall in kidney function due to a decline in glomerular filtration rate
What is diuresis?
Extra urine output/excretion of urinary solute
Explain the action of loop diuretics.
- Diuretics increase diuresis
- With less excess fluid it is easier for the heart to pump so is used to treat heart failure
- “All or nothing response” see graph
- Want to achieve mimimum optimal dose for desired diuresis
- Loop diuretics enter the lumen of the kidney to be effective, efficacy of diuretics declines with renal function
- If diuretics are not working: restrict salt and water intake, add thiazide diuretic, stop NSAIDs, stop ACE inhibitors
What is the stage 1 treatment for chronic heart failure (HFrEF)?
(Ejection fraction below 40%)
- ACE inhibitor or angiotensin II receptor blocker (losartan, candesartan)
- Beta blockers
- Aldosterone antagonist e.g. spironolactone is other therapies are unsuccessful
What is the stage 2 treatment for chronic heart failure (HFrEF)?
- SGLT-2 inhibitor e.g. Dapagliflozin (increases renal lossof sugar)
- Sacubitril valsartan (increases diuresis and vasodilation)
- Ivabradine (reduces heart rate, risk of QT prologation-dysrhythmia)
