Heart Failure Flashcards
Define heart failure.
The inability of the heart to supply adequate blood flow, and therefore oxygen, to peripheral tissues and organs.
How many people in the UK have heart failure?
1,000,000.
What proportion of patients diagnosed with heart failure die within a year of diagnosis?
40%.
What is the most common cause of heart failure?
Post-MI.
Define myocardial infarction.
Death of cardiac tissue due to a loss of blood flow (ischaemia) to an area of the myocardium.
List 4 changes that occur to tissue when ischaemia occurs.
1 - The tissue becomes hypoxic.
2 - The tissue becomes hypercapnic.
3 - The tissue becomes glycolytic.
4 - The tissue becomes acidotic.
What is a percutaneous coronary intervention (PCI)?
Give an example of when it might be used.
- A non-surgical procedure that uses a catheter to place a stent to open up blood vessels in the heart that have been narrowed.
- It is often used following an MI.
List 3 causes of heart failure (other than the most common cause).
1 - Pressure overload (due to baroreceptor reflex).
2 - Volume overload (due to baroreceptor reflex).
3 - Contractile dysfunction.
List 4 causes of contractile dysfunction.
1 - Coronary artery disease.
2 - Myocardial disease.
3 - Pregnancy.
4 - Congenital cardiomyopathies.
How does heart failure affect the starling ventricular function curve?
1 - The graph becomes increasingly shallow with more severe heart failure.
2 - The graph is translated downwards with more severe heart failure.
What is the risk of increasing cardiac work over long periods of time?
Pathological hypertrophy.
List 3 mechanisms by which persistent adrenergic stimulation of the heart can cause disease.
1 - Hyperphosphorylation of Ca2+ handling proteins, which can lead to dysfunctional Ca2+ homeostasis, contractile dysfunction and arrhythmia.
2 - Pathological hypertrophy by increasing cardiac work.
3 - Beta adrenoceptor internalisation, leading to a loss of adrenergic sensitivity.
What are delayed afterdepolarisations?
Depolarisations that occur after repolarisation is completed but before another action potential would normally occur.
Describe the process by which delayed afterdepolarisations (DADs) occur.
1 - An increase in beta adrenoceptor stimulation increases PKA activity.
2 - PKA causes elevated phosphorylation of L-type calcium channels, increasing their permeability to Ca2+.
3 - PKA causes elevated phosphorylation of RyR2 channels (channels responsible for Ca2+ release from the SR).
4 - PKA causes elevated phosphorylation of PLB (an inhibitor of SERCA), inhibiting its function.
5 - This acts to increase the SR Ca2+ load, and therefore raises the probability of spontaneous Ca2+ leak.
List 2 treatments that reduce the risk of DADs.
1 - Beta blockers.
2 - Calcium channel blockers.
Why are DADs dangerous?
They can cause arrhythmias and ectopic activity.
Define lusitropy.
The rate of myocardial relaxation.
How is Ca2+ removed from the cytosol of a myocyte?
Via the Na+/Ca2+ exchanger (NCX), which removes 1 Ca2+ for 3 Na+.
Why do patients with heart failure have chronically high plasma angiotensin ii?
- Patients with heart failure have a low arterial blood pressure.
- This reduces baroreceptor afferent activity.
- This increases sympathetic activity to the kidney, causing an increase in renin release.
- Renin results in an increase in angiotensin ii through the renin-angiotensin system.
How does the kidney contribute to pressure and volume overload in patients with heart failure?
- Patients with heart failure experience a decrease in arterial blood pressure. This causes:
1 - Low Na+ delivery to the macula densa.
2 - Decreased tubule wall tension in renal afferent arterioles.
3 - Increased sympathetic activity to the kidney via decreased baroreceptor activity.
- These factors increase renin release, increasing angiotensin ii.
- Angiotensin ii increases secretion of aldosterone from the adrenal cortex and ADH from the posterior pituitary, as well as increasing thirst.
Why might volume loading cause (and exacerbate) heart failure?
- An increase in blood volume results in an increase in central venous pressure.
- This increases cardiac filling, and therefore EDV.
- Initially, this results in an increase in SV, but as EDV increases further, the plateau of the Starling curve is exceeded and SV starts to decrease.
How does oedema occur with heart failure?
- If there is a mismatch in LV and RV cardiac output due to poor cardiac function, then blood can start to accumulate in the systemic or pulmonary system.
- This leads to an increase in capillary hydrostatic pressure and therefore increased capillary filtration.
- This is worsened by increases in blood volume.
How does oedema impair diffusion across alveoli?
By increasing diffusion distance.
List 3 treatments of oedema.
1 - Loop diuretics.
2 - ACE inhibitors.
3 - Angiotensin ii receptor type 1 (AT1R) antagonists.
What effect can volume loading have on valves?
Volume loading can cause aortic / mitral valve regurgitation (leaky valves).
List 3 treatments that reduce risk of development of hypertrophy in patients with heart failure.
1 - Reducing afterload with vasodilators.
2 - Surgical valve replacement.
3 - Beta blocker therapy to reduce cardiac work.
Why is cardiac hypertrophy dangerous?
1 - Increases susceptibility to ischaemia.
2 - Increases incidence of arrhythmias.
