S10: heart failure

Question 1

Define heart failure

Answer 1

Clinical syndrome of reduced cardiac output, tissue hypoperfusion, increased pulmonary pressures and tissue congestion

Question 2

Describe the signs and symptoms of heart failure

Answer 2

Breathlessness
Fatigue
Swollen ankles and legs
Persistent cough
Wheezing
Bloated tummy

Question 3

What is the ejection fraction?

Answer 3

Fraction ejected in single heartbeat of total volume available
SV/EDV
Typically 60-70%

Question 4

Explain the pathophysiology of heart failure

Answer 4

Either caused by an ejection or filling problem
HFrER = a contractility ejection problem, can’t pump with enough force (LOW EJECTION FRACTION)
-muscle walls thin/fibrosed
-chamber space enlarged
-abnormal/uncoordinated myocardial contraction
HFpER = a filling problem, ventricular volume/capacity for blood is reduced (EJECTION FRACTION NORMAL)
-ventricular chambers too stiff/not relaxing enough
-ventricular walls thickened (hypertrophied)

Question 5

Explain the normal relationship between central venous pressure (or end diastolic pressure) and cardiac output and how that relationship alters with increasing severity of heart failure due to impaired contractility

Answer 5

Increasing blood volume in ventricle at end of diastole causes increased stretch -> more ventricle stretch means a greater stroke volume ejected in systole (up until a certain point)
Contractility improved with greater stretch & increased sympathetic activity
Increased afterload impairs stroke volume
In heart failure: remodelling of cardiac muscle in response to adverse conditions changes ventricular function & ventricular shape/size -> impairment of ventricular filing/ventricular ejection

Question 6

Explain the presentation circumstances which lead to the development of heart failure with preserved ejection fraction/reduced ejection fraction

Answer 6

Manifest with the same symptoms in patients
Dyspnoea & fatigue (limiting exercise tolerance) – due to tissue hypoperfusion
Tissue fluid retention (pulmonary/peripheral oedema depending on which ventricle involved)

Question 7

Explain the presentation circumstances which lead to the development of left ventricular failure, biventricular failure and isolated right ventricular failure

Answer 7

Left ventricular failure: fatigue/lethargy, breathlessness (exertional), orthopnoea, paroxysmal nocturnal dyspnoea, basal pulmonary crackles, cardiomegaly (displaced apex beat which shows enlarged LV)
Right ventricular failure: fatigue/lethargy, breathlessness, peripheral oedema (pitting), raised JVP, tender, smooth enlarged liver
Congestive heart failure: accumulation of fluid in interstitium of pulmonary and peripheral tissues

Question 8

Describe the involvement of the renin-angiotensin-aldosterone system and the sympathetic nervous system in heart failure

Answer 8

Decreased cardiac output -> decreased BP -> baroreceptors -> increased sympathetic drive (increased HR, increased peripheral resistance) -> increased afterload & increased cardiac work
Decreased CO -> decreased BP -> decreased renal perfusion -> activation of RAAS pathway -> increased circulating volume & ADH stimulated (increased preload); sympathetic activity enhanced & vasoconstriction (increased afterload) -> increased cardiac work

Question 9

Explain why pulmonary oedema can develop in heart failure

Answer 9

1) Increased pressures within left ventricle -> increased pressures in pulmonary circulation
2) Increased hydrostatic pressures at venule end of pulmonary capillary beds -> less favourable for fluid to return to capillary due to pressure gradients
3) Tissue fluid accumulation within pulmonary interstitium -> PULMONARY OEDEMA

Question 10

Identify targets for drug action to manipulate cardiac output

Answer 10

RAAS system
Beta receptors on heart
Water and sodium retention

Question 11

Describe the principles involved in the general management of heart failure, and the categories of drugs used in its therapy

Answer 11

Furosemide
Left ventricular systolic dysfunction: community heart failure team, ACE, beta blocker
HFpEF: control BP
Valvular/structural heart failure: surgery/key hole surgery
Right ventricular failure: if LV function is good, needs specialist assessment

Question 12

Describe the role of intervention and device therapy in managing patients with heart failure

Answer 12

Lifestyle changes
Biventricular pacemaker
Goals are to alleviate symptoms, delay progression & reduce mortality

Question 13

Explain why peripheral oedema can form in heart failure

Answer 13

1) Increased pressures within right ventricle -> increased pressures in systemic venous circulation
2) Increased CVP = increased JVP
3) Increased hydrostatic pressures at venule end -> less favourable for fluid to return to capillary due to pressure gradients
4) Increased volume of tissue fluid accumulates -> PERIPHERAL OEDEMA