Heart Failure

Question 1

Define heart failure

Answer 1

A state in which the heart fails to maintain an adequate circulation for the needs of the body despite an adequate filling pressure

Question 2

What is the aetiology of heart failure?

Answer 2

Ischemia heart disease, coronary artery disease, MI, hypertension, dilated cardiomyopathy, valvular heart disease, restrictive cardiomyopathy, arrhythmias (lead to changes in heart structure)

Question 3

Explain the pathophysiology of heart failure

Answer 3

Impaired LV function = reduced CO/SV = reduced renal perfusion = activation of RAAS = retain circulating vol = retain Na = swollen ankles and visible JVP, lung consolidation/oedema = RV becomes effected = impaired RV function

Question 4

What factors influence CO?

Answer 4

HR, venous capacity (LV preload, blood into the heart), myocardial contractility, aortic and peripheral impedance (after load, pressure to pump against)

Question 5

Draw and explain the normal relationship between end diastolic pressure and CO

Answer 5

starlings law = the force developed in a muscle fibre depends on the degree to which the fibre is stretched

Question 6

What is left ventricular systolic dysfunction?

Answer 6

Increased LV capacity, thinning of wall/loss of muscle = necrosis/matric proteases = reduced LV CO, mitral valve incompetence seen with changes in the LV structure

neural-hormonal activation, cardiac arrhythmias

Question 7

What does neuro-hormonal activation regarding heart failure include?

Answer 7

SNS, RAAS, natriuretic hormones (atrial stretch ANP, ventricle BNP), ADH, prostaglandins/NO, endothelin (secreted by vascular endothelial cells, potent renal vasoconstrictor)

Question 8

What structural changes are seen in heart failure?

Answer 8

Loss of muscle, uncoordinated/abnormal myocardial contraction, changes in extra cellular matrix, cellular structure and function (first hypertrophy, then fibrosis, then necrosis), remodelling around weak/damaged areas

Question 9

How the relationship between EDP and CO alters with increasing severity of heart failure

Answer 9

normal = higher the EDP = higher CO

HF = At the same level of EDP, CO is lowered – the higher the severity of heart failure = the lower the CO

Question 10

What types of heart failure are there?

Answer 10

Left sided HF, right sided HF, biventricular (congestive) cardiac failure, LVSD (pump failure), heart failure with preserved ejection fraction (failure of LV relaxation)

Question 11

What is heart failure with preserved ejection fraction (HFpEF)?

Answer 11

Normal LV function with concentric remodelling = collagen deposition, thicker/shorter cardiomyocytes = LV stiffness = impaired diastolic LV filling = filling becomes dependent on high LA pressure = RV dysfunction = neuro-hormonal activation

ejection fraction = % pumped out of heart

Question 12

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

Answer 12

Reduced renal blood flow = angiotensin II acting on AT1 receptors = potent vasoconstrictor, promotes LVH and myocyte dysfunction, promotes aldosterone release, promotes Na/H2O retention.

Angiotensin II acting on AT2 receptors = increase NO = vasodilation

Question 13

Describe the involvement of the sympathetic nervous system in heart failure

Answer 13

Initially there to improve CO. Long-term = chronic high level of adrenaline = down regulation of receptors, increased myocyte hypertrophy, up-reg of RAAS

Question 14

Explain the involvement of natriuretic hormones in heart failure?

Answer 14

Myocyte stretch = release of ANP/BNP = constricts renal afferent and vasodilates efferent arterioles, increased urinary Na excretion

Question 15

Explain the formation of normal tissue fluid and why oedema can develop in heart failure

Answer 15

Increased capillary hydrostatic pressure = oedema. Left sided heart failure = pulmonary congestion = pulmonary oedema. Right sided heart failure = peripheral oedema.

Question 16

How does heart failure result in skeletal muscle changes?

Answer 16

Increase in peripheral arterial resistance (SNS, RAAS) = reduced skeletal muscle blood flow = reduction in mass (cachexia)

Question 17

What are the renal effects in severe HF?

Answer 17

Renal blood flows falls = reduced GFR = rise in serum urea and creatinine (GFR maintained in early HF)

Question 18

Identify targets for drug action to manipulate cardiac output

Answer 18

Beta-blockers, RAAS inhibitors (ACEI)

Question 19

What is the most common cause of right sided heart failure?

Answer 19

Secondary to left sided heart failure

Question 20

What clinical signs and symptoms characterise chronic heart failure?

Answer 20

Pulmonary congestion, venous congestion, dependent oedema, dyspnoea (shortness of breath), lethargy, othopnoea (shortness of breath lying flat)

Question 21

Describe the principals involved in the general management of heart failure

Answer 21

Management centres around neuro-hormonal blockage = B-blockers, RAAS inhibitors (ACEI), MRA (mineralocorticoid receptor antagonist)