Pathophysiology Of Heart Disease

Question 1

Give a definition of heart failure

Answer 1

A state in which the heart fails to maintain adequate blood supply to the body despite an adequate filling pressure

Question 2

What is the primary cause of systolic heart failure?

Answer 2

Ichaemic heart disease

Question 3

Describe the 4 classes of heart failure

Answer 3

Class I- asymptomatic, no limitation in physicial activity

Class II- Slight limitation of physical activity, comfortable at rest

Class III- Marked limitation of physical activity, comfortable at rest

Class IV- unable to carry on any physcial activity without discomfort, symptoms at rest

Question 4

What is the approximate normal value for cardiac output?

Answer 4

5 l/min

Question 5

What is the approximate normal volume for stroke volume?

Answer 5

75ml/beat

Question 6

What is an approximation of a “normal” ejection fraction?

Answer 6

50%

Question 7

What is Starling’s Law of the Heart?

Answer 7

Stroke volume of the heart increases in response to an increase in the volume of blood in the ventricles, before contraction i.e. the end diastolic volume

Question 8

List some causes of heart failure

Answer 8

Coronary artery disease

Hypertension

AF

Valve disease

Cardiomyopathies

Infective endocarditis

Anaemia

Endocrine disorders

Cor pulmonale

Question 9

How can heart failure be classified based on the cause of the inadequate cardiac output?

Answer 9

Left ventricular failure

Right ventricular failure

Congestive heart failure

Low output high output heart failure (excessive afterload, excessive preload, pump failure)- LVSD, HFpEF

Question 10

Give some of the symptoms of LVF and RVF

Answer 10

LVF: paroxysmal nocturnal dysponea, wheeze, nocturnal coughing with pink sputum (caused by pulmonary oedema)

RVF: caused by LVF usually, peripheral oedema, ascites

Question 11

What are the three broad methods of treating heart failure?

Give some examples of each.

Answer 11

Conservative - smoking cessation, weight loss, healthy diet, exercise

Medical - ABCDDS

ACE inhibitors, Beta blockers, Candesartan(if intol. for ACEi) Digoxin, Diuretics, Spironolactone

Surgical- heart transplant, valve replacement

Question 12

What investigations might you want to carry out to test for heart failure?

Answer 12

FBC

U & Es

LFTs

TFTs

Lipid profile

BNP (suggests measure of stretch of cardiac myocytes)

CXR: “ABCDE”

Alveolar oedema, Kerley B lines, Cardiomegaly, Dilated upper lobe vessels, pleural Effusion

ECHO

ECG

Question 13

Name some causes of LEFT sided heart failure

Answer 13

Coronary artery disease

Hypertension

Aortic valve disease

Mitral valve disease

Myocardial disease

Question 14

Name some causes of RIGHT sided heart failure

Answer 14

*LEFT sided heart failure*

Tricuspid valve disease

Pulmonary valve disease

Pulmonary vascular disease (Cor pulmonale)

Question 15

Briefly explain the pathophysiology of heart failure one LVF or RVF has been established

Answer 15

Ischaemic injury leads to reduced myocardial efficiency

Increases workload, decreased cardiac output, decreased contractility

COMPENSATORY MECHANISMS: Activation of RAAS, Activation of sympathetic nervous system, increased myocyte size

These worsen HF overtime + cardiac damage

Question 16

How do chronically activated compensatory mechanisms such a RAAS and the sympathetic nervous system lead to worsening of heart failure?

Answer 16

RAAS activated: Increased Na+ and H20 retention

Increased PRELOAD

SNS activated: Increased HR and peripheral vasoconstriction

Increased AFTERLOAD

Question 17

In HF, what is the cause of cardiac dilation?

Answer 17

Increased end-diastolic volume

Question 18

In HF, what is the cause of raised JVP?

Answer 18

Right sided-heart failure and fluid overload

Question 19

What causes hepatomegaly in right sided heart failure?

Answer 19

Congestion of the hepatic circulation

Question 20

What is heart failure with preserved ejection fraction?

Answer 20

HF that is not caused by LV systolic dysfunction, but LV diastolic dysfunction i.e. not a problem with contraction but a problem with relaxation of the LV leading to reduced filling- caused by concentric remodelling of the LV

Question 21

Explain how heart failure leads to peripheral oedema and ascites

Answer 21

Heart failure leads to increased capillary hydrostatic pressure at the venous end which pushes fluid out of the capillaries and into the interstitium

RAAS activation also leads to fluid retention

Question 22

List some of the neuro-hormonal activation that occus due to heart disease

Answer 22

Sympathetic nervous system

RAAS

Natriuretic hormones

ADH

Endothelin

Prostaglandins/ NO

Kallikrien System

TNFalpha

Question 23

Describe how the activation of the sympathetic nervous system attempts to improve cardiac output in HF and how this manifests in the long-term.

Answer 23

Increased cardiac contractility

Vasoconstruction

Tachycardia

Long- term:

Beta adrenergic receptors down-regulated

Cardiac hypertrophy, myocyte apoptosis and necrosis

Upregulation of RAAS

Reduction in HR variability

Question 24

Why is RAAS commonly activated in HF?

Answer 24

Reduced renal blood flow

Sympathetic nervous system induction of renin from the macula densa (More AngI to AngII)

Question 25

List some of the downstream effects of elevated angiotensin II

Answer 25

Vasoconstriction LVH, myocyte dysfunction Aldosterone release Na+ and H20 retention Thirst Enhanced sympathetic activity

Question 26

What is are the roles of natriuretic hormones: ANP and BNP?

Answer 26

Balance the effects of RAAS on vascular tone and Na/H20 balance Constrict afferent and vasodilates efferent arterioles Decrease Na+ reabsorption in the kidney Decrease renin and aldosterone secretion

Question 27

What important role does BNP have in the diagnosis of HF?

Answer 27

Used as a sensitive marker for HF (released from the ventricles in response to stretch)

Question 28

What happens to ADH levels in a patient with HF? Would you expect this? Explain.

Answer 28

Increased No, not expected- increased atrial pressure and blood volume should decrease the production of ADH so the body can lose some fluid RAAS and SNS seem to override this in HF and cause increased ADH

Question 29

The hormone endothelin may be _______ in some patients with heart failure. Its role is to __________ systemic and renal blood vessels, thus _________ RAAS.

Answer 29

Increased Constrict Activate

Question 30

What is the role of prostaglandin in HF?

Answer 30

Vasodilates Afferent renal arterioles--\> increases the effects of NA/RAAS

Question 31

How does NO relate to heart failure?

Answer 31

NO synthase is blunted in HF Lose vasodilation --\> contributes to HF

Question 32

Is TNFalpha increased or decreased in HF?

Answer 32

Increased

Question 33

List some causes of increased peripheral arterial resistance in HF

Answer 33

Sympathetic nervous system RAAS Reduced NO Increased endothelin

Question 34

What is cachexia and what is its relevance in HF?

Answer 34

Reduction in skeletal musle mass Can be caused by HF due to reduced skeletal blood flow

Question 35

Explain the renal effects of HF and how this changes throughout its progression.

Answer 35

Early HF: GFR maintained by haemodynamic changes at the glomerulus Later: Increased Na+ and H20 retention, lose nephrons, kidney shrinks Late HF: renal blood flow falls--\> reduced GFR, rise in serum urea and creatinine This can be exacerbated by inhibition of AngII (HF medication)