L21. Ventricular Hypertrophy

Question 1

What side of the heart does ventricular hypertrophy affect the most?

Answer 1

The left side

Question 2

What is the difference between hyperplasia and hypertrophy?

Answer 2

Hyperplasia when cells proliferate and this processes ceases in the heart a few months after birth.
Hypertrophy is wen cells grow and this is normal parallel to growth. This stops after adolescence.

Hypertrophy can be restarted due to pressure demands throughout life.

Question 3

How is normal hypertrophy controlled and influenced?

Answer 3

Endocrine control: Growth Hormones, IGF, and Thyroxine

Question 4

What does the normal heart size depend on?

Answer 4

Body size, family history and genetics, athletic conditioning, blood pressure, angiotensin II and catecholamines

Question 5

What is the mean left ventricular mass in young healthy adults?

Answer 5

160 g

Question 6

How are the dimensions of the left ventricle normally measured?

Answer 6

Echocardiography or MRI

Question 7

What is meant by cardiac remodelling and hypertrophy?

Answer 7

Any change in the size, shape and/or function of the heart following some form of cardiac injury

Hypertrophy = increase in LV mass

Question 8

What kinds of cardiac injury lead to ventricular hypertrophy?

Answer 8

Myocardial Infarction
Cardiac Inflammation (Eg. myocarditis)
Volume Overload (Regurgitation)
Pressure Overloads (stenosis)

Question 9

What is cardiac remodelling?

Answer 9

Normal LV mass but there is an increase in the relative thickness of the walls (redistribution)

Question 10

What is Concentric Hypertrophy?

Answer 10

An increase in BOTH mass and LV thickness of the wall
= More sarcomeres in parallel to one another
= Overall diameter of the heart doesn’t necessarily change
= reduced chamber volume
= due to PRESSURE OVERLOAD (eg. aortic stenosis, chronic hypertension)

Question 11

What is Eccentric Hypertrophy?

Answer 11

An increase in BOTH mass and thickness RELATIVE TO EACH OTHER
= More sarcomeres in series (cardiomyocyte elongation)
= large dilated ventricle
= due to VOLUME OVERLOAD (eg. regurgitation)

Question 12

What are the characteristic of hypertrophy (at the cellular level)?

Answer 12

Increase in cell size (not number)
More mitochondria, myofibrils, SR
Increased fibroendothelial cell numbers
Increased interstitial matrix

Question 13

What happens when the compensation (hypertrophy) fails and thus decompensation occurs?

Answer 13

LV dilation
Major increases in the pressure and volume in the ventricle
Reduced Ejection Fraction
Reduced systolic function and Cardiac Output
Eventual cardiac failure

Question 14

What is the ejection fraction?

Answer 14

The percentage of blood leaving your heart each time it contract

Question 15

Is hypertrophy symptomatic?

Answer 15

Normally hypertrophy is compensation and is asymptomatic. However at a some tipping point ‘something’ happens to cause decompensation

Question 16

Why does concentric hypertrophy occur as a result of pressure overload?

Answer 16

A thicker wall is thought to reduce the wall stress (tension) according to Laplace’s Law
An adaptation to maintain the systolic function, cardiac output and end diastolic pressure

Question 17

Why does eccentric hypertrophy occur as a result of volume overload?

Answer 17

Dilation of the ventricle and thicker wall maintains the stroke volume and ejection fraction.

Question 18

Why are the explanations for why concentric and eccentric hypertrophy occur controversial?

Answer 18

Because some studies that analyse subjects that don’t undergo hypertrophy have observed that they survive better than those that do - the compensatory mechanism may actually be making it worse

Question 19

What are environmental/pathogenic causes of left ventricular hypertrophy?

Answer 19

Pressure Overload or Volume overload
Following Myocardial Infarct of Cardiac Injury
Obesity
Diabetes
Renal Failure
Infiltration (amyloidosis or sarcoidosis)

Question 20

What are genetic causes of left ventricular hypertrophy?

Answer 20

Hypertrophyic cardiomyopathy

Fabry’s Disease (absence of an enzyme)

Question 21

What are some clinical features of LVH?

Answer 21

Forceful apex beat

Abnormal or extra heart sounds: S3 and S4

Question 22

What would an ECG display for LVH?

Answer 22

Tall voltages (QRS) and T wave insertions

Question 23

What would a cardiac xray (CXR) show for LVH?

Answer 23

An eccentric would show a large heart while concentric a normal sized heart

Question 24

What are the mechanisms that lead to left ventricular hypertrophy?

Answer 24

Still a widely unknown cause:

Angiotensin, aldosterone, catacholamines, local factors, cellular and molecular mechanisms, stem cells(?)

Question 25

What are the consequences of LVH?

Answer 25

Increased risk of ischaemic heart disease, cardiac failure, atrial fibrillation and stroke Diastolic dysfunction (inability to fill)

Question 26

How do we currently treat LVH?

Answer 26

Treat the underlying condition/s

Question 27

What type of hypertrophy leads to the most highest increased risk of death following cardiovascular disease?

Answer 27

Concentric > Eccentric > Remodelling

Question 28

Why does diastolic dysfunction occur in LVH?

Answer 28

The thick muscle loses its compliance and thus it is difficult to relax This means there is a poor filling and a higher pressure is required for dilation and for filling

Question 29

What is a result of diastolic dysfunction?

Answer 29

Increased EDP to achieve adequate filling. This means a back flow of pressure into the left atrium and into the pulmonary system. = pulmonary hypertension and left heart failure

Question 30

Why are patients with diastolic dysfunction more susceptible to fluid loading?

Answer 30

Administering too much fluid leads to shortness of breath and pulmonary oedema Administer too less fluid leads to lost CO, decreased BP and dizziness

Question 31

Why are these patients with diastolic dysfunction more prone to atrial fibrillation?

Answer 31

Because the atrial kick is very important and is stronger to achieve adequate diastolic filling. This more forceful pressure kick is sensitive to fibrillation

Question 32

What is Left Ventricular Remodelling?

Answer 32

A post-MI remodelling - scar tissue that becomes thin and dilated out - myocyte hypertrophy and apoptosis occurs increasing the LV volume - interstitial fibrosis occurs

Question 33

What are the causes of left ventricular remodelling?

Answer 33

Renin-Angiotensin-Aldosterone system, the adrenergic nervous system, endothelin, cytokines, local factors

Question 34

How is left ventricular remodelling prevented?

Answer 34

Giving angiotensin blocking and beta adrenergic blocking upon MI

Question 35

What are the consequences of LV remodelling?

Answer 35

Increased risk of heart failure and mortailtiy

Question 36

What two types of cardiomyopathy affect the size and shape of the heart?

Answer 36

Hypertrophic cardiomyopathy | Dilated cardiomyopathy

Question 37

What are some of the consequences of hypertrophic cardiomyopathy?

Answer 37

Depends on the severity: | Outflow obstruction, ventricular arrhythmia, shortness of breath, heart failure, syncope, sudden cardiac death

Question 38

What is the mechanism of hypertrophic cardiomyopathy?

Answer 38

Unclear: | May have to do with calcium transport, ATP usage, signalling?

Question 39

What is dilated cardiomyopathy?

Answer 39

When the heart enlarges and becomes weaker as a result. Mostly idiopathic causes (may have some genetic cause)

Question 40

What is athletes heart?

Answer 40

Common among competitive athletes where wall thickness decreases with ECCENTRIC HYPERTROPHY while cardiac FUNCTION IS NORMAL it usually regresses with deconditioning

Question 41

What are the causes of right ventricular hypertrophy?

Answer 41

Congenital (rare) Pulmonary Hypertension ie. cor pulmonale, lung disease, PE Chronic Left ventricular hypertension leading to right Right heart valve problems