L21. Ventricular Hypertrophy Flashcards
What side of the heart does ventricular hypertrophy affect the most?
The left side
What is the difference between hyperplasia and hypertrophy?
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.
How is normal hypertrophy controlled and influenced?
Endocrine control: Growth Hormones, IGF, and Thyroxine
What does the normal heart size depend on?
Body size, family history and genetics, athletic conditioning, blood pressure, angiotensin II and catecholamines
What is the mean left ventricular mass in young healthy adults?
160 g
How are the dimensions of the left ventricle normally measured?
Echocardiography or MRI
What is meant by cardiac remodelling and hypertrophy?
Any change in the size, shape and/or function of the heart following some form of cardiac injury
Hypertrophy = increase in LV mass
What kinds of cardiac injury lead to ventricular hypertrophy?
Myocardial Infarction Cardiac Inflammation (Eg. myocarditis) Volume Overload (Regurgitation) Pressure Overloads (stenosis)
What is cardiac remodelling?
Normal LV mass but there is an increase in the relative thickness of the walls (redistribution)
What is Concentric Hypertrophy?
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)
What is Eccentric Hypertrophy?
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)
What are the characteristic of hypertrophy (at the cellular level)?
Increase in cell size (not number)
More mitochondria, myofibrils, SR
Increased fibroendothelial cell numbers
Increased interstitial matrix
What happens when the compensation (hypertrophy) fails and thus decompensation occurs?
LV dilation
Major increases in the pressure and volume in the ventricle
Reduced Ejection Fraction
Reduced systolic function and Cardiac Output
Eventual cardiac failure
What is the ejection fraction?
The percentage of blood leaving your heart each time it contract
Is hypertrophy symptomatic?
Normally hypertrophy is compensation and is asymptomatic. However at a some tipping point ‘something’ happens to cause decompensation
Why does concentric hypertrophy occur as a result of pressure overload?
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
Why does eccentric hypertrophy occur as a result of volume overload?
Dilation of the ventricle and thicker wall maintains the stroke volume and ejection fraction.
Why are the explanations for why concentric and eccentric hypertrophy occur controversial?
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
What are environmental/pathogenic causes of left ventricular hypertrophy?
Pressure Overload or Volume overload
Following Myocardial Infarct of Cardiac Injury
Obesity
Diabetes
Renal Failure
Infiltration (amyloidosis or sarcoidosis)
What are genetic causes of left ventricular hypertrophy?
Hypertrophyic cardiomyopathy
Fabry’s Disease (absence of an enzyme)
What are some clinical features of LVH?
Forceful apex beat
Abnormal or extra heart sounds: S3 and S4
What would an ECG display for LVH?
Tall voltages (QRS) and T wave insertions
What would a cardiac xray (CXR) show for LVH?
An eccentric would show a large heart while concentric a normal sized heart
What are the mechanisms that lead to left ventricular hypertrophy?
Still a widely unknown cause:
Angiotensin, aldosterone, catacholamines, local factors, cellular and molecular mechanisms, stem cells(?)
What are the consequences of LVH?
Increased risk of ischaemic heart disease, cardiac failure, atrial fibrillation and stroke
Diastolic dysfunction (inability to fill)
How do we currently treat LVH?
Treat the underlying condition/s
What type of hypertrophy leads to the most highest increased risk of death following cardiovascular disease?
Concentric > Eccentric > Remodelling
Why does diastolic dysfunction occur in LVH?
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
What is a result of diastolic dysfunction?
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
Why are patients with diastolic dysfunction more susceptible to fluid loading?
Administering too much fluid leads to shortness of breath and pulmonary oedema
Administer too less fluid leads to lost CO, decreased BP and dizziness
Why are these patients with diastolic dysfunction more prone to atrial fibrillation?
Because the atrial kick is very important and is stronger to achieve adequate diastolic filling.
This more forceful pressure kick is sensitive to fibrillation
What is Left Ventricular Remodelling?
A post-MI remodelling
- scar tissue that becomes thin and dilated out
- myocyte hypertrophy and apoptosis occurs increasing the LV volume
- interstitial fibrosis occurs
What are the causes of left ventricular remodelling?
Renin-Angiotensin-Aldosterone system, the adrenergic nervous system, endothelin, cytokines, local factors
How is left ventricular remodelling prevented?
Giving angiotensin blocking and beta adrenergic blocking upon MI
What are the consequences of LV remodelling?
Increased risk of heart failure and mortailtiy
What two types of cardiomyopathy affect the size and shape of the heart?
Hypertrophic cardiomyopathy
Dilated cardiomyopathy
What are some of the consequences of hypertrophic cardiomyopathy?
Depends on the severity:
Outflow obstruction, ventricular arrhythmia, shortness of breath, heart failure, syncope, sudden cardiac death
What is the mechanism of hypertrophic cardiomyopathy?
Unclear:
May have to do with calcium transport, ATP usage, signalling?
What is dilated cardiomyopathy?
When the heart enlarges and becomes weaker as a result. Mostly idiopathic causes (may have some genetic cause)
What is athletes heart?
Common among competitive athletes where wall thickness decreases with ECCENTRIC HYPERTROPHY
while cardiac FUNCTION IS NORMAL
it usually regresses with deconditioning
What are the causes of right ventricular hypertrophy?
Congenital (rare)
Pulmonary Hypertension ie. cor pulmonale, lung disease, PE
Chronic Left ventricular hypertension leading to right
Right heart valve problems
