43 - Consequences, Determinants of Ventricular Hypertrophy Flashcards

1
Q

Normal growth of the heart
1)
2)
3)

A

1) Cell hyperplasia in embryo. Ceases after a few months of life
2) Cell hypertrophy in childhood. Parallels body growth.
3) Doubles in size in six months. Triples in size by 1 year.

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2
Q

How is cardiac hypertrophy during childhood mediated?

A

Thyroxine, Growth hormone, IGF control

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3
Q
Factors that normal heart size depends on 
1)
2)
3)
4)
5)
A

1) Body size (lean body mass)
2) Family history
3) Athletic conditioning
4) Blood pressure
5) Angiotensin II, catecholamines

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4
Q

Mean adult left ventricular mass

A

159g

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5
Q

How are LV dimensions measured?

A

Echocardiogram or MRI

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6
Q

Definition of cardiac hypertrophy

A

Increase in LV mass relative to body size

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7
Q

Relative LV wall thickness

A

LV wall thickness/LV chamber size

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8
Q
Causes of cardiac remodelling and hypertrophy
1)
2)
3)
4)
A

1) Myocardial infarction
2) Cardiac damage, EG: myocarditis
3) Volume overload
4) Pressure overload

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9
Q

Hypertrophy patterns
1)
2)
3)

A

1) Concentric hypertrophy
2) Eccentric hypertrophy
3) Remodelling

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10
Q

Morphology of LV concentric hypertrophy

A

Increased LV mass with increased relative wall thickness.
LV mass increases, but LV enlargement doesn’t occur.
IE: lumen narrows, wall thickens into lumen.
More sarcomeres in parallel

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11
Q

Morphology of LV eccentric hypertrophy

A

Increase in LV mass, relative wall thickness stays the same (heart increases in size).
IE: lumen doesn’t narrow
More sarcomeres in series

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12
Q

Difference in aetiology of concentric and eccentric hypertrophy

A

Concentric - often due to pressure overload

Eccentric - Often due to volume overload

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13
Q
Dallas heart study classifications of cardiac hypertrophy 
1)
2)
3)
4)
A

1) Thick
2) Dilated
3) Thick and dilated
4) Indeterminate

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14
Q

Concentricity

A

Increased wall thickness

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15
Q

Cellular makeup of hypertrophic cardiac tissue
1
2
3

A

1) Increased myocyte size
2) Increased fibroendothelial cell numbers
3) Increased interstitial matrix

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16
Q

Why might the body thicken LV wall in response to high pressure?

A

Thicker wall reduces or normalises stress (Laplace’s law)
Maintains systolic function, CO, LVEDP
This might not actually be a beneficial adaptation, though

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17
Q

Why might the body dilate LV wall in response to high volume?

A

To compensate for volume load by increasing area of LV.

Maintain stroke volume by increasing LVEDV and ejection fraction

18
Q

Ejection fraction

A

Percentage of blood in ventricle ejected with each beat

19
Q

How can dilation lead to eventual cardiac decompensation?
1)
2)
3)

A

1) Dilation leads to increased LVEDV and LVESV, and reduced ejection fraction.
2) Increased end diastolic pressure reduces systolic function and CO
3) Eventual cardiac failure

20
Q

How does a heart appear when it decompensates?

A

Very dilated

21
Q

Cause of concentric hypertrophy

A

Excessive pressure, afterload (EG: hypertension, aortic stenosis)

22
Q

Causes of eccentric hypertrophy

A

Excessive volume, preload (EG: mitral, aortic regurgitation, ventricular septal defect)

23
Q
How can left ventricular hypertrophy be identified?
1)
2)
3)
4)
5)
6)
A

1) Forceful apex beat
2) Extra heart sounds (S3, S4)
3) Tall voltages, T-wave inversion on ECG
4) Echocardiogram
5) MRI
6) Cardiac CT

24
Q

Hypertrophic cardiomyopathy

A

Enlarged LV wall, particularly septum.
Cellular hypertrophy.
Cellular disarray

25
Functional consequences of LVH
Diastolic dysfunction
26
``` LVH gives increased risk of: 1) 2) 3) 4) ```
1) Ischaemic heart disease 2) Cardiac failure 3) Atrial fibrillation 4) Stroke
27
``` Effects of LV hypertrophy on heartbeat 1 2 3 4 5 ```
1) Thickened muscle is stiff 2) Increased LVEDP required for the same LVEDV. 3) This increases left atrial pressure, therefore increases pulmonary vein pressure 4) This increases likelihood of pulmonary congestion 5) More sensitive to fluid loading (heart failure) or dehydration (low bp)
28
When is atrial 'kick' more important?
Diastolic dysfunction from LV hypertrophy. LV end diastolic pressure too high, so can't fill ventricle from atrium passively. Need atrial contraction to fill ventricle. In a healthy person, this atrial kick isn't as important
29
Symptoms of left ventricular diastolic dysfunction 1) 2)
1) If drink too much fluid, become short of breath (pulmonary oedema) 2) If drink too little, become dizzy (low bp)
30
``` What is left ventricular remodelling? 1) 2) 3) 4) ```
1) Follows a myocardial infarct. 2) Infarct zone can become thin and elongated (fibrous scar) 3) Spherical ventricular dilation can occur through whole ventricle (not just at infarct zone) 4) Interstitial fibrosis occurs
31
``` Causes of LV remodelling 1) 2) 3) 4) ```
1) Renin-angiotensin-aldosteorne system 2) Sympathetic nervous system 3) Endothelin 4) Cytokines
32
How can LV remodelling be reduced or blocked?
Block angiotensin or beta-adrenoceptors
33
``` Predictions of mortality from LV hypertrophy types 1) 2) 3) 4) ```
In order of increasing likelihood of mortality: 1) Normal 2) Concentric remodelling 3) Eccentric hypertrophy 4) Concentric hypertrophy
34
Causes of RV hypertrophy 1) 2) 3)
1) Congenital 2) Pulmonary hypertension 3) Right heart valve issues
35
Congenital problem that could lead to RV hypertrophy
Transposition of the great arteries. | Aorta connected to RV, pulmonary artery connected to LV.
36
Right heart valve problems that could lead to RV hypertrophy 1 2 3
1) Pulmonary valve stenosis 2) Pulmonary valve regurgitation 3) Tricuspid regurgitation
37
How does hypertrophic cardiomyopathy develop?
Autosomal dominant. Mutations in genes for sarcomere proteins. Over 900 mutations in 12 genes found. Heterogenous phenotype
38
Most common mutant genes implicated in hypertrophic cardiomyopathy
Beta cardiac myosin heavy chain | Cardiac myosin binding protein
39
Effects of hypertrophic cardiomyopathy 1 2 3
1) LV outflow tract obstruction 2) Diastolic dysfunction 3) Ventricular arrhythmias (can result in sudden death)
40
``` Phenotypes of hypertrophic cardiomytopathy 1 2 3 4 5 6 7 ```
1) Can be mild, asymptomatic 2) Outflow obstructions 3) Ventricular arrhythmias 4) Shortness of breath 5) Heart failure 6) Syncope 7) Sudden cardiac death
41
Causes of dilated cardiomyopathy
Multiple causes, mostly idiopathic
42
``` Athlete's heart 1) 2) 3) 4) 5) ```
1) Especially endurance athletes 2) Wall thickness over 14mm (normal is about 10mm) 3) Eccentric hypertrophy 4) Cardiac function normal 5) Usually regresses with deconditioning