Cardiac hypertrophy pathology pt.1

Question 1

Hypertrophy of the left ventricle causes

Answer 1

Most commonly caused by hypertension and aortic or mitral valvular disease

Question 2

Pathogenesis of left ventricular hypertrophy (LVH) and right ventricular hypertrophy (RVH)

Answer 2

1. Sustained pressure in the ventricles increases wall stress.
2. Changes in wall stress alter gene expression in the muscle.
3. Changes in gene expression lead to duplication of sarcomeres

Question 3

What are sarcomeres?

Answer 3

The contractile elements of muscle

Question 4

When do changes in wall stress occur?

Answer 4

When there is an increase in afterload or preload

Question 5

What are the changes that occur to the ventricular wall due to increased afterload?

Answer 5

• Produces concentric hypertrophy of the ventricular wall
• Sarcomeres duplicate parallel to the long axis of the cells, causing the individual muscle fibers to be thicker

Question 6

What are causes of concentric LVH due to increased afterload?

Answer 6

Include primary hypertension (most common), aortic valve (AV) stenosis (hypertrophic obstructive cardiomyopathy), and hypertrophic cardiomyopathy (HCM)

Question 7

Hypertrophy of the right ventricle causes

Answer 7

a. Left ventricular failure
b. Chronic lung disease
c. Mitral valve disease
d. Congenital heart disease with left-to-right shunt
e. Cor pulmonale

Question 8

Causes of concentric RVH due to increased afterload

Answer 8

Include pulmonary HTN and pulmonary valve (PV) stenosis

Question 9

What are the changes that occur to the ventricular wall due to increased preload?

Answer 9

• Increased preload increases stroke volume (volume of blood ejected) via the Frank-Starling pressure relationship.
• Increased preload causes dilation and hypertrophy (eccentric hypertrophy) of the ventricular wall
• Sarcomeres duplicate in series (on top of each other),
  causing the individual muscle fibers to increase in length and width

Question 10

What is preload?

Answer 10

The amount of sarcomere stretch experienced by cardiac muscle cells, called cardiomyocytes, at the end of ventricular filling during diastole

Question 11

What does preload correlate with?

Answer 11

Correlates with left and right ventricle end-diastolic volumes

Question 12

What are causes of eccentric hypertrophy of the left ventricle (LV) due to increased preload?

Answer 12

(1) mitral valve (MV) or AV regurgitation.
(2) left-to-right shunting of blood (e.g., ventricular septal defect [VSD]) In left-to-right shunting, more blood returns to the left side of the heart because the right side of the heart is receiving more blood than usual.

Question 13

What are causes of eccentric hypertrophy of the right ventricle (LV) due to increased preload?

Answer 13

Causes of eccentric hypertrophy of the right ventricle (RV) due to increased preload include tricuspid valve (TV) and PV regurgitation.

Question 14

What are the consequences of ventricular hypertrophy?

Answer 14

1- Left and Right heart failure
2- Angina Pectoris (only a complication of LVH)
3- Pathologic S4 heart sound is commonly present in either LVH and/or RVH
4- Pathologic S3 heart sound is commonly present in either left- or right-sided eccentric
hypertrophy

Question 15

How many heart sounds are found?

Answer 15

4 heart sounds (S3 pathological in individuals over age of 40)

Question 16

What does the S1 heart sound correspond to?

Answer 16

Closure of the MV and TV during systole

Question 17

What does the S2 heart sound correspond to?

Answer 17

The S2 heart sound is caused by closure of the AV and
PV and marks the beginning of diastole

Question 18

What does the S4 heart sound correspond to?

Answer 18

S4 heart sound (see schematic) coincides with atrial contraction in late diastole

Question 19

What does the S3 heart sound correspond to?

Answer 19

• It is thought to be caused by a sudden rush of blood entering a volume-overloaded left or right ventricle (stiff ventricle)
• This is analogous to a river emptying into a large volume of water

Question 20

Why can ventricular hypertrophy lead to heart failure?

Answer 20

Excess work, caused by either an increase in afterload or preload, is imposed on the ventricles (LVH and/or RVH)

Question 21

Why can ventricular hypertrophy lead to angina pectoris?

Answer 21

• In the normal LV, the subendocardium receives the least amount of blood from the coronary arteries (CAs)
• Therefore, if the muscle is concentrically thickened, angina may occur with exercise because the muscle wall is so thick that the subendocardium tissue receives dangerously low levels of O2, causing chest pain. Recall that with exercise, the heart rate (HR)
  increases, which decreases the time for diastole and the filling of the CAs. Therefore, there is even less blood flow to the subendocardium.

Question 22

Cause of hypertrophic cardiac myopathy

Answer 22

60–70% of cases are familial, autosomal dominant
(most commonly due to mutations in genes
encoding sarcomeric proteins, such as myosin
binding protein C and β-myosin heavy chain)

Question 23

Treatment for hypertrophic cardiomyopathy

Answer 23

• Cessation of high-intensity athletics, use of β-blocker or nondihydropyridine Ca2+ channel blockers (eg, verapamil).
• Implantable Cardioverter Defibrillatorif high risk
• Avoid drugs that decrease preload (eg, diuretics,
  vasodilators).

Question 24

Cause of abnormal S4 sound in LVH and RVH

Answer 24

a. Abnormal heart sound that correlates with atrial contraction in late diastole. S4 heart sound produces an atrial gallop
b. Caused by blood entering a noncompliant ventricle (problem in filling the ventricle, diastolic dysfunction)
(1) Noncompliant ventricle is present in concentric hypertrophy involving the LV and/ or RV.
(2) Noncompliant ventricle is also present in left- and/or right-sided eccentric hypertrophy because the ventricles are volume overloaded and resist receiving more blood in late diastole

Question 25

Where do we see a noncompliant ventricle?

Answer 25

(1) Noncompliant ventricle is present in concentric hypertrophy involving the LV and/ or RV.
(2) Noncompliant ventricle is also present in left- and/or right-sided eccentric hypertrophy because the ventricles are volume overloaded and resist receiving more blood in late diastole

Question 26

Examples of a noncompliant ventricle producing an S4 heart sound

Answer 26

(1) concentric LVH in primary HTN or AV stenosis (↑afterload).
(2) concentric RVH in pulmonary hypertension (PH) or PV stenosis (↑afterload).
(3) eccentric hypertrophy from volume overload in MV or TV regurgitation (↑preload).
(4) eccentric hypertrophy from volume overload in AV or PV regurgitation (↑preload).

Question 27

Cause of abnormal S3 sound in LVH and RVH

Answer 27

S3 heart sound is caused by blood entering a volume overloaded chamber in early
diastole (see Box 11-1). An analogy is the Mississippi River emptying into the Gulf of
Mexico. The water is very turbulent where the two bodies of water meet

Question 28

Examples of volume overloaded ventricles producing an S3 heart sound

Answer 28

(1) volume overload in MV or TV regurgitation.
(2) volume overload in AV or PV regurgitation.