Cardiovascular Pathology

What is the first organ to form in the embryo?

Heart

Name the FOUR chambers of the heart that birds and mammals possess.

How are reptiles different?

Left atrium

Right atrium

Left ventricle

Right ventricle

Only have one ventricle

Name the FOUR cardiac valves that work together to prevent backflow in the heart.

Right AV (Tricuspid)

Pulmonary

Left AV (Mitral)

Aortic

What is the formula for cardiac output?

Heart rate x stroke volume

What is cardiac dilation?

Increased stroke volume

What effect does myocardial hypertrophy have on the heart?

Greater contractility and ejection force

True or False: Cardiac dilation and hypertrophy can be beneficial to a point.

True!

When myocardial fibers stretch in cardiac dilation, what THREE things increase? What is this relationship called?

Contractile force

Stroke volume

Cardiac output

Frank-Starling

Increased contractile force has a limit. What does increased stretch do to tension?

Decrease

What does acute volume overload of the heart lead to? Chronic?

Acute: Dilation

Chronic: Eccentric ventricular hypertrophy

What are the TWO major differences between the TWO different types of cardiac hypertrophy?

Physiological: mild increase in HW (10-20% normalized to BW); cardiac function maintained or increased

Pathological: up to 4-fold increase in HW; depressed cardiac function

What are the stimuli for physiological and pathological cardiac hypertrophy?

Physiological: exercise

Pathological: congenital anomaly; acquired disease

What causes primary cardiac hypertrophy?

What is secondary cardiac hypertrophy due to?

What kind of overload is seen in preload vs afterload?

Mutation in cardiac myocyte

Sustained increase in cardiac workload

Preload: volume overload

Afterload: pressure overload

True or False: Cardiac hypertrophy can begin either left or right-sided, but usually becomes biventricular since the heart is a closed system.

True!

Aortic stenosis, arterial hypertension, and resistance training cause —- overload, which leads to compensated —- hypertrophy.

Pressure

Concentric

Valvular regurgitation and endurance training cause —- overload, which lead to compensated —— hypertrophy.

Volume

Eccentric

True or False: Both concentric and eccentric hypertrophy will eventually lead to decompensated disease or heart failure.

True!

What are the THREE important general rules related to pressure and volume overload?

1. Valvular insufficiency increases preload on ventricles

2. Semilunar valvular stenosis, outflow tract stenosis and hypertension increase ventricle afterload

3. AV valvular stenosis and pericardial disease decrease ventricle preload

Describe the difference in ventricle wall and chamber in eccentric vs concentric hypertrophy.

Eccentric: thin ventricular wall and distended ventricle chamber

Concentric: thick ventricular wall and reduced ventricle chamber

What is the LV:RV ratio?

3:1

Name and describe the THREE cellular stages in cardiac hypertrophy.

Initiation: increase cell size (sacromeres/mitochondria)

Compensation: stable hyperfunction (no clinical signs)

Deterioration: degeneration of hypertrophied cardiomyocyte (loss of ventricular contractility/compliance)

What do you expect with happen in cardiac histology with cardiomyocytes? What about with chronicity?

Initial: Increase size

Chronic: Cardiomyocyte loss and fibrosis

Match the location of heart failure to the gross change and underlying cause:

Left

Right

Bi-ventricular

Globose

Increased length

Broad base

Pulmonic stenosis; pulmonary hypertension

Mitral valve disease; aortic stenosis; HCM

DCM; VSD

Right -> Broad base -> Pulmonic stenosis; pulmonary hypertension

Left -> Increased length -> Mitral valve disease; aortic stenosis; HCM

Bi-ventricular -> Globose (rounded) -> DCM; VSD

Heart should be weighed and compared to the body weight (———%). In cats, heart > —- grams is hypertrophied, irrespective of body weight.

0.3-0.8%

18

What are the THREE main shunts of fetal circulation?

Ductus venosus

Foramen ovale

Ductus arteriosus

True or False: At birth, fetal shunts and umbilical vessels are not needed and become occluded functionally and then structurally.

True!

Patent ductus arteriosus, atrial septal defect, ventricular septal defect, and valvular dysplasia all cause —- overload.

Aortic and pulmonic stenosis cause —- overload.

Tetralogy of Fallot is a complex congenital heart disease.

What does persistent right aortic arch cause.

Volume

Pressure

Esophageal obstruction

What does the ductus arteriosus connect in the fetus?

What does it become when closed?

What is it called when there is failure to close?

Pulmonary artery and aorta

Ligamentum arteriosum

Patent ductus arteriosus (PDA)

True or False: PDA closes functionally very quickly, but it can take weeks after birth to close structurally.

True!

PDA Hemodynamics:

Increased blood flow to the —- -> Increases venous return to the —- and —- -> Volume overload in the —- -> —- —- hypertrophy

Lung

Left atrium and ventricle

Left ventricle

LV eccentric hypertrophy

What can happen in rare cases of PDA?

What do we call this occurrence?

Pulmonary hypertension -> pressure overload RV -> RV concentric hypertrophy

Eisenmenger Syndrome

What is the communication between right and left atria that can occur in all species, but most often happens in dogs and cattle?

Atrial septal defect

True or False: Patent foramen ovale is considered a true atrial septal defect.

What happens is LA pressure > RA pressure here?

What about RA pressure > LA pressure?

False! It is NOT a true ASD. A flap covers the foramen ovale.

LA>RA: closed

RA>LA: open

ASD Hemodynamics:

Blood shunts from —- to —- -> Increased blood volume in the —- -> Volume overload of —- -> —- —- hypertrophy

LA to RA

Right ventricle

Right ventricle

RV eccentric

What occurs in the communication between RV and LV that occurs in all species, but is common especially in horses and cattle?

Ventricular septal defect

What is the difference between a high VSD and low VSD?

High VSD: defect in membranous portion

Low VSD: defect in muscular portion

VSD Hemodynamics:

Blood shunts from —- to —- -> Increase blood volume in —- -> Equalization of —- across ventricles -> ————————.

LV to RV

Right ventricle

Pressure

LV and RV hypertrophy

Explain what happens when pulmonary hypertension causes a shunt reversal in VSD.

R -> L Eisenmenger complex -> Cyanosis

What is pulmonic stenosis most common in?

Dogs (French bulldog)

What are the THREE major types of pulmonic stenosis?

Which is most common?

Valvular

Subvalvular

Supravalvular

Valvular

Pulmonic stenosis Hemodynamics:

Stenotic valve restricts outflow —> Pressure overload of —- -> —- —- hypertrophy -> ————-

RV

RV concentric

Right heart failure

True or False: Subaortic stenosis (SAS) is most common in pigs and dogs.

True!

Subaortic stenosis (SAS) Hemodynamics:

Stenotic valve restricts outflow -> Pressure overload of —- -> —- —- hypertrophy.

If severe, this can lead to what TWO things?

LV

LV concentric

Arrhythmias/sudden cardiac death

Left heart failure

In what condition does fibrous tissue constrict the aortic outflow tract beneath the valve where LV hypertrophy is marked and mitral valve dysplasia is also present?

Subaortic stenosis (SAS)

What is the small wild cat with a broad but fragmented distribution in the grasslands and montane steppes of Central Asia?

The Pallas's cat (idk maybe its bonus lol)

Name the THREE major types of cardiomyopathies.

Hypertrophic cardiomyopathy

Dilated cardiomyopathy

Restrictive cardiomyopathy

What type of cardiomyopathy is a diastolic disorder with reduced compliance, restricted ventricular filling, and may have a genetic basis in contractile proteins (myosin, troponin T, myosin binding protein)?

Hypertrophic cardiomyopathy

What type of cardiomyopathy involved a dilated ventricle, systolic dysfunction causing decreased contractility, and may have a genetic basis in genes associated with cytoskeletal proteins and mitochondria?

Dilated cardiomyopathy

What type of cardiomyopathy is a diastolic disorder with restriction of ventricular filling and severe endomyocardial fibrosis?

Restrictive cardiomyopathy

What is the most common form of feline cardiomyopathy? Name FOUR of the clinical signs.

Feline HCM

Lethargy

Dyspnea

Tachypnea

Acute paralysis of hindlimbs

Sudden death

Anesthetic death

Name the TWO breed predispositions to feline HCM and what cardiac protein is associated with mutations leading to disease.

Maine coons and ragdolls

Myosin binding protein C

Explain what happens in the heart with feline HCM.

Thickening of ventricle walls -> Decreased ventricular chamber volume and abnormal ventricular relaxation (impairs diastolic function)

How might you expect feline HCM to look histologically?

Disarray of myofibers in interweaving pattern

Name the TWO major associated lesions with feline HCM.

Severe LA enlargement (stagnant flow -> LA thrombus)

Saddle thrombus (pain, paresis, cold limbs, pulse changes; can lead to acute renal failure if proximally lodged in aorta)

What condition is characterized by decreased contractile force, progressive cardiac dilation, and systolic dysfunction?

Dilated cardiomyopathy

What deficiency is linked to cats with DCM?

Taurine

Describe the histology of DCM.

Wavy cardiomyocytes; degeneration and fibrosis

What condition is primarily in cats (that usually do not survive more than a year after diagnosis), often used as a functional term rather than disease entity, and characterized by LV stiffness and impaired diastolic function?

How is this diagnosed?

Are murmurs common here?

Restrictive cardiomyopathy

Echocardiography

Yes

True or False: In restrictive cardiomyopathy, systolic function is usually normal and one or both atria are enlarged.

True!

What kind of heart failure often occurs in restrictive cardiomyopathy?

Left

What condition is common amongst young to middle-aged, large breed dogs like St. Bernards and Great Danes with an unknown etiology?

What are FOUR of the major clinical signs?

DCM

Cough

Dyspnea

Pulmonary edema

Left heart failure

What would you expect to see on echocardiogram that leads to a poor prognosis with DCM?

Cardiomegaly with increased end diastolic volume and poor contractile function

What condition is related to mutations in the striatin gene in Boxers?

Arrhythmogenic right ventricular cardiomyopathy (ARVC)

ARVC is a ventricular arrhythmia of —- origin.

What are the TWO major signs?

What replaces the myofibers lost in this condition that leads to poor ability for heart to eject blood?

RV

Syncope

Sudden death

Adipose tissue