CVS S2+3 - The Heart as a Pump & Congenital Heart Disease + DR Work Flashcards Preview

► Med Misc 01 > CVS S2+3 - The Heart as a Pump & Congenital Heart Disease + DR Work > Flashcards

Flashcards in CVS S2+3 - The Heart as a Pump & Congenital Heart Disease + DR Work Deck (58):

What are the properties of cardiac muscle that allow the heart to pump? (TOB)



Central nuclei

Intercalated disks

Gap junctions - Electrical transmission

Adherens type junctions - Anchorage for actin


Muscle cells in the heart are connected physically, but how else?



Electrical activity in one cardiac muscle cell of the heart leads to what? (in normal circumstances)

Activity in all cardiac muscle cells


What are 'pacemaker' cells?

A small group of cells that generate action potentials in the heart to produce coordinated contraction


How long is a cardiac action potential and what does this amount of time correspond to physically?


The length of systole


Define 'systole'

The period where the myocardium is contracting


Define 'diastole'

How long does it last typically?

The relaxation in between contraction of the heart, lasting about 700ms


Is the length of systole and diastole variable?

Length of systole is fixed, however diastole is variable


Describe how electrical excitation spreads through the heart during systole

Relate this to the physical events of systole

1. Sino-atrial (SA) node fires and AP which spreads over the atria (atrial systole), it reached the Atrioventricular (AV) node where it is delayed for 120ms

2. From the AVN, excitation spreads down the ventricular septum

3. Excitation spreads from inner (endocarial) to outer (epicardial) myocardial surfaces

4. Ventricles contract from the apex up, forcing blood out of the outflow valves


How is ventricular muscle organised?

How does this facilitate the pumping of blood?

Organised in figure of 8 bands that squeeze the ventricular chambers simultaneously from apex upward

The apex contracts first and relaxes last to prevent back flow


How do the left and right side of the heart differ?

Left has thicker myocardium (as it must pump blood around the body, not just the lungs)

Right side has the SA node, the main pacemaker


Describe the sequence of pressure and volume changes over the course of one cardiac cycle beginning at the start of diastole

Hint: Long card, but it's no use in small chunks

Early diastole:

- Ventricles relax and intraventricular (IV) pressure falls - Inflow valves (Mitral/Tricuspid) open

- Atria now distended from continuous venous return during systole

- Blood forced rapidly into ventricles (Rapid Filling) due to low IV pressure

NB: No atrial contraction yet!

Diastole Cont.:

- Ventricles fill at steadily decreasing rate

- Stops when IV and atrial pressures equalise

- At low heart rates, ventricles mostly full

Atrial systole:

- Small amount of extra blood forces into ventricles by contraction as atrial pressure rises

- IV pressure rises as result

Ventricular systole:

- As IV pressure rises blood tends to flow into the atria turbulently, closing the inflow valves

- Then delay of 100-150ms

- Ventricles contract isovolumetrically, raising pressure rapidly

- Outflow valves open

- Rapid ejection period where arterial and intraventricular pressures rise to max

End of Ventricular systole:

- IV pressure falls below arterial pressue

- Arterial pressure closes outflow valves

- IV pressure falls below atrial pressure



When do the heart's outflow valves open and close

What causes them to open and close?

Open in systole

Open due to Intraventricular pressure being higher than arterial

Close at the end of systole

Close due to arterial pressure being higher than intraventricular pressure (causing a backflow of blood)


When do the heart's inflow valves open and close?

What causes them to open and close?

Open in early diastole

Open due to atrial pressure being higher than ventricular pressure

Close at the start of ventricular systole

Close due to ventricular pressure being higher than atrial pressure (causing a backflow of blood)


What is the origin of the 1st heart sound?

What does it sound like?

AV valves close causing oscillations in a variety of structures

A mixed sound with crescendo-descendo quality - 'lup'


What is the origin of the 2nd heart sound?

What does it sound like?

AS the semi-lunar valves close oscillations are induced in a variety of structures, including the column of blood in the arteries

Sound is shorter duration, higher frequency and lower intensity than the 1st sound - 'dup'


When might the 3rd and 4th heart sounds be heard?

3rd may be heard early in diastole

4th sometimes associated with atrial contraction


What is a heart murmur?

What causes them?

Additional or distorted heart sounds

Caused by turbulent blood flow (E.g. in exercise or stenotic valves)


What is depicted in this diagram?

Label the Axes

What is represented by the red, blue and grey lines?

Select from A, B, C or D:

- Where valves open and close

- Where the 1st and 2nd heart sounds are produced



Pressure in the left atrium, left ventricle and aorta over the course of one cardiac cycle

Y = Time (s)

X = Pressure 

Red = Left ventricular pressure

Blue = Aortic pressure

Grey =  Left atrial pressure

A = Mitral valve closes, 1st heart sound

B = Aorta opens

C = Aorta closes, 2nd heart sound

D = Mitral valve opens


What is the incidence rate for congenital heart disease?

6-8 per 1000 births


What are the most common two heart defects?

Ventricular septal defects (VSDs)

Followed by Atrial septal defects (ASDs)


What are the 5 Acyanotic defects we need to consider?


Patent foramen ovale


Patent ductus arteriosus

Coarctation of the Aorta


Why are the acyanotic defects acyanotic?

They do not result in lower than normal oxygen concentration in the blood leaving the left ventricle


What is ASD?

What is the incidence rate?

An acyanotic defect

An opening in the septum of the two atria which persists following birth

Allows left to right flow (higher pressure in left atrium) hence acyanotic

67 in 100,000 live births


Where in the atrial septum does ASD occur?

Include examples of two sites where it might occur

Can occur almost anywhere

Most common is the foramen ovale (ostium secundum ASD)

Ostium primum ASD occurs in the inferior septum and is less common


What is the foramen ovale?

An opening in the atrial septum that exists prenatally to allow right to left shunting of oxygenated blood


What haemodynamic effects does left to right shunting of blood in ASD have?

Increased pulmonary resistance

Pulmonary hypertension (rarely)

Eventual right heart failure (rarely)

If pulmonary resistance increases to the degree that right atrial pressure increases past left atrial pressure the shunt direction will reverse (Eisenmenger syndrome)


What is a patent foramen ovale?

How common is it?

A form of ASD that is clinically silent

This is due to higher left atrial pressure closing the flap valve in the septum

Occurs in 20% of the population


Patent foramen ovale can lead to paradoxical embolism, explain how

Allows venous embolisms into the left side of the heart if right atrial pressure increases (even transiently)


What is ventricular septal defect? (VSD)

Where does VSD most commonly occur?

An acyanotic defect

An opening in the interventricular septum

Most commonly occurs in the membranous portion of the septum


In VSD, which direction is blood shunted?


What are the other haemodynamic effects of VSD?

Left to right due to higher pressure in the left ventricle


Pulmonary venous congestion

Eventual pulmonary hypertension


What would you heart upon ascultation of a newborn with patent ductus arteriosus?

A mechanical murmur constantly through systole/diastole


What is coarctation of the aorta?

An acyanotic defect

A narrowing of the aortic lumen in the region of the ligamemtum arteriosum (former ductus arteriosus)


What effects does aortic coarctation have on the body?

Increases afterload on the left ventricle that can lead to left ventricular hypertrophy

Vessels of the head and upper limbs supplied by branches of the aorta that are proximal to the coarctation therefore blood supply to head + arms not compromised

Blood flow to the rest of the body is reduced


Aortic coarctation ranges from mild to severe, what is the symptomatic difference?


Defect might only be detected in later life


An infant might present with the symptoms of heart failure shortly after birth


What are the signs for aortic coarctation that you might pick up during a physical exam?

Femoral pulses will be weak and delayed

Upper body hypertension


What are the 4 cyanotic defects we need to consider?

Tetralogy of Fallot

Tricuspid Atresia

Transposition of the great arteries

Hypoplastic left heart


What is tetralogy of Fallot?

Cyanotic defect

A group of 4 lesions occuring together as a result of a single developmental defect which places the outflow portion of the interventricular septum too far anterior and cephelad

The 4 lesions are:


- Overriding Aorta

- Pulmonary stenosis (variable degree)

- Right ventricular hypertrophy (variable degree)


In tetralogy of fallot, what causes the right ventricular hypertrophy?

Caused by pulmonary stenosis as the right ventricle must operate at a higher pressure as a result of this

This causes the RV hypertrophy


In which direction does blood flow through the VSD present in tetralogy of fallot?

Explain why

Right to left shunt, hence cyanotic defect:

- This is because of the pressure in the right ventricle is higher than in the LV due to pulmonary stenosis

- Aortic valve has a biventricular connection (over-riding aorta)


What does the severity of the shunt in tetralogy of fallot depend on?

When do mild cases present versus severe cases?

The degree of pulmonary stenosis determines the magnitude of the shunt

Mild cases may present in adulthood

Severe cases will present with cyanosis in infancy


What is tricuspid atresia?

A cyanotic condition in which there is lack of development of the tricuspid valve resulting in lack of blood flow from the right atria to the right ventricle


How can someone with tricuspid atresia survive past birth?

There must be a complete right to left shunt in the atria:

- Patent foramen ovale

- Atrial septal defect

And a left to right shunt in the ventricles or vessels:


- Patent ductus arteriosus


What is transposition of the great arteries?

Connection of the right ventricle to the aorta and the left ventricle to the pulmonary trunk

Resulting in two unnconnected parallel circulations


In what situations may someone with transposition of the great arteries survive?

The condition untreated is incompatible with life

A shunt must be made after birth to sustain life until surgical correction can be made to allow the pateint to survive


What is hypoplastic left heart?

How is it compensated for?

A cyanotic condition in which the left ventricle and aorta are severely underdeveloped

To compensate an ASD or patent foramen ovale must be present

A patent ductus arteriosus forms a fight to left shunt to allow systemic circulation


Can a pateint with hypoplastic left heart survive with just endogenous compensation?

No, requires surgical intervention to correct


What are some variations of the coronary artery?

Can arise from a common trunk

Can be three CAs (additional posterior)

May exist as a double structure (two RCAs for example)


What is dominance in reference to cardiac blood supply?

Give percentages of people in which each type of dominance is found

Dominance is determined by which coronary artery supplies the posterior interventricular artery (a.k.a. posterior descending artery)

Right dominant: 70%

Left dominant:  10%

Co-dominant: 20%


From which vessels does blood flow into the right atrium?

Where do these vessels enter the right atrium?

Superior and inferior vena cavae

The coronary sinus

Superior vena cavae enters the superior portion of the atrium

Inferior VC and coronary sinus enter from the posterior portion of the atrium


The right atrium is divided into two spaces, describe the structure of each space's walls

What defines the border between them and where is it located?

What are the walls of these spaces derived from embryologically? 

Sinus of the vena cavae:

Smooth, thin walls

Posterior to the crista terminalis

Derived from the right horn of the sinus venosus 

Atrium proper:

Walls are covered in ridges (muscli pectinati) that fan out from the crista terminalis

Anterior to the crista terminalis

Includes the right auricle

Derived from the primitve atrium


Two spaces divided by:

Crista terminalis interiorly

Sulcus terminalis cordis exteriorly



Discounting the structure of the walls and vessel openings of the right atrium, what other important structures may be found there?

Describe their location in the atrium and embryological derivation or importance (if applicable)

Valves of the Inferior vena cavae and coronary artery:

Associated with their respective valves

Not of any use to an adult, direct blood toward the foramen ovale in the embryo

The interatrial septum:

Can been seen in the posterior of the right atrium

Fossa ovales and its prominant margin, the limbus of the fossa ovales:

Just above the orifice of the inferior vena cavae on the interatrial septum 

Fossa ovales marks the location of the embryonic foramen ovale

Right atrioventricular orifice:

Seen on the right of the atrium facing anterior and medially



The left atrium is divided into two spaces, What are they called and what is their structure analogous to?

What are the walls of these spaces derived from embryologically? 

What defines the border between them and where is it located?

Posterior inflow portion:

Analogous in structure to the sinus of the vena cavae in the right atrium

Derived from the proximal portions of the pulmonary veins


Anterior half:

Analogous in structure to the right atrium proper (includes the left auricle)

Derived from the primitive atrium


Nothing clearly separates the two components


Discounting the structure of the walls of the left atrium, what other structures or important sites may be found here?

Interatrial septum:

Part of the anterior wall

Valve of the foramen ovale:

Found on the interatrial septum

Prevented blood from passing left to right in the embryo

Pulmonary vein inflows:

Posterior wall recieves the inflows of the 4 pulmonary veins



Why are the walls of the ventricles differnt thickness?

The left ventricular wall is thicker than the right as it must support systemic circulation

The right ventricle must only support pulmonary circulation


Describe the structure of the pulmonary and aortic valves

Hint: Describe the general structure and point out any differences as you go along

Consist of three semi-lunar cusps

Left and right common

3rd cusp posterior in the aorta, anterior in the pulmonary

Superior edge of each cusp has a central nodule and lateral lunula

Each cusp forms a pocket like sinus

In the aorta, the left and right coronary arteries originate from the left and right sinuses



Describe the structure of the mitral and tricuspid valves (including their associated structures in the ventricles)

Found in the atrioventricular orifices

Consist of:

- Cusps

Anterior and posterior cusps in the mitral

Anterior, posterior and septal in the tricuspid

Each cusps has an associated papillary muscle:

Named according to the cusp they anchor (eg. Right septal papillary muscle)

These project from the walls of the ventricle

Chordae tendineae:

Connect the papillary muscles and the cusps


What is the function of the papillary muscles and the chordae tendineae?

Anchor the mitral and tricuspid valve cusps to prevent their inversion into the atria during ventricular systole