Cardiovascular - Cardiac anatomy and function Flashcards
Define and describe the structure of intercalated discs
These are the structures between myocardial cells that allow for cardiac muscle to be electrically, chemically and mechanically coupled together as a ‘functional syncytium’
Structures within intercalated discs
- Gap junctions - permit direct passage of molecules between cells –> no need for neurotransmission: electrical and chemical coupling
- Fascia adherens - anchor actin filaments within the cell to the cell membrane
- Macular adherens - (desmosomes) anchor cardiac cells to one another - mechanical coupling
What are gap junctions
Structure within the intercalated discs. These are junctions between cells that permit direct passage of molecules between myocardial cells including intracellular ions and larger molecules. This allows direct electrical spread of action potentials from cell to cell without need for neurotransmission
What is the fascia adherens
Structure within the intercalated disc. These anchor actin filaments within sarcomere of cardiomyocytes to the cell membrane
What is the macular adherens
Structure within the intercalated disc, also known as desomosomes, that anchor cardiac cells to one another
how are the aortic valve cusps kept away from the aortic walls and why is this important
eddies created by the sinuses of valsalva - prevent occlusion of the origins of the coronary arteries
Left coronary - originates left posterior sinus of valsalva (adjacent to left coronary cusp)
Right coronary - originates from left anterior sinus of valsalva (adjacent to right coronary cusp)
Describe the path of the left coronary artery
- Left posterior aortic sinus –> Lateral to pulmonary trunk –> left atrioventricular groove –> divides: 1. left anterior descending (inferiorly into anterior interventricular groove and anastomose at inferior border with posterior interventricular a. Many patients –> diagnonal and septal branches extend across the sternocostal surface of the heart and into the septum
- left circumflex branch which proceeds in the AV groove towards the left border where it gives off a left obtuse marginal branches and then turns around to the posterior AV groove where it commonly anastomoses with the terminal end of right coronary artery.
What does the left coronary artery supply
- LV
- LA
- AV septum
- Some of RA
- Maybe SA node (40%)
Describe the path of the right coronary artery
- Left anterior aortic sinus –> passes between pulmonary trunk and RA –> Descends in the AV groove and gives off the following branches
- SA branch (60% SA node)
- Right marginal
continues along the AV groove posteriorly until it reaches the posterior interventricular groove where it
- posterior interventricular artery
What does the right coronary artery supply
1. SA node (60%) 2 AV node (90%) 3. RA 4. RV 5. Postero-inferior portion of LV
What does the left anterior descending artery supply
- Anterolateral myocardium
- Apex
- Interventricular septum
What does the left circumflex artery supply
- SA node (40%)
2. Posterolateral LV
What does the right marginal branch of the right coronary artery supply
The right ventricle
What does the posterior interventricular artery supply
- The posterior septum
2. AV node
What is left dominance and in what % of the population does this exist
15% of population the posterior interventricular artery is supplied by the left circumflex artery rather than the right coronary artery
Summarise the venous drainage systems of the heart
Coronary sinus (85% venous blood) - lies in the posterior part of the atrioventricular groove –> receives tributaries from 5 cardiac veins:
- The great cardiac vein (next to LAD)
- The middle cardiac vein (Next to PDA)
- The small cardiac vein (Next to RCA)
- The posterior vein of the left ventricle
- The oblique vein of the left atrium (along posterior surface of left atrium.
All coalesce to form the coronary sinus
- The oblique vein of the left atrium (along posterior surface of left atrium.
The Anterior Cardiac veins (minimal)
The Thebesian veins (causes of shunt)
Describe the pathway of the veins that coalesce into the coronary sinus
The great cardiac vein - with LAD
The middle cardiac vein - with PDA
The small cardiac vein - with RCA
The posterior vein of LV
The oblique vein of LA (along posterior surface of LA)
Describe the anterior cardiac veins
Arise on anterior RV
Drain into RA directly (not carotid sinus)
Describe the Thebesian veins
Smallest
Drain directly into 4 chambers of heart
Predominantly in RA and RV
(Thebesians that drain into left contribute toward physiological shunt)
Where does the coronary sinus open and where is it
Posterior aspect of heart adjacent to right coronary artery
The sinus opens into the right atrium between the inferior vena cava and the tricuspid valve
What associated findings may be associated with inferior wall iscahemia
Inferior heart supplied by RCA
RCA often also supplies SA node
RCA also supplies RV
SA node –> bradycardia
RV –> hypotension (reduced LV preoload)
What is the result of infarction in leads I, aVL, V5 and V6
Lateral wall ischaemia –> LV dysfunction
What does STE/STD mean in V1 and V2
Septal ischaemia –> occlusion of septal branch of LAD
What does STE/STD mean in V3 and V4
Apical ischaemia –> distal LAD
What ECG findings will be present in anterior wall ischaemia
STE/STD: I, aVL, V1 —-> V6
LAD !
Associated with severe LV dysfunction
