Seasons Structure Wk3 LO's

Blood Flow Through the Heart, Blood Supply to the Heart & Pathology of Cellular Injury to the Heart

LO 1: where do coronary arteries arise from & what do they do

The heart’s "self-service" fuel system consists of coronary arteries arising from the aorta to deliver oxygen and cardiac veins that return deoxygenated blood to the right atrium via the coronary sinus.

LO 1: arterial origin

• left & right coronary arteries

Arterial Origin: The left and right coronary arteries (LCA, RCA) are the very first branches of the ascending aorta, emerging just superior to the aortic valve cusps.

LO 1: right coronary artery branches (RCA)

• what are the branches

• sinoatrial (SA) nodal branch

• right marginal branch

• posterior interventricular branch (in posterior interventricular groove)

LO 1: right coronary artery branches (RCA)

• locations

Right Coronary Artery (RCA) Branches:

• SA Nodal Branch: Usually passes posterior to the superior vena cava (SVC) to the pacemaker.

• Right Marginal Branch: Travels along the acute (right) margin toward the apex.

• Posterior Interventricular Branch (PDA): Runs in the posterior interventricular groove.

LO 1: left coronary artery branches

• what are the branches

• anterior interventricular branch (left anterior descending aka LAD) in the anterior interventricular groove

• circumflex branch (in coronary groove)

• left marginal branch

LO 1: left coronary artery branches

• locations

• LAD what are branches called

• LCX what are branches called

• what is a possible variation

1. Left Coronary Artery (LCA) Branches:

   • Left Anterior Descending (LAD): Passes along the anterior interventricular groove; it gives off diagonal branches.

   • Circumflex Artery (LCX): Follows the coronary groove to the left; it gives off left marginal branches.

   • Variation: A ramus intermedius may arise as a third branch directly from the left main coronary.

LO 1: what does the great cardiac vein run with

left anterior descending artery (LAD)

LO 1: what does the middle cardiac vein run with

The Middle Cardiac Vein runs with the posterior interventricular branch (PDA) in posterior interventricular groove.

LO 1: what does the small cardiac vein run with

The Small Cardiac Vein runs with the right coronary (RCA) marginal branch.

LO 1: what do the great cardiac vein, middle cardiac vein, & small cardiac vein drain into

All these drain into the Coronary Sinus, a large vein on the posterior heart that empties into the Internal Opening (Os) in the right atrium, located between the IVC and the tricuspid valve.

LO 2: what is dominance determined by

Defining Dominance: Dominance is determined by which coronary artery gives rise to the Posterior Descending Artery (PDA) (posterior interventricular branch).

LO 2: right dominance

• what it is

• % of ppl

Right Dominance (80–90% of people): The PDA arises from the RCA.

LO 2: left dominance

• what it is

• % of ppl

Left Dominance (10–20% of people): The PDA arises from the LCX.

LO 2: in a right-dominant person what kind of MI does a RCA occlusion cause & what blood supply is at risk

Infarct Territory: In a right-dominant person, an RCA occlusion causes an inferior wall MI and risks the blood supply to the AV node.

LO 2: which vessels collateralize at the apex

Collateral Circulation: The PDA and LAD often collateralize at the apex; the extent of this determines how well a patient survives a sudden blockage in one of those vessels.

LO 2: what dominance is a patient with an inferior wall MI and they also develop a heart block

Clinical Correlation A patient with an inferior MI (ST elevation in leads II, III, aVF) is likely right-dominant. If they also develop a heart block, it confirms the RCA is the culprit because it is likely supplying the AV node.

LO 3: SA node

• where is it located

• what is it’s blood supply from

Sinuatrial (SA) Node:

• Location: Superior end of the crista terminalis, near the SVC/Right Atrium junction.

• Supply: SA nodal artery, arising from the RCA (60%) or LCA/LCX (40%).

LO 3: AV node

• location

• what is it’s blood supply

Atrioventricular (AV) Node:

• Location: Floor of the right atrium near the opening of the coronary sinus.

• Supply: AV nodal artery, arising from the RCA (85–90%) or LCX (10–15%).

LO 3: Bundle of His

• location

• blood supply

Bundle of His (AV Bundle):

• Location: Passes from the AV node through the fibrous skeleton into the interventricular septum.

• Supply: Primarily the LAD (anterior interventricular artery).

LO 3: moderator band (septomarginal trabecula)

• what does it contain

• where does it carry the signal to

Moderator Band (Septomarginal Trabecula):

• Contains the Right Bundle Branch; carries the signal to the anterior papillary muscle of the right ventricle.

LO 4: what is the mediastinum divided into & by what

Division: Divided into Superior and Inferior by a plane through the sternal angle (Angle of Louis) to T4/T5.

LO 4: inferior mediastinum

• what are the 3 divisions & what do they contain

Inferior Mediastinum Subdivisions:

• Anterior: Fat and thymus remnants.

• Middle: Contains the Heart and pericardium.

• Posterior: Contains the esophagus, thoracic aorta, and azygous system.

LO 4: position of the heart

• what forms the apex

• what is the base formed by

• what is the anterior surface formed by

• where are the esophagus & descending aorta in relation to the heart

• where do the phrenic nerves run

Position of the Heart:

• Apex: Formed by the left ventricle; points inferolaterally at the 5th left intercostal space midclavicular line.

• Base: Posterior aspect formed mostly by the Left Atrium.

• Anterior surface: Mostly Right Ventricle.

• Relations: Esophagus and descending aorta are posterior to the heart. Phrenic nerves (C3-C5) run anterior to the lung roots along the pericardium.

LO 4: what portion of the mediastinum is the heart in & what intercostal space is the apex at

• Heart is in the middle inferior mediastinum.

• apex at the left 5th intercostal space and its base formed by the left atrium.

LO 5:

• where are the coronary arteries located in terms of heart muscle layers

• which layer is most vulnerable to ischemia & why

Anatomical Vulnerability:

• Coronary arteries sit on the epicardial surface and dive down.

• The subendocardium (inner layer) is the last to get blood and faces the highest pressure from the ventricle, making it the most vulnerable to ischemia.

LO 5: Subendocardial Ischemia (NSTEMI / Stable Angina)

• what is the cause

• what occurs physiologically

Subendocardial Ischemia (NSTEMI / Stable Angina):

• Cause: Partial occlusion or increased demand (e.g., exercise with 70% stenosis).

• Physiology: Blood reaches the surface but can't reach the deepest "end of the line" subendocardium

LO 5: Transmural Ischemia (STEMI / Prinzmetal)

• what is the cause

• what occurs physiologically

• Prinzmetal angina, also known as vasospastic or variant angina, is a type of chest pain caused by a sudden, severe spasm of the coronary arteries that temporarily reduces blood flow to the heart

Transmural Ischemia (STEMI / Prinzmetal):

• Cause: Complete occlusion by a thrombus or severe, prolonged vasospasm.

• Physiology: The entire thickness of the wall is starved of oxygen.

LO 5: subendocardial MI

• artery state

• ECG finding

• clinical type name

LO 5: transmural MI

• artery state

• ECG finding

• clinical type name

LO 6: what leaks out when myocyte membranes are damaged by necrosis

Mechanism: When myocyte membranes are damaged by necrosis, Troponin I and T leak into the blood.

LO 6: unstable angina

• what it is

• troponin status

Unstable Angina: Ischemia without necrosis. Troponins remain negative.

LO 6: NSTEMI & STEMI

• what do they both involve

• troponin status

NSTEMI & STEMI: Both involve necrosis. Troponins are positive.

LO 6: troponin time course

• rise

• peak

• duration/how long it remains elevated

Time Course:

• Rise: 2–4 hours after onset.

• Peak: ~24–48 hours.

• Duration: Remains elevated for 7–10 days.

LO 6: A patient has chest pain at rest and ST depression on ECG. If Troponin is negative at 6 hours, it is __________. If it is positive, it is an ___________

A patient has chest pain at rest and ST depression on ECG. If Troponin is negative at 6 hours, it is Unstable Angina. If it is positive, it is an NSTEMI.

LO 7: what do these represent on ECG

• p-wave

• PR interval

• QRS complex

• T wave

• ST segment

1. P Wave: Atrial depolarization (squeeze).

2. PR Interval: Time for the signal to travel from the SA node through the AV node (the "gatekeeper").

3. QRS Complex: Ventricular depolarization (the big squeeze). Should be narrow.

4. T Wave: Ventricular repolarization (the reset).

5. ST Segment: The pause between depolarization and repolarization; it should be flat on the "isoelectric line".

Lo 8: STEMI

• ECG

• what does this mean about heart muscle

STEMI: ST-segment Elevation (the "Fireman's Helmet"). Indicates full-thickness (transmural) damage.

LO 8: NSTEMI

• ECG

• what does this mean about heart muscle

NSTEMI: ST-segment Depression or T-wave inversion (no elevation). Indicates partial-thickness (subendocardial) damage.

LO 9: leads V1-V2

• infarct location

• vessel involved

LO 9: leads V3-V4

• infarct location

• vessel involved

LO 9: leads V5-V6, I, aVL

• infarct location

• vessel involved

LO 9: leads II, III, aVF

• infarct location

• vessel involved

LO 9: vessel

• V1–V4 =

• II, III, aVF =

• I, aVL, V5–V6 =

• V1–V4 = LAD.

• II, III, aVF = RCA.

• I, aVL, V5–V6 = LCX.

LO 10: myocardium response to ischemia/injury

• 0-30 min

• gross

• micro

• is this reversible

0–30 min: Reversible injury. Gross/Micro: None.

LO 10: myocardium response to ischemia/injury

• 30min-4hrs

• gross

• micro

• is this reversible

30 min – 4 hours: Irreversible injury begins. Micro: Wavy fibers at borders.

LO 10: myocardium response to ischemia/injury

• 4-24hrs

• gross

• micro

4–24 hours: Micro: Coagulative necrosis (darker pink cells, loss of nuclei, intact outlines). Gross: Dark mottling.

LO 10: myocardium response to ischemia/injury

• 1-3 days

• gross

• micro

1–3 days: Demolition starts. Micro: Heavy neutrophil infiltrate. Gross: Yellow pallor.

LO 10: myocardium response to ischemia/injury

• 3-7 days

• gross

• micro

3–7 days: Peak danger. Micro: Macrophages cleaning up debris. Gross: Central yellow softening (risk of rupture!).

LO 10: myocardium response to ischemia/injury

• 1-3 weeks

• gross

• micro

1–3 weeks: Reconstruction. Micro: Granulation tissue (new capillaries, fibroblasts). Gross: Red, hyperemic border.

LO 10: myocardium response to ischemia/injury

• >2 months

• gross

• micro

>2 months: Finished. Micro: Dense collagenous scar. Gross: White scar.

LO 10: myocardium response to ischemia/injury

• Wavy fibers = earliest sign (______).

• Neutrophils =_______ days; Macrophages = _______ days.

• Day 3-7 is the _________ _____ ____.

• Wavy fibers = earliest sign (30m-4h).

• Neutrophils = 1-3 days; Macrophages = 3-7 days.

• Day 3-7 is the highest rupture risk.

LO 11: what is arthrosclerosis

Atherosclerosis is a chronic inflammatory response to vessel wall injury, resulting in a "pimple" of fat and scarring inside an artery.

LO 11: arthrosclerosis

• endothelial dysfunction: what are triggers

Endothelial Dysfunction: Triggers (smoking, HTN) injure the lining.

LO 11: arthrosclerosis

• fatty streak: what does this look like & what are they made from

Fatty Streak: The earliest visible sign; flat yellow dots made of Foam Cells (macrophages that ate LDL).

LO 11: what are foam cells

Fatty Streak: The earliest visible sign; flat yellow dots made of Foam Cells (macrophages that ate LDL).

LO 11: mature plaque (atheroma)

• fibrous cap: what it’s composed of

• necrotic core: what it’s composed of

The Mature Plaque (Atheroma):

• Fibrous Cap: A hard "roof" composed of smooth muscle cells, dense collagen, and proteoglycans.

• Necrotic Core: A "cheesy" center under the cap containing extracellular lipids, cell debris, and Cholesterol Clefts (needle-shaped spaces where crystals once were).

LO 11: complicated plaque

• what does it show

Complicated Plaque: Can show calcification, ulceration, or thrombosis (the trigger for an MI).

LO 11: what is the risk with plaques that have a thin fibrous cap

Plaques with a thin fibrous cap and many macrophages are "vulnerable" plaques; they are more likely to rupture and cause a sudden heart attack than large, stable, thick-capped plaques.

LO 11: Atherosclerosis is characterized by an intimal plaque containing a fibrous cap and a necrotic lipid core with_______ and ________

Atherosclerosis is characterized by an intimal plaque containing a fibrous cap and a necrotic lipid core with foam cells and cholesterol clefts

LO 11: Atherosclerosis is characterized by an intimal plaque containing a _________ and a _______________with foam cells and cholesterol clefts

Atherosclerosis is characterized by an intimal plaque containing a fibrous cap and a necrotic lipid core with foam cells and cholesterol clefts