Cardiology - Intro + Equations

Question 1

Describe how the blood reaches the coronary circulation.

Answer 1

Blood from the coronary sinus drains into the RA -> RV -> pulmonary arteries -> pulmonary veins -> LA -> LV -> aortic root -> coronary arteries -> coronary sinus

**note: blood enters coronary arteries during diastole**

Question 2

Describe the different coronary blood vessels and what they supply.

Answer 2

LCA branches into Left Circumflex (LCX) and the LAD.

• LAD: supplies anterior wall of LV and anterior interventricular septum
• LCX: supplies blood to the lateral and posterior walls of LV
• LCA: supplies AV node (10%), SA node (35%)

RCA branches into right marginal artery and posterior descending artery (80%)

• Right marginal artery: supplies RV
• RCA: supplies papillary muscles of RV, posterior wall of the heart, AV node (90%), SA node (65%)

Question 3

What contributes most to peripheral resistance?

Answer 3

arterioles

Question 4

what chamber of the heart does the esophagus lie posterior to?

Answer 4

LA

Question 5

what vessel contains the most deoxygenated blood?

Answer 5

coronary sinus

Question 6

SV = ?

Answer 6

SV = EDV - ESV

SV = Stroke volume = volume of blood pumped by the heart every beat

EDV = end diastolic volume

ESV = end systolic volume

Question 7

CO = ?

Answer 7

Cardiac Output represents the volume of blood pumped by the heart every minute. Two main equations:

CO = SV * HR

CO = rate of O2 consumption/(arterial O2 content = venous O2 content)….*Fick Principle*

Rate of O2 consumption = mL O2/min

arterial/venous O2 content = mL O2/100 mL blood

Question 8

Ejection Fraction (EF) = ?

Answer 8

EF = (EDV - ESV) / EDV = SV/EDV

Question 9

Stroke work = ?

Answer 9

stroke work = aortic pressure * SV

this is the work created by the heart in a single beat

Question 10

resistance = ?

Answer 10

Key thing to note: resistance is inversely proportional to radius^4

This means that if the radius decreases by 1/2, the resistance will increase by 16

Question 11

MAP = ?

Answer 11

MAP = CO * TPR

mean arterial pressure is a function of the hydrostatic forces exerted by the volume of blood in the circulation and the resistance within the vessel

Question 12

pulse pressure = ?

Answer 12

pulse pressure = systolic BP - diastolic BP

normal is between 30-50 mmHg

Question 13

blood flow = Q = ?

Answer 13

Two main equations:

Q = change in P / R

Q = V * A

V = velocity

A = cross sectional area

**Note: velocity is inversely proportional to cross-sectional area and proportional to blood flow**

Question 14

what blood vessels have the lowest velocity of blood flow?

Answer 14

capillaries

Question 15

Capillary fluid exchange = ?

Answer 15

Question 16

Compliance = C = ?

Answer 16

C = V/P

Compliance indicates the ability of the tissue to expand as pressure rises

Question 17

Elastance = E = ?

Answer 17

E = P/V

Elastance is the ability of the tissue to recoil upon distension.