11/1/2014 1 The Coronary Circulation Guyton Chapter 21 Coronary Circulation Heart blood flow second only to kidney on per gram basis Heart weighs ~300 gms CBF ≈ 250cc/min Cardiac Hemodynamics Region Mass (kg) Blood flow mL/m Blood flow mL/100 gm/m O2 mL/100 g/m % Cardiac Output % O2 Use Brain 1.5 750 50-55 3.5 15% 20% Kidneys 0.3 1240 420 6.0 25% 7% Liver 2.6 1500 58 2.0 28% 20% Heart 0.3 250 84 9.7 5% 12% Whole Body 63 5500 8.6 0.4 100% 100%
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11/1/2014
1
The Coronary Circulation
Guyton Chapter 21
Coronary Circulation
� Heart blood
flow second only to kidney
on per gram
basis
� Heart weighs ~300 gms
� CBF ≈
250cc/min
Cardiac Hemodynamics
Region Mass
(kg)
Blood
flow
mL/m
Blood
flow mL/100
gm/m
O2
mL/100
g/m
%
Cardiac Output
% O2
Use
Brain 1.5 750 50-55 3.5 15% 20%
Kidneys 0.3 1240 420 6.0 25% 7%
Liver 2.6 1500 58 2.0 28% 20%
Heart 0.3 250 84 9.7 5% 12%
Whole
Body
63 5500 8.6 0.4 100% 100%
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Coronary Arteries
� Two main coronary arteries arise from root of aorta
� Large, low resistance
� Lie on surface of the heart (epicardium) –penetrate into cardiac muscle
Coronary Arteries
Left coronary a. supplies the LA, the anterior and lateral LV, and the right and left bundle branches
1. Left coronary artery
� anterior descending
� circumflex
Coronary Arteries
Right coronary a. supplies the RA, RV, posterior LV, SA node (60%), AV node (90%), and AV bundle
2. Right coronary artery
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3
Coronary Venous Blood
� Coronary Sinus
� Collects 75% of total
CBF; empties into RA
� Anterior Cardiac Vein
� Collects venous blood from RV; empties into
RA
� Thebesian Veins
� Collect blood from all
over the heart; empty directly into chambers
� Contributes to venous
admixture
Coronary Perfusion Pressure (CPP)
� Coronary arteries are perfused during diastole
Normal
Why does coronary perfusion occur
during diastole?
� CBF to LV falls during systole (opposite all other vascular beds)
� Why? Strong compression of LV muscle around coronary a. during contraction