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Coronary circulation..ppt
1. Coronary Blood Flow
Normal resting CBF is 60-80ml/100 gm/min.
or 250ml/min.
O2 consumption .
A – V O2 difference in myocardium is 19-6=13ml/dl
other parts of body 19-14=5ml/dl
2. Phasic Coronary Flow
Phasic Coronary flow is 80% during diastole and 20%
during systole.
All other parts of the body receives blood supply during
systole but heart receives blood supply during diastole.
Right coronary artery supplies right ventricle and atrium. Less
forceful contraction of right ventricle does not inhibit flow
from high pressure aorta.
6. Compensatory mechanism
DEEP MYOCARDIAL
(ENDO/SUBENDOCA
RDIAL) LAYER
SUPERFICIAL(EPICAR
DIAL) LAYER
CAPILLARY DENSITY 1100 capillaries/mm2 750 capillaries/mm2
DIFFUSION DISTANCE 16.5µm 20.5µm.
MYOGLOBIN
CONTENT
HIGHER LOWER
LACTATE PYRUVATE
RATIO
HIGHER LOWER
7. Regulation of Coronary Blood Flow
1. Local control mechanism
Autoregulation
Local metabolites
Role of endothelial cells
Coronary perfusion pressure
2.Nervous control mechanism.
Sympathetic
Parasympathetic
Myocardium extracts 70% o2 at rest , but during activities o2 demand
is compensated by increased CBF not by increased o2 extraction.
8. Metabolic Theory
CO2
H+
NO
Adenosine
Prostaglandins
K+
Bradykinin.
Myogenic Theory.
Heart rate
Autoregulation
LOCAL CONTROL MECHANISMs
9. BERNE HYPOTHESIS
(ADENOSINE)
FALL IN ART.PO2 ↑MYOCARDIAL METABOLISM
ISCHEMIA/HYPOXIA
INTRACELLULAR
ADENOSINE
NUCLEOTIDE
ADENOSINE
CORONARY
VASODILATOR
↑ CORONARY BLOOD FLOW
11. HR-
75/min
HR-
200/min
%
CHANGE
DURATION OF
CARDIAC CYCLE
0.80 sec 0.30 sec 62.50
DURATION OF
SYSTOLE
0.27 sec 0.16 sec 40.70
DURATION OF
DIASTOLE
0.53 sec 0.14 sec 73.58
CORONARY BLOOD FLOW WILL BE MORE COMPROMISED AT
HIGHER HEART RATES DUE TO FALL IN DURATION OF DIASTOLE.
NEUROGENIC CONTROL OF CORONARY PERFUSION
21. Applied physiology
Ischemic Heart Disease
Atherosclerosis of coronary arteries
Thrombus formation
Embolus from other areas
Spasm of coronary arteries
22. Angina Pectoris means severe chest pain (usually
retrosternal i.e. behind the sternum) due to ischemia
of the cardiac muscle.
• The anginal pain may radiate to the left shoulder, left
arm or forearm (referred pain).
Angina pectoris is usually due to narrowing of the
coronary arteries ischemia.
Anginal pain may be relieved by rest & coronary VD
drugs.
ANGINA PECTORIS
23. MYOCARDIAL INFARCTION
• Myocardial Infarction means necrosis of a part of
the myocardium due to
a) Severe & prolonged ischemia due to narrowing
of the coronary arteries.
b) Occlusion of one of the coronary arteries or its
branches by coronary thrombosis severe
ischemia.
Myocardial Infarction produces also chest pain
which is more severe than that of angina and it
cannot be relieved by rest or coronary VD drugs.
It is frequently complicated by ventricular
fibrillation death.