Coronary Circulation Flashcards
Mention the normal coronary blood flow
During rest: 250 ml/min (80ml/100gm tissue/min)
During exercise: 1000 ml/min
Mention the charecteristics of coronary blood flow
Very rich blood flow
Very low O2 reserve
Blood flow increases to supply extra O2 needs to cardiac tissues
Coronary vessels are functional end arteries
Systole helps blood supply and nutrition for all tissues except LV
Enumerate methods for measurement of coronary blood flow
- Experimental (cannulation of coronary sinus)
- Kety method (based on Fick’s principle)
- Coronary angiography
- Radionucleotides
The phase in which atria & RV
Rapid ejection phase
LV blood flow occurs in …..
Why?
Isometric relaxation phase
The wall tension is much reduced and at the same time the aortic diastolic pressure is still high enough to force blood through coronary arteries
Compare blood flow in RCA & LCA
R, recives blood maximally during rapid ejection phase
L, early in diastole
Mention bases in which DBP is reduced & LC blood flow is minimal
High pulse pressure and tachycardia (diastolic period is reduced)
Autoregulation occurs in the range ……
60-140 mmHg mean aortic pressure
Mention the metabolic conditions which cause coronary VD
Inc K, lactic acid, H, CO2, adenosine
Lack of O2
The mahor coronary VD agent is ….
Adenosine
Describe the role of adrenergic receptors in coronary BV
It has alpha (VC) & beta (VD) receptors, the alpha are found more in epicardial vessels while beta are found more in myocardial vessels.
Describe effect of ANS on coronary BV
Symp causes direct VC leading to accumulation of metabolites and O2 lack, this continues to certain level till local factors override neural factors and produce VD indirectly.
Vagal stimualation results in diminished activity of heart, which decreases cardiac metabolites and leads to coronary VC.
