Coronary and Systemic Circulation; Vascular Control Flashcards
(37 cards)
What coronary arteries branch off of the R coronary artery?
The acute marginal and in a right dominant heart, the posterior descending
What coronary arteries branch off of the L coronary artery? What are their branches?
The L circumflex (obtuse marginals and the posterior descending in a L dominant heart), the L anterior descending (diagonal and septal branches)
What are thebesian vessels? Are they found in a normal person?
Vessels that do not follow the normal path of flow and may drain into chambers besides the R atrium.
Yes.
Why are anastomoses in coronary circulation important?
They allow blood flow (and thus perfusion) to most of the heart, even in cases of significant three vessel coronary artery disease
What is a coronary perfusion territory? Why might territories overlap?
The area supplied by a vessel. They overlap in areas that are important to the heart’s function (i.e. the papillary muscles for the mitral valve) so if flow from one artery is compromised, the papillary muscle and thus the valve will still work.
What is coronary dominance? Approximately how often are people right dominant? Left dominant? Co-dominant?
Which artery supplies the posterior descending artery. In right dominant people (70%), it’s the R coronary artery. In left dominant people (10%), it’s the left circumflex. In codominant (10%), it’s both.
What is the major variable controlling coronary blood flow?
Resistance. (P=QR where Q= coronary blood flow)
What are the three components of coronary vascular resistance? When are they significant?
R1- if you push on the artery, it pushes back; significant in pathology, not normally
R2- metabolic resistance; resistance changes based on metabolic needs of tissue
R3- mechanical resistance; arteries travel through the thickness of cardiac muscle. Not much flow during systole
What is autoregulation of flow? What is a consequence of this? Give an example of a small molecule involved.
The intrinsic ability of the heart to maintain a constant coronary blood flow across a range of coronary perfusion pressures. Thus, a change in pressure (as long pressure stays between 30 and 150 mm Hg) will not affect flow. NO
When does most coronary perfusion occur? Why?
During diastole. Because R3 is really high in systole
What clinical diagnostic tests would one use to diagnose impaired myocardial perfusion?
An EKG with a stress test. Then potentially catheterization and an angiogram (inject dye, see where it goes) to identify blockages
What is an angioplasty? How does it work?
A procedure to re-open an artery. A catheter is introduced and a stent is placed at the site of occlusion. The stent expands, keeping the artery open and increasing flow and thus downstream perfusion
What is coronary artery bypass surgery/grafting?
“replumbing the heart.” Creating new vascular pathways to that areas distal to an occlusion will still be perfused
What does an intra-aortic balloon pump do? Why is this important?
It reduces heart pressure just before systole and increases it during diastole (reduces PP). This means the heart does less work. It also improves coronary blood flow and thus the oxygen supply to the heart.
Where do most of the cardiac veins drain to? What about the anterior cardiac veins?
Most drain to the coronary sinus just behind the RA. The anterior cardiac veins drain to the RV
What are two major endogenous vasodilators?
Adenosine and NO
Define vascular compliance. How would you calculate it mathematically? How is it related to elastance?
Compliance is how stiff a vessel is; it is determined by the elastic fiber content and arrangement in a tissue. C= (change in V)/(change in P). Elastance = 1/compliance
How does arterial compliance change with age? How does this affect arterial pressure?
Compliance decreases with age. Thus, for a given pressure, a vessel has a smaller increase in volume because arteries are less elastic. Since vessels are more rigid, TPR increases and Blood pressure increases (MAP = CO x TPR)
How is tension related to transmural pressure of a vessel? How is tension defined in this context?
Tension= transmural pressure x radius
Tension is the amount of force required to pull apart the walls of a vessel (or how much energy required to hold a slit in the walls of a vessel together)
How does increased pressure change the resistance of an elastic vessel?
As pressure increases, r increases (arteries vasodilator) and R falls
What is the slope of a volume v. pressure curve? Of a pressure v. volume curve?
Volume v. pressure: slope= (change in P)/(change in V)= 1/compliance
Pressure v. volume: slope = (change in V)/(change in P)= compliance
How does an arterial volume v. pressure curve differ from a venous curve? Why is this important?
The arterial curve has a much steeper slope so for a small change in volume, there is a large change in pressure. The venous curve has a less steep slope and thus is more compliant as a system. This is why the venous system is a reservoir for blood.
What happens to arterial and venous volume v. pressure curves if a person has a hemorrhage?
Hemorrhage= decreased volume so both curves shift to the L so that a reasonable pressure can be maintained at the new volume. [Remember, curves can shift based on the ANS control of the blood vessel]
How do arteries store energy for blood circulation? Why is this clinically significant?
When blood is pumped into the aorta during systole, some of the energy created by movement distends the elastic walls of the aorta, creating a transmural pressure. When the heart fills during systole, this transmural pressure is converted into movement energy and drives forward flow. This is why we have a diastolic BP and why BP never = 0
