3.4.1. Coronary Circulation

Question 1

What do we mean by conduit vessels

Answer 1

Arteries and veins

Question 2

What are resistance vessels?

Answer 2

Precapillary arterioles

Question 3

What are exchange vessels?

Answer 3

Capillaries

Question 4

What are capacitance vessels?

Answer 4

Venuoles

Question 5

Characterize the relation between myocardial metabolic activity and coronary blood flow; describe the resultant physiologic adaptations with changing physiologic and pathologic circumstances

Answer 5

Increases in activity cause a resultant increase in local metabolites; this necessitates an increase in coronary blood flow (up to 300-400 % increase over resting rate)

At rest, perfusion of the myocardium is evenly distributed, while exertion limits blood flow to the apex of the heart due to its narrow coronary vessels
this results in a transient, reversible ischemia

Question 6

Describe CO and HR during the early stages of exercise

Answer 6

During the early stages of exercise, CO is maintained by increased HR and increased SV. During the late stages of exercise, CO is maintained by increased HR only (SV plateaus).

Question 7

Effect of an increased HR on CO

Answer 7

Diastole is preferentially shortened with increased HR; less filling time causes DECREASED CO (e.g., ventricular tachycardia)

Question 8

Shear forces across endothelial cells of the coronary vessels stimulate what?

Answer 8

Shear forces across endothelial cells of the coronary vessels stimulate the release of NO and subsequent vasodilation

Question 9

myocardial perfusion occurs during the _____ phase due to ____________________________.

Answer 9

myocardial perfusion occurs during the diastolic phase due to decreased pressure exerted on the coronary vessels

Question 10

diastolic intraventricular pressure can cause what?

Answer 10

diastolic intraventricular pressure can compress the myocardial microvessels (and collaterals)

Question 11

Myocardial ischemia

10 seconds to 10 minutes

Answer 11

Acute ischemia - Fully reversible

Question 12

Myocardial ischemia

10 min - 10 hours

Answer 12

(slowly reversible - “stunned myocardium”, irreversible - infarcted)

Question 13

Myocardial Ischemia for over 10 hours

Answer 13

Sustained: over 10 hours occurring very slowly: “hibernating myocardium” which is irreversible

Question 14

Death from cardiac causes within 1 hour onset of symptoms most commonly due to what?

Answer 14

Lethal arrhythmia (like ventricular arrhythmia)

Question 15

Sudden cardiac deaths are associated with what two conditions

Answer 15

CAD (70% of cases)

Hereditary ion channelopathies (like Long QT syndrome)

Question 16

What is Stable Angina?

• EKG?
• Course of condition

Answer 16

Usually secondary to artherosclerosis. Exertional chest pain in classic distribution (usually with ST depression on ECG) resolves with rest

Question 17

What is Variant Angina? Alternative name?

• ECG?
• Treatments?

Answer 17

Prinzmetal angina

Occurs at rest secondary to coronary artery spasm. Transient ST elevation on ECG.

Treat with Ca channel blockers , nitrates, and smoking cessation

Question 18

Unstable/Crescendo Angina?

Answer 18

Thrombosis with incomplete coronary artery occlusion. ST depression on ECG (increases in frequency or intensity of chest pain)

Question 19

Coronary Steal Syndrome

Answer 19

Distal to coronary stenosis, vessels are maximally dilated at baseline.

Administer vasodilators to relieve stress and reperfuse.

Question 20

When does an MI show ST elevation?

Answer 20

When it is transmural, i.e., full thickness.

Question 21

When do we see an MI with ST depression?

Answer 21

If it is subendochondral

Question 22

Flow limitation with progressively _____ arteries results in decreased perfusion in a _____ fashion

Answer 22

Flow limitation with progressively narrowing arteries results in decreased perfusion in a non-linear fashion

Question 23

Formula for functional flow reserve

Answer 23

FFR = P(distal)/P(aorta)