3.4.1. Coronary Circulation Flashcards
What do we mean by conduit vessels
Arteries and veins
What are resistance vessels?
Precapillary arterioles
What are exchange vessels?
Capillaries
What are capacitance vessels?
Venuoles
Characterize the relation between myocardial metabolic activity and coronary blood flow; describe the resultant physiologic adaptations with changing physiologic and pathologic circumstances
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
Describe CO and HR during the early stages of exercise
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).
Effect of an increased HR on CO
Diastole is preferentially shortened with increased HR; less filling time causes DECREASED CO (e.g., ventricular tachycardia)
Shear forces across endothelial cells of the coronary vessels stimulate what?
Shear forces across endothelial cells of the coronary vessels stimulate the release of NO and subsequent vasodilation
myocardial perfusion occurs during the _____ phase due to ____________________________.
myocardial perfusion occurs during the diastolic phase due to decreased pressure exerted on the coronary vessels
diastolic intraventricular pressure can cause what?
diastolic intraventricular pressure can compress the myocardial microvessels (and collaterals)
Myocardial ischemia
10 seconds to 10 minutes
Acute ischemia - Fully reversible
Myocardial ischemia
10 min - 10 hours
(slowly reversible - “stunned myocardium”, irreversible - infarcted)
Myocardial Ischemia for over 10 hours
Sustained: over 10 hours occurring very slowly: “hibernating myocardium” which is irreversible
Death from cardiac causes within 1 hour onset of symptoms most commonly due to what?
Lethal arrhythmia (like ventricular arrhythmia)
Sudden cardiac deaths are associated with what two conditions
CAD (70% of cases)
Hereditary ion channelopathies (like Long QT syndrome)
What is Stable Angina?
- EKG?
- Course of condition
Usually secondary to artherosclerosis. Exertional chest pain in classic distribution (usually with ST depression on ECG) resolves with rest
What is Variant Angina? Alternative name?
- ECG?
- Treatments?
Prinzmetal angina
Occurs at rest secondary to coronary artery spasm. Transient ST elevation on ECG.
Treat with Ca channel blockers , nitrates, and smoking cessation
Unstable/Crescendo Angina?
Thrombosis with incomplete coronary artery occlusion. ST depression on ECG (increases in frequency or intensity of chest pain)
Coronary Steal Syndrome
Distal to coronary stenosis, vessels are maximally dilated at baseline.
Administer vasodilators to relieve stress and reperfuse.
When does an MI show ST elevation?
When it is transmural, i.e., full thickness.
When do we see an MI with ST depression?
If it is subendochondral
Flow limitation with progressively _____ arteries results in decreased perfusion in a _____ fashion
Flow limitation with progressively narrowing arteries results in decreased perfusion in a non-linear fashion
Formula for functional flow reserve
FFR = P(distal)/P(aorta)
