40 Coronary Regulation Flashcards
What are the 3 main conduit coronary arteries? Do they contribute to coronary vascular resistance? Are they susceptible to atheroscclerosis?
- LAD, LCFlex, RC
- very little
- They are the site of atherosclerosis
What vessels regulates coronary vascular resistance?
resistance vessels- intramural arteries <100micrometers in diameter
What develops in response to epicardial stenosis? What are the main stimulus?
- collateral vessels
2. VEGF, bFGF, PDGF
What are veins and venues role in coronary regulation or dysregulation?
They have no role
What are the 3 most important factors of regulation for coronary blood flow?
- metabolic factors
- Autoregulation
- Wall tension
[neural regulation, humoral regulation, myogenic tone]
Myocardial oxygen consumption/metabolism overrides any other stimulus. What are the 3 major determinants?
contractility, HR, Wall tension [preload and after load]
What are the 2 determinants of O2 supply to the heart?
coronary flow
oxygen extraction
What is unique about oxygen extraction in the heart?
max at rest and exercise…you must change coronary flow then
Where is wall stress greatest? Where is blood flow greatest at rest?
- greater in endocardium
2. greater in endocardium than epicardium
What is auto regulation?
maintaining constant flow with changing perfusion pressure= range in the heart = 40 to 120
What is myogenic regulation?
stretch on blood vessel wall produces an increase in smooth muscle contraction—occurs over minutes
What does a1 stimulation and a2 stimulation direct effects?
a1=increase epicardial and resistance vessel tone
a2=increase release of NO
What are the adrenergic stimulation indirect effects?
- increase in arterial pressure
2. reflex decrease in HR
What is the net effect of alpha adrenergic stimulation? beta?
modest decrease in flow
increase in flow
What are direct effects of beta 2? indirect effects of beta 1?
- decrease epicardial and resistance vessel tone
2. up HR, up contractility, increase MVO2 and vasodilation
What are the direct effects of paraSNA? Indirect effects?
- decrease epicardial and resistance vessel tone
2. down HR, down arterial BP, down MVO2 and vasoconstrict
What is the overall paraSNA effect on blood flow?
decrease flow
What are ROS effects in cardiovascular disease?
O2- and NO combine to form ONOO- , the decreased NO decreases cGMP which leads to less relaxation
What are ROS increased by in regards to vascular dysfunction? 5
atherosclerosis diabetes hypertension AngII Inflammation
What antioxidants may be beneficial?
E and C vitamins NO!!!
SOD/Catalase–maybe but not available
How is Rho kinase involved in CV disease?
it is increased, which it inhibits MLC phosphatase, which leads to increased phosphorylation of Myosin light chain which is the contractile state
What is angina?
When the O2 supply does not meet the MVO2 demand
[Can happen from a decrease in supply or an increase in demand]
CHD, CVD, IHD and angina are all the same and have reduced myocardial perfusion. What are the 3 main causes?
- coronary artery narrowing with atherosclerosis or plaque
- Vasospasm (with or without thrombus)
- Plaque rupture
When does maximal flow start diminishing in stenotic patients?
past 50%, but resting flow maintains normal until past 75%
