A&P Chapter 21
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A&P Chapter 21
Ischemic Heart Disease and Coronary Flow
Increasing age, Male gender, Genetic predisposition/family history are all what types of risk factors for IHD?
Cigarette smoking, hypertension, obesity, and sedentary lifestyle are all what types of risk factors for IHD?
How does hypertension increase the risk of IHD?
direct vascular injury, left ventricular hypertrophy, and increased myocardial oxygen demand
hypercholesterolemia, hyperglycemia, low hdl levels are what type of risk factor for IHD?
What all does the Right coronary artery perfuse?
1) Right Atrium
2) Right Ventricle
3) LV inferior Wall
4) IF right dominant
: PDA --> posterior LV & superior/posterior IV septum and inferior wall
What all does the Left coronary artery perfuse?
1) Left Atrium
2) IV Septum
3) Left Ventricle (septum, anterior, lateral wall)
What does the LAD perfuse?
septum and anterior wall of LV
What does the circumflex artery perfuse?
lateral wall of LV
If the patient has left dominant circulation, what does the circumflex artery perfuse?
posterior septum and inferior wall of LV
What perfuses the SA node?
RCA in 60%
LAD in 40%
What perfuses the AV node?
What perfuses the bundle of His?
LAD and PDA
The anterior papillary muscle of the mitral valve is perfused by?
LAD and Circumflex
The posterior papillary muscle of the mitral valve is perfused by...? What indication does this have?
PDA only - more vulnerable to ischemic dysfunction
How much is normal resting coronary blood flow?
Does the heart get any blood directly from the chambers of the heart?
yes - from the inner 0.1 mm of endocardial surface but it is an insignificant amount
Where does the hearts most significant source of blood supply come from?
epicardial vessels - outer surface vessels that supply most of the muscle
What is the significance of HR on coronary perfusion?
increased HR = less diastolic time = less perfusion time
Why doesn't the heart receive blood during systole?
The contraction of the LV raises the intramyocardial pressures to equal systemic pressure --> almost total occlusion of the intramyocardial part of the coronary arteries
How do you determine coronary perfusion pressure?
CPP = ADP - LVEDP
Does the RV receive perfusion during systole?
What are 4 things that control coronary blood flow?
1) heart rate (time spent in diastole)
2) CPP = ADP - LVEDP
3) CaO2 (SaO2 x Hgb)
4) Coronary Vessel diamter (Poiselle's flow, radius)
How do you determine the delivery of oxygen to an organ? (DO2)
DO2 = CaO2 x CO
CaO2 = (SaO2 x 1.39 x Hgb) + (0.0031 x PaO2)
Which is more important when determining myocardial blood flow: MAP or ADP?
Why is it bad to be hypotensive with a PCWP of 40?
You've narrowed the gradient between ADP and LVEDP = decreased CPP
What is the SvO2 in the coronary sinus?
If myocardial oxygen demand increases, what must happen? How is this different form other tissues?
coronary blood flow must increase. Other tissues can simply extract more oxygen from Hgb.
How does the heart increase coronary blood flow?
It releases vasodilating substances:
- Adenosine (ATP degradation)
- K ions
- H ions
- Nitric Oxide
Alpha 1 receptors are located _______ and cause ______
epicardial vessels - stimulation causes vasoconstriction (excessive stimulation can proceed ischemia and angina)
Beta 1 receptors cause ____ and _____
Increased HR and increased contractility
Beta 2 receptors are located mainly in ____ and _____ and cause _____
intramuscular and subendocardial vessels...causes vasodilation
Where does the myocardium get most of its energy?
breakdown of fatty acids
What are the 3 venous drainage systems of the heart? Which one is different, how?
1) Coronary Sinus
2) Anterior Cardiac Veins
3) Thebesian veins
Thebesian veins dump into all chambers (including LV) which means a portion of outflow blood is deoxygenated
What is angina pectoris thought to be caused by?
glycolosis --> lactic acid
Which two coronary arteries have the highest mortality when occluded?
1) Left Main
What is a nuclear stress imaging?
Pharmacologically induced stress (dobutamine, adenosine, dypyridamole) followed by imaging to assess wall motion and/or tracer (thallium, technetium) uptake to assess perfusion
What is the gold standard for determining the condition of coronary arteries?
The fundamental purpose of beta blockers is to....
decrease oxygen demand
Why might Ca Channel blockers be risky?
decrease BP and contractility --> narrowing of gradient between ADP and LVEDP --> decreased CPP --> further infarction
Ace inhibitors have replaced which drug?
What are the 4 causes of death after an MI?
1) pump failure
2) pulmonary edema
3) V fib
4) ventricular rupture
What does it mean when a portion of muscle becomes dyskinetic?
it bulges out - the volume of blood in the bulge reduces CO
What contributes to post MI pulmonary edema?
weak pump and decreased renal perfusion --> increased blood volume
How does ischemia affect the repolarization of myocardial muscle?
It often cannot completely repolarize --> irritability --> Vfib
What 4 things increase the risk of Vfib post MI?
1) depletion of K --> increased extracellular K
2) Injury current
3) Increased sympathetic response
4) LV dilation