Peripheral and Coronary Circulation Flashcards
Coronary arteries and branches
- Right coronary artery (supplies RA, RV, SA and AV nodes)
- Right posterior descending artery
- Acute marginal artery
- Left coronary artery (supplies LA and LV)
- Left anterior descending artery
- Left circumflex artery
Veins that supply the Coronary sinus
- Small cardiac vein (tracks with superior part of right descending artery)
- Middle cardiac vein (tracks with inferior part of right descending artery)
- Posterior cardiac vein (tracks withinferior part of left circumflex artery)
- Great cardiac vein (tracks with the left anterior descending artery and goes along with circumflex its back superior branches)
Anterior vein
Does not join with coronary sinus, but rather drains directly into right atrium.
Tracks with the anterior, superior branches of the right coronary artery
All heart blood vessels diagram (ant and post view)
Peripheral arterial disease
Atherosclerosis of the lower extremeties. Intermittent claudication (pain, aching, cramping). Most commonly felt in calf during exercise. May present as exercise-inducible ischemia.
Ankle-brachial index
Measure the BP in the ankle and brachium and take a ratio of the systolic blood pressures. If 0.9 > Pankle systole / Pbrachium systole, then this result is diatnostic for PAD.
Major determinants of myocardium oxygen supply and demand
The predominance of coronary flow takes place during ___.
The predominance of coronary flow takes place during diastole.
Coronary flow is unimpaired in diastole because the relaxed myocardium does not compress the coronary vasculature. Thus, in the case of the coronaries, perfusion pressure can be approximated by the aortic diastolic pressure.
Moreover, when the myocardium contracts ___ is subjected to greater force than are the outer muscle layers.
Moreover, when the myocardium contracts the subendocardium is subjected to greater force than are the outer muscle layers.
It is also the poorest perfused, and, like the rest of the heart, uses a high level of the available oxygen from hemoglobin at baseline. All of these make it especially vulnerable to ischemia.
Factors that participate in the regulation of coronary vascular resistance
- Accumulation of metabolites (ADP and AMP build up. Released as adenosine, which is a potent vasodilator)
- Endothelium-derived substances (ACh / eNOS / NO axis, prostacyclin, endothelin-1, etc)
- Neuronal innervation (α and β2 receptors)
endothelium-derived relaxing factor (EDRF)
Normally, acetylcholine results in smooth muscle contraction. However, when endothelium covers the smooth muscle, it results in vasodilation. This is due to the activity of EDRF, which is released from endothelial cells in response to acetylcholine.
EDRF is really a nitric oxide radical, generated by eNOS from L-arginine.
Blood - Endothelium - Smooth muscle axis
Adrenergic receptors on coronary endothelium
Coronary vessels contain both α-adrenergic and β2-adrenergic receptors
Stimulation of α-adrenergic receptors results in vasoconstriction, whereas β2-receptors promote vasodilatation.
The hemodynamic significance of a coronary artery narrowing depends on. . .
- degree of stenosis
- compensatory vasodilatation the distal resistance vessels are able to achieve
When a stenosis narrows the diameter by more than approximately 70% . . .
When a stenosis narrows the diameter by more than approximately 70%, resting blood flow is normal, but maximal blood flow is reduced even with full dilatation of the resistance vessels.
Resting and max coronary flow
Endothelial dysfunction in coronary artery disease
Abnormal endothelial cell function can contribute to the pathophysiology of ischemia in two ways:
(1) by inappropriate vasoconstriction of coronary arteries and
(2) through loss of normal antithrombotic properties.
It is postulated that in typical people, the relaxation effect of NO outweighs . . .
It is postulated that in typical people, the relaxation effect of NO outweighs the direct α-adrenergic constrictor effect of catecholamines on arterial smooth muscle, such that vasodilatation results.
endothelial dysfunction occurs ___ in the atherosclerotic process.
endothelial dysfunction occurs very early in the atherosclerotic process.
Platelet/endothelium interactions in vascular tone
ther common causes of decreased myocardial oxygen supply
- decreased perfusion pressure due to hypotension (e.g., in a patient with hypovolemia or septic shock)
- a severely decreased blood oxygen content (e.g., marked anemia, or impaired oxygenation of blood by the lungs)
- profound increase in myocardial oxygen demand can cause ischemia even in the absence of coronary atherosclerosis (rapid tachycardias, acute hypertension, or severe aortic stenosis)
Stable vs Unstable angina diagram
Levine sign
While describing angina, the patient may place a clenched fist over his or her sternum, referred to as the Levine sign, as if defining the constricting discomfort by that tight grip.
Things that influence oxygen demand in order of magnitude
- Contractility
- Heart rate
- Wall stress
Systolic vs diastolic heart failure on PV diagram
