Chapter 13 Flashcards
T or F CAD is the second largest cause of death in adults
False, its the first, and is the most common cause of premature deaths in adults before the age of 65.
what are the 4 major determinants of prognosis in patients with CAD?
- coronary obstruction- # of vessels and severity of obstruction.
- L ventricular function- ability to pump blood over body
- presence of ischemia - frequency and severity of episodes
- risk factor analysis - age, gender, clinical hx (labs, co-morbids),
Define the Left Main coronary artery (LMCA) system
- uppoer portion of L aortic sinus, and passes behind R V outflow.
- contaisn Left circumflex arter (LCx) at right andles and con’t into LAD.
- Most important system
What is the purpose of the LAD?
artery supplies the anterior and septal walls of the L V, passing down the anterior interventrical groove toward the cardiac apex.
- LAD + branches are usually considered most important system after LMCA
What is the purpose for the L circumflex artery?
travels the AV groove, and responsible for blood suply to the Lateral ventricular wall.
- can terminate in one or more large obtuse marginal (OM) branches, or can continue as a large artery in the AV groove.
- in 10-15% of cases it gives rise to the posterior descending artery, which provides circulation to the inferior and posterior walls of the LV.
Define the Right coronary artery (RCA)
located in R sinus of Valsalva. and courses upways from plane of the Aortic Valve and travels in the R AV goove to reach posterior LV wall.
- 85% of cases, posterior descending artery arises from RCA before it reaches the ‘crus’ of the heart.
After ficing rise to posterior descending artery, the RCA becomes intramuocardial at the crux and gives rise to the AV node artery.
what is the crux?
junction of the interatrial and interventricular septa.
Which parts of the coronary circualtion are visualized via angiography?
major branches and their second, third, and perhaps fourth order brances.
The term “dominance” often is used to describe what?
the anatomic configuration of the blood supply to the posterior descending artery. R dominance (posterior descending artery emerging from RCA) occurs in 85% of cases L domiance( LCx provides the posterior descending circulation) 15% of cases.
What are the 3 layers of teh coronary arterial wall?
- intima - inner layer connecting with blood.
- media- smooth muscle cells and connective tissues responsible for the vasodilatory properties
- adventitia. - outer layer made of up fibroelastic tissues without smooth muscle cells. it houses nutrient vessels of the vascular wall and never fibers. gives vascular wall stability by connecting the artery to its surrounding tissues.
What is the lumen?
the open space thorugh which blood flows between cell layers.
What is the most important structure in the itima layer of teh coronary artery?
endothelium- its a layer of endothelial cells lining the whole vascular wall. it protects agaisnt atherosclerosis and acts as a selective barrier to prevent plasma lipid ACCUMULATION within the vessel wall. It also has been shown to prevent blood clot formation and arterial spasm.
Astherosclerosis affects mainly the medium-sized coronary arteries on the epicardial (outer) surface of the heart. There are several types of lesions, please name 3.
- initial lesion- fatty streak- yellow slightly raised lesions that are accumulations of lipidladen cells (foam cells)
- more advanced lesions- atheroma- rounded raise lesions whiter, that cause some degree of vascular lumen narrowing. compossed of fibrotic cap and a cretotic core containing cellular debris, lipids, cholesterol crystals, calcific deposits and blood-borne material.
- lesion associated with coronary events- complicated plaque, ruptures or dissured plaques arose from the thin fibrotic cap or d/t fissure from subsequent exposure of teh interval contituents of teh atherosclerotic plaue into the flowing blood. They have high thrombogenic properties
In spontaneous atherosclerosis, what is the tenet cause of endothelial injury?
result of disturbance of the pattern of blood flow in certain parts of the coronary arterial tree.
What are typical CAD risk factors?
HTN, hypercholesterolemia as well as circulating vasoactive amines, immune complexes, infection, chemical irritants in tobacco smoke, and potentiate chronic endothelial injury.,
There are 3 types of vascular injuries. Describe them
- early form of injury. causes functional alteration of endothelial cells without morphological changes. leads to increase permeability to plasma lipids and monocutes, and change in EDFR reponse to stimuli.
- more sever injury with endothelial denudation and intima injury caused by release of toxic products by macrophages. Macrophages+platelets+endothelium causes release of various growth factrs which leads to simultaneous migration and proliferation of smooth muscle cells, forming fibrous capsuls over lipid ledions.
type 3- accelerated version of atherosclerotic process appears to account for premature CAD in those undergoing heart surgery. Its usually critical initiating event.
T or F: fissuring or rupture of complicated atherosclerotic plaque with subsequent occlusive thrombi plays a fundamental role in developement of the acute ischemic syndromes?
yes,
plaque distributiom, thrombosis and scarring can be also important in the progression of atherosclerosis in Asxs individuals or those with stable angina.
What are some current approaches to stabilizing or retarding the progression of atherosclesosis, or even causing its regression?
- reducing risk factors such as lipid levels.
- use of antithrombotic therapy- since thrombus formation is an important factor in the initiation of an acute cardiac event and progression of the disease.
Define Myocardial ischemia
occurs when myocardial O2 supply cannot meet the myocardial oxygen demand in a region of the ventricle.
Define Myocardial infarction
It is the irreversible myocardial cell injury and death that occurs following prolonged ischemia.
When does muscle necrosis occur?
when an ischemic episode is prolonged beyond 30-40 mins.
Coronary artery size is controlled by a number of factors that influence coronary artery smooth muscle activation. What are they (3)?
- neural regulation
- locally-produced chemicals, such as adenosine.
- endothelium-derivered relaxing factors (EDRF) such as nitrous oxide and the prostaglandins.
What does the EDRF do for the coronary blood flow?
optimizes it in response to a variety of stimuli and also exerts potent anti-aggregant effects on platelets at the release site.
What controls Myocardial oxygen demand?
- heart rate
- contractility of the myocardium
- LV wall tension.
What happens when a epicardial coronary artery is briefly occluded?
- there is a change in myocardial metabolism (detected by PET scannig) > changes in myocardial function
- diastolic dysfunction appears > systolic dysfunction with contractile disturbances. - detected by radionuclide or MUGA scan or cardiac catherization. At the same time, reversible regional myocardial perfusion defects appear, detectable with radionuclide imaging.
- relatively late in the myocardial ischemia stages, EKG abN and CP appears.
- these findings are potentially reversible with restoration of blood flow.
What happens after prolonged disruptions in the myocardial supply and demand balance,?
potential to result in myocardial injury and cell death (MI- infarctions).
T or F: hybernation myocardium can persist for months without cell death.
True
Define an exercise stress test
- most frequently performed test for dx and assessment of CAD.
- done with treadmill usuing standardized protocols, where the pt starts with low workloads and increases to high ones, wth BP, and pulse monitored through an EKG.
What are the EKG signs of myocardial ischemia?
What are the important stress testing parameters?
horizonal or ST segment depressions or >1mm. 0.08 seconds after the J point. --------------- exercise duration ST segment changes with exercise blood pressure reponse sxs with exercise EF, with resting and exercise Thallium/ SPECT defects ECHO wall motion abN
What are some possible reasons for a false positive stress test?
- Electrolyte disturbances
- digoxin therapy
- ventricular hypertrophy
- mitral valve prolapse
- conduction abnormalities
What has been done to improve the dx accuracy of stress tests?
use of supplementary radionuclide and ECHO/Doppler imaging during test.
what is the most widely applied radionuclide for myocardial perfusion imaging?
thallium.
its related to regional blood flow and myocardial viability.
reversible defects on thallium scans generally reflect ischemic myocardium, whereas non-reversible defects often indicate scarring from previous MI.
Which exercise tests have the highest sensistivity and the highest specificity. Order them in best to worse
sensitivity:
SPECT> exercise ECHO> exercise EKG
specificity
exercise ECHO > exercise EKG > SPECT
ECHO/doppler studies or gated-blood pool scanning using radioisotopes as contrast agents can be done during exercise and compared with resting studies. What would you see if myocardial ischemia is detected?
- decrease in LV EF during exercise
2. development of regional wall motion abnormalities not present at rest.
Define the PET test
very accurate test for identifing how much the heart has been damaged by infarction and how much is still viable.
- tracer is injected then detection then radiactive decay is measured by use of a scanner./
- high resolution and detaiol.
- limited ability and $$
Define how a CAT scan is used for cardiac diagnosis
rapid CT systems low for less blurry images then regular Ct scans of the heart. 64 slices per second. This results in two important cardiac testing modalities- the Coronary calcium scan and the CT angiogram
When is an ultrafast CT scanner, also known as EBCT used?
they take xray images so quiclkly they can freeze the motion of the heart and snap pics between beats with no blurriness.
pics in a 1/10 of a secon.
EBCT - can detect very early signs of atherosclerosis by detecting flkes of Ca in coronary arteries- which are though to be associated with plaque.
How is a CT angiogram used in the study of CAD
rapid sequence imaging which reveals coronary artery anatomy non-invasively.
- can detect small non-obstructive atherosclerotic plaque as well as flow-limiting larger stenotic coronary lesions.
- dense Ca particles in aterial walls reduce image quality and there is high radiation exposure
