Coronary Blood Flow/Ischemic Heart Disease
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Where are the larger epicardial arteries??
they lie on the surface of the heart
such as RCA, circumflex and LAD
Where are the smaller myocardial arteries??
they penetrate the myocardium and are known as a patients collateral circulation
There are no ______ between the larger arteries.
blockage of one vessel does not cause blockage of another major vessel
What percentage of oxygen is pulled from the coronary blood flow to supply oxygen to the heart??
this is why blockage of blood flow to the heart is so profound
When does the most amount of blood flow to the muscle of the heart??
this is why it's most important to control the HR during an MI.
As the HR increases, diastole decreases therefore less blood filling in the heart or less blood flow to the heart muscle. Want to keep the HR <60!
An imbalance between the supply (blood flow) and demand (O2 consumption) can cause _____.
ischemia = angina pectoris
What is stroke volume??
The volume of blood pumped from the heart with each beat
What is afterload??
the impedance against which the heart must work
or what the heart must work against (something that impedes or causes an obstacle to overcome)
What is preload?
the amount of filling of the ventricle at the end of diastole
What is the Frank-Starling relationship??
up to a certain point, the more the ventricle is stretched, the greater the contraction.
If the preload increases what happens to the SV?
the SV will increase
If the afterload increases, how does it affect the SV?
the SV will decrease
What is the major cause of sudden death with Ischemic Heart Disease??
What does ST elevation on an EKG mean about the cardiac muscle??
means that the damage that has occurred goes all the way thru the wall of the heart.. or thru the muscle layer of the heart
What are the two most important risk factors for the development of atherosclerosis??
- other risk factors include:
- high cholesterol
- sedentary lifestyle
- family hx
- Type A personality
REMEMBER: atherosclerosis is a thickening that occurs in the tissue of the lumen not the lumen itself. See page 2 for pics.
What is stable angina?
partial occlusion or chronic narrowing of a segment of coronary artery
normally greater than 70% occluded to cause pain
An extreme imbalance between the supply and demand of blood to the heart causes what 3 things....
- electrical instability
What causes the shortness of breath patients often experience with an MI?
it is actually caused by the sense of chest constriction or the need to take a deep breath rather than deep breathing...
the SOB is not because they can't breath
Describe MI related chest pain characteristics..
- pain typically lasts several minutes
- pain is crescendo/decrescendo in nature
- retrosternal chest pain, discomfort, pressure or heaviness
- radiates to the neck, L shoulder, jaw or arm, back or down both arms
- epigastric discomfort = indigestion
- shortness of breath
What can induce angina??
- physical exertion
- cold weather
- emotional tension
If the pain a patient feels is truly cardiac related chest pain, what relieves it??
What is chronic stable angina??
chest pain or discomfort that does not change in frequency or severity over two months or longer
What is unstable angina??
Angina that occurs even at rest (meaning the heart is not getting enough O2 even while resting). The onset is NEW. Unstable angina will have increasing severity or frequency over time.
The lumen size of the affected vessel will be decreased by 90%
True chest pain does not get worse with movement or deep breaths.
If that is the case.. your pain is probably muscle related.
Sharp pain with deep breathing, coughing or a change in body position is indicative of ??
Why is it so important to obtain an EKG during chest pain?
because an EKG can show you exactly what is happening to the heart in real time
ST segment depression =
inversion of the Twave can also occur with ischemia
If you have ST elevation in all 12 leads..what does this mean??
normally indicative of an inflammatory process
How is a stress test or exercise electrocardiography useful ??
it can be useful in detecting signs of ischemia and establishing relationships to angina
During an exercise electrocardiography, what 2 signs can add diagnostic value to detecting the signs of angina??
new murmur of mitral regurg or decrease in BP during exercise
List some contraindications of exercise testing for angina...
- inability to exercise
- paced rhythms
- L ventricular hypertrophy
- severe aortic stenosis
- severe HTN
- Uncontrolled HF
- Infective endocarditis
- acute myocarditis
What findings during a stress test indicate myocardial ischemia??
1mm of horizontal or down sloping ST segment depression during or within 4 minutes of exercise
ST segment abnormality associated with angina that occurs early in exercise and lasts for several minutes after is indicative of???
Means CAD is highly likely
What does a negative stress test indicate??
It does not necessarily mean that CAD is not present
but does mean that the presence of 3 vessel disease or L main disease is very low
In noninvasive imaging tests (tests performed for patients who can not complete exercise testing), what is used to produce an increased heart rate to create cardiac stress that normal exercise could cause??
atropine, dobutamine, artificial cardiac pacing
can also use adenosine or dipyridamole (coronary vasodilators) to cause stress
Why is nuclear stress test imaging more effective than a standard exercise test??
It is used to assess coronary artery perfusion
can define vascular regions in which stress-induced coronary blood flow is limited and can estimate left ventricular systolic size and function
When is imaging taken in nuclear stress tests??
- 1. immediately after to detect regional ischemia
- 2. 4 hours later to detect reversible ischemia
Which tests provides the best information related to the cause of angina??
What are 3 reasons to perform coronary angiography???
- 1. if a patient continues to have angina despite maximal medical therapy
- 2. for those patients being considered for coronary revascularization
- 3. for definitive diagnosis of coronary disease
What are 3 prognostic determinants of performing a CABG?
- 1. anatomical extent of atherosclerotic disease
- 2. state of L ventricular function
- 3. stability of coronary plaque
What is the most dangerous anatomic lesion??
lesion of the L main coronary artery
____ stenosis of the L main coronary artery is associated with mortality rate of 15%/year
According to Anesthesia Brain,
if you have an Anterior wall MI what leads are affected and which artery is implicated??
According to Anesthesia Brain,if you have an Inferior wall MI what leads are affected and which artery is implicated??
According to Anesthesia Brain,if you have an Lateral wall MI what leads are affected and which artery is implicated??
- Left circumflex artery (LCX)
According to Anesthesia Brain,if you have an Posterior wall MI what leads are affected and which artery is implicated??
Blockage of beta 1 receptors causes what??
- decreases HR and contractility
- decreases O2 demand, decreasing ischemic events during exertion
- increased diastole which increases coronary perfusion
The blocking of Beta 2 receptors causes what??
Avoid BB in what health conditions??
severe bradycardia, SSS, severe reactive airway, atrioventricular heart block, severe uncontrolled CHF
What are two common side effects of BB?
fatigue and insomnia
How are calcium channel blockers used for the treatment of anginal pain?
they decrease the frequency and severity of angina due to coronary spasm although they are not as effective as BB in decreasing the risk of re-infarction
work by decreasing smooth muscle tone, dilating coronary arteries, decreasing contractility and oxygen consumption ultimately decreasing BP
you should not give CCB in patients with what health condition??
What are common side effects of CCB?
hypotension, peripheral edema, h/a
use with caution in patients who are already on BB
How do nitrates improve angina??
- -they decrease the frequency, duration and severity of angina
- -they increase the amount of exercise needed before the onset of ST segment depression
- -they dilate coronary arteries and improve collateral blood flow
- -they decrease PVR, left ventricular after load and myocardial consumption
Nitrates are contraindicated in patients with??
hypertrophic obstructive cardiomyopathy and severe aortic stenosis
they should not be used within 24 hours of patients taking Viagra, Cialis or Levitra
what is the most common side effect of nitrates?
What is important to remember with the development of tolerance with nitrates??
to avoid tolerance--a daily 8-12 hour free interval from nitrate exposure is recommended
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