Cardiology Flashcards
What are the 2 branches of the left coronary artery?
- Anterior Descending Coronary Artery
- Left Circumflex Coronary Artery
What is the branch of the right coronary artery?
-Posterior Descending Coronary Artery
What does the Anterior Descending Coronary Artery supply?
-Anterior septum and left ventricle
What does the Left Circumflex Artery supply?
-Anterior and lateral aspects of the left ventricle
What does the posterior descending coronary artery supply
-Right ventricle and posterior part of left ventricle
This is tissue death with necrosis of the myocardium
Myocardial infarction
Characteristics of a STEMI
- Transmural
- Q wave
- All layers of tissue die
- BAD
Describe non-STEMI
- Non Q wave
- Subendocardial
- Only the inner most layer dies
- Not as extensive necrosis
The EKG changes after an infarct (like a tattoo)
STEMI
The full thickness of the heart is affected in….
STEMI
This layer is the furthest from the coronaries
Subendocardium
If you have a Non-STEMI, what does the EKG look like?
-You cannot tell if the patient ever had a MI
Describe the use of a EKG
- Quick
- All electrical activity of 12 different leads
What happens to the Q wave after a STEMI
-You get a significant drop in Q wave
If a person is currently having a STEMI, what changes on the EKG?
ST elevation (goes away after the STEMI is done)
What changes to the EKG does ischemia cause?
- ST depression
- T wave inversion
This is a very small protein that enters the blood very quickly, and it is also a muscle oxygen binding protein
Myoglobin
Within how many hours is myoglobin detectable?
2-4 hours
When does myoglobin peak?
8-12 hours
When do myoglobin levels return to normal after a MI?
24-30 hours
Describe the sensitivity and specificity of myoglobin
- Very sensitive
- Not specific (because is high during any muscle injury- not specific to myocardial injury)
What is the percentage of patients that have abnormal lab tests when they are initially seen in the ER?
25-40%
T/F- Normal results should be used to decide whether to discharge a patient from the ER?
FALSEEEEEE
This is the major muscle enzyme
Creatinine Kinase
Is CK sensitive or specific?
SENSITIVE- due to a large amplitude of change
Describe CKs large amplitude of change
They can rise 6-12 times normal
What is the sensitivity rate of CK?
98%
Does CK have a high false positive rate?
Yes- because there are many causes of increased CK (any type of muscle injury)
Where is CK found in high concentrations?
Brain and muscle
What are CK levels related to?
- Muscle mass
- Muscle activity
Who has high levels of CK?
- Males
- African Americans
When are CK levels the highest?
- Weight lifting
- Endurance exercise
- Contact sports
Why is it different to create a reference range for CK?
-Wide range of normal CK values (compare the football player to your gramma)
What are the 3 CK isoenzymes?
- MM
- MB
- BB
Where are CK BB enzyme found?
- Brain
- Prostate
- Placenta
- Fetal Tissue
When are levels of CK BB high?
Stroke
Where is CK MM found?
Skeletal muscle
When is CK MM levels high?
- Trauma
- Falls
When are CK MB found?
- Cardiac muscle
- Primarily but not exclusively
- Also associated with skeletal and respiratory muscles
What are CK MB levels in a normal individual?
Less than 1% of normal CK
What are CK MB levels in a patient with an MI?
Greater than 3% of the total CK in 99% of cases
When do CK MB levels begin to rise after an MI
3-6 hours after the onset of a MI
When do levels of CK MB peak after an MI?
12-24 hours after MI
When do levels of CK MB return to normal after an MI?
24-48 hours
Should you do 3 or more sequential samples for tests?
Yes- more frequent sampling is more likely to identify a peak value
When should the first blood work sample be drawn from the patient?
Immediately at presentation
How many hours should the subsequent tests be run apart?
6 hours during the first 24 hours
How is the CK MB index calculated?
CK MB/total CK *100
When is CK MB diagnostic of an MI?
If the CK MB index is greater than 3-4%
When is the diagnosis of an acute MI confirmed? (hours)
Confirmed by 8-12 hrs
Is sampling beyond 24 hours needed?
Not really- except to diagnose early reinfarction
How should CK MB be recorded?
CK MB should be reported in unit as well as a percentage because of injury to both cardiac and skeletal muscle
-CK MB percentage/index may not be elevated
This is the gold standard test for cardiac troponin
Cardiac troponin
Describe cardiac troponin
- Regulatory protein
- Very little floating around at a given time
- Small reference range
- Very sensitive and specific
T/F- Cardiac troponin isoforms are completely specific to the myocardium in adults
Cardiac troponin
How does depolarization spread through the cell?
Through the T tubules
Where is more calcium released from?
Sarcoplasmic reticulum
When calcium rises, it binds to
Troponin C
Once it binds to troponin C, it changes to the
troponin complex
What happens when the tropomyosin is formed?
Causes tropomyosin to be moved out of the way allowing cross binding formation and effective cardiac muscle contraction
How can you study troponin even though it is found in skeletal and cardiac muscle
-They are structurally different and can be measured separately by immunoassay
Why is troponin highly sensitive?
The plasma ratio is much higher than for enzymes or myoglobin
Is cardiac troponin effected by muscle injury?
NOPPPPEEEEEE KIDDDDOOOOO
What is the more important measurement of troponin? (Rate of change or the value)
Rate of change
How many hours after an acute event do cardiac troponin levels rise?
4-6 hours
When does troponin peak?
12 hours
How many days can troponin levels be elevated?
7-10 days
What is 1 pro and 1 con to a long duration of troponin?
- Provides a longer diagnostic window
- Difficult to recognize reinfarction
