E2: MI And Infarction Flashcards
What are the characteristics of a normal Q wave?
- The first part of the QRS complex and the first negative deflection following the PR segment
- Amplitude is <25% of the R wave and duration is <0.04 seconds
Are normal T waves symmetrical?
No, the upstroke of a normal T wave is less steep than the downstroke
What are the common causes of myocardial ischemia?
Atherosclerosis, vasospasms, thrombosis, embolism, decreased ventricular filling time, decreased filling pressure in coronary arteries
What causes myocardial injury?
Results if ischemia progresses unresolved or untreated. Injury is a greater degree of cell damage than ischemia, but without actual cell death
-ST-T wave changes will be present
What are the characteristic signs of myocardial ischemia?
- Inverted T waves
- Tall and peaked T waves
- Depressed ST segment
What happens in transmural ischemia?
- Ischemia involving the entire myocardial wall
- repolarization reverses direction and becomes endocardium to epicardial, resulting in T wave inversion in leads overlying the ischemic regions
- T waves are symmetric
When do peaked T waves occur?
May be seen in the earl stages of acute MI
When is ST segment depression significant?
If >1mm below baseline measured 0.04 s to the right of the J point in two or more contiguous leads
What is subendocardial ischemia?
Involves the inner layers of the heart, but does not extend through the entire ventricular wall
-Progressive subendocardial ischemia and injury may progress to subendocardial MI, also called Non-Q wave infarction
What can cause flat ST segment depression?
Subendocardial injury or infarction
What does ST segment elevation indicate and when is it significant?
- Indicates myocardial injury and may indicate that infarction is in progress
- Significant is ST segment is >1mm above baseline measured 0.04s to the right of J point in 2 or more contiguous leads
Other than MI, when can ST segment elevation be seen?
-Ventricular hypertrophy
-conduction abnormalities
-pulmonary embolism
-Spontaneous pnuemothorax
-intracranial hemorrhage
-Hyperkalemia
Pericarditis
What EKG finding is characteristic of pericarditis?
Diffuse ST segment elevation, except aVR will have depression
What do pathologic Q waves indicate?
Presence of irreversible myocardial damage or MI
What is the criteria for Q waves to be pathologic?
- > 0.04s duration
- At leas 1/3 the height of the R wave in the same QRS complex
- AND present in 2 or more leads
What does it mean if there is a Q wave infarct?
Transmural infarct and more extensive damage
What does it mean if there is a non-Q wave infarct?
-Subendocardial and less extensive damage
How can you recognize a non-Q wave MI?
- Evolving St segment and T wave changes without Q waves
- Patients with typical chest pain symptoms and elevation of cardiac enzymes
What part of the heart does the RCA perfuse?
The right atrium, right ventricle, and inferior and posterior walls of the LV
What are the two branches off the LCA?
Left anterior descending (LAD) and left circumflex (LCX)
What part of the heart does the LAD perfuse?
Anterior and lateral left ventricle, anterior 2/3 of the ventricular septum, and R and L bundle branches
What part of the heart does the LCX perfuse?
Left atrium, anterolateral, posterolateral, and posterior LV
What will you see on EKG if there is an anterior MI?
-Changes in precordial leads (V1-V4) with reciprocal changes in inferior leads
What are the different types of anterior MI?
Septal (V1-2), anteroseptal (V1-3), and anterolateral (V1 or V2 to V5 or V6)
