ECG Myocardial infarction

Question 1

what are the two different types of leads and how are they viewing the heart

Answer 1

Limb leads: show the depolarization of the heart in the frontal or coronal plane

Precordial leads: show the depolarization of the heart in the horizontal (axial aka transverse) plane

Question 2

in determining the cardiac axis is determined by looking at what two leads and what is normal and abnormal

Answer 2

leads I and AVF

positive in I and AVF = normal axis

positive in I and negative in AVF = Left axis deviation
-MI, large stomach

negative in I and positive in aVF = right axis deviation
-chronic lung disease

Question 3

Coronary Heart disease history and symptoms

Answer 3

STEMI accounts for 30percent of all MIs

chest discomfort (more severe than angina)

• heavey, crushing pressure
• retrosternam, left, across chest; radiating into neck, jaw, left arm/shoulder
• epigastrium or between shoulder blades

associated Sxs
-nausea, vomiting, diaphoresis, dyspnea

20 percent of acute myocardial infarctions are painless (silent) in diabetics and elederly women

symptoms can be atypical especially in women and diabetics

Question 4

Pathophysiology of Coronary heart disease

Answer 4

Narrowing of coronary arteries secondary to Erosion, fissuring or rupture of plaque; thrombus (platelet, fibrin rich thrombus is generated)

if partial occlusion = unstable angina or NSTEMI

if coronary flow is occluded = STEMI

Most MI caused by athersclerosis and other causes include vasospasms, vascuulitis, dissection, genetics

Question 5

What is the progression of Coronary artery disease

Answer 5

Normal heart

Stable angina: plaque with fibrous cap

Unstable angina: cap ruptures

NSTEMI: blood clot forms blocking artery

STEMI: dead heart tissue at site of blockage

Question 6

what are the zones of infarction

Answer 6

Ischemia: deficient blood supply impaired repolarization
-T wave changes

then

Injury: Deficient blood supply inability to fully polarize
-ST segment shifts

then

Infarction: Dead tissue lacks depolarization
-Q waves

Question 7

during NSTEMI where in the cardiac tissue is the injury happening, and how does it transition to the STEMI

Answer 7

subendocardial injury and myocardial ischemia (no infarction yet)

then

for STEMI the ischemia and injury extend to the epicardial surface, subendocardial muscle dying in area of most severe injury

Question 8

when seeing issues with the T waves, what could it mean

Answer 8

Myocardial Ischemia: inverted T waves, tall peaked T waves, or depressed

Myocardial Injury
-ST elevation

Myocardial infarction: Q waves

Question 9

What are some cardiac biomarkers of Necrosis

Answer 9

Troponin I (cTnI) or T(cTnT)

• thisis 1-4 hours detectable after onset of AMI
• 10 to 24 hours its at its peak
• will persist fr 5-14 days

Renal failure can cause false positive cTnT

other markers:

• Myoglobin
• CK
• CK-MB

Question 10

what are some signs of a NSTEMI

Answer 10

Elevated troponin, CK, and CK/MB but no ST segment elevation

usually a ST depression or T wave inversion but could be anything
-changes usually found in contiguous leads

Question 11

signs of STEMI

Answer 11

ST elevation of 2mm or greater at J point for leads V2-V3 in men or 1.5mm in women

an absence of LVH or 1 mm or greater in 2 or more contiguous chest or limb leads

also can be called a Acute myocardial infarction

Complete interruption of blood flow
-will eventually show leak of troponin and cardiac enzymes

Question 12

Localization of Myocardial infarction/ischemia, Area and leads for artery: Left anterior descending A

Answer 12

LAD or anterior interventricular A

Area: Anterior wall infarction

leads V1-V7

Question 13

Localization of Myocardial infarction/ischemia, Area and leads for artery: Right Coronary Artery

Answer 13

area: Inferior wall infarction (Right Ventricular infarction)
leads: II, III, aVF, V3R - V6R

Question 14

Localization of Myocardial infarction/ischemia, Area and leads for artery: Circumflex artery

Answer 14

area: lateral wall
leads: I, aVL, V5-V6

Question 15

Localization of Myocardial infarction/ischemia, Area and leads for artery: Posterior descending artery

Answer 15

or called posterior interventricular artery

area: Posterior wall infarction
leads: V1-V3

Question 16

what are the leads associated with
Anterior:
Septal:
Inferior:
Lateral:

Answer 16

Anterior V3, V4:
Septal: V1, V2 (also considered anterior)
Inferior: II, III, aVF
Lateral: I, aVL, V5, V6

Question 17

what makes an old MI

Answer 17

no R wave usually

Question 18

how to notice a Posterior MI

Answer 18

most often missed MI since no artery associate with it

in V1 will have a depressed ST also in V2 and V3

if flip ECG will see a firemans hat and notice that it is an elevated ST symbol in lead V1