EKG interpretation

Question 1

Describe placement and polarity of leads I, II, III

Answer 1

All are bipolar: lead is I has the positive electrode at the left arm and the negative electrode at the right arm. Lead II is positive in the left leg and negative in the right arm. Lead III is positive in left leg and negative in left arm.

Question 2

Describe placement of aVr, aVL, and aVF

Answer 2

All are unipolar: aVR is positive in the right arm, aVL is positive in the left arm and aVF is positive in the left leg.

Question 3

Describe placement of the chest leads

Answer 3

Unipolar leads: V1 is positive at right 4th intercostal left sternal border, V2 is + at left 4th intercostal left sternal border, V3 is + at left sternal border btw V2 and V4, V4 is + at 5th intercostal left sternal border, V5 is + at midclavicular line below nipple, V6 is + near axilla

Question 4

What does V1 and V2 monitor? V5 and V6?

Answer 4

V1 and V2 are close to right ventricle and septum, so they measure RV hypertrophy and septal infarcts. V5 and V6 are close to anterolateral portion of left ventricle thus they measure infarcts and hypertrophy of LV

Question 5

Which direction is the QRS axis oriented?

Answer 5

Ventricle is dominant voltage producer because of muscle mass. Depolarization of ventricles goes from right to left, posterior, and downward from right arm towards left leg. Ranges from -30 to +90 degrees

Question 6

Which leads are usually positive and which are usually negative

Answer 6

leads I and II are positive (b/c they are on the left arm and leg where current runs towards). V1 and V2 are mostly negative because predominant forces are away from right ventricle

Question 7

What is left axis deviation?

Answer 7

QRS axis from -30 to -90. Lead II is predominantly negative (abnormal) and lead I is positive

Question 8

What is right axis deviation?

Answer 8

QRS axis from +90 to +180. Lead I is predominantly negative (abnormal) and lead II is positive

Question 9

What is indeterminate axis?

Answer 9

QRS from +180 to -90. Lead I and II are negative

Question 10

Causes of widened QRS complex

Answer 10

Bundle branch block, ectopic ventricular beat b/c conduction is outside of the specialized conduction system so it is slower

Question 11

Right bundle branch block EKG

Answer 11

Late forces to the right ventricle results in a tall late positive deflection (R’) in V1 and V2 (right sided leads) and a negative deflection (a wide S wave) in I and V6 (left sided leads). This extra deflection is due to the right ventricle depolarizing later than the left.

Question 12

Know what Right atrium and left atrium enlargement look like on a EKG

Answer 12

See images

Question 13

Left bundle branch block EKG

Answer 13

QRS is widened and all forces are away from the right sided leads (V1) and towards the left sided leads (V6)

Question 14

How do hemiblocks affect EKG

Answer 14

Partial block in the left bundle (only one fascicle out of 2) Causes axis shifts without widening QRS

Question 15

Left Anterior fascicle hemiblock EKG

Answer 15

left axis deviation- Lead 1 is positive but lead II is negative

Question 16

Left posterior fascicle hemiblock EKG

Answer 16

right axis deviation- lead I is negative and lead II is positive

Question 17

Left ventricular hypertrophy EKG

Answer 17

more muscle= more volts= greater amplitude. Large positive deflection of R waves in V5 and V6. Large negative deflection of S waves in V1. Normal QRS duration though

Question 18

Right ventricular hypertrophy EKG

Answer 18

Large R waves in V1 and V2

Question 19

Generally, how does ischemia affect EKG

Answer 19

Alters ventricular repolarization , affects ST segment and T wave

Question 20

EKG- ischemia due to high oxygen demand in presence of coronary obstruction

Answer 20

depressed ST segment

Question 21

EKG- ischemia due to acute coronary artery obstruction during low oxygen demand

Answer 21

T wave inversion

Question 22

EKG- transmural injury from acute coronary syndrome (MI, etc)

Answer 22

ST elevation

Question 23

EKG- transmural necrosis

Answer 23

sizable Q waves in at least 2 adjacent leads. The leads affected indicate the area of infarction (ie. Anterior leads indicate anterior infarct)

Question 24

List the sequence of EKG events in a transmural acute myocardial infarct

Answer 24

Hyperacute T waves (brief) > inverted T waves (ischemia) > ST elevation (injury) > Q waves (necrosis)

Question 25

Compare EKG of transmural vs subendocardial infarct

Answer 25

Transmural: involves full thickness of ventricular wall, ST elevation with Q waves. Subendocardial: localized to inner layer of left ventricle wall, NO Q waves, ST depression

Question 26

Which leads detect infarcts in: anteroseptal wall, anterior wall, anterolateral wall, inferior wall?

Answer 26

anteroseptal wall: V1-V2. Anterior: V3-V4. Anterolateral: V5-V6. inferior : II, III, aVF

Question 27

EKG- acute pericarditis

Answer 27

Diffuse ST elevations in multiple leads with no localization