EKG EXAM II

Question 1

P wave

degrees of vector
duration
amplitude

Discuss atrial enlargement (what leads to look for)
Dx criteria

Answer 1

0 to 70 degrees
0.12 seconds duration
Not exceed 2.5mm (0.25mV)

Use leads II (parallel to P wave; largest amplitude) and V1 (perpendicular to P wave; biphasic). Use biphasic or isoelectic line to determine exact P wave degree.

P waves: P wave mean electrical axis may move toward or be more than +90 degrees (P pulmonale). In P mitrale axis deviation is not appreciated because the left atrium is normally electrically dominant.

Right atrial enlargement (1)- with an amplitude exceeding 0.25mV in at least on of the inferior leads II, III, and aVF

Left atrial enlargement (2)- 1. Terminal left atrial portion should drop more than 0.1 mV below the isoelectric line in Lead V1. 2. Terminal portion of the P wave should be at least 0.04 second in duration.

Question 2

Essential for Dx of Right ventricular hypertrophy on EKG.

Observations in other leads.

Answer 2

Essential: The QRS complex in lead I is negative.

Lead V I, the R wave is larger than the S wave
Lead V 6, the S wave is larger than the R wave.

Left axis deviation of QRS complex greater than +100 degrees which puts the normal QRS complex up to -30 degrees.

Question 3

Observation for Left ventricular hypertrophy on EKG

4 criteria for precordial leads ( the more positive criteria the increased likelihood the pt. has left ventricular hypertrophy)

NOTE: Sensitivity of EKG criteria for LVH is low ~50%, but the specificity is high ~90%.

Answer 3

Sometimes left axis deviation beyond -15 degrees.

In general the R wave amplitude will increase with leads overlying the left ventricle and the S wave amplitude will increase will leads overlying the right ventricle.

Precordial leads are more useful when Dx left ventricular hypertrophy.

1.* R wave amplitude in lead V5 or V6 plus the S wave amplitude in lead VI or V2 exceeds 35 mm.

2. R wave amplitude in lead V5 exceeds 26 mm
3. R wave amplitude in lead V6 exceeds 20 mm
4. R wave amplitude in lead V6 exceeds the R wave amplitude in lead V5.
   * has the best predictive value.

Note: These criteria are of little value to individuals younger than 35 yo because of a relatively thin chest (will have increased voltage).

Question 4

Observation for Left ventricular hypertrophy on EKG

4 criteria for limb leads

Criterion of combined limb/precordial limb leads

NOTE: Sensitivity of EKG criteria for LVH is low ~50%, but the specificity is high ~90%.

Answer 4

1. • R wave amplitude in lead aVL exceeds 1 1 mm
2. R wave amplitude in lead I exceeds 13 mm
3. R wave amplitude in lead aVF exceeds 20 mm
4. R wave amplitude in lead I plus the S wave amplitude in lead III exceeds 25 mm
   * most specific, but not very sensitive
5. R wave amplitude in aVL plus the S wave amplitude in V3 exceeds 20 in women and 28 in men.

Question 5

Secondary repolarization abnormalities of ventricular hypertrophy.

2 criteria

What leads will show these criteria more?

Answer 5

Can occur secondary to LVH and may herald the ONSET of ventricular dilatation. Reason is UNK.

1. Downsloping ST segment depression
2. T-wave inversion (i.e., the T wave changes its axis so that it is no longer closely aligned with the QRS axis)

Right ventricular repolarization abnormalities –> V 1 and V 2

Left ventricular repolarization abnormalities –> leads 1, aVL, V5, and V6

Question 6

Determine QRS mean electrical axis and T wave

Answer 6

Use leads I and aVF. Then use a biphasic QRS to determine the exact degree.

T wave is +/- 50-60 degrees from QRS.