Chapter 2 Hypertrophy and enlargement

Question 1

Define hypertrophy?

Answer 1

increase in muscle mass. (could be caused by pressure overload, do to aortic stenosis and systemic hypertension)

Question 2

define enlargement?

Answer 2

Dilation of a chamber so it can hold more blood. (in contrast to hypertrophy? (do to volume overload). This is seen in some valvular diseases.

• aortic insufficiency: left ventricular enlargement
• Mitral insufficiency may result in left atrial enlargement.

Question 3

is the EKG good at distinguishing between hypertrophy and enlargement?

Answer 3

NO

Question 4

what areas of the EKG do we look at to see any atrial of ventricular enlargement?

Answer 4

atrial enlargement = P-wave

Ventricular hypertrophy = QRS

Question 5

what 3 things could happen upon atrial hypertrophies.

Answer 5

1. chambers may take longer to depolarize (longer EKG waves)
2. the chamber can generate more current and thus larger voltage. the wave will then increase in amplitude
3. larger percentage of the total electrical current can move through the expanded chamber (the electrical axis may shift)

Question 6

why can thin people have larger EKG waves?

Answer 6

because of the lower amount of tissue between the leads and the heart.

Question 7

the difference between mean vector and mean electrical axis?

Answer 7

Mean vector: the average vector of all of the instantaneous vectors
Mean electrical axis: the direction of the mean vector.

Question 8

how can you quickly tell if the electrical axis of the heart is normal.

Answer 8

we look at leads I and aVF. If the QRS complex is predominantly positive in leads I and aVF then the QRS axis must be normal.

• In right axis deviation the Lead I will be negative.
• In EXTREME right axis deviation both aVF and lead I will be negative.

Question 9

what is a more precise method of determining the electrical axis of the heart?

Answer 9

find the lead that is bi-phasic and the axis will be perpendicular to it.

Question 10

what is the axis of the P-wave?

Answer 10

0-70 degrees in adults and 0-90 in children.

for the P-wave and T-wave check to see which leads have a flat wave and the axis should be perpendicular to that wave.

Question 11

what are the 3 things that can occur during a hypertrophy of the heart?

Answer 11

1. the wave can increase in duration
2. the wave can increase in amplitude
3. the electrical axis of the wave can deviate from normal.

Question 12

describe the P-wave?

Answer 12

atrial depolarization;

the 1st part is the right side and the second part if left atrial depolarization.

Question 13

what leads do you need to look at to determine atrial hypertrophy?

Answer 13

Leads II and VI.
Lead 2: is useful because it is oriented nearly parallel to the flow of current through the atria.
Lead VI: is useful because it it oriented perpendicular to the atria and biphasic. This lead can be used to differentiate between left or right atria components.

Question 14

Right atrial enlargement appearance on ECG?

Answer 14

1st portion of P-wave increases. The width does not change.
the tallest P-wave may no longer appear in Lead II but in lead aVF or lead III.
- VI experiences an upward deviation during right atrial hypertrophy.

Question 15

Left atrial enlargement appearance on ECG?

Answer 15

2nd portion of the P-wave increases.
Lead VI the left atrial portion of the P-wave is lower then the isoelectric line.
the atrial depolarization duration increases to about 1 block (0.04seconds).
No significant axis deviation is seen since the left atrium is electrically dominant.

Question 16

what is the ECG picture of left atrial enlargement called?

Answer 16

P mitrale since mitral valve disease is a common cause of left atrial enlargement.

Question 17

what to look for in ECG during ventricular hypertrophy?

Answer 17

Since the left ventricle is more electrically dominant, right ventricular hypertrophy shows up better.
In the precordial leads the R-wave increases as leads move closer to the left ventricle, during right sided hypertrophy the opposite may occur.
The R-wave in lead 1 maybe large while small in Lead 5-6.
S-wave in lead V1 is small, whereas the S wave in lead V6 is large.

LEAD V1 = R-wave is large and S-wave is small
LEAD V6 = S-wave is larger than the R-wave.

Question 18

How to diagnose left ventricle hypertrophy?

Answer 18

increased R-wave amplitude in those leads overlying the left ventricle forms the basis for the EKG diagnosis of left ventricular hypertrophy. And increased S-wave amplitude in leads overlying the right ventricle.

Question 19

what is seen in precordial leads during left ventricular hypertrophy?

Answer 19

1. The R-wave amplitude in lead V5 or V6 PLUS the S-wave amplitude in lead V1 or V2 exceeds 35mm.
2. The R-wave amplitude in lead V5 exceeds 26mm
3. The R-wave amplitude in lead v6 exceeds 20mm
   4 The R-wave amplitude in lead V6 exceeds the R-wave amplitude in lead V5.

Question 20

what is seen in the limb leads during left ventricular hypertrophy?

Answer 20

1. The R-wave amplitude in lead aVL exceeds 11mm
2. The R-wave amplitude in lead aVF exceeds 20mm
3. The R-wave amplitude in lead I exceeds 13mm
4. The R-wave amplitude in lead I plus the S-wave amplitude in lead III exceeds 25mm.

Question 21

what is the most accurate criterion for left ventricle hypertrophy?

Answer 21

the R wave amplitude in aVL + S-wave amplitude in V3 exceeds 20 in women or 28 in men.
Any hypertrophy of EITHER ventricle has little change in QRS duration.

Question 22

right ventricular repolarization abnormalities will be seen in leads?

Answer 22

V1 and V2

Question 23

Left ventricular repolarization abnormalities will be seen in leads?

Answer 23

Leads I, aVL, V5 and V6.

Question 24

what are the EKG signs of left ventricular hypertrophy with secondary repolarization abnormalities.

Answer 24

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)