Ch 12 - ECG Vector Analysis

Question 1

Mean electrical axis shifts to the left

Answer 1

1. At the end of deep expiration
2. When a person lies down (abdominal contents pressu upward agains the diaphragm
3. Obese people (diaphragms press upward)

Question 2

Mean electrical axis shifts to the right

Answer 2

1. At the end of deep inspiration
2. When a person stands up
3. Tall, Lanky people whose hearts hang downward

Question 3

Electrical axis shift due to hypertrophy

Answer 3

1. Greater quantity of muscle on hypertrophied side
2. More time is required for the depolarization wave to travel through the hypertrophied ventricle

Question 4

Right ventricle hypertrophy

Answer 4

1. Congenital pulmonary valve stenosis
2. Tetralogy of Fallot
3. Interventricular septal defect

Question 5

Left ventricle hypertrophy

Answer 5

1. Hypertension

Question 6

Left Bundle Branch Block

Answer 6

• Left axis deviation of about -50 degrees
• Prolonged QRS complex

Question 7

Right Bundle Branch Block

Answer 7

• Right axis deviation occurs to +105 degrees
• Prolonged QRS complex

Question 8

Increased ECG Voltage

Answer 8

• The sum of the voltages of all the QRS complexes of the three standard leads is greater than 4 mV
• Increased muscle mass of heart
• Hypertrophy
  
  • Hypertension
  • Valve stenosis

Question 9

Decreased ECG Voltage

Answer 9

1. Series of old myocardial infarctions with diminished muscle mass
2. Fluid in the pericardium
3. Pleural effusion
4. Pulmonary emphysema

Question 10

Prolonged QRS Complex

Answer 10

1. Hypertrophy
2. Purkinje system blocks
3. QRS complex > 0.09 sec.

Question 11

ECG Current of Injury

Answer 11

• Mechanical trauma
• Infectious processes
• Ischemia of local areas by coronary occlusions

Question 12

Acute Anterior Wall Infarction

Answer 12

• Strong negative injury potential during the T-P interval
• Negative Lead I
• Positive Lead III
• Thrombosis of Anterior descending branch of the left coronary artery

Question 13

Posterior Wall Infarction

Answer 13

• Negative in leads II and III
• Typically the apex of heart

Question 14

T wave inversion

Answer 14

• Shortened period of depolarization
• Mild ischemia
  
  • ​possible with mild exertion
• Digitalis (drug)