17. EKG Evidence of Hypertrophy and Ischemia

Question 1

How is the EKG evidence of hypertrophy and ischemia different than that of arrhythmias?

Answer 1

• Primarily affects voltage (Y axis of EKG) rather than time (X axis)
• Conditions persist for minutes to days and present in each complex unlike the on/off nature of arrhythmias

Question 2

How does hypertrophy affect voltage?

Answer 2

Hypertrophy adds myocardial mass –> more voltage

Question 3

How does death of myocardial tissue affect an EKG?

Answer 3

• Diminish voltage

- Pathological Q waves

Question 4

How does transient ischemia affect an EKG?

Answer 4

Delays & distorts repolarization –> elevates/depresses the ST segment

Question 5

What is the significance of a flipped T wave?

Answer 5

“Soft indication” of ischemia

Question 6

In what order is hypertrophy assessed?

Answer 6

RA –> LA –> RV –> LV

Question 7

What characterizes RA enlargement on an EKG? Cause? What lead?

Answer 7

Extra mass “stacked” around the SA node produces a tall (>2.5 mm), peaked P wave in lead II

Question 8

What characterizes LA enlargement on an EKG? Cause?

Answer 8

• Adds mass far to the left of the SA node, making for a long P wave > 0.12 sec, often w/ a 0.04 sec “notch”
• Commonly results from mitral valve abnormalities

Question 9

What characterizes RV enlargement on an EKG?

Answer 9

• A large upright R waves in lead I
• R wave is greater than S wave in V1
• Peaked, tall P wave in lead II
• “Strain” pattern (inverted T wave, especially in V1 and V2)

Question 10

What are the common causes of RV hypertrophy?

Answer 10

• Increased pulmonary vascular resistance due to emphysema and other chronic pulmonary diseases
• Pulmonary hypertension
• Pulmonic valve disease

Question 11

How is LV hypertrophy assessed on an EKG?

Answer 11

Scott’s Criteria:

• measure the deepest S wave in lead V1 or V2 and add it to the tallest R wave in leads V5 or V6
• a sum > 35 mm suggests LVH

Question 12

Summarize the steps of analyzing an EKG for hypertrophy.

Answer 12

1. Measure the P wave height in lead II: > 2.5 mm is RA hypertrophy
2. Measure P wave duration in lead II: >/= 0.12 sec w/ notch is LA hypertrophy
3. R taller than depth of S wave in lead V1 is RV hypertrophy
4. Measure deepest S wave in V1 or V2 and add this to the tallest R wave in V5 or V6. > 35 mm is LV hypertrophy

Question 13

What does the final diagnoses of chamber hypertrophy require?

Answer 13

Echocardiography

Question 14

What distinguishes athletic LV hypertrophy from pathologic LV hypertrophy?

Answer 14

• Athletic: LV hypertrophy only meets voltage criteria
• Pathologic (due to valve disease, hypertension, cardiomyopathy): often have additional signs like axis deviation, atrial involvement, depolarization abnormalities like “strain” pattern of T wave

Question 15

What are the 3 criteria that are examined in each lead for ischemia? What does each mean?

Answer 15

• Pathologic Q waves > 0.03 sec suggest dead myocardium from an old MI
• ST elevation > 1mm represents acute, transmural ischemia (MI is starting)
• ST depression > 1mm represents sub-endocardial ischemia (reversible by lowering demand on the heart)
• T wave inversions are a “soft” indication of ischemia

Question 16

What are the 2 varieties of ST elevation?

Answer 16

• Early repolarization

- Acute transmural ischemia

Question 17

What characterizes early repolarization on an EKG?

Answer 17

• ST elevation that is seen in young athletes
• Concave upward (nike swoosh)
• Accompanied by other signs of athleticism

Question 18

What characterizes an acute transmural ischemia on an EKG?

Answer 18

ST elevation concave downward suggest an MI is starting

Question 19

In what leads are T waves allowed to be inverted? Why?

Answer 19

aVR, III, V1 b/c these are the only 3 leads whose (+) poles are to the right of the body’s mid-line