ECG

Question 1

What direction should aVR always be in a normal EKG?

Answer 1

Downgoing

Question 2

What are 2 ways to determine the rate from an EKG?

Answer 2

1. Count the # of QRS complexes in the rhythm strip. Multiply by 6.
2. Count the number of “big boxes” in an R-R interval. Divide 300 by this number.

Question 3

How do you determine if the rhythm of an ECG is normal?

Answer 3

QU: there should be a p-wave before every QRS complex and a QRS complex after every p-wave

Question 4

How do you document abnormal rhythms? (3)

Answer 4

Sinus arrythmia

Atrial Fib

Ventricular Fib / tachycardia

Question 5

With regards to the QRS comples:

• What does a negative deflection on an EKG mean?
• What does a positive deflection mean on an EKG?
• What does both a positive and negative deflection of QRS mean?

Answer 5

• The electrical current is moving away from the lead
• The electrical current is moving toward the lead
• The electrical current is moving exactly perpindicular to the lead

Question 6

In general, if the QRS complex is positive in both lead 1 and aVF, then the EKG is […]

Answer 6

Normal

Question 7

If you can find the isoelectric lead, what does this tell you about the electrical axis of the heart?

Answer 7

It must be perpindicular to this lead

Question 8

Answer 8

Question 9

Answer 9

Question 11

What is a normal PR interval?

Answer 11

120ms - 200ms

Question 12

What is a normal QRS interval?

Answer 12

60ms - 100ms

Question 13

What is a normal QT interval?

Answer 13

Roughly less than half the RR interval

< 440ms

Question 14

What is a prolonged QT interval associated with?

Answer 14

Sudden cardiac death

Question 15

• Lead 1, aVL and V5 detect electrical activity from the […] part of the heart that is supplied by the […] artery
• Leads 2, 3 and aVF detect electrical activity from the […] part of the heart that is supplied by the […] artery
• Leads V1 and V2 detect electrical activity from the […] part of the heart that is supplied by the […] artery

Answer 15

Question 16

If a person had an MI on the lateral part of their heart that resulted in ischemia and decreased blood supply to the circumflex artery, how would you detect this on their EKG?

Answer 16

Severe, acute ischemia makes the resting membrane potential less negative, thus making the membrane easier to depoarlize. It also shortens the duration of the action potential, and changes the shape of the plateau of the action potential in the ischemic area. These changes create a voltage gradient between normal and ischemic zones, leading to current flow between these regions during both systolic and diastolic portions of the cardiac cycle. These electrophysiologic fluxes, referred to as “currents of injury,” are represented on the surface electrocardiogram (EKG) by deviations of the ST segment from the isoelectric (TP) baseline. The polarity and magnitude of these changes depend upon the location and the severity of the ischemic insult.