Arrhythmias Part 1

Question 1

What is the quick way to estimate HR on an EKG with a regular rhythm?

Answer 1

1. Count the number of large boxes from one QRS to the next.
2. Divide 300 by the number of large boxes.
3. Alternative: Count the number of QRS complexes on the running lead and multiply by 6. (EKGs are 10s)

Alternative is preferred when you have an irregular rhythm.
A telemetry strip is usually 6s only, so you multiply by 10.

Question 2

What is the requirement for a rhythm to be considered “sinus”?

Answer 2

The origin of the P-wave must come from the SA node. (ideally check II and aVR)

Irregular P-wave might suggest a different origin.

Question 3

What is considered a wide QRS?

Answer 3

More than 3 small boxes wide.

QRS tells us if our bundle conduction is normal.

Question 4

What do we look at to determine normal rhythm? (4 Qs)

Answer 4

1. Do we have P-waves?
2. Do we have NORMAL P-waves? (II and aVR)
3. Are our QRS complexes wide or narrow?
4. Does every QRS have a P-wave?

Atrial enlargement does not change origin of the P-wave.

Question 5

What is the maximum HR of the sinus node?

Answer 5

220-age

Also the general calculation for max HR.

Stress test max is 85% of max HR.

Question 6

What might happen to P-waves in very fast tachycardia?

Answer 6

They can be covered by the QRS complexes.

Question 7

What rhythm can be mistaken for AFib commonly? Why does it occur?

Answer 7

Sinus arrhythmia, due to breathing changing our rhythm.

HR increases when breathing.

Inspiration causes increases in intrathoracic pressure, which decreases venous return and preload.
You can ask a patient to hold their breath.

Question 8

What is a junctional rhythm?

Answer 8

The P-wave is either inverted, retrograde, or within the QRS complex.

Junctional rhythm usually means AV node origin.

No P-wave may also suggest junctional rhythm.

Question 9

What exactly is occurring in the inversion or retrograde of a p-wave?

Answer 9

The AV node is depolarizing back to the SA node.

Question 10

What defines a PAC?

Answer 10

• Early contraction of the atria.
• Generally appear as different P-waves than the regular ones.
• Often will interrupt the current rhythm.

Question 11

How do you tell a premature junctional contraction (PJC) vs a PAC?

Answer 11

• PJCs typically present as inverted or retrograde P-waves. They also tend to lack P-R segments, since they are originating within the junction itself.
• PACs typically present as an additional P-wave (non-sinus) and have a QRS following them.

In real life, a person will describe both as a skipped heartbeat.

Question 12

How do you name the rate of a junctional rhythm?

Answer 12

• 40-60 = junctional
• 60-100 = accelerated junctional rhythm
• 100+ = junctional tachycardia

Question 13

What is a high vs a low junctional rhythm?

Answer 13

• High junctional rhythm = P-wave prior to QRS.
• Low junctional rhythm = P-wave after the QRS.

You will not see a P-R segment!!! That is the key feature.