Basic ECG

Question 1

What is the conducting pathway of the heart?

Answer 1

1. SA node
2. Anterior, posterior, and middle fascicles
3. AVN
4. Bundle of His
5. Right bundle branch (RBB) and left bundle branch (LBB)
6. Purkinje fibers

Question 2

What are the 3 types of cardiac cells?

Answer 2

1. Pacemaker Cells
   ‒Determine the heart rate and initiate heart beats
2. Electrical Conducting Cells
   ‒Deliver the impulse to the myocardial cells
3. Myocardial Cells
   ‒Contract and pump blood out of the heart

Question 3

What are the two types of pacemaker cells?

Answer 3

1. SA node (SAN)
   - This is the primary pacemaker of the heart (is responsible for setting the heart rate)
   - The SA node rate is 60-100 beats per minute (bpm)
2. AV node (AVN)
   - The AV node becomes the pacemaker if for some reason the SA node fails
   - The AV node rate is 40-60bpm

Question 4

If the AV and SA node fail, what sends the impulse to contract?

Answer 4

Myocardial cells transmit current more slowly (less effectively) than electrical conducting cells

Question 5

What is a normal QRS complex?

Answer 5

Question 6

What leads to a wide QRS complex?

Answer 6

When current travels through the muscle, current transmission is a lot slower, and this leads to a “wide” (normal) QRS complex

Question 7

What are leads 1 and 2?

Answer 7

Question 8

What is a 3 lead ECG?

Answer 8

A 3 lead ECG utilizes electrodes on the right arm, left, arm, and left leg

Question 9

Lead 1

Answer 9

Lead I (white to black) detects the electrical difference between the right arm (-) and left arm (+)

Question 10

Lead 2

Answer 10

Lead II (white to red) detects the electrical difference between the right arm (-) and left leg (+)

Question 11

Lead 3

Answer 11

Lead III (black to red) detects the electrical difference between the left arm (-) and left leg (+)

Question 12

5 Lead ECG

Answer 12

Question 13

What does a small and large box indicate on ECG paper?

Answer 13

5 large boxes
‒1 second

300 large boxes
‒1 min

Question 14

What is this patients heart rate?

Answer 14

HR will be 300 divided by the number of large boxes between each beat

So… ~140bpm

Question 15

Label waves, segments, and intervals in a ECG wave

Answer 15

Question 16

What does a p wave represent?

Answer 16

Question 17

What does a QRS complex represent?

Answer 17

Question 18

What can cause a wide QRS complex?

Answer 18

1. The heart muscle gets “irritated” (which can happen with ischemia, pH imbalance, electrolyte abnormalities, caffeine, stress, etc)
   - This can cause “premature ventricular contractions” (PVCs), which are visible on the ECG
2. The electrical conduction system fails, and the ventricles have to take over as the pacemaker of the heart
   - This is known as a “ventricular escape rhythm” on the ECG
3. Current traveling across the myocardium, instead of through the Purkinje system
   - This can happen in Wolf Parkinson White syndrome or in right bundle branch blocks (RBBBs) and left bundle branch blocks (LBBBs)

Question 19

What does a t wave represent?

Answer 19

Question 20

What does a u wave represent?

Answer 20

Question 21

What does a j wave represent?

Answer 21

A “J wave” is a “bump” on the S wave, and is seen in hypothermia

Question 22

What is a normal PR interval?

Answer 22

A normal PR interval is 120-200msec (3-5 small boxes)
‒This tells us that conduction is delayed in the AV node, which allows the atria to finish contracting before the ventricles contract (which allows optimal ventricular filling)

Question 23

What is a premature beat?

Answer 23

A beat that happens before it should

‒Examples include premature atrial contractions (PACs), premature junctional contractions (PJCs), and premature ventricular contractions (PVCs)

Question 24

Escape beats

Answer 24

Heart beat that happens after a long pause

-Ventricular escape and junctional escape beats

Question 25

Factors that can reduce ventricular filling? (3)

Answer 25

1. Heart beat that occurs without an atrial contraction 2. Premature heart beats 3. Rapid heart beats

Question 26

Treatment for sinus tachycardia

Answer 26

1. Give fluids if caused by hypovolemia 2. Deepen the anesthetic 3. Consider a B-blocker if not other options

Question 27

Ectopy

Answer 27

Any heart beat that originates outside the SA node 1. AV node 2. Atrial myocardium 3. Ventricular myocardium

Question 28

Premature Atrial Contraction (PAC)

Answer 28

How often are they happening? 1. Upright p wave 2. Normal/narrow QRS complex

Question 29

Atrial flutter

Answer 29

1. Saw tooth pattern of 250-350 p waves/min 2. More P waves than QRS complexes

Question 30

Atrial fibrillation

Answer 30

1. No p waves 2. Irregularly irregular rhythm Atria are just chaotically quivering with up to 500 atrial impulses/min - Risk of blood clotting - Cardiac output can decrease by 25-30% causing hypotension

Question 31

Premature junctional contraction (PJC)

Answer 31

Premature beat 1. Missing or inverted p wave 2. Normal QRS complex Level of concern is how often it is happening

Question 32

Junctional rhythm

Answer 32

Beat or rhythm is originating in the AV node 1. Inverted or absent p wave 2. Normal QRS complex Normal = 40-60bpm Accelerated = 60-100bpm Junctional tachycardia = \>100bpm

Question 33

Junctional escape beat

Answer 33

Escape beat with junctional properties 1. Inverted or absent p wave 2. Normal/narrow QRS complex

Question 34

Premature ventricular contractions (PVCs)

Answer 34

1. No p wave 2. Wide, "bizarre" or "different" QRS complex Concerned with frequency, can develop into V-tach _Treatment_: 1. Antiarrhythmics (lidocaine or amiodarone) 2. Sometimes they go away by speeding up the heart with robinul

Question 35

Ventricular Escape Beats

Answer 35

1. Long pause followed by a ventricular beat (wide QRS complex) 2. No P wave 3. Similar to junctional escape beat (no P wave), but the QRS complex is wide

Question 36

Venticular tachycardia

Answer 36

1. No P waves 2. Wide complex QRS 3. Heart rate \>100bpm _Treatment_: 1. Antiarrhythmics (amiodarone, lidocaine) 2. Electrical cardioversion

Question 37

Summary of premature beats

Answer 37

Question 38

Ventricular fibrillation

Answer 38

The ventricles aren’t contracting, but are rather “quivering” at a very rapid rate, which means: 1. The heart is consuming a lot of oxygen 2. There is no pulse or cardiac output _Treatment_: 1. Defibrillation 2. CPR until a perfusing rhythm returns

Question 39

1st degree AV block

Answer 39

Long PR interval (\>200msec, or 1 large box) Period. End of story.

Question 40

2nd degree AV block

Answer 40

“Dropped” QRS complexes ‒Sometimes two in a row can be dropped There are _2 types of 2nd degree heart block_: 1. Mobitz Type I (Wenckebach) 2. Mobitz Type II

Question 41

Type I 2nd Degree AV Block (Wenkebach)

Answer 41

1. Dropped QRS complexes 2. Increasingly longer PR intervals before the QRS is dropped

Question 42

Type II 2nd Degree AV Block

Answer 42

1. Dropped QRS complexes 2. Constant (unchanging) PR interval before the QRS complex is dropped

Question 43

3rd degree AV block

Answer 43

Here, there are P waves and QRS complexes, but they are not associated with one another(this is referred to as “atrioventricular dissociation”) ‒It has been described as an ECG with “wandering” P waves The ventricular rate is usually slow (≈30-40bpm) **Complete heart block**

Answer 44

1. ST segment changes 2. Abnormal T waves 3. Abnormal Q waves