1. Basic Overview ECG Rhythm Interpretation

2. Objectives
To recognize the normal rhythm of the heart - “Normal Sinus Rhythm.”
To recognize the most common rhythm disturbances.
To identify emergency interventions for life threatening arrhythmias

3. I. Impulse Conduction & the ECG
Sinoatrial node
AV node
Bundle of His
Bundle Branches
Purkinje fibers

4. 1. The “PQRST”- Reminder-the EKG only reflects the heart’s electrical activity-not its contraction
P wave - Atrial depolarization
QRS - Ventricular depolarization
T wave - Ventricular repolarization

5. Atrial depolarization +
2. The PR Interval
Atrial depolarization +
delay in AV junction
(AV node/Bundle of His)
(delay allows time for the atria to contract before the ventricles contract) normal time 0.12 to 0.20 sec.

6. 3. Pacemakers of the Heart
SA Node - Dominant pacemaker with an intrinsic rate of beats/minute.
AV Node - Back-up pacemaker with an intrinsic rate of beats/minute.
Ventricular cells - Back-up pacemaker with an intrinsic rate of beats/minute.

7. 4. The ECG Paper Horizontally Vertically One small box - 0.04 s
One large box s
Vertically
One large box mV

8. 4. The ECG Paper (cont)
3 sec
3 sec
Every 3 seconds (15 large boxes) is marked by a vertical line (hash mark).
This helps when calculating the heart rate.
You need a 6 second strip to calculate heart rate (30 large boxes)

9. 4. The ECG Paper (cont) 3 sec 3 sec
Count the number of P waves in a 6 second strip (30 large boxes) and multiply by 10 to determine atrial rate
(9 x 10 = 90) Atrial rate = 90 beats/min
Count the number of QRS complexes in a 6 second strip (30 large boxes) and multiply by 10 to determine ventricular rate
(9 x 10 =90) Ventricular rate + 90 beats/min

10. Normal Sinus Rhythm (NSR) Normal Rhythm of Heart--etiology
Etiology: the electrical impulse is formed in the SA node and conducted normally.
This is the normal rhythm of the heart; other rhythms that do not conduct via the typical pathway are called arrhythmias.

11. Normal Sinus Rhythm (NSR) Characteristics
Rate – 60 to 100
Regularity – rhythm is regular
P waves – one P wave preceding each QRS
PR interval – normal between 0.12 and 0.20 seconds and constant in length
QRS – all look the same
QRS duration – equal to or less than 0.12 seconds and constant in width
QT interval – equal to or less than 0.44 seconds and constant in length

12. SA Node Problems defined
The SA Node can:
fire too slow 
fire too fast 
Sinus Bradycardia
Sinus Tachycardia

13. A. Sinus Bradycardia Rate less than 60 beats per minute--etiology
Etiology: SA node is depolarizing slower than normal, impulse is conducted normally (i.e. normal PR and QRS interval).
Significance: Lower rate may cause decrease in cardiac output

14. A. Sinus Bradycardia-- Characteristics
Rate: less than 60 beats per minute
Regularity: rhythm is regular
P wave: normal; one precedes each QRS
PR interval: normal between 0.12 and 0.20 seconds
QRS: normal, equal to or less than 0.12 seconds
QT: normal or may be prolonged

15. A. Sinus Bradycardia Signs and Symptoms due to Sinus Bradycardia
May have no symptoms at all
May have signs of decreased cardiac output
- hypotension, cool clammy skin,
- shortness of breath, chest pain or pressure
- light headed, dizziness or blurred vision
- syncope

16. A. Sinus Bradycardia Treatment for Sinus Bradycardia
Treat only if symptomatic
- IV atropine
- IV dopamine
- Transcutaneous pacemaker

17. B. Sinus Tachycardia--etiology Rate greater than 100 beats per minute but less than 150 beats per minute
Etiology: SA node is depolarizing faster than normal, impulse is conducted normally.
Significance: increased workload of the heart
Remember: sinus tachycardia is a response to physical or psychological stress, (hypoxia, pain, hypovolemia).

18. B. Sinus Tachycardia-characteristics Rate greater than 100 beats per minute but less than 150 beats per minute
Rate: 100 beats per minute but less than 150 beats per minute.
Regularity: rhythm is regular
P wave: normal, one precedes each QRS
PR interval: normal between 0.12 and 0.20 seconds
QRS: normal, equal to or less than 0.12 seconds
QT: normal

19. B. Sinus Tachycardia Signs and Symptoms
May have no symptoms at all
May have signs of decreased cardiac output
- hypotension, syncope and blurred vision
- chest pain and/or palpitations
- may report a sense of nervousness or anxiety

20. B. Sinus Tachycardia Treatment
Look for the cause (ie. pain, anxiety, fever, hemorrhage) and treat the cause.
If tachycardia leads to cardiac ischemia treatment may include medications to slow the heart rate
Beta blockers or
Calcium channel blockers

21. III. Atrial Arrhythmias
Atrial tissue
Single or Multiple irritable areas can depolarize and “take over” from the SA node.

22. A. Atrial Fibrillation etiology
Etiology: Atrial impulses are formed in a totally unpredictable fashion-there are no p waves.
Significance:
The atria do not contract in a coordinated way therefore, the cardiac output is decreased.
The atria do not empty fully, so there is a risk of atrial clots
The AV node allows some of the impulses to pass through at variable intervals (so rhythm is irregularly irregular). Rates can get dangerously high

23. A. Atrial Fibrillation characteristics
Rate:
Atrial rate: not measurable exceeds 400 beats per minute.
Ventricular rate: 30 to 220 beats per minute
Regularity: grossly irregular
P waves: absent; erratic baseline
PR interval: not measurable
QRS: normal QT: not measurable

24. A. Atrial Fibrillation Signs and symptoms
Patients with chronic atrial fibrillation may be asymptomatic
New onset atrial fibrillation patients may have symptoms related to decreased cardiac output (loss of atrial contraction and fast ventricular rate)
hypotension, cool clammy skin,
shortness of breath, chest pressure or pain,
dizziness, blurred vision or syncope

25. A. Atrial Fibrillation treatment
If treatment is required:
Beta Blocker, Calcium Channel blockers will decrease rate
IV Amiodarone may decrease rate and convert rhythm (NOT IV bolus!)
Synchronized Cardioversion will convert the rhythm

26. B. Atrial Flutter Deviation from NSR
No P waves. Instead flutter waves (note “sawtooth” pattern) are formed at a rate of per minute
Only some impulses conduct through the AV node
Significance & treatment -as in Atrial Fibrillation

27. Supra Ventricular Tachycardia (SVT) Atrial Tachycardia
Deviation from NSR
Heart rate: speeds up to greater than 150 beats per minute
Rhythm: regular, with normal QRS complexes.
Significance:
Greatly increased myocardial oxygen demand
Could become life threatening

28. C. SVT – Signs and symptoms
Patient may be asymptomatic
May have signs of decreased cardiac output:
Hypotension, cool clammy skin,
shortness of breath, chest pain or pressure,
dizziness, blurred vision or syncope
Review the key characteristics of PSVT.

29. C. SVT Treatment Treatment:
Adenosine followed by Beta Blocker or Calcium Channel Blocker
Synchronized Cardioversion in emergency
Review the key characteristics of PSVT.

30. IV. Ventricular Cell Problems
Ventricular cells can:
fire occasionally from 1 or more irritable area
fire continuously from multiple irritable areas
fire continuously from a single irritable area
Premature Ventricular Contractions (PVCs)
Ventricular Fibrillation
Ventricular Tachycardia
(VT)

31. IV. Ventricular beats When an impulse originates in a ventricle:
conduction through the ventricles will be abnormal
QRS will be wide (greater than 0.12 seconds) and bizarre.
Multi-focal PVCs

32. IV. Ventricular Conduction
Abnormal
Signal moves slowly through the ventricles result is a wide QRS
Normal
Signal moves rapidly through the ventricles

33. A. PVCs--characteristics
Deviation from NSR
Early beats originate in the ventricles resulting in wide (greater than 0.12 sec.) and bizarre QRS complexes.
When there is more than one premature beat, and the beats look alike, they are called “unifocal”.
When there is more than one premature beat, and the beats look different, they are called “multifocal”.

34. A. PVCs etiology
Etiology: Ventricular irritability can be caused by hypoxia, electrolyte imbalances.
Significance: Early beats from the ventricle do not deliver full cardiac output; if untreated may lead to VT/VF.

35. B. Ventricular Tachycardia
Deviation from NSR:
Impulse is originating in the ventricles (no P waves, wide QRS, rate greater than 100).
Significance:
greatly reduced cardiac output--Life threatening arrhythmia!!
Treatment:
IV Lidocaine or IV Amiodarone (NOT IV bolus)

36. C. Ventricular Fibrillation
Etiology: Hundreds of ventricular cells are excitable and depolarizing randomly
Significance: no cardiac output; no pulse
Death producing arrhythmia
Treatment: CODE BLUE
Defibrillation
IV Epinephrine
IV Amiodarone

37. V. Heart Blocks (Bradycardia)
Etiology: weakness, fatigue or damage to the AV node
Significance: Bradycardia may result in decreased cardiac output
Treatment (same as for bradycardia):
IV Atropine
IV Dopamine
Transcutaneous Pacing

38. A. 1st Degree AV Block
Etiology: Prolonged conduction delay in the AV node or Bundle of His.
PR interval: greater than 0.20 seconds and is constant

39. B. 2nd Degree AV Block, Type I
Etiology: Each successive atrial impulse encounters a longer and longer delay in the AV node until one impulse (usually the 3rd or 4th) fails to make it through the AV node.
P waves: More than QRSs
P-R interval: gets progressively longer

40. C. 2nd Degree AV Block, Type II
Etiology: Conduction is all or nothing (no prolongation of PR interval);
typically block occurs in the Bundle of His.
More P waves than QRSs
PR interval does not vary in length

41. D. 3rd Degree AV Block
Etiology: There is complete block of conduction in the AV node; atria and ventricles form impulses independently of each other.
More P: waves than QRSs
QRS to QRS (ventricular rate) is regular
P to P (atrial rate) is regular—faster than ventricular rate

42. 3rd Degree AV Block Characteristics
Rate?
40 bpm
Regularity?
regular
P waves?
no relation to QRS
PR interval?
none
QRS duration?
wide (greater than 0.12 s)

43. Summary Rhythm Rate (beats per minute) Regularity Comments Treatment
Sinus
60-100
Regular
Normal rhythm of heart
None
Sinus Bradycardia
Less than 60
Slow rhythm-can cause symptoms of decreased cardiac output
If symptomatic: atropine 0.5 mg IV push
Sinus Tachycardia
100 – 150
Fast rhythm-caused by fever, pain, dehydration
Treat the cause
Suprventricular Tachycardia (SVT)
Greater than 150
Fast-can cause symptoms of decreased cardiac output
Adenosine, -blockers, Diltiazem (Cardizem), Cardioversion if unstable
Atrial Fibrillation
Irregular
No p-waves, PR not measurable
-blockers, Diltiazem (Cardizem)
Atrial Flutter
Regular or Irregular
No p-waves, flutter waves—sawtooth pattern
Premature Ventricular Contractions
Varies—can be normal
Early beats, wide, bizarre
Amiodarone
Ventricular Tachycardia
Wide, regular, fast; no p-waves
Amiodarone—if pulse
Defibrillation—if pulseless
Ventricular Fibrillation
Rapid,
Chaotic
No pattern; Can lead to death
Defibrillation!

44. Summary—Heart Blocks Name of Block
# p-waves compared to # QRS complexes
PR interval
QRS complexes
Treatment
First degree
# p-waves = # QRS complexes
PR interval longer than 0.20; constant
All present
Atropine, if slow
Second degree type I
More p-waves than QRS complexes
PR interval gets longer and longer
QRS dropped periodically
Second degree type II
PR interval is constant
Transcutaneous pacing
Third degree Complete block
No PR interval; P to P constant
QRS to QRS constant
End of Reading