cardiac

1. Cardiac
Rhythms/Arrhythmias
(the beginning)

2. Review of Conduction
System

3. Sinoatrial Node
Located in R Atrium
The primary pacemaker
Moderated by vagus nerve
Contains cells which generate regular,
spontaneous action potentials
Principal ions involved are Na+ and K+

4. Intrinsic Rates
Under certain conditions non-pacemaker cells
may become pacemakers
SA node 60-100bpm
AV node 45-50bpm
His Bundle 40-45bpm
Myocardial cells 30-35bpm

5. Step by step electrical activation of
the heart
• First half of P wave when sinus
impulse activates R atrium
• L atrium and AV node have
been activated by the time the P
wave is completed

6. Normal electrical activation of the heart
• During PR segment the His –
Purkinje system is activated
• Activation of the IV septum
from right to left produces a
small q wave
• Steep spike of the QRS
complex reflects activation of
the ventricles – the larger left
ventricle dominates

7. Electrical activation
• The electrical currents
generated during
repolarisation of the
ventricles are reflected
in the ST segment and
the T wave

10. The ECG paper
All paper is standard
Records the current produced by the
electrical activity of the heart with regard to
time and voltage
Time – horizontal axis
Voltage –vertical axis

11. ECG paper
• Small square 0.04sec
• Large square 0.2sec
• 5large squares 1sec
• 300larges squares
= 1min

12. Use a systematic approach
• Calculate both atrial and ventricular rates
• Assess for regularity – atrial and ventricular
• Are atrial and ventricular activity
co-ordinated

13. Rate Calculation
1. Count the number of large squares between two
QRS complexes. Divide 300 by that number
2. Count the number of QRS complexes in six
second strip (30 large squares) and multiply by
10 – good for irregular rhythms
3. Count number of QRS complexes in 10 second
strip and multiply by 6

14. P waves
• Represents atrial depolarization
• Are they present
• Is there a P wave before each QRS complex
• Are they all the same shape – should be smooth
• Usually seen best in lead II - upright
• Normal PR interval (adult) 0.12 - 0.2sec

15. QRS complex
• Represents ventricular depolarization
• Should be regular
• If irregular is there a pattern
• Measure the width
• Normal QRS width <0.12sec

16. T wave
• Represents ventricular repolarisation
• Should be asymmetrical
• Should begin in the same direction as the
QRS complex
• Should be less than 2/3 height of R wave

17. ST segment
• Immediately succeeds
QRS
• Any elevation or
depression is abnormal

19. SINUS RHYTHM: KEY POINTS
• All rhythms that originate in the sinus node will have upright P
waves. This is because the electrical current flows from the
atria toward the ventricles, which is toward positive electrode in
Lead II.
• Rhythms that originate in the sinus node include:
• Normal Sinus Rhythm
• Sinus Bradycardia
• Sinus Tachycardia
• Sinus Arrhythmia

20. 1. SA NODE INDUCED
RHYTHM
• SINUS RHYTHM: 60 - 100 BPM
• SINUS BRADYCARDIA: < 60 BPM (FIT
PEOPLE; POST MI)
• SINUS TACHYCARDIA: 100 - 150 BPM
• INFECTION, EXERCISE, LVF,
HAEMORRHAGE, PAIN, FEAR

21. Rules for NORMAL SINUS RHYTHM
Regularity: The R-R intervals are constant; the rhythm is regular.
Rate: The atrial and ventricular rates are equal; heart rate is between 60
- 100 beats per minute.
P Waves: The P waves are uniform. There is one P wave in front of every
QRS complex.
PRI: The PRI interval measures between .12 and .20 seconds; the PRI
measurement is constant across the strip.
QRS: The QRS complex measures less than .12 seconds.

22. Rules for Sinus Tachycardia
Regularity: The R-R intervals are constant; the rhythm is regular.
Rate: The atrial and ventricular rates are equal; heart rate is greater than
100 beats per minute (usually between 100 and 160 beats per
minute).
P Waves: There is a uniform P wave in front of every QRS complex.
PRI: The PR interval measures between .12 and .20 seconds; the PRI
measurement is constant across the strip.
QRS: The QRS complex measures less than .12 seconds.

23. Rules for Sinus Bradycardia
Regularity: The R-R intervals are constant; the rhythm is regular.
Rate: The atrial and ventricular rates are equal; heart rate is less than 60
beats per minute.
P Waves: There is a uniform P wave in front of every QRS complex.
PRI: The PRI interval measures between .12 and .20 seconds; the PRI
measurement is constant across the strip.
QRS: The QRS complex measures less than .12 seconds.

24. Rules for Sinus Arrhythmia
Regularity: The R-R intervals vary; the rate changes with the patient’s
respirations.
Rate: The atrial and ventricular rates are equal; heart rate is usually in a
normal range (60-100 beats per minute) but can be slower.
P Waves: There is a uniform P wave in front of every QRS complex.
PRI: The PRI interval measures between .12 and .20 seconds; the PRI
measurement is constant across the strip.
QRS: The QRS complex measures less than .12 seconds.

25. Atrial Fibrillation

26. ATRIAL FIBRILLATION
• Ectopic stimuli - 350 - 600 BPM
• Random blocking of impulses by AV
Node
• No P waves (F WAVES: II OR V1)
• Irregular QRS
• Reduced cardiac output, symptoms will
depend on ventricular rate

27. CAUSES
• UNKNOWN
• ELECTROLYTE IMBALANCE
• VALVE DISEASE (MS)
• CARDIOMYOPATHY
• COPD/PE
• THYROTOXICOSIS
• STIMULANTS

28. EFFECTS
• REDUCED CARDIAC OUTPUT – due
to loss of ‘atrial kick’
• REDUCED CORONARY BLOOD
FLOW – if fast rate

29. Rules for Atrial Fibrillation
Regularity: The atrial rhythm is unmeasurable; all atrial activity is chaotic.
The ventricular rhythm is grossly irregular, having no pattern to its
irregularity.
Rate: The atrial rate cannot be measured because it is so chaotic;
research indicates that it exceeds 350 beats per minute. If the
ventricular rate is below 100 beats per minute, the rhythm is said to
be “controlled”; if it is over 100 beats per minute, it is considered to
have a “rapid ventricular response”.
P Waves: In this arrhythmia the atria are not depolarizing in an effective way;
instead they are fibrillating. Thus, no P wave is produced. All
atrial activity is depicted as “fibrillatory” waves, or grossly chaotic
undulations of the baseline.
PRI: Since no P waves are visible, no PRI can me measured..
QRS: The QRS complex measurement should be less than .12 seconds.

30. TREATMENT
• CARDIOVERSION:SYNCHRONISED
DC
• MUST BE ANTI-COAGULATED
• IV OR ORAL DRUGS
• PROBLEMS: RISK OF EMBOLI, LVF,
ANGINA

31. Comparison of Cardiac Output
Sinus Rhythm v Atrial Fibrillation

32. VENTRICULAR
ARRHYTHMIA’S

33. VENTRICULAR
TACHYCARDIA
• ECTOPIC VENTRICULAR RATE OF 100 -
200 BPM
• USUALLY REGULAR
• A-V DISSOCIATION
• WIDE QRS
• CONCORDANT IN CHEST LEADS
• ABNORMAL CARDIAC AXIS
• CAPTURE OR FUSION BEATS MAY BE
SEEN

34. Rules for Ventricular Tyachycardia
Regularity: This rhythm is usually regular, although it can be slightly
irregular.
Rate: Atrial rate cannot be determined. The ventricular rate range is
150-250 beats per minute. If the rate is below 150 beats per
minute, it is considered a slow VT. If the rate exceeds 250
beats per minute, it’s called Ventricular Flutter.
P Waves: Non of the QRS complexes will be preceded by P waves. You
may see disassociated P waves intermittently across the strip.
PRI: Since the rhythm originates in the ventricles, there will be no
PRI.
QRS: The QRS complexes will be wide and bizarre, measuring at
least .12 seconds. It is often difficult to differentiate between
the QRS and the T wave.

35. CAUSES
• MI
• ISCHAEMIC HEART DISEASE
• CARDIOMYOPATHY
• ELECTROLYTE IMBALANCE
• ESCAPE RHYTHM
• DRUG INDUCED

36. TREATMENT
• DEFIBRILLATION IF PULSELESS
• UNDER SEDATION IF SYMPTOMATIC
(SYNCHRONISED SHOCK)
• ANTI-ARRHYTHMIC DRUGS
• CORRECT IMBALANCES AND
STABILISE PATIENT
• TREAT CAUSE

37. VENTRICULAR
FIBRILLATION
• DISORGANISED ELECTRICAL
ACTIVITY IN VENTRICLES
• INCAPABLE OF PUMPING BLOOD
• NO RATE, NO P OR QRS WAVES
• ERRATIC FIBRILLATING WAVY
BASELINE

38. CAUSES
• MI
• MYOCARDIAL ISCHAEMIA
TREATMENT:
• RAPID DEFIBRILLATION
• CPR
• ADRENALINE, AMIODORONE