2. Overview
● SHORT REVIEW OF
CONDUCTION SYSTEM OF
THE HEART
● ECG-INTERPRETATION
● DYSRHYTHMIAS -TYPES AND
INTERPRETATION
3. INTRODUCTION
● The ability to recognize normal and abnormal cardiac
rhythms, called dysrhythmias, is an essential skill for the
nurses.
● Prompt assessment of dysrhythmias and the patient's
response to rhythm is critical.
4. Intrinsic rate of impulse conduction
SA node : 60-100 times /min
AV node : 40-60 times/min
Bundle of His &
Purkinje fibers : 20-40 beats/min
6. ELECTROCARDIOGRAPHIC MONITORING
● An electrocardiogram reflects the electrical activity of
the of cardiac cells and records electrical activity at a
speed of 25mm / Sec.
● The wave forms on the ECG are produced by the movement
of charged ions across the membranes of myocardial cells,
representing depolarization and repolarization.
9. The standard paper speed is 25mm/sec:
● 1 SMALL square (1mm) = 0.04 sec
(40ms)
● 5 SMALL squares (5mm) = 1 LARGE
square = 0.2 sec (200ms)
● 5 LARGE squares = 1 second
10. P - Wave
P Wave Represents Atrial Depolarization
● Normal:
○ Duration: 0.06 to 0.12 s OR 3 small boxes
○ Amplitude: < 2.5mm OR 2.5 small boxes)
11. PR Interval
Measured from beginning of P wave
to beginning of QRS complex
Normal:
● Duration: 0.12- 0.2s OR 3-5 small boxes
● Will shorten during exercise as heart
rate increases
12. PR Segment
The PR segment is the flat, usually
isoelectric segment between the end of
the P wave and the start of the QRS
complex.
13. QRS - Complex
The Q wave is the first negative deflection after
the P wave and the first element in the QRS
complex.
The R wave is the first upward deflection after
the P wave..
The S wave is the first downward deflection of
the QRS complex that occurs after the R wave.
14. QRS - Complex Cntd…
Indicates Ventricular Depolarization
❖ Duration: 0.04- 0.12s OR 1-2.5 small
boxes
❖ Amplitude:
➢ 5 to 30mm height or 0.5 to 2.5 or
3.0mV
15. ST segment:
● Represents: The interval between
ventricular depolarization and
repolarization.
● Normal: Measured from the S wave
of the QRS complex to the beginning
of the T wave.
● Isoelectric line
● 0.12 Sec
16. T - Wave:
● Represents: Time for ventricular repolarization
● Duration: 0.16 Sec
● Amplitude: 3 to 6 mm
17. QT interval
It represents the time taken for
ventricular depolarisation and
repolarisation.
● QT interval is the time from the start of the Q
wave to the end of the T wave.
● Normal
○ Duration: 0.34- 0.44s OR
10-11 small boxes
.
18. J Point
Junction between the
termination of the QRS complex and
the beginning of the ST segment.
● Represents: The initiation of
ventricular repolarization
Q S
P
R
19. RR Interval
In an electrocardiogram, the
interval from the onset of one R wave to
the onset of the next one, one complete
cardiac cycle
● Normal: 0.6-1.2 seconds
.
20. Intervals and Segments
● PR Interval:From the start of
the P wave to the start of the
QRS complex
● PR Segment:From the end of
the P wave to the start of the
QRS complex
● J Point:The junction between
the QRS complex and the ST
segment
● QT Interval:From the start of
the QRS complex to the end of
the T wave
21. Normal values
● Heart rate 60 - 100 bpm
● P wave < 0.12 s OR 3 small boxes
● PR interval 0.12 - 0.20 s
● QRS interval ≤ 0.12 s
● QT interval < half RR interval (males < 0.40 s; females < 0.44 s)
● Q wave < 0.04 s (1 mm) and < 1/3 of R wave amplitude in the
same lead
22. Methods of Heart rate calculation:
1. Triplet HR technique.
2. Large square method
3. Small square method
4. R - R method and
5. 6 second method
23. ● With the Triplets HR technique we obtain a quick 'estimate' of heart rate to get
1.
24. Triplets HR technique Cntd…
The rhythm above is a REGULAR rhythm. With a REGULAR rhythm you can do the T
34. Systemic approach to ECG assessment
1. Determine the rate
2. Determine rhythm ( compare P-P intervals, R-R
intervals)
3. Evaluate P waves
4. Measure the duration of PR interval
5. Evaluate the ventricular rhythm
6. Measure the duration of QRS complex
7. Assess the ST segment
8. Evaluate the T wave
9. Measure the duration of QT interval
10.Look for other abnormality
35. Arrhythmias:
The term "arrhythmia" refers to any change from the
normal sequence of electrical impulses. The electrical
impulses may happen too fast, too slowly, or erratically –
causing the heart to beat irregularly.
- American Heart Association
36. Types of arrhythmias:
In general, heart arrhythmias are grouped by the speed of the
heart rate. For example:
● Tachycardia or tachyarrhythmias: Is a fast heart beat.
The resting heart rate is greater than 100 beats a minute.
● Bradycardia or bradyarrhythmia : Is a slow heartbeat.
The resting heart rate is less than 60 beats a minute.
38. Sinus rhythm:
First always determine whether the rhythm is Sinus rhythm or Non - Sinus rhythm
● Look at P wave
● Every QRS is preceded by a P wave
● P waves appear normal, that is they
are of sinus node origin
Normal morphology:
1. P - wave duration <0.12 Sec (<3boxes)
2. P - Wave height < 2.5 mm
39. Sinus bradycardia:
In sinus bradycardia the conduction pathway is the same as that in sinus rhythm, but SA node fires at a rate less
than 60 beats/minute
41. Sinus tachycardia:
The conduction pathway is the same in sinus tachycardia as that in normal sinus
rhythm. The discharge rate from the sinus node is increased. The sinus rate is
greater than 100 beats/ min
42. Sinus tachycardia:
Rate : 100 or greater. In adults, rates higher
than 160 are rarely
sinus in origin
P wave : Normal
P-R interval : Normal
QRS : Usually narrow
Ratio : 1:1
Rhythm : Regular
43. Premature atrial contraction:
Premature atrial contractions (PACs) are contractions of the atria that are
triggered by the atrial myocardium but have not originated from the sinoatrial
node (SA node). PACs are also commonly referred to as atrial premature
complexes (APCs), premature supraventricular complexes, premature
supraventricular beat, and premature atrial beat.
This phenomenon can be caused by an assortment of medical diseases,
structural abnormalities, pharmaceuticals, and non-regulated compounds.
44. Premature atrial contraction:
Rate : The underlying heart rate may vary
P wave : In order for the premature beat to be called a PAC, it
must have an
upright P wave
P-R Interval : Normal or prolonged
QRS : Usually narrow
Ratio : 1:1
Rhythm : Underlying rhythm is regular except where it is distributed
45. Paroxysmal supraventricular tachycardia (PSVT)
Paroxysmal supraventricular tachycardia (PSVT) is a type of
abnormal heart rhythm, or arrhythmia. It occurs when a short circuit
rhythm develops in the upper chamber of the heart. This results in a
regular but rapid heartbeat that starts and stops abruptly.
PSVT occurs because of a short circuit — an abnormal electrical
pathway made of heart cells — that allows electricity to speed around in a
circle and repeat the signal over and over. As a result, the chambers
46. Paroxysmal supraventricular tachycardia (PSVT)
Rate : 150 to 300, usually ranges from
120-200
P wave : Often hidden
QRS : Usually narrow
Ratio : 1:1 if visible P wave
Rhythm : Regular
47. Atrial flutter
Atrial flutter is a tachydysrhythmia
identified by recurring regular, saw tooth-
shaped flutter waves that originate from a
single ectopic focus in the right atrium.
48. Atrial flutter:
Atrial Rate : Usually ranges from 250 to 350
Ventricular rate : Depends on the impulse conducted through,
approximately 150
P wave : Multiple F waves or flutter waves ( saw
tooth shape)
Ratio : 2:1 or 3:1
Rhythm : Regular, can be irregular
51. Atrial fibrillation:
In atrial fibrillation, electrical signals fire
from multiple locations in the atria
(typically pulmonary veins), causing
them to beat chaotically. Since the
atrioventricular (AV) node doesn't
prevent all of these chaotic signals from
entering the ventricles, the heart beats
faster and irregularly.
52. Atrial fibrillation:
Atrial Rate : 350 to 600 beats/min
Ventricular rate : Rapid ventricular response (RVR): >100,
controlled
ventricular response(<100)
P wave : Non discernable, may be flutter waves
sometimes
QRS : Usually narrow
53. Junctional dysrhythmias:
Junctional rhythm refers to a rhythm originating at the
atrioventricular node, with P waves buried in the QRS
complex, which is traveling towards the base of the heart as
well as to the bundle branches in the ventricular septum. It
results primarily as the SA node has failed or the signals are
been blocked.
56. HEART BLOCK OR AV BLOCK
1. FIRST DEGREE AV BLOCK
2. SECOND DEGREE AV BLOCK
TYPE I ( MOBITZ I OR WENCKEBACH HEART BLOCK)
TYPE II ( MOBITZ II HEART BLOCK)
1. THIRD DEGREE AV BLOCK ( COMPLETE HEART BLOCK)
TYPES:
57. HEART BLOCK OR AV BLOCK
A first - degree atrioventricular node block occurs when
conduction through the AV node is slowed, thereby delaying the time it
takes for the action potential to travel from the sinoatrial node through
the AV node, and to the ventricles.
First degree AV block
59. SECOND DEGREE AV BLOCK
It includes a gradual lengthening of PR interval and absence of QRS
complex. It occurs because of a prolonged AV conduction time until an
atrial impulse is non conducted and a QRS complex is blocked.
TYPE I / Mobitz I / Wenckebach Heart Block
62. SECOND DEGREE AV BLOCK
In Mobitz II heart block a P wave is non conducted without
progressive antecedent PR interval lengthening. It almost occurs when
there is a block in one of the bundle branches.
TYPE II / Mobitz II
68. A premature ventricular contraction is a contraction originating in an ectopic
focus in the ventricles. It is the premature occurence of a QRS complex, which is
wide and distorted in shape compared with a QRS complex initiated from normal
conduction pathway
It can be Unifocal or multifocal:
● PVCs that appear to have the same shape are called unifocal PVCs, that arise from
single ectopic foci
● PVCs that are initiated from different foci appear different in shape from each other
and are called multifocal PVCs
PVC: Premature Ventricular contractions
69. ECG characharacteritics:
● Can occur at any time and with any rate
● Different QRS morphology
● T waves in opposite direction
● Usually followed by a compensatory pause
Types
● When every other beat is a PVC, it is called ventricular
Bigeminy
● When third beat is a PVC, it is called ventricular Trigeminy
● Two consecutive PVCs are called Couplet.
PVC: Premature Ventricular contractions cntd…
75. Ventricular tachycardia:
Ventricular tachycardia is made when a run of three or more PVCs
occur. It occurs when an ectopic foci fire frequently and the ventricles
takes control as the pacemaker.
Types:
Monomorphic VT: Waves that appear same in shape
Polymorphic VT : waves that appear abnormal shapes of varied types.
76. Ventricular tachycardia:
ECG changes:
● Ventricular rate: 150-250 beats/min
● Atria are depolarized by ventricles in retrograde manner
● P wave: no P waves preceding QRS, Av dissociation ( P
waves marching through)
78. Polymorphic VT
Polymorphic VT occurs when the QRS complexes gradually change back and
forth one shape, size, and direction to another over a series of beats
80. Ventricular fibrillations:
● Ventricular fibrillation is a severe derangement of the heart
rhythm characterized on ECG by irregular undulations of
varying shapes and amplitude. This represents the firing of
multiple ectopic foci in the ventricle.
● Mechanically the ventricles are simply quivering and no effect
of contraction, and consequently no CO, occurs.
● Heart rate is not measurable, needs immediate cardiac
resuscitation
81.
82. Asystole
● Represents the total absence of ventricular electrical activity
● Occasionally p waves are seen, no QRS complexes as there is no
depolarization of the ventricles
● Life threatening condition
83.
84. Conclusion:
● Continuous electrocardiographic (ECG) monitoring is one of the
most common technologies used in acute care today. ECG
monitoring guides patient care, particularly for patients with or
at risk for arrhythmias and myocardial ischemia.
● Prompt and right time identification of arrhythmias aids in proper
cardiac resuscitation and life saving.
● Though the presentation consists of basic arrhythmias we strongly
believe that this session would have ignited an interest to look into
the details which might just be a beginning.
Editor's Notes
It consists of large squares and small squares
Each large square incorporates 25 small squares
An electrocardiogram strip consists of horizontal lines representing seconds and vertical lines representing voltage.
Each small square represents 0.04 sec horizontally and 0.1mV vertically, it is of 1mm square
Each large square represents 0.20 Sec and equal to 0.5 mV
Five large squares makes a second
Represents: The propagation of the cardiac action potential from the atria through the AV node into the ventricles.
Represents: The propagation of the cardiac action potential from the atria through the AV node into the ventricles.
Triplets HR technique starting with '0' using a R wave deflection directly on top of a darkline of a large box (plus or minus one small box).
The rhythm below is a REGULAR rhythm. With a REGULAR rhythm you can do the Triplets HR technique starting with '0' using a R wave deflection directly on top of a darkline of a large box (plus or minu one small box). Which of the 14 QRS complexes in the rhythm below could you do a Triplets HR technique?
Recall above that 300 large squares is equal to 1 minute at a paper speed of 25mm/sec
We can thus calculate bpm by dividing 300 by the number of LARGE squares between each R-R interval (space between two consecutive R waves = one beat)
For example, two large squares between each R-R interval implies a rate of 150 bpm, three implies a rate of 100 bpm and so forth:
Large square method: Divide 300 by the number of large squares between R-R interval. Useful for regular rhythms
Useful as quick calculation for regular rhythms at regular rate
2) Small square method
Similar to above, except 1500 is divided by the number of SMALL squares between consecutive R waves
For example, 10 small squares between R-R interval implies a rate of 150 bpm, 15 implies a rate of 100 bpm, and so forth
Small square method: Divide 1500 by number of small squares between R-R interval.
Useful for abnormal rhythms, as likely to provide more accurate rate than large square method
Count total seconds between two R waves. 1 small square is 0.04 sec. Obtain the total no. of small squares and multiply it by 0.04 Sec. and then usee base line 60 and divide 60 with obtained value and there you will get the heart rate of the client
P wave: are they are present before each QRS, is it same, upright or not.
PR interval: The normal PR interval is 0.12 seconds to 0.20 second
T wave:
Are T waves present?
Are T waves smooth and rounded?
Do they have a normal amplitude of 0.5 mV or less?
Is the deflection the same as the preceding QRS?
SA node fires at a rate of more than 100 beats / min. Feature of ECG is Camel hump
These ectopic impulses are not carried down to ventricles. It gets normalized in AV node.
Common causes of PSVT are : Atrioventricular Nodal Re-entrant Tachycardia (AVNRT), Wolff-Parkinson-White Syndrome ( extra electrical pathway), Atrial Tachycardia
Cause of abnormal atrial contraction is from the emergence of ectopic electrical activity within the upper chambers of the heart. atrial flutter is a fast, but is a regular heart rhythm, because the electrical impulses are organized into one large circular pathway. Because the abnormal electrical circuit in atrial flutter is a well defined pathway, the abnormal impulses follow this same path over and over again, at a fast rate of 250-300 times per minute, activating the top chambers of the heart at this rate. Luckily, the gatekeeper action of “the AV Node” which connects the top and bottom chambers, allows only every other electrical impulse to travel to the bottom chambers, or ventricles. This is still quite fast, leading to a ventricular heart rate and pulse of 150 beats per minute.
For every one QRS there are two P waves.
Four p waves exist for one QRS complex
AV node generates the impulse and sends retrograde signals to atria resulting in atrial contraction. Thus no visible P wave is seen.
There are three types of junctional dysarrhythmia: Junctional escape rhythm ( heart rate of 40-60 beats /min), accelerated junctional rhythm ( 60 - 100 beats / min) and junctional tachycardia ( where by AV node fires at a rate of 100-180 beats/min)
Normal PR interval is of 0.12 to 0.20, in first degree AV block the PR interval is of greater than 0.20 Sec. Time taken for signals to pass from SA node to AV node gets delayed but after conduction through AV node it passses normally and normal ventricular contractions are noticed.significant finding in ECG is extended PR interval.
It is a more serious type of heart block as more number of impulses are not conducted from SA node to ventricles. This occurs in ratio of 2:1 or 3:1 and so on. That is two p waves to one QRS.
Atrial rate ranges from 60-100 beats/min
Ventricular depends on the site of block- if it is in the AV node the rate is 40-60, if it is in bundle of his or purkinje fibers rate would be 20-40 beats / min. Atrial and ventricular rhythms are normal, but independent of each other.