Transcript EKG2: dDiagnosis of Cardiac Rhythms

DIAGNOSIS OF
CARDIAC
RHYTHMS
Lecture #2
I. Common Terminology
Supraventricular vs. Ventricular Rhythms
• The differential is made on the basis of QRS duration
• If the QRS complex is narrow (< 0.12 sec):
– The ventricular myocardium is depolarized rapidly
– The rhythm is supraventricular in origin
• If the QRS complex is wide (> 0.12 sec):
– There is a delay in the spread of the electrical
activation throughout the ventricles
– The origin of the rhythm may be in the ventricle
itself
Premature Atrial Contraction (PAC)
• P-waves differ from normal
• P-waves appear early
• P-waves are followed by a normalappearing QRS complex
MECHANISM
PVC
PAC
Premature Ventricular Contraction (PVC)
• NO P-waves present
• QRS complex is wide
• Ventricular Tachycardia (VT)
 3 consecutive PVC’s, at a rate  100 bpm
(Non-sustained VT - <30 sec)
I. Common Terminology (cont’d)
Arrhythmia
• Generally referred to as any rhythm other than normal
sinus rhythm
3 general mechanisms that can cause arrhythmias:
Disorders of impulse formation:
1.
Altered Automaticity
2.
Triggered activity
Disorders of impulse conduction:
3.
Re-entry
Mechanism of Arrhythmias:
Re-entrant Tachycardia
• Rhythm is secondary to a “loop” in the electrical
circuitry (the re-entry pathway) resulting in
tachycardia
• Requires:
1. Unidirectional block (with recovery)
2. Slowed conduction through loop
• It may occur within the SA node, the AV node, or
actually any ectopic foci in the atria or ventricles
MECHANISM:
Re-entry
Tachycardia
II. Diagnosing Cardiac Rhythms
A. Regular Supraventricular
Rhythms
1. Sinus Rhythm
A.
Normal Sinus Rhythm
• Rate = 60 – 99 bpm
B.
Sinus Bradycardia
• Rate  59 bpm
C.
Sinus Tachycardia
• Rate  100 bpm
Sinus Rhythm Criteria:
1. Every QRS complex is preceded by a P-wave
2. P-waves appear normal, that is they are of sinus
node origin:
A. Normal Morphology:
1. P-wave duration < 0.12 sec (< 3 boxes)
2. P-wave height < 2.5 mm (< 2.5 boxes)
B. Normal Axis:
1. P-waves is upright in leads II, III & aVF
2. P-waves is negative in lead aVR
2. Paroxysmal Atrial Tachycardia (PAT)
A.
Re-entrant tachycardia of supraventricular origin,
with a rate of 120 – 180 bpm (narrow complex)
B.
P-waves may or may not be visible, depending on
the rate
C.
If present, P-waves are usually regular and
inverted in lead II (they may be seen before,
during, or after the QRS complexes)
D.
Usually idiopathic, but can also be seen in RHD,
COPD, MVP & digitalis toxicity
Paroxysmal Atrial Tachycardia
Paroxysmal Atrial Tachycardia
3. Atrial Flutter
A. Atrial rate ~ 250 – 350 bpm
B. Characterized by rapid, undulating“flutter-waves”:
1. Are best seen in leads aVF & V1
2. Have a longer duration & a greater amplitude
than a normal P-wave
3. Have a saw-toothed appearance
C. There is always some degree of AV-block present
(2:1, 3:1 or variable), which is why the atrial rate is
always much greater than the ventricular rate
Atrial Flutter
Atrial Flutter (cont’d)
D. Carotid sinus massage – may exaggerate the
degree of AV-block & consequently slow down the
QRS rate, to assist with the diagnosis
– This makes the flutter-waves more obvious!
4. Junctional Rhythm
A. Impulses originate in the AV node with retrograde &
antegrade conduction
B. QRS complexes are narrow & regular (this is still
considered supraventricular!)
C. P-waves may be inverted in leads II, III & aVF &
may occur before, during or after the QRS complexes
D. Junctional Rate = 40 – 55 bpm
E. This is usually an escape rhythm due to SA node
dysfunction or digitalis toxicity!
Junctional Rhythm
Junctional Rhythm
5. AV-Nodal Re-entrant
Tachycardia (AVNRT)
A.
One of the most common causes of PSVT
B.
P-waves may not be visible or may occur before,
during or after the QRS complexes
C.
Two pathways usually exist: slow (anterograde
conduction) & fast (retrograde conduction)
D.
More common in younger patients
E.
Abrupt onset & offset
6. AV Re-entrant Tachycardia
(AVRT)
A.
Another common cause of PSVT
A.
Involves an “accessory pathway” (1:1500)
C.
D.
Usually utilizes the AV node as the anterograde &
the accessory pathway as the retrograde limbs
(Orthodromic AVRT) – accessory pathway may be
“concealed”
In 10%, impulse travels retrograde across AVN,
and anterograde over accessory pathway
(Antidromic AVRT) – “pre-excitation” present
Pre-excitation
Pre-excitation: Impulse travels anterogradely th’
AV node + accessory pathway to ventricles
Examples include pre-excitation syndromes:
– Wolff–Parkinson–White syndrome
(pre-excitation + tacchycardia)
– Lown-Ganong-Levine (LGL) syndrome
– “Mahaim fiber tachycardias”
Wolff–Parkinson–White (WPW)
A. A supraventricular rhythm originating in the SA
node with normal & regular P-waves
B. PR interval is abnormally short (< 0.12 sec)
C. QRS is wide with a “slurred upstroke” (AKA the
delta-wave)
D.
E.
Delta-waves are due to the accessory conduction
pathway (bundle of Kent) from the atria to the
ventricles, that bypasses the AV node
Must manifest a tacchycardia at some point in time
E. Rx: Procainamide
Wolff–Parkinson–White
B. Irregular Supraventricular
Rhythms
1. Sinus Arrhythmia
2. Wandering Atrial Pacemaker
(WAP)
A. Pacing is from various foci within the atria
B. Heart rate <100 bpm
C. Contour or shape of P-waves vary from beat to
beat, in a single lead (always try to look at lead II!)
D.
Associated with variations of P-R & P-P intervals,
resulting in an irregularly irregular rhythm
E. A common cause is rheumatic heart disease
F.
So, Dx Criterion: Three consecutive P-waves with
different morphologies, on a single EKG lead,
with a heart rate <100 bpm
Wandering Atrial Pacemaker
Wandering Atrial Pacemaker
3. Multifocal Atrial Tachycardia
(MAT)
A. Multifocal Atrial Tachycardia (MAT) is similar to
wandering atrial pacemaker, except that the heart
rate 100 bpm
B.
Again, you must have three different consecutive
P-wave morphologies on a given lead (again,
examine lead II!)
C. Irregularly irregular rhythm
D. Usually associated with end-stage COPD
E. Rx: Control the rate & treat the underlying problem
Multifocal Atrial Tachycardia
4. Atrial Fibrillation
A. Random chaotic depolarizations of the atria at rates
> 300 bpm
B. NO effective pumping of the atria takes place
– You loose ~25% of C.O., AKA the “atrial kick”
C. Irregularly irregular rhythm
D.
May occur in any clinical situation which causes
LAE, hyperthyroidism, or also with EtOH use
(“holiday heart”)
E. Rx: Rate control & anti-coagulation
Atrial Fibrillation
Atrial Fibrillation

The ventricular rate can be either rapid or wellcontrolled, depending on the conduction through
the AV node
C. Ventricular Rhythms
…these are generally regular…!
1. Idioventricular Rhythms
A.
Rhythm originates in the ventricles, giving
rise to wide & bizarre QRS complexes
B. The AV node & sometimes the SA node are
not functioning normally!
D. The axis of T-waves is in the opposite
direction of the QRS complexes
E. Rate = 20 – 40 bpm
Idioventricular Rhythms
Idioventricular Rhythm
2. Accelerated Idioventricular
Rhythm (AIVR)
A. Often develops following an acute MI!
B. Occurs in short bursts & lasts < 20 sec
C. Rate = 40 – 120 bpm
Accelerated Idioventricular Rhythm
3. Ventricular Tachycardia (VT)
Once again, you see broad & bizarre QRS
complexes (> 0.12 sec)
B. Often with an abrupt onset
C. Rate  120 – 140 bpm
D. Can be monomorphic or polymorphic (Torsades)
E.
Look for ventricular capture & fusion beats
A.
– Capture beat: a normal atrial beat “breaks through”
BEFORE the ventricular beat has occurred
– Fusion beat: the atrial beat “breaks through” DURING
the ventricular beat
Monomorphic Ventricular Tachycardia
Polymorphic Ventricular Tachycardia
(Torsades de Pointes)
Wide complex tacchycardia: SVT v/s VT
SVT
VT
QRS duration
<0.14
>0.14
s/o AV dissociation (fusion,
capture bts)
absent
may be seen
Response of vagal maneuvers
+
-
Concordance of QRS
complexes in V1-V6
-
+
rare
may be seen
uncommon
Usually present
Axis: extreme axis deviation
h/o CAD
4. Ventricular Fibrillation (VF)
A.
Chaotic depolarization of the ventricles
B.
Loss of organized QRS complexes
C.
Complete loss of the cardiac contractile function
D.
Circulatory arrest comes about within seconds
E.
The most common cause of sudden cardiac
death
Ventricular Fibrillation
Ventricular Fibrillation
General Rule for Arrhythmia Rates
Rhythm
•
•
•
•
•
•
•
•
Rate (bpm)
Normal Sinus Rhythm
60 – 100
Idioventricular “Escape” Rhythm
20 – 40
Junctional “Escape” Rhythm
40 – 60
Accelerated Idioventricular (AIVR) 40 – 120
Sinus Tachycardia (ST)
100 – 150
*SVT & Ventricular Tach. (VT)
150 – 250
Atrial Flutter & Torsades de Pointes 250 – 350
Atrial Fib. & Ventricular Fib.
350 – 450
* Excludes
ST, atrial fibrillation & atrial flutter
D. Arrhythmias: Review!
Regular Narrow-Complex
Tachycardias
1.
Sinus Tachycardia: Normal P-waves, HR usually
<150 bpm
2.
Proxysmal Atrial Tachycardia (PAT): P-waves are
different from sinus (may be inverted) or absent
3.
Atrial Flutter: Large “saw-toothed” flutter-waves,
+/– variable AV-block
4.
AV-Nodal Re-entrant Tachycardia (AVNRT): Most
common form of PSVT, +/– P-waves
5.
AV Re-entrant Tachycardia (AVRT): A common
form of PSVT, +/– P-waves, + accessory pathway
Irregularly Irregular NarrowComplex Tachycardias
1.
Atrial Fibrillation: No recognizable P-waves
2.
Multifocal Atrial Tachycardia (MAT): Three (3)
consecutive P-waves with different morphologies,
usually associated with COPD
3. Any “regular” SVT with variable AV-block:
Examples: PAT or a. flutter with variable AV-block
Approach to EKG Interpretation

ALWAYS, ALWAYS, ALWAYS:
1.
2.
3.
4.
5.
Rate
Rhythm (includes analysis of intervals)
Axis
Hypertrophy
Ischemia, Injury, or Infarct
Atrial (non-sinus) Rhythm
Multifocal Atrial Tachycardia
Atrial Flutter with 2:1 Conduction
Sinus Rhythm with Unifocal PVC’s
Atrial Fibrillation with a
Slow Ventricular Response
Sinus Rhythm with Bigeminal PVC’s
Atrial Fibrillation with RVR
The End
Thank you for your attention!
Questions?