Arrhythmic
pathology
The following are some heart arrhythmic diseases, with
their most significant ECG criteria.
The sense of these notes is to be able to identify a disease beyond the clinic, by the
only electrocardiographic signals.
AtrioVentricular
Block (AVB) 1st degree
- PR interval> 0.2 sec.
AtrioVentricular
Block (AVB) 2nd t degree
- PR interval more and more prolonged (2-3 beats)
until the atrial contraction is not' followed by a ventricular one. Then the
cycle begins again. (Mobitz type I, or Luciani / Wenckebach)
P-P = constant.
- As before, but with constant PR interval (Mobitz type II)
AtrioVentricular
Block (AVB) Type 2:1 (2 P: 1 R)
Conduction of every 2. The PR may be normal or
stretched
AtrioVentricular Block (AVB) Advanced Type:
Conduction type 3:1, 4:1. The PR can be normal or
stretched.
AtrioVentricular
Block (AVB) 3d degree (Complete AV block)
- No relationship between the atria and ventricles. No
pulse passes from the atria to the ventricles and we have a ventricular escape
rhythm.
Anterior
fascicular block
(The electrical impulse is transmitted by the left
posterior fascicle whose vector is directed to the left, so we would have a
marked Left Axis Deviation)
- Left axis deviation
- Small Q in I
- Small R in III
- Deep S in V4-5-6
- Normal or slightly prolonged QRS interval.
Atrio - Ventricular Dissociation :
when, in a third degree AVBlock
, the frequency of atrial beats is less than ventricular beats .
Atrial
fibrillation ( 350-650 bpm)
Disorganized and ineffective contractions of the atria
, very high frequency ( 350-600 bpm). Absent P waves and an irregular
ventricular response . Narrow QRS or wide QRS complex due to presence of
RBBB/LBBB , or aberrancy.
Atrial flutter
(fluctuation 250-350 bpm)
The pathway is located in the right atrium.
Parameters for the diagnosis:
• Consistency of the intervals F-F
• Consistency of the morphology of F
Type I atrial flutter (cava-tricuspid isthmus
dependent). It is divided into:
A) Common Atrial Flutter:
the electric impulse “run” counterclockwise
between the atrial septal wall, the isthmus between the inferior vena cava and
the tricuspid and the free wall of the atrium.
F-wave positive in V1
Negative F waves in V6
B) Uncommon
Atrial Flutter: the impulse “run” clockwise.
Negative F waves in V1
Positive F waves in V6
Type II Atrial Flutter:
Type II flutter follows a significantly different
re-entry pathway to type I flutter, and is typically faster, usually 340-440
beats/minute. Left atrial flutter is common after incomplete left atrial
ablation procedures.
Atrial
tachycardia (supraventricular) with aberrant
ventricular conduction (QRS normal or enlarged).
The Premature Atrial Beat (or tachycardia) meets the
ventricle in a almost- refractory period and is
carried out with aberrancy.
This may seem like ventricular tachycardia, but often
we can distinguish the P wave that overlap with the previous T, and then
triggers from the atrial premature beats.
Can present a wide QRS when:
• the patient has a previous AMI or RBBB or LBBB, or
cardiomyopathy
• tachycardia-dependent bundle branch block
• ventricular pre-excitation (WPW)
AtrioVentricular
Nodal Reentrant tachycardia ((AVNRT)).
P is not easily identifiable because the activation of
the atrium corresponds to that of the ventricle. If visible, it is negative in
the inferior leads and positive in aVR and aVL. In V1 may look like a small r
'simulating RBBB.
Bifascicular
block (RBBB + anterior fascicular block)
- RBBB in the precordial leads and anterior fascicular
block in limb leads
Bifascicular
block (RBBB + posterior fascicular block)
- RBBB in the precordial leads and anterior fascicular
block in limb leads
Brugada Syndrome
Signs and Symptoms: syncope and arrests mostly
nocturnal and in conjunction with fever, polymorphic VT that can degenerate
into VF.
RBBB type QRS , ST elevation and T neg. in V1 -V3 .
The syndrome is usually "hidden" on ECG and
it is manifested by the infusion of flecainide * (
2mg/kg in 10 min ) and by moving the V1 and V2 on the 2nd and 3rd intercostal
space .
Therapy: isoprenaline in
acute ( arrhythmic storm ) , quinidine ( 1200-1500 mg / day) , cilostazol .
* Acts on sodium channels in the membrane of the myocytes and prolongs the PR
Electromechanical dissociation (EMD)
When persists electrical activity (of any pacemaker )
of the heart , without resulting in muscle contraction.
Ectopic atrial
Focus (rhythm)
- P pos. in I
- P neg. in II,
III
Escapement
Junctional rhythm
When atrial impulses fail to reach the AV node.
Fusion Beat
When a ventricular stimulus and an atrial meet halfway
(to the AV node) there is a fusion beat that is not tight but not so wide as a
ventricular beat.
Idioventricular
rhythm
It is a ventricular rhythm with an intrinsic frequency
very low (at 20-40 bpm) not compatible with life.
Junctional
rhythm
The atrioventricular junction can generate rhythm and
could be able to become the dominant pacemaker when the SA node is depressed.
His intrinsic frequency is 40-60 bpm. The P waves are typically positive in I
and negative to II and III, and may precede, follow, or be simultaneous to the
QRS. The QRS complexes are normal, while the P-waves may be absent.
[P positive I]
[P negative in II and III]
[P absent]
Junctional
tachycardia
(Supraventricular Tachycardia)
• negative P waves in II, III and aVF
• positive P waves in I or absence of P waves
Lown-Ganonh-Levine Syndrome.
It’s a WPW syndrome without the Delta wave.
Left bundle
branch block (LBBB)
- QRS> = 0.12 sec.
- QRS (QS) negative in V1, V2
- QRS positive, often bifid in V5, V6
- RSR '("M") in I, aVL, V4-6
- Small, normal Q waves are absent in I, aVL, V5, V6
- QRS-T axis angle widened
- ST-segment depression in I, II, aVF, V5, V6.
- SUMMARY = QRS with "W" aspect in V1, 2 and
"M" into V5, 6.
Long QT
syndrome
Long QT interval, T wave alternans
Recurrent episodes of syncope, family history of
sudden death, congenital deafness.
Often causes VT, torsade de pointes.
Depending of the genes responsible, there are three
types of the syndrome:
|
|
Reason
of arrest |
mortality
at 1st event |
|
LQT1 |
physical effort |
<5% |
|
LQT2 |
Emotion |
<5% |
|
LQT3 |
During rest |
20% |
Posterior
fascicular block
The electrical impulse is transmitted from the left
anterior fascicle whose vector is directed toward the right, so we would have a
marked Right Axis Deviation.
- Right axis deviation
- Small r in I (S wave larger than R in I)
- Small q in III
- Normal or slightly prolonged QRS interval.
Premature
Atrial Contraction (PAC)
Are due to ectopic atrial pacemakers that trigger an
impulse before the next normal beat . The premature impulse whose P wave
differs in form from that sinus , can be conducted to the ventricles , if not,
it is PAC blocked. As a rule, the PR interval following the PAC and is normal
or enlarged . The PAC may be a prelude to paroxysms of atrial tachycardia .
Premature
Ventricular Contractions (PVC)
They occur when an electrical impulse is propagated by
a ventricular focus before the next normal beat . At the QRS complex , usually
enlarged and not preceded by a P wave , follow a pause more than usual , called “compensatory” . If they
occur in groups of 2 are called bigemine , 3 triplets
.
Right bundle
branch block (RBBB)
- QRS interval> = 0:12 sec.
- Presence of S wave in I, V6 (often negative but not
always)
- Presence of wave RSR 'in V1, 2,3 ("M"
aspect)
Short QT
syndrome
Palpitations, syncope, sudden death, supraventricular tachyarrhythmias. QT <300 ms
No effective drug therapy to date, useful ICD
(defibrillator).
Sinus arrest
Failure creation of
electrical impulse from the SA node .
- P waves absent.
The PP interval is NOT a multiple of the basic cycle .
Sinus
arrhythmia :
Sinus rhythm in all criteria except for the frequency
ranges, often with the respiratory cycle. RR intervals ( between 2 QRS
complexes ) have continuous variations .
PR interval constant.
Sinoatrial
block
The impulse arises in the SA node but the propagation
is blocked. P absent.
The interval P-P is a multiple of the basic cycle.
Sinus
bradycardia:
Sinus rhythm in all criteria except for the frequency
(<60 bpm).
Sinus
tachycardia
Sinus rhythm in all criteria except for the frequency
between 100-160 bpm.
Supraventricular
tachycardia
That originates above of the ventricles so with a
narrow QRS complex.
Torsade de
pointes
Ventricular tachycardia with alternating cycles of
electrical polarity.
It gives a paradoxical response to various
antiarrhythmic drugs that prolong the QT interval.
The trigger is due to a VEB with a very short coupling
interval, which is superimposed on the T wave of the previous beat (in the
presence of a long QT), phenomenon "R wave on T".
Responds positively to the high frequency PACING, and isoprenaline which shortens the time of ventricular
repolarization.
It often occurs during pronounced bradycardia.
Trifascicular
block.
- AtrioVentricular block 1st degree +
bifascicular block
(Alternatively, the trifascicular block is formed by
the alternation of right bundle branch block and left bundle branch block,
which combines left fascicular anterior block and left fascicular posterior
block).
Ventricular
ectopic beats (VEB)
If the fast rhythm self-terminates within 30 seconds,
it is considered a non-sustained ventricular tachycardia.
If the rhythm lasts more than 30 seconds, it is known
as a sustained ventricular tachycardia (even if it terminates on its own after
30 seconds).
If the VEB originates in the wall of the right ventricle the morphology of the QRS
will look like LBBB, and vice versa. Similarly, if the seat of the VEB is in
the lower part of the ventricle, the axis of the QRS deflects upward ( -90 ° )
.
While if the seat of the VEB is in the upper part of
the ventricle, the axis of the QRS deflects downwards ( 90 ° ) .
After an ectopic beat almost always there is a
compensatory pause ( the next atrial depolarization meets the ventricle is
refractory period ).
Ventricular
fibrillation
Multiple and disorganized contractions of the
ventricles, cardiac arrest => cardiopulmonary resuscitation is needed.
Often occurs in case of "R wave on T".
Ventricular
flutter
Intermediate situation between tachycardia and
ventricular fibrillation. Frequency between 250-350 bpm. immediate CPR and
defibrillation treatment .
Ventricular
tachycardia (VT)
Multiple premature contractions caused by an ectopic
ventricular pacemaker.
• Complex QRS> 140 ms
• Axis deviated on left (> - 30 °) or to the right
(the stimulus travels upward).
• frequency between 140-250 bpm
• Pace almost always regular.
• AV dissociation (atrial rhythm during VT can be
fast, slow, atrial flutter or fibrillation, complete AV block).
• Start and end abrupt. Often triggered by VPB.
Wandering
Pacemaker
Presence of more than one dominant pacemaker. P waves
take on different configurations.
Wolff Parkinson
White ( WPW ) Syndrome
Existence of an abnormal conduction pathway between
the atria and ventricles , called by-pass :
- Short PR interval (<= 0.12 sec . )
- QRS interval > 0.1 sec .
- Presence of delta wave
TYPE A :
The accessory pathway is on the left , so the Delta
wave is directed front / right.
QRS positive in all precordial leads . Absence of S
wave in the precordial leads.
TYPE B:
The accessory pathway is on the right, for which the Delta
wave is directed posteriorly / left.
Negative QRS in V1 , positive in I , aVL , V4 , V5 ,
V6 .
…