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 .