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Ventricular Extrasystoles

  1. Gastroepato
  2. Cardiology
  3. Ventricular extrasystoles
  4. Arrhythmias 
  5. Atrio-ventricular block (BAV)
  6. ECG
  7. Sick sinus syndrome
  8. Criteria for reading an ecg
  9. T waves of ischemia  

notes by dr Claudio Italiano

We speak about ventricular extrasystoles when a pulse that originates a QRS complex, rather than originating as it should from the sinus node, is generated abnormally in the ventricles, downstream of the bifurcation of the beam of His.

The ECG shows large QRS complexes, not preceded by the P wave, and therefore clearly distinguishable from the sinus ones. Also in this case the retroactivation of the atria may occur or not, ie an impulse, retrograde, can go back towards the atria.

 

Causes of the extasistoli

In general, cardiac ischemia is a cause of extra-systolic disease, or hyperthyroidism can be associated with extrasystoles.

The extrasystoles, however, can be innocent and appear in healthy subjects, at any age including childhood.

They can occur in subjects subjected to stress, in situations of fatigue, physical exertions, sleep deprivation, in smokers, but especially in hypertensive and in color that take coffee. Even gastritis are "irritating spines" for the genesis of extrasystoles.

In some cases they may appear after a large meal, related to distension of the gastric bottom, or related to the presence of a hiatal hernia or in hyperthyroidism. More rarely they can be an expression of a heart disease, an electrolyte disturbance (eg, potassium deficiency).

Effects of the extrasystoles

The subjects in whom this arrhythmia occurs describe such manifestations as "thump to the heart", the sensation of a missed heartbeat, a knot in the throat, palpitation, anxiety. In many cases the extrasystole, especially if isolated, is not subjectively perceived. Sometimes the patient becomes aware of the phenomenon by controlling the pulse or the arterial pressure on his own, but it can happen that the extrasystoles, completely asymptomatic, are occasionally recorded to an electrocardiogram (ECG) performed for other reasons.

If isolated, monomorphic, extrasystoles are found in a patient with a normal cardiovascular objectivity, the extrasystoles have no meaning and the patient does not need further investigation.

 

Diagnosis of extrasystoles

The ECG allows detection of a premature QRS complex.
Based on its characteristics, we can distinguish the origin of the extrasystole, ie from which part of the specific myocardial tissue originated:
a) a premature QRS when it is preceded by a wave P means that this extra-systolic beat originated from the atrium, so it is similar to a normal QRS complex.
b) If it is not preceded by a wave P, the origin of the extrasystole can be determined from the width of the QRS. In fact a QRS complex is narrower, more similar to a normal complex and, therefore, it is atrial; vice versa if it is flared and preceded by an anomalous P wave, then the extrasystole is atrial and may have originated in a branch of His beam.
In particular we will have the following possibilities depending on the origin of the extrasystole:
They originate below the bifurcation of the trunk of the HIS beam: right and left branches of the HIS beam, sub-endocardial tissue of Purkinje, undifferentiated right and left ventricular myocardium.
- They are so characterized:
• QRS complexes always large, higher or equal to 0.12 s
• Total absence of the relationship between the P waves between the P waves and the QRS complexes: the QRS complexes are not regularly preceded by P waves. When the atrial activity is visible, it is completely dissociated from the ventricular activity, so that the interval PR varies constantly from one complex to another without clear periodicity.

Ventricular Extrasystoles (VES)

It is a matter of premature systole, which arise both from the branches of the HIS beam, both from the Purkinje network and from the undifferentiated myocardium.,

They are characterized by:
• They are precocious, ie they fall sooner than expected for the QRS complex
• The complexes have a QRS-like appearance, with a duration equal to 0.12 or more  than 0.12 seconds, with high deflections
• They are followed immediately by a T wave, without an RST segment; the axis of T being opposite to that of QRS
• The P wave is absent and is always missing before the QRS widened complex
• There is a compensatory pause
In fact, the ectopic activation wave, starting from its point of origin, does not use any of the normal conduction pathways. In fact, it progresses very slowly through the undifferentiated myocardium to reach the opposite ventricular wall with considerable delay. So:
1 - a VES born in the left ventricular wall is recognized by the "right-handed" aspect:
positive QRS complex with significant delay in the appearance of intrinsicoid deflection in the right precordial derivations. In contrast, the QRS complex is negative in the left precordial derivations.
2 - a VES born in the right ventricular wall is recognized for a "left delay" appearance: a positive QRS complex with an important delay in the appearance of intrinsicoid deflection in the left precordial derivations. In contrast, the QRS complex is negative in the right precordial derivations.
3 - a VES born in the apical region manifests itself with a positive QRS complex in the derivatives that explore the base (V8 - V9) and with a QRS negative complex in the precordial derivations that explore the tip (from V3a V5).
4 - a VES born in the basal region manifests itself with a positive QRS complex in most precordial derivations (from V1 to V6) and with a QRS negative complex in V8 - V9.

1 - A VES that is born before the Purkinje network or in the undifferentiated myocardium is recognized for:
- a very important widening of QRS, oscillating from 0.14 to 0.16 seconds.
- an almost exclusive positivity of QRS and a noticeable delay in the appearance of the intrinsicoid deflection in the derivations that explore the opposite wall to its point of origin.
- an almost exclusive negativity of QRS in derivations that explore the wall of origin.
The QRS flare, however, is not an absolute criterion. The duration of QRS can be almost normal if the origin of the VES is high

Dangerous extrasystoles

They are those extrasystoles that can give rise to sustained arrhythmias. An atrial  extrasystole can initiate paroxysmal supraventricular tachycardia, flutter, atrial fibrillation, or junctional tachycardia; a ventricular extrasystole  can trigger an AV re-entry tachycardia or a ventricular tachycardia. - prognostic aspects: the frequency (more than five per minute), the precociousness (R / T aspect) and the VES polymorphism have a pejorative value, leaving to fear the triggering of more severe ventricular rhythm disorders (tachycardia or ventricular fibrillation), especially in the acute phase of myocardial infarction. When the ventricular extrasystole is particularly precocious so as to appear when the T wave of the previous QRS complex is registered (VES of the R / T type) there is to be feared the onset of a ventricular fibrillation, and this risk is the higher when the VES approaches the top of the T wave, especially in the acute phase of myocardial infarction.

 Modifications after extrasystoles

Modifications of the basic rhythm
- The VES is usually followed by a compensatory rest, the duration of which exactly compensates for the effect of the VES's prematurity on the basic rate. Thus the interval separating the two QRS complexes that frame the VES is equal to twice the previous cycle (R-R interval), ie the cycle of the basic rhythm. In this way the basic rhythm is not disturbed by the VES.
- VES usually have the same morphology on the same track: they are monomorphic.
- the VES, however, can also have a different morphology on the same path, that is to say POLIMORPHY.
- The appearance of VES can also occur according to a regular sequence: VES bigemine, ie an extra-systolic bat and a QRS complex, or VES trigemine, that is, every two normal beats an intercalated extrasystole. This variety of VES can have a particular meaning: for example, during a digital cure, they attest to an overdose.
- When VESs are frequent they may follow one another, that is they may appear one after the other without interposing normal QRS complexes (nevertheless, it should be borne in mind that, by convention, starting from 3 successive VES it is no longer a simple extrasystole, but
of a ventricular tachycardia.

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