Atrioventricular dissociation

Atrioventricular dissociation happens when the atria and ventricles work independently. Atrioventricular dissociation is characterized by the sameventricular rate or faster than the atrial rate. Complete heart block may appear when the atrial rate is faster but this is not the case of the condition above mentioned .

There is a type of rhythm disturbance called isorhythmic AV dissociation that happens when the atrial rate is the same as the ventricular rate but the P wave is not conducting. There is also the type called interference AV dissociation when occasionally the atria conduct to the ventricles but the rates are similar.

One of the causes of atrioventricular dissociation is a high catecholmine level. Other causes that may generate such a condition are: drugs that block catecholamines levels , surgical and anesthesia interventions, intubations, myocardial infarction, sinus node disease. Also, there are some structural heart disease like vagal activation, ventricular tachycardia, hyperkalemia, or ventricular pacing that can cause Av dissociation. If vagal fibers are harmed , Av dissociation can be seen after radiofrequency ablation of the slow pathway responsible for AV nodal reentry.

Atrial dissociation alone can be benign. If adverse effects appear this happens because of ensuing bradycardia, underlying conditions or AV dyssynchrony.

Symptoms in case of Av dissociation can not be present. If they appear, they are related to tachycardia, loss of atrial “kick”, and they include : throbbing sensation in neck, palpitations, exertional dyspnea, light-headedness, fatigue.

The physical exam related to tachycardia, bradycardia, AV dyssynchrony will appear because of the changes in contractions between the atria and ventricles , a variable pulse with fast or slow rates; a variable blood pressure, beat-to-beat variation in systolic murmurs, variable intensity of first heart sound and beat-to-beat.

The term AV dissociation is often used incorrectly as a synonym for third-degree block, but not all AV dissociation are related to a block.

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