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User question:
How to see a complete dissociation between the atria and ventricles on an EKG (electrocardiogram)?
A complete dissociation between the atria and ventricles, as seen in third-degree AV block, is depicted on an EKG (electrocardiogram) with the following characteristics:
P Waves: These are regular and indicate normal atrial rhythm, but they have no temporal relationship to the QRS complexes.
QRS Complexes: These may appear at a regular or irregular rate, independent of the P waves. The rate is usually slower than the atrial rate because it is set by an escape rhythm from a pacemaker site below the block.
Dissociation: There is a complete lack of coordination between the P waves and QRS complexes, demonstrating that the atria and ventricles are beating independently.
In some cases, P waves may occur on the ST-T segment, and if the atrial and ventricular rates are equal, it can be challenging to diagnose third-degree AV block as it may simulate sinus rhythm. This scenario is referred to as isoarrhythmic AV dissociation.
The escape rhythm that maintains ventricular activity can have narrow or wide QRS complexes, depending on where the impulses are discharged and whether there is a concomitant bundle branch block. Narrow QRS complexes suggest a junctional escape rhythm, while wide QRS complexes indicate a ventricular escape rhythm.
These features on an EKG are critical for diagnosing third-degree AV block and determining the appropriate treatment, which often includes the implantation of a pacemaker for symptomatic patients. It’s essential for healthcare professionals to interpret these signs in the context of the patient’s overall health status.
