What defines third-degree (complete) AV block?

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Multiple Choice

What defines third-degree (complete) AV block?

Third-degree AV block means complete failure of AV conduction, so the atria and ventricles beat independently. You see AV dissociation: P waves occur at their own rate, and QRS complexes appear at a separate, slower escape rhythm. There is no fixed relationship between P waves and QRS, so the PR interval isn’t meaningful and neither rhythm drives the other. The QRS morphology can be narrow or wide depending on where the escape pacemaker sits: above the ventricles tends to produce narrow QRS, while below the His-Purkinje system yields wide QRS. This independence of atrial and ventricular activity with two separate rhythms is what defines complete AV block. Options describing intermittent nonconducted P waves, normal conduction with regular P waves and QRS, or a fixed prolonged PR interval correspond to other types of AV block or normal conduction.

Third-degree AV block means complete failure of AV conduction, so the atria and ventricles beat independently. You see AV dissociation: P waves occur at their own rate, and QRS complexes appear at a separate, slower escape rhythm. There is no fixed relationship between P waves and QRS, so the PR interval isn’t meaningful and neither rhythm drives the other. The QRS morphology can be narrow or wide depending on where the escape pacemaker sits: above the ventricles tends to produce narrow QRS, while below the His-Purkinje system yields wide QRS. This independence of atrial and ventricular activity with two separate rhythms is what defines complete AV block. Options describing intermittent nonconducted P waves, normal conduction with regular P waves and QRS, or a fixed prolonged PR interval correspond to other types of AV block or normal conduction.

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