AEMCA Practice Exam

How is a wide QRS complex typically presented in heart block type 3?

1. In sync with P waves.

2. Irregular and chaotic.

3. As isolated events without matching P waves.

4. Occurring more frequently than usual.

The correct answer is: As isolated events without matching P waves.

A wide QRS complex in heart block type 3, also known as complete heart block, typically appears as isolated events without matching P waves. In complete heart block, there is a disassociation between the atrial and ventricular activity. This means that the sinus node continues to send P waves, but the electrical impulses do not reach the ventricles due to the blockage in the conduction pathway. The wide QRS complexes occur because they arise from ectopic ventricular pacemakers, which can generate impulses independently of the atrial rhythm. This results in the QRS complexes being wide (often greater than 0.12 seconds) and not synchronized with the P waves, as there is no coordination between the atria and the ventricles. In contrast, the other options do not accurately describe the behavior of the QRS complexes in complete heart block. P waves being in sync with the QRS would indicate that there is some level of conduction, which is not the case in heart block type 3. An irregular and chaotic presentation might suggest other types of arrhythmias, such as atrial fibrillation, rather than the isolated wide QRS complexes characteristic of complete heart block. Lastly, stating that wide QRS complexes occur more frequently than usual does not align