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The nurse is teaching a beginning ECG class to staff nurses. As the nurse begins to discuss the parts of the ECG complex, one of the students asks what the normal order of conduction through the heart is. The correct response would be which of the following?

A.

SA node, AV node, bundle of His, right and left bundle branches, and the Purkinje fibers

B.

SA node, AV node, bundle of His, the Purkinje fibers, and the right and left bundle branches

C.

AV node, SA node, bundle of His, right and left bundle branches, and the Purkinje fibers

D.

SA node, AV node, right and left bundle branches, bundle of His, and the Purkinje fibers

Answer and Explanation

The Correct Answer is A

A. This is the correct sequence of normal electrical conduction through the heart: the impulse originates in the sinoatrial (SA) node, travels to the atrioventricular (AV) node, then to the bundle of His, down the right and left bundle branches, and finally through the Purkinje fibers.
B. This choice places the Purkinje fibers before the bundle branches, which is incorrect.
C. The AV node does not initiate conduction; the SA node is the natural pacemaker of the heart.
D. This sequence incorrectly places the bundle branches before the bundle of His.
 


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Related Questions

Correct Answer is A

Explanation

A. Ventricular tachycardia is characterized by a ventricular rate >100 bpm, regular rhythm, no visible P waves, and wide QRS complexes (>0.12 seconds). The findings described—ventricular rate of 162, regular R-R intervals, no visible P waves, and a QRS duration of 0.18 seconds—are consistent with ventricular tachycardia.
B. Ventricular fibrillation shows a chaotic, irregular rhythm with no identifiable QRS complexes, which is not the case here.
C. Sinus tachycardia would have visible P waves and a normal QRS duration.
D. Atrial flutter typically has "sawtooth" flutter waves and a more organized atrial rhythm with a distinct P wave pattern, which is absent in this scenario.

Correct Answer is C

Explanation

A. The T wave is in the inverted position – In a normal sinus rhythm, the T wave should be upright in most leads. An inverted T wave may indicate ischemia or other pathology.
B. The P-R interval measures 0.22 seconds – A normal P-R interval is between 0.12 and 0.20 seconds. A P-R interval of 0.22 seconds suggests a first-degree heart block.
C. The P wave falls before the QRS complex – In normal sinus rhythm, each P wave precedes a QRS complex, indicating that the electrical impulse originates from the sinoatrial (SA) node.
D. The QRS duration is 0.20 seconds – A normal QRS duration is 0.06 to 0.10 seconds. A QRS duration of 0.20 seconds is prolonged and suggests a conduction abnormality such as a bundle branch block.

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