When the appropriate electrocardiogram (ECG) complex follows the pacing spike, it is said to be:

• A. undersensed
• B. fused
• C. captured
• D. non-captured

Answer: (C)

Verified step by step guidance

1. Understand the context of the problem: The question is about interpreting an electrocardiogram (ECG) in relation to a pacing spike, which is a signal generated by a pacemaker to stimulate the heart. The goal is to determine the term that describes the situation when the ECG complex appropriately follows the pacing spike.
2. Review the concept of 'captured': In pacemaker terminology, 'capture' refers to the successful depolarization of the heart muscle (myocardium) in response to a pacing stimulus. This is evidenced by the appearance of an appropriate ECG complex (e.g., a P wave or QRS complex) immediately after the pacing spike.
3. Clarify the other terms for comparison: 'Undersensed' refers to the pacemaker failing to detect intrinsic cardiac activity. 'Fused' describes a scenario where the paced and intrinsic beats occur simultaneously, creating a hybrid ECG complex. 'Non-captured' means the pacing stimulus did not result in myocardial depolarization, and no ECG complex follows the pacing spike.
4. Analyze the situation described: The problem states that the appropriate ECG complex follows the pacing spike. This indicates that the pacing stimulus successfully caused myocardial depolarization, which aligns with the definition of 'captured.'
5. Conclude the reasoning: Based on the definitions and the situation described, the term 'captured' is the correct answer because it signifies the successful response of the heart to the pacemaker's pacing spike.