# The ECG shows wide QRS complexes with a ______ pattern, suggesting a left bundle branch block.

> source: MyMerci (mymerci.kr)  
> url: https://mymerci.kr/pages/nclex_q.php?qn_id=168397  
> language: ko  
> subject: Diseases of the circulatory system

## 문제

The ECG shows wide QRS complexes with a ______ pattern, suggesting a left bundle branch block.

## 보기

1. conduction **✔ 정답**
2. electrical
3. rhythmic
4. depolarization
5. activation

**정답: 1**

## 해설

A conduction pattern showing wide QRS complexes (>120ms) with specific morphology changes is characteristic of left bundle branch block. This indicates that electrical conduction through the left bundle branch is blocked, forcing the electrical signal to take an alternate path through the ventricles.

## 임상 시나리오

Left Bundle Branch Block (LBBB)
- QRS duration >120ms
- Delayed left ventricular activation
- Characteristic conduction abnormality
- Altered ventricular depolarization sequence
- Typical ECG features:
* Wide QRS complexes
* Dominant S wave in V1
* Broad R wave in V6
* Left axis deviation
- Clinical implications:
* Common in hypertension
* Associated with coronary artery disease
* Can indicate structural heart disease
* May affect cardiac resynchronization
- Diagnostic criteria:
* QRS ≥120ms
* Absence of Q waves in leads I and V6
* Monophasic R waves in leads I and V6
* ST and T wave changes opposite to QRS

## 핵심 개념

- **conduction** — The process of transmitting electrical signals through cardiac tissue, specifically the movement of electrical impulses through the heart's conduction system
- **electrical** — Relating to or produced by electricity, referring to the heart's natural electrical activity that controls cardiac function
- **rhythmic** — Occurring in a regular, repeated pattern or sequence, particularly in relation to cardiac contractions
- **depolarization** — The process where cardiac cells become electrically activated, changing from their resting state to an excited state
- **activation** — The process of stimulating or initiating electrical activity in cardiac tissue, leading to muscle contraction

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