Table of contents

1. Introduction to Anatomy & Physiology5h 43m
2. Cell Chemistry & Cell Components12h 36m
3. Energy & Cell Processes10h 6m
4. Tissues & Histology10h 3m
5. Integumentary System2h 20m
6. Bones & Skeletal Tissue2h 16m
7. The Skeletal System2h 35m
8. Joints2h 17m
9. Muscle Tissue2h 33m
10. Muscles1h 11m
11. Nervous Tissue and Nervous System1h 35m
12. The Central Nervous System1h 6m
- Introduction to the Central Nervous System
  18m
- The Cerebrum
  48m
13. The Peripheral Nervous System1h 26m
14. The Autonomic Nervous System1h 38m
15. The Special Senses2h 41m
16. The Endocrine System2h 48m
17. The Blood3h 22m
18. The Heart3h 42m
19. The Blood Vessels3h 35m
20. The Lymphatic System3h 16m
21. The Immune System14h 37m
22. The Respiratory System3h 20m
23. The Digestive System2h 5m
24. Metabolism and Nutrition4h 0m
25. The Urinary System2h 39m
26. Fluid and Electrolyte Balance, Acid Base Balance37m
27. The Reproductive System2h 5m
28. Human Development1h 21m
29. Heredity3h 32m

18. The Heart

Electrocardiogram (ECG)

Anatomy & Physiology

18. The Heart

Electrocardiogram (ECG)

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Multiple Choice

When a premature ventricular contraction (PVC) appears on the ECG, which of the following is most characteristic?

A regular rhythm with identical P waves before each QRS complex

A narrow QRS complex with an inverted T wave

A prolonged PR interval with a normal QRS complex

A wide and bizarre QRS complex not preceded by a P wave

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Verified step by step guidance

Understand the context of the problem: A premature ventricular contraction (PVC) is an abnormal heartbeat originating in the ventricles. It disrupts the normal sequence of electrical conduction in the heart.

Review the normal ECG pattern: Normally, a P wave precedes the QRS complex, representing atrial depolarization followed by ventricular depolarization. The QRS complex is typically narrow and uniform in appearance.

Analyze the characteristics of a PVC: Since the electrical impulse originates in the ventricles rather than the atria, the QRS complex becomes wide and bizarre in shape. Additionally, there is no preceding P wave because the atria are not involved in initiating the contraction.

Compare the options provided: Eliminate choices that do not match the hallmark features of a PVC. For example, a regular rhythm with identical P waves before each QRS complex describes normal sinus rhythm, not a PVC. Similarly, a narrow QRS complex or prolonged PR interval does not align with the characteristics of a PVC.

Conclude that the correct answer is: 'A wide and bizarre QRS complex not preceded by a P wave,' as this is the most characteristic feature of a PVC on an ECG.