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Questions and Answers
What is considered a normal heart rate?
What condition is indicated by a heart rate less than 60 BPM?
How can you quickly estimate the heart rate from the ORS complexes?
What does a heart rate greater than 100 BPM indicate?
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What characterizes a sinus rhythm?
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What term is used to describe a heart rate greater than 100 beats per minute?
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What is the normal range for the PR Interval?
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Which rhythm is characterized by an irregular heart rate?
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What is the maximum length for a normal QT Interval in females?
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Which condition is indicated by a heart rate of 60 beats per minute or less?
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What does the P wave on an ECG represent?
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Which component of the ECG is associated with ventricular repolarization?
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What is the approximate duration of one large box on an ECG?
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Which wave reflects the repolarization of Purkinje fibers?
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What is the vertical length of the QRS complex in a large box on an ECG?
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Study Notes
ECG Basics
- Sinoatrial node (Puran) initiates the heart's electrical impulses; cycle duration is 0.20 seconds.
- Horizontal length of a large box on ECG paper equals 0.20 seconds; useful for timing.
- Vertical height of QRS complex on a large box measures 5mm, indicating the amplitude of ventricular depolarization.
Waves and Segments
- P wave indicates atrial depolarization, a crucial phase for heart contraction.
- QRS complex represents ventricular depolarization, a key component of heart activity.
- ST segment reflects the period when the ventricles are contracting and emptying.
- T wave signifies ventricular repolarization, restoring the resting state.
- U wave may represent Purkinje fiber repolarization, appearing occasionally after the T wave.
Heart Rate
- Normal heart rate ranges from 60 to 100 beats per minute (BPM).
- Bradycardia occurs when the heart rate drops below 60 BPM.
- Tachycardia is identified when the heart rate exceeds 100 BPM.
- To estimate heart rate:
- Count the number of QRS complexes over 6 seconds and multiply by 10.
- Alternatively, use the formula: Rate = 60 / (R-R interval time).
- Another method: Rate = 300 / (number of large boxes between R-R intervals).
Rhythm Assessment
- Sinus rhythm: Waves occur in consistent positions.
- Sinus Tachycardia: Heart rate exceeds 100 BPM, with regular P waves preceding each QRS complex.
- Sinus Bradycardia: Heart rate is at or below 60 BPM, with regular rhythm.
- Sinus Arrhythmia: Irregular heart pattern observed despite normal structure.
Other Rhythms
- Atrial Fibrillation: Irregular and often rapid heart rate originating from chaotic electrical signals.
- Atrial Flutter: Regular but rapid heart rhythm due to reentrant circuits in the atria.
- Premature Atrial Contraction (PAC): Extra heartbeats originating in the atria.
- Premature Ventricular Contraction (PVC): Extra heartbeats originating in the ventricles.
Intervals and Durations
- PR Interval: Normal duration is between 0.12 to 0.20 seconds, reflecting atrial depolarization and conduction through the AV node.
- QRS Duration: Ranges from 0.07 to 0.10 seconds; indicates the time taken for ventricular depolarization.
- QT Interval is critical for assessing the heart's electrical recovery:
- Normal duration is ≤0.44 seconds.
- Males: ≤0.45-0.46 seconds.
- Females: ≤0.47-0.48 seconds.
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Description
Test your knowledge on the concepts of ECG, including speed, rate, and rhythm. This quiz covers essential components like the P wave, QRS complex, and intervals crucial for understanding cardiac depolarization and repolarization. Ideal for students and professionals in the medical field.
