56 Questions
Which segment of an EKG tracing represents the time between the end of the P wave and the start of the QRS complex?
PR segment
What is responsible for the various waves, segments, and intervals seen on an EKG tracing?
Electrical conduction system of the heart
In the frontal plane, how is the mean QRS vector (axis) determined?
By comparing the bipolar limb leads with the augmented limb leads
What is the physiological cause for upward and downward deflections on an EKG tracing?
Electrical activity of the heart
What is the heart rate range for bradycardia?
Less than 60 bpm
What term is used for arrhythmias originating above the ventricles?
Supraventricular tachycardia (SVT)
What is the term for a rhythm in which every other beat is premature?
Bigeminy
What is the heart rate range for fibrillation?
Between 350 and 450 bpm
What is the term for deviation from the normal range in the electrical axis in the frontal and horizontal planes?
Rotation
How is the mean QRS axis in the horizontal plane determined?
R to S ratio
Which type of blocks have distinct characteristics in terms of QRS axis and EKG patterns?
Fascicular blocks
What are the learning objectives of the workshop related to EKG interpretation?
Defining automaticity focus and overdrive suppression
What is the rate range for atrial automaticity foci?
60-80 per min
What does overdrive suppression refer to?
Fastest pacemaker rate dominance
What is escape in the context of cardiac pacing?
Activation of the dominant pacemaker
What is covered in the workshop in terms of EKG tracings?
Recognizing and differentiating various rhythms
What is recommended reading for the workshop?
Specific chapters from Dubin's book on EKG interpretation
What does overdrive suppression refer to?
Fastest pacemaker rate dominance
What does escape in the context of cardiac pacing refer to?
Activation of the dominant pacemaker
What is covered in the workshop in terms of EKG tracings?
Recognizing and differentiating various rhythms
What is the clinical utility of EKG attributed to?
Widespread availability, ease of performance, and lack of procedural risk or contraindications
What determines myocyte contraction?
Myocyte depolarization
What distinguishes intervals from segments in electrocardiography nomenclature?
Intervals include waves, while segments are sections of baseline between waves
What does the QT interval include?
The QRS complex and the T wave
Where is the J point located on an EKG tracing?
Where the QRS complex and the ST segment meet
What causes the U wave on an EKG tracing?
The slowest repolarizer, often the Purkinje fibers
How can the heart rate be determined on a standard EKG tracing?
By the number of 'big blocks' between consecutive beats
What does the mean electrical axis provide important information about?
The heart's function and structure
Who developed Electrocardiography (EKG)?
Dr. Willem Einthoven
What is the role of the Purkinje fibers in the heart's electrical activity?
They are often the slowest repolarizers
What is the standard 12-lead EKG used for determining?
The mean electrical axis in the frontal and horizontal planes
What does myocyte depolarization depend on?
Myocyte depolarization
What is used to determine the positive electrode position for bipolar limb leads based on the abbreviation of the limbs?
D'Amico's rule of "L"'s
How can the QRS axis be estimated when lead I is positive and aVF is negative?
Between 0° to –90°
Where are chest leads V1-V6 placed to record electrical activity?
Specific locations on the heart surface
How many limb leads are there in an EKG, including both bipolar and augmented unipolar leads?
6
What is essential for interpreting electrocardiograms accurately?
Understanding the lead positions and QRS axis determination
What is used to determine the QRS axis in the frontal plane?
Locating the most isoelectric lead and the lead 90 degrees from it
What indicates the area of electrical activity when estimating the QRS axis by looking at leads I and aVF?
The polarity of the leads
Why is the placement of the positive and negative electrodes in limb leads and chest leads crucial?
For accurate EKG recordings
What is fundamental for healthcare professionals involved in cardiac monitoring and diagnosis?
Proper placement of EKG leads and understanding QRS axis determination
What relies on the correct placement of leads and the precise determination of the QRS axis?
The accurate interpretation of EKGs
What does D'Amico's rule of "L"'s help determine?
The positive electrode position for bipolar limb leads
What is crucial for accurate EKG recordings?
The placement of the positive and negative electrodes in limb leads and chest leads
Which EKG finding indicates AV nodal dysfunction if the PR interval is not prolonged?
Completely inverted P wave in lead II
What is the most common cause of sinus arrhythmia?
Respiration
What does sinus bradycardia refer to?
Heart rate less than 60 beats per minute
What is the heart rate range for sinus tachycardia?
Greater than 100 beats per minute
What is the key criterion for identifying sinus rhythm on an EKG?
Each QRS complex preceded by a positive P wave in lead II and negative in lead aVR
What does a sinus arrhythmia indicate?
Greater than 0.16 sec difference between the shortest and longest PP intervals
What is the effect of irritability on automaticity foci's tendency to generate electrical impulses?
Increase
What is the characteristic heart rate range for sinus rhythm?
Between 60 and 100 beats per minute
What is the defining feature of junctional beats on an EKG?
Retrograde P wave preceding ventricular depolarization
What does an escape beat indicate?
Transient escape of an automaticity focus to generate one beat
What is the main cause of escape rhythm?
Cessation of pacing activity in the dominant pacemaker
What does a completely inverted P wave in lead II indicate?
AV nodal dysfunction if PR interval is not prolonged
Study Notes
Electrocardiography Basics and Principles
- Electrocardiography (EKG) was developed by Dr. Willem Einthoven in 1901 and is the most frequently used cardiac diagnostic test.
- The clinical utility of EKG is attributed to its widespread availability, ease of performance, relative cost permissiveness, and lack of procedural risk or contraindications.
- Myocyte contraction depends on myocyte depolarization, which occurs as a wave traveling from one end of the myocyte to the other.
- Different directions of depolarization and repolarization cause specific up or down deflections on the EKG tracing.
- Nomenclature in electrocardiography distinguishes intervals (which include waves) from segments (which are sections of baseline between waves).
- PR interval includes the P wave but not the QRS complex, QT interval includes the QRS complex and the T wave, and ST interval includes the T wave but not the QRS complex.
- There are idiosyncratic conventions for naming intervals and segments involving the QRS complex.
- The J point is where the QRS complex and the ST segment meet.
- The U wave on an EKG tracing is caused by the slowest repolarizer, often the Purkinje fibers.
- The heart rate can be determined by the number of "big blocks" between consecutive beats on a standard EKG tracing.
- The mean electrical axis can be determined in the frontal plane and the horizontal plane using the standard 12-lead EKG with limb and precordial leads.
- The electrical axis can provide important information about the heart's function and structure.
Electrocardiography Rhythm Summary
- Escape beat: transient escape of an automaticity focus to generate one beat due to pause in pacing activity in the dominant pacemaker
- Escape rhythm: escape of an automaticity focus with subsequent pacing at its inherent rate due to cessation of pacing activity in the dominant pacemaker
- Sinus Rhythm EKG Criteria: each QRS complex preceded by a positive P wave in lead II and negative in lead aVR
- Sinus rhythm: heart rate between 60 and 100 beats per minute
- Sinus bradycardia: heart rate less than 60 beats per minute
- Sinus tachycardia: heart rate greater than 100 beats per minute
- Sinus arrhythmia: same criteria as sinus rhythm with greater than 0.16 sec difference between the shortest and longest PP intervals
- Sinus arrhythmia most common cause: respiration, heart rate increases with inspiration and decreases with expiration
- Completely inverted P wave in lead II indicates AV nodal dysfunction if PR interval is not prolonged
- Junctional beats recognized by three possible EKG patterns based on location of automaticity focus and conduction variability
- Retrograde P wave preceding ventricular depolarization confirms origin above the ventricles
- Irritability: increase in automaticity foci's tendency to generate electrical impulses due to various reasons such as hypoxia, electrolyte disturbances, and sympathetic stimulation
Test your knowledge of electrocardiography basics and principles with this quiz. Learn about EKG nomenclature, intervals, segments, and the clinical utility of EKG. Also, review EKG rhythm criteria and characteristics such as sinus rhythm, bradycardia, tachycardia, arrhythmia, escape beats, and irritability.
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