Normal EKG Flashcards
What is the function of the SA node?
- Initial depolarization of the myocardium.
- Sets the heart rate at 60-100 bpm.
What does the AV node do?
Delays the electrical signal, allowing the ventricles time to fill with blood, with an inherent rate of 40-60 bpm.
What is the function of the Bundle of His?
Transmits impulses from the AV node to the ventricles.
What are the Purkinje fibers responsible for?
Spread the impulse through the ventricles, causing them to contract.
Conduction Principles
- Automaticity = ?
- Rhythmicity = ?
- Conductivity = ?
- Automaticity: The heart’s ability to contract on its own without external stimuli.
- Rhythmicity: The heart’s ability to contract in a regular, rhythmic manner.
- Conductivity: The heart’s ability to transmit impulses throughout the myocardium.
What are the main components of the cardiac cycle?
- Starts at the end of systole
- Includes closing of semilunar valves
- Opening of mitral valves for ventricular filling.
What information does a 12-lead ECG provide?
Rate, rhythm, impulse conduction, myocardial pathology, and physiologic status.
How many electrodes are used in a 12-lead ECG?
10 electrodes.
Name the 6 limb leads in a 12-lead ECG.
- Lead I
- Lead II
- Lead III
- aVR
- aVL
- aVF
What is the ‘Rule of L’s’ in ECG?
- Lead I (Right to Left Arm)
- Lead II (Right Arm to Left Leg)
- Lead III (Left Arm to Left Leg)
What does the QRS complex represent?
- Depolarization of the ventricles
- Initiation of ventricular systole
- 0.06-0.10 sec
What is the significance of the ST segment?
- Represents early ventricular repolarization
- Abnormalities may indicate heart disease
What does the T-wave represent?
- ventricular repolarization
- beginning ventricular filling
- 0.16 sec
What is the normal duration of the PR interval?
- 0.12-0.20 seconds
- 3-5 small boxes
What does the P-wave represent?
- Depolarization of the atria
- 0.08-0.11
What does a normal sinus rhythm look like?
- P waves are upright and precede every QRS complex
- PR interval 0.12-0.20 seconds
- QRS complex is identical and 0.06-0.10 seconds
- HR 60-100 bpm
Define
- sinus bradycardia = ?
- sinus tachycardia = ?
Sinus Bradycardia: A sinus rhythm with a heart rate of less than 60 bpm.
Sinus Tachycardia: A sinus rhythm with a heart rate of more than 100 bpm.
Define sinus tachycardia.
A sinus rhythm with a heart rate of more than 100 bpm.
What is sinus arrhythmia?
An irregular sinus rhythm, often associated with breathing cycles.
What does a 5-lead ECG typically assess?
Heart rate and rhythm in clinical settings.
How is heart rate calculated using the 1500 method?
1500 divided by the number of small boxes between two R-waves.
How is heart rate calculated using the 6-second method?
- Count the number of R-waves in a 6-second strip and multiply by 10.
- Use if abnormal
What does the PR segment represent?
Transmission of the electrical impulse from the atria to the ventricles.
What is the normal duration of the QRS complex?
0.06-0.10 seconds.
What does the R-R interval measure?
The regularity of the heart rate.
What might cause an abnormal QRS complex?
Conditions like ventricular hypertrophy or conduction block.
What is the role of the Purkinje fibers in the ECG?
They cause the ventricles to contract, represented by the QRS complex.
What does the QT interval represent?
The total time for ventricular depolarization and repolarization.
What does an elevated ST segment indicate?
Possible myocardial infarction (STEMI).
What does the P-R interval indicate in terms of conduction?
The time it takes for the electrical impulse to travel from the SA node through the AV node.
Why is the T-wave important?
It indicates ventricular repolarization, and abnormalities can indicate electrolyte imbalances or ischemia.
What does sinus arrest mean?
A pause in the heart’s activity when the SA node fails to initiate an impulse.
How do you calculate the heart rate using the Box Counting Method?
Count the number of large boxes between two R-waves and divide 300 by this number.
What is the significance of a biphasic P-wave?
It may indicate atrial enlargement.
What is the ‘sawtooth’ pattern on an ECG indicative of?
Atrial flutter.
What might a wide QRS complex suggest?
Ventricular conduction delays or bundle branch blocks.
What is the significance of the P-R segment being isoelectric?
It indicates that the atria have depolarized and the impulse is traveling to the ventricles.
What does a notched P-wave indicate?
Possible left atrial enlargement.
How does the 6-second method differ for figuring out heart rhythm?
It’s the only method suitable for calculating heart rate in irregular rhythms.
What is the normal duration of a T-wave?
Approximately 0.16 seconds.
How can electrode misplacement affect an ECG reading?
It can lead to incorrect interpretation of heart rhythms and conditions.
What does a normal T-wave look like?
Upright and same direction as the P-wave, with a duration of about 0.16 seconds.
What is the purpose of a caliper in ECG analysis?
To measure the R-R interval and check for regularity of the rhythm.
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What does the term ‘sinus rhythm’ imply?
A heart rhythm originating from the SA node.
What are the characteristics of sinus tachycardia?
Normal P, PR, and QRS but with a heart rate over 100 bpm.
What is the main feature of sinus bradycardia?
Normal P, PR, and QRS but with a heart rate under 60 bpm.
