EKG Basics Flashcards
On an EKG strip, what does the vertical axis represent?
Time
On an EKG strip, what does the horizontal axis represent?
Voltage (mV)
What does 1 small box represent?
0.04s and 0.1mV
What do 5 small boxes represent?
1 big box = 0.2s, 0.5mV
What is used to ensure the ECG machine is properly calibrated?
Calibration mark
(standard = 1.0mV = 2 large boxes = 10 vertical squares)
What is defined as a flat line in which there is no electrical activity or impulses are too weak to be detected?
Isoelectric line
What is used as a baseline to ID changes in electrical movement?
Isoelectric line
What is defined as markings that are not products of heart’s electrical activity (ex. pt movement)?
Artifact
What can artifacts mimic?
Life threatening dysrhythmias (therefore must r/o)
The P wave represents depolarization of the RA and LA and is typically of what duration and what amplitude?
Duration- 0.06- 0.10s
Amplitude- 0.5- 2.5mm
Where is the PR interval measured and what is the typicaly duration?
Start of P wave to beginning of QRS complex
Normal = 0.12- 0.20s
The PR segment represents depolarization of the heart from the SA node through the atria, AV node, and His-purkinj system and is measured where?
Flat/ isoelectric line between end of P wave and start of QRS complex
The QRS complex represents depolarization of the ventricles, is typically upright and narrow and is of what duration?
0.06- 0.12s
(will always be named QRS regardless if missing a wave)
What is the Q wave on an EKG strip?
1st negative deflection
What is the R wave on an EKG strip?
Any positive deflection following Q wave or PR segment
What is the S wave on an EKG strip?
Any negative deflection below baseline following R wave
Where is the ST segment measured on an EKG strip?
Flat line following QRS complex
Where is the T wave on an EKG segment?
Larger, slightly, asymmetrical (vs P wave) waveform that follows ST segment (ventricular repolarization)
What is the J point on an EKG strip?
Where QRS complex meets ST segment
Where is the QT interval measured and what is a normal duration?
Beginning of QRS complex to end of T wave
Normal = 0.36- 0.44ms
The QT segment will increase as what parameter slows?
HR
With regular rhythm, how does the QT segment compare to R waves?
QT segment should be < 1/2 the distance between consecutive R waves
What provide an electrical “view” of the heart to help distinguish a focal problem?
Leads
What are the anterior leads?
V1-4
What are the lateral leads?
I, aVL, V5-6
What are the inferior leads?
II, III, aVF
Bipolar leads record difference in electrical potential between what?
Positive and negative electrode with 3rd electrode as a ground
What is postitive and negative with lead I?
RA neg, LA pos
What is postitive and negative with lead II?
RA neg, LL pos
What is postitive and negative with lead III?
LA neg, LL pos
What is the reference point for unipolar leads?
Center of the heart (as calculated by ECG machine)
What type of leads are enhanced by the ECG because waveforms produced by these leads are normally small?
Augmented limb leads
Augmented limb leads use the same electrodes as limb leads but only 1 is positive and the other two…?
Have no charge and serve as common ground
What electrode is positive with aVR and what view of the heart does it provide?
RA pos, views base of heart (atria and great vessels)
What electrode is positive with aVL and what view of the heart does it provide?
LA pos, views lateral wall of LV
What electrode is positive with aVF and what view of the heart does it provide?
LL pos, views inferior wall of LV
What leads are all positive electrodes and provide anterior and lateral views of the heart in a horizontal plane?
Precordial leads (V1-6)
Where is V1 placed?
4th ICS, right of sternum