Waveforms/intervals/segments/complexes Flashcards
First deflection of the cardiac cycle
Caused by depolarization of the atria
P wave
Normal ____ are smooth and round, positive in lead II, no more than 2.5mm in height, and no more than 0.10 second in width
P waves
Abnormal P waves that are tall and peaked
Abnormal sinus P wave resulting from RAE
Abnormal P wave that is wide and notched
Abnormal sinus P wave resulting from LAE
Abnormal P waves that are small and pointed, inverted, or absent
Ectopic P waves
Represents the time from the onset of atrial depolarization to the onset of ventricular depolarization
PR Interval
The ______ includes the P wave and the short isoelectric line (PR segment) that follows it
PR Interval
Normal PR Interval (seconds)
0.12 to 0.20 seconds
Reasons a PR interval may be shorter than normal
- electrical impulse is conducted from the atria to the ventricles through an accessory conduction pathway that bypasses the AV node
- impulse originates in an ectopic pacemaker site in the AV node
Reasons for prolonged PR interval
- first-degree AV block
- hypothyroidism
- certain drugs (digitalis, beta-blockers, calcium channel blockers)
- aging
Measured from when the first wave of the complex leaves the baseline to when the last wave of the complex begins to level out into the ST segment
QRS Complex
Predominantly positive in lead II with a duration of 0.10 seconds or less
normal QRS complex
T/F
R waves are always positive
True
If the entire complex is negative, it is termed a QS complex
In regards to QRS labeling, a wave must cross the baseline to be labeled separately. A wave that changes direction but doesn’t cross the baseline is called a ____
Notch
QRS labeling
capital letters are used to designate waves of _____ amplitude
Large (5mm or more)
QRS Labeling
Lowers case letters are used to designate waves of ____ amplitude
5mm or less
4 causes of an abnormally wide QRS Complex
- a block in the conduction of impulses through the right or left bundle branch
- An electrical impulse that has arrived early at the bundle branches before depolarization is complete, allowing the electrical impulses to initiate depolarization of the ventricles earlier than usual
- an electrical impulses that has been conducted from the atria to the ventricles through an abnormal accessory pathway that bypasses the AV node
- an electrical impulse that has originated in an ectopic site in the ventricles
Represents the end of ventricular depolarization and the beginning of ventricular repolarization
Normally flat (isoelectric)
ST Segment
ST segment elevation is considered significant if the displacement is more than ____ and is seen in ____ facing the same area of the heart
1 mm; 2 or more leads
ECG sign of myocardial injury
Ex: MI, coronary vasospasm, pericarditis, ventricular aneurysm, hyperkakemia, and early repolarization
Elevated ST segment
Variant of myocardial repolarization seen in healthy people that produces a ST segment elevation closely mimicking acute MI or acute pericarditis
Early repolarization
ECG sign of myocardial ischemia
Other causes: ventricular hypertrophy, bundle branch block, or drug effects
ST Segment depression
What ECG finding is characteristic of digitalis?
Sagging ST segment depression
“Scooped-out” appearance
Represents the latter phase of ventricular repolarization
T wave
