CPR Physiological Basis of ECG Flashcards
What does an ECG illustrate?
Changes of electrical activity of cardiac muscle tissue (depol and repol)
At baseline = no active depol or repol happening
Why does an ECG not report electrical differences between atria and ventricles?
They are electrically isolated from each other. ECG only reports voltage differences between both atria or both ventricles
What is the P wave?
Atrial depol. First cells near SA node to depolarize, goes until last cells of L atrium depolarize
What is the QRS wave?
Ventricular depol. First cells in septum to depolarize, goes until last cells of upper ventricles depolarize
What does the baseline line between QRS and T waves represent? (ST segment)
Phase 2, ventricular cells all depolarized, waiting on repolarization
What is the T wave?
Repolarization of ventricles
What is a U wave?
Sometimes follows normal repolarization (T wave), unknown cause
What does a segment represent?
Duration of a single event on an ECG
Ex: P wave or time between QRS and beginning of T wave
What does an interval represent?
Duration of two or more events
Ex: P wave plus beginning of QRS
What does a solid vertical line on an ECG represent?
0.2 seconds
5 large boxes = 1 sec
What does a solid vertical line on an ECG represent?
0.5 mv
2 large boxes = 1.0 mv
What is the PR interval?
Distance between beginning of P wave and beginning of QRS (usually 0.16 ms)
What is the QT interval?
Beginning of QRS until end of T wave (usually 0.35 ms)
What is the PR segment?
End of atrial depol until beginning of QRS, not super clinically relevant
What is the ST segment?
End of QRS until beginning of T wave
