CD Midterm

60-100 bpm

40-60 bpm

20-30 bpm

From beginning of Q to the end of the T wave. Represents total ventricular activity.  Normal range= 0.44 or >

represents ventricular repolarization

End of the S wave, beginning of the T wave

R & S waves represent the depolarization of the L & R ventricles.

Negative waveform that follows the R wave.

First positive deflection following the P Wave or Q wave (if present).  Always appears as a positive waveform.

a negative deflection following the P wave. Always appears as a negative waveform.

• Represents the depolarization of the ventricles and HR.
• Normal range= 0.06- 0.12

• From the beginning of the P wave to the beginning of QRS Complex.  Reflects the impulse travel time from the SA node through the AV node, HB, R & L bundles, and into the Purkinje fibers.
• Normal range= 0.12- 0.20

atrial depolarization and spread of impulse across the L & R atria

Small square: 1mm x 1mm, 0.04 sec

Large square: 5mm x 5mm, 0.2 sec

"Vulnerable Period" because cells are repolarizing and can be stimulated (if stimulus is strong enough) thus possibly resulting in ventricular chaos. Downslope of T wave.

From the onset of QRS to approximately the peak of T wave.  Cells are depolarized and cannot be stimulated.

• Normal electrical activity.
• Impulse originates in the SA node & follows the normal pathway of conduction, resulting in atrial & ventricular depolarization

SA node discharges impulses fewer than 60 beats/min.  Originates in the SA node and follows the normal pathway of conduction.

Occurs when the SA node discharges irregularly

• Originates from the AV junction & is considered an SV rhythm.
• 40-60 bpm
• Usually regular.

• An ectopic rhythm caused by altered automaticity in the Bundle of His.
• 60-100 bpm
• Usually initiated by a few PJCs.

Three or more sequential PJCs occurring at 100/min or more is considered JT   (100-180 bpm).

• When JT starts & ends suddenly, it is called paroxysmal junctional tachycardia (PJT) & is often initiated by a PJC.
• When JT is >150 bpm, often difficult to distinguish JT from AT since P waves are not easily seen - then rhythm is called   supraventricular tachycardia (SVT)

P waves vary in size, shape, & direction across the rhythm strip.  Need to identify 3 different P wave shapes in the same lead to call the rhythm MFAR.

SVT can be called atrial tachycardia if a visible P wave (atrial activity) is present.

Describes an SVT that starts & stops suddenly.

• An irritable atrial site depolarizes regularly at an extremely rapid rate (250-350 bpm).
• Results in waveforms that resemble the teeth of a saw or a picket fence.

• Multiple atrial ectopic sites initiate rapid impulses (350-600 bpm) which causes ineffectual atrial contraction or quiver (fibrillate).
• Results in subsequent decrease in CO, loss of “atrial kick”, & risk of clot formation.