EKG (WAVES,SEGMENTS,INTERVALS)🌟

1 EKG cycle consist of

P wave, QRS complex,T wave

P wave represents

Atrial depolarization/contraction

QRS complex

Ventricular depolarization

T wave

Ventricular repolarization (relaxation)

U wave

(Occasionally follows T wave)small wave associated w/ repolarization

Baseline

Divided into segments & intervals

Segment (SEG)

Portion of baseline b/w 2 waves (named by waveform &that precedes or follows it)

Interval (INT)

Length of wave & segment together

P-R segment

Time interval from end of atrial depolarization to beginning of ventricular depolarization

S-T interval

Time interval from end of ventricular depolarization to beginning of ventricular repolarization

P-R interval

Time interval from beginning of atrial depolarization to beginning of ventricular depolarization

Q-T interval

Time interval

From beginning of ventricular depolarization to end of ventricular repolarization

Baseline

When entire heart returns to its resting(polarized) state

Deflection which doesnt return to baseline

Spike (also seen if Pt. has artificial pacemaker)

P wave duration

0.12 second

PR segment equivalent to

Repolarization/Relaxation of atria

PR interval equivalent to

time it takes for electrical impulse to travel from S/A node to A/V node

PR interval duration

0.12- o.20 seconds

QRS complex (depolarization/contraction) of ventricles duration

less than 0.10 seconds

ST segment

initial state of ventricular repolarization/relaxation

T wave equivalent to

Repolarization/relaxation of ventricles (final phase)

QT interval duration

0.36 -0.44 seconds

P wave represents

Sinoatrial node impulse

QRS complex represents

Contraction of ventricles

Q wave represents

Impulse traveling down septum toward purkinje fibers

R wave

Impulse going through left ventricle

S wave

Impulse going through both ventricles

T wave

Recovery of ventricles

U wave

Slow recovery of purkinje fibers

P-R interval

Depolarization of right & left atria,spread impulses through AV node etc.

Q-T interval

Time it takes for ventricles to contract & recover (repolarization)

S-T segment

Time b/w contraction of ventricles & recovery

5 LB=? sec

1 second

15 LB=? sec

3 second

30 LB=? sec

6 second

SB width =

0.04 sec

1 LB =

5 small boxes

LB width =

0.20

Distortion of an EKG tracing

Artifact

P-P interval

Used to determine atrial rate & regularity

Artifact causes

loose electrodes,broken EKG cables,muscle tremor,Pt.movement,external chest compressions

1.Muscle Artifacts-characterized by fuzzy,irregular baseline

Pt.movement,physical condition,Pt.discomfort,apprehensivePt.

2.Wandering Baseline-Swaying & shifting of baseline.can be caused by

loose electrodes,body creams,

3.Alterinating current-due to electrical inference from appliances in room. Caused by

lead wires not following body contour,other electrical equipment in room,wiring in walls ceilings & floor,improper grounding of electrocardiograph

Interrupted Baseline caused by

metal tip lead wire become detached from alligator clip,broken Pt. cable