The Basic Interpretation of EKG Waveforms, Arrhythmias, and Dysrhythmias

By Zachary R Freeman, RPSGT

Two things to remember

1. An EKG measures the ELECTRICAL activity of the heart, not actual movement.

2. What we see REPRESENTS the movement of the muscle.

“Interval” refers to the distance between two points.FOR EXAMPLE: P-R interval, Q-T Interval

The distance between two points represents the time it takes for a signal to travel from one point in the muscle to another.

ELECTRICAL ACTIVITY

Electrical activity in the Atrium depolarizes.

ASSOCIATED MOVEMENT

Contraction of the Atrium muscle.

ELECTRICAL ACTIVITY

Electrical activity in the Ventricle depolarizes.

ASSOIATED MOVEMENT

Contraction of the Ventricle muscles.

ELECTRICAL ACTIVITY

Electrical activity in the Ventricle repolarizes.

ASSOIATED MOVEMENT

No movement.

1. Calculate the Rate2. Measure the Regularity (Rhythm) of

the R-Waves3. Examine the P-Waves4. Examine the P-R Interval5. Examine the QRS Complex

1. The Rate is normal.2. The Regularity

(Rhythm) of the R-Waves is abnormal.

3. The P-Waves are normal.

4. The P-R Intervals are abnormal.

5. The QRS Complex are normal. These findings will lead you to a type of

Heart Block. Comparing of the different types of Heart Blocks to the EKG we are looking at, we can see the type of block we have here is a 2nd Degree Type 1

Now, by comparing the answers from those 5 steps to a list of EKG rhythms and their descriptions, you can assume the type of beat or rhythm you are seeing. The example to the left is Sinus Arrhythmia!

Common Examples

AV Block (relatively common) › 1st degree AV block› Type 1 2nd degree AV block› Type 2 2nd degree AV block› 3rd degree AV block

SA Block (relatively rare)

EKG Characteristics: Prolongation of the PR interval, which is constant

All P waves are conducted

The Alan E. Lindsay ECG Learning Center ; http://medstat.med.utah.edu/kw/ecg/

Type 1 (Wenckebach)

EKG Characteristics: Progressive prolongation of the PR interval until a P wave is not conducted.

As the PR interval prolongs, the RR interval actually shortens

EKG Characteristics: Constant PR interval with intermittent failure to conduct

Type 2

EKG Characteristics: No relationship between P waves and QRS complexes

Relatively constant PP intervals and RR intervals

Greater number of P waves than QRS complexes

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EKG Characteristics: Presence of sinus P waves

Variation of the PP interval which cannot be qattributed to either SA nodal block or PACs

When the variations in PP interval occur in phase with respiration, this is considered to be a normal variant. When they are unrelated to respiration, they may be caused by the same etiologies leading to sinus bradycardia.

Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine, 7th ed., 2005.

Sinus bradycardia (rate of ~43 bpm) with a sinus pause

PJC: Premature Junctional Complexes  EKG Characteristics: Usually 60-100 beats per minute.

Rhythm: Irregular, due to PJC. P Wave: Can occur before, during, or after QRS complex. The P wave also can be inverted in lead II. PR Interval: Less than 0.12 seconds. QRS Complex: Normal in configuration and duration. The QRS complex just occurs sooner due to the PJC. ST Segment: Could be distorted if the P wave follows QTS complex. 

Most cases of atrial flutter are caused by a large reentrant circuit in the wall of the right atrium

EKG Characteristics: Biphasic “sawtooth” flutter waves at a rate of ~ 300 bpm

Flutter waves have constant amplitude, duration, and morphology through the cardiac cycle

There is usually either a 2:1 or 4:1 block at the AV node, resulting in ventricular rates of either 150 or 75 bpm

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Atrial fibrillation is caused by numerous wavelets of depolarization spreading throughout the atria simultaneously, leading to an absence of coordinated atrial contraction.

Atrial fibrillation is important because it can lead to:

Hemodynamic compromise

Systemic embolization

Symptoms

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EKG Characteristics. Rate: Atrial and ventricular usually normal. Rhythm: Irregular. P Wave: Ectopic P Wave. PR Interval: Usually normal, but could also be greater than 020 seconds. QRS Complex: normal configuration. ST Segment: Normal configuration. T Wave: Usually normal, but could have P Wave hidden in it, which distorts T Waves. 

Arrhythmias in which each normal sinus beat is followed by a premature contraction (PAC, PJC, or PVC).

Results in a couplet rhythm which can be detected by pulse or auscultation.

Generally benign

EKG Characteristics: The QRS fires too early. Rate: Normal for the intrinsic rhythm. Rhythm: Regular, except for the PVC.  P Wave: None. PR Interval: None. QRS Complex: Greater than 0.12 seconds.

A form of ventricular premature beats that have at least two different forms . Every form has its own constant interval from the normal QRS complex (coupling interval)

EKG Characteristics: Rate: 100-250 beats per minute. Rhythm: QRS complex and wide and bizarre. QRS Complex: This is the determining factor for VT. It must be greater than 0.12 seconds.

Rate unattainable P wave may be present, but obscured by ventricular waves QRS not apparent Conduction chaotic electrical activity Rhythm chaotic electrical activity

For more examples and information, check out:

http://www.skillstat.com/ECG_Sim_demo.html

http://www.rnceus.com/course_frame.asp?exam_id=16&directory=ekg

The End