EKG QRS complexes

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5 steps of examining EKGs

1. Rate
2. Regularity
3. P wave
4. PR interval
5. QRS complex

A positive impulse immediately following the R wave is called:

R prime (R')

S prime (S'), a double negative impulse immediately following the S wave is called double S prime (S").

A double positive impulse immediately following the R wave is called

Double R prime (R'')

A negative impulse immediately following the S wave is called

S prime (S')

A double negative impulse immediately following the S wave is called

Double S prime (S")

Normal duration of QRS complex

0.06-0.12 sec

Normal duration of P wave

0.06-0.10 sec

Normal duration of PR interval

0.12-0.20 sec

Abnormal pacemaker sites bringing about irregular QRS complexes

SA node, an ectopic pacemaker in the atria, AV junction, bundle branches, Purkinje network, or ventricular myocardium

Causes of abnormal QRS complexes

Ventricular hypertrophy
Intraventricular conduction disturbance
Aberrant ventricular conduction
Ventricular preexcitation
Ventricular ectopic or escape pacemaker
Ventricular pacing by cardiac pacemaker

Tall QRS complexes are generally caused by:

Hypertrophy of one or both ventricles
An abnormal pacemaker
Aberrantly conducted beat

Low voltage QRS complexes are usually caused by

Obese patients
Hyperthyroid patients
Pleural effusion

Wide Bizarre QRS complexes (of supra ventricular origin) are often caused by

Often result from intraventricular conduction defect
Typically a result of right or left bundle branch block

Ventricular Preexcitation
Definition
Causes
May Produce/present on EKG how?

Premature depolarization of the ventricles
Occurs when an impulse arising from a supraventricular site travels through abnormal accessory conduction pathways to the ventricles
May produce:
Wider than normal QRS complexes
Abnormal slurring at its onset (called the delta wave)

Cardiac pacemaker induced QRS complexes

Generally ≥ 0.12 seconds in width and appear bizarre
Preceding each pacemaker-induced QRS complex is a pacemaker spike

What are Premature Ventricular Complexes (PVC)?

Early beats that arise from the ventricles before SA node can fire

When does idioventricular rhythm occur?

Arises from the ventricles when stimuli from the SA node, AV junction fail to reach the ventricles or their rate falls to less than that of the ventricles.

May present as a wide QRS complex

True/False: Wide QRS complexes may be seen with ventricular tachycardia

True

How many PVCs in a row are considered VT?

3 or more in a row
May come in bursts of 6 to10 complexes or be sustained

What is the HR range in sustained VT?

100-250 bpm

What is it called when you have for example 3 PVCs, then 3 regular, then 3 PVCs then 3 regular for example

Nonsustained VT

Explain the presentation of torsades de points

Appears as a series of QRS complexes that rotate about the baseline between upright deflections and downward deflections
This produces a "spindle-like" appearance of the ECG rhythm

True/False: Wide QRS complexes are seen in 3rd degree AV heart block

True

What do wide, large (bizarre looking) QRS complexes indicate about the ventricles?

The ventricles are likely being paced by a ventricular focus.

Ventricular fibrillation causes the heart muscle to quiver, instead of contracting and pumping blood throughout the body.
what is considered the definitive treatment of vent. fib that must be delivered promptly?

Defibrillation

Explain Ventricular Fibrillation on an EKG

Represents erratic firing of multiple sites in the ventricles
On ECG monitor it looks like a chaotic, wavy line with no discernible waveforms

What is the 4th step in analyzing EKGs?

QRS complexes (0.06-0.12 sec)

What is the 1st step in analyzing EKGs?

Rate

What is the 2nd step in analyzing EKGs?

Regularity

What is the 3rd step in analyzing EKGs?

P wave (0.06- 0.12 sec)

What is the 5th step in analyzing EKGs?

PR interval (0.12-0.20 sec)

Where do you start and end when measuring QRS complexes?

QRS complex starts where first wave of complex begins to move away from the baseline. It ends at the point where the last wave of the complex transitions into the ST segment.

Amplitude of a normal QRS complex

5-30 mm

What is the duration of an abnormal QRS complex?

Greater than 0.12sec

Wide QRS complexes may be seen in:

Aberrant conduction
Ventricular preexcitation
Cardiac pacemaker

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