Cardiac Dysrhythmia: Review
NSU Ron & Kathy Assaf College of Nursing
NUR 4120: advanced concepts of adult nursing
Reminder
Required Review before class
1. Chapter 25 (Assessment of Cardiovascular Function)
2. Students are expected to review the content of this presentation before class as this is integral to
understanding NUR 4120 dysrhythmia content.
Dysrhythmias

Disorder of the formation or conduction of the electrical impulse within the heart

Irregularity causes disturbances in:
o
HEART RATE
o
HEART RHYTHM
o
Both

Hemodynamic effects

Regular rate and rhythm required to circulate oxygenated blood and life-sustaining nutrients to body
organs

Diagnosed by analyzing the electrocardiogram

Named according to the site of origin
Normal Electrical Conduction
Review of Cardiac Conduction System
In the Normal Heart
Electrical impulses cause and are followed by the mechanical contraction of the heart:
**ELECTRICAL STIMULATION= Depolarization
**MECHANICAL STIMULATION= Systole
**ELECTRICAL RELAXATION= Repolarization
**MECHANICAL RELAXATION= Diastole
Influences on HR and Contractility
Sympathetic Nervous System Stimulation

Increases HR (positive chronotropic)

Increases conduction through AV node (positive dromotropy)

Increases force of myocardial contraction (positive inotropy)
Parasympathetic Nervous System Stimulation

Reduces HR

Reduces AV conduction

Reduces force of myocardial contraction
The Electrocardiogram
EKG/ECG is a graph tracing of the ELECTRICAL ACTIVITY OF THE HEART (Not the mechanical
activity)
Information obtainable from an EKG rhythm strip analysis:
1. Heart rate? Yes
2. Rhythm/regularity? Yes
3. Impulse conduction time intervals? Yes
4. Pumping action? No
5. Blood pressure? No
6. Cardiac Output? No
The Electrocardiogram
What else does the EKG reflect?

ISCHEMIA

INFARCTION (ST- elevate)

Electrolyte disturbances (Like hyperkalemia T wave elevation and Hypokalemia ST segment
depression)

Drug toxicity

Enlarged cardiac chambers
EKG Waveforms/Segments/Intervals
•
P wave
•
PR interval
•
QRS complex
•
ST segment
•
T wave
P wave

Represents the electrical impulse starting in the SA node and spreading through the atria. Not
P wave for atrium fibrillation. It is usual for an older adult in south Florida.

Atrial muscle depolarization

<0.11 seconds in length
PR Interval

Measured from the beginning of the P wave to the beginning of the QRS complex

Represents time needed for sinus node stimulation, atrial depolarization and conduction
through the AV node

0.12-0.20 seconds in length
QRS Complex
Represents ventricular depolarization
1. 1st NEGATIVE deflection: Q wave
2. 1st POSITIVE deflection: R wave
3. 1st NEGATIVE deflection after the r wave:
S wave
<0.12 seconds in length
ST Segment

Represents early ventricular repolarization

Lasts from the end of the QRS complex to the beginning of the T wave

Normally isoelectric

Analyzed above or below the baseline
Note: ST-SEGMENT ELEVATION usually indicates a total blockage of the involved coronary artery and that
the heart muscle is currently dying. Non-STEMI HEART ATTACKS usually involve an artery with partial
blockage, which does not cause as much heart muscle damage. HYPERKALEMIA.
ST DEPRESSION is a specific outcome that may appear in a person's ECG results. It occurs when the ST
segment appears abnormally low and sits below the baseline in a person's results. An ST depression can occur
due to medical conditions including HYPOKALEMIA, MYOCARDIAL ISCHEMIA, ACTIVE MI, and a left
bundle branch block.
T wave

Represents ventricular muscle repolarization

Resting phase

Follows the QRS complex; usually in the same direction as the QRS
General Rules in Identifying Heart Rhythms
•
Rapid assessment of your patient first
•
Read every strip from left to right, starting at the beginning of the strip.
•
Apply a systematic approach
•
Avoid shortcuts and assumptions
•
Ask and answer each question in the five-step approach…this is important for consistency!
Before the EKG, look at the patient first and do systematic
Systematic Analysis of the ECG
1. Identify P wave: is there a p-wave before every QRS? A-FIB = NO P WAVE.
2. Identify the P wave shape: consistent? Upright?
3. Determine each PR interval: Consistent? Irregular but with a pattern? Irregular?
4. Identify the QRS: Duration consistent? Shape consistent?
5. Evaluate the ST segment: Isoelectric? Depression vs. Elevation? Peaked?
6. Identify the T wave: Upright? Inverted?
7. Identify ventricular rate and rhythm.
Heart Rate Determination
Regular

The minute strip contains 300 large boxes (1500 small boxes)

Count the number of small boxes within an RR interval and divide 1,500 by that number
Irregular

Less accurate method:

The top of the ECG paper is marked at 3-second intervals (15 large boxes horizontally)

Count the number of RR intervals (not QRS complexes) in 6-seconds and multiply that
number by 10
Heart Rate Determination
1500 Method
Count the boxes in between R to R and divide by 300.
Heart Rhythm Determination

RR interval used to determine the ventricular rhythm

PP interval used to determine the atrial rhythm

If intervals are the same: the regular rhythm

If intervals are different: irregular rhythm
Sometimes the NCLEX will give you the normal rhythm, and you will continuously monitor the patient.
Normal EKG
Abnormal EKG
Lead II ST elevation means the patient has a heart attack.