Basic EKG Refresher

Basic Cardiac
Rhythms –
Identification
and Response

Module 1
ANATOMY, PHYSIOLOGY, &
ELECTRICAL CONDUCTION

Objectives

▪ Describe the normal cardiac anatomy and physiology and normal
electrical conduction through the heart.

▪ Identify and relate waveforms to the cardiac cycle.

Cardiac Anatomy

▪ 2 upper chambers

▪ Right and left atria

▪ 2 lower chambers

▪ Right and left ventricle

▪ 2 Atrioventricular valves (Mitral &
Tricuspid)

▪ Open with ventricular diastole
▪ Close with ventricular systole

▪ 2 Semilunar Valves (Aortic & Pulmonic)

▪ Open with ventricular systole
▪ Open with ventricular diastole

The Cardiovascular System

▪ Pulmonary Circulation

▪ Unoxygenated – right side of the heart

▪ Systemic Circulation

▪ Oxygenated – left side of the heart

Anatomy
Coronary Arteries

How The Heart Works

Anatomy
Coronary Arteries

▪ 2 major vessels of the coronary circulation

▪ Left main coronary artery

▪ Left anterior descending and circumflex branches

▪ Right main coronary artery

▪ The left and right coronary arteries originate at the base of the
aorta from openings called the coronary ostia behind the aortic
valve leaflets.

Physiology
Blood Flow

Unoxygenated blood flows from
inferior and superior vena cava

Right Atrium
Tricuspid Valve
Right Ventricle
Pulmonic Valve

Lungs
Through Pulmonary system

Physiology
Blood Flow

Oxygenated blood flows from the
pulmonary veins
Left Atrium
Mitral Valve
Left Ventricle
Aortic Valve

Systemic Circulation

▪ Blood Flow Through The Heart
▪ Cardiology Rap

Physiology

▪ Cardiac cycle

▪ Represents the actual time sequence between ventricular contraction
and ventricular relaxation

▪ Systole

▪ Simultaneous contraction of the ventricles

▪ Diastole

▪ Synonymous with ventricular relaxation
▪ When ventricles fill passively from the atria to 70% of blood capacity

Physiology

▪ Heart rate (HR)

▪ Number of contractions (beats per minute)
▪ Normal heart rate is 60 – 100 beats per minute (bpm)

▪ Stroke volume (SV)

▪ Volume of blood being pumped out of ventricles in a single beat or
contraction

▪ Normal stroke volume is 60 – 130 mL

Physiology

▪ Cardiac output (CO)

▪ Amount of blood pumped by the left ventricle in one minute
▪ Normal cardiac output is 4 – 8 L/min

Cardiac Output =
Stroke Volume x Heart Rate

**Our Swan boxes give us a continuous cardiac output reading!

Physiology

▪ Pre-load

▪ Volume and stretch of the ventricular myocardium at the end of
diastole

▪ After-load

▪ Amount of pressure against which the left ventricle must work during
systole to open the aortic valve

▪ Clinically measure by systolic blood pressure

Normal Electrical Conduction System

SA node
Inter-nodal pathways
AV node
Bundle of his
Left & Right bundle branches
Purkinje fibers

The SA Node and the AV Node

Electrical Conduction System
EKG Waveforms

One complete cardiac cycle =
P, Q, R, S, (QRS complex),
and T wave

Electrical Conduction System
EKG Waveforms

▪ P wave

▪ Atrial depolarization (contraction)

▪ QRS Complex

▪ Ventricular depolarization, atrial repolarization

▪ T wave

▪ Ventricular repolarization (resting phase)

Module 2
INTERPRETING EKG
RHYTHM STRIPS

Objectives

▪ Utilize a systematic process when approaching the interpretation
of the EKG.

▪ Identify normal and abnormal components on the EKG.

EASI Lead Color Code
Lead Placement
E Brown: Lower sternum (5th intercostal
space)

A Red: Left mid-axillary line (5th
intercostal space)

S Black: Upper sternum (just below sternal
angle)

I White: Right mid-axillary line (5th
intercostal space)

Green: Anywhere

Electrical Conduction Systems
EKG Waveforms

Reading EKG Graph Paper

Graph paper allows a visual
measurement of:

▪ Time (rate)

▪ Measured on the horizontal line

▪ Amplitude (voltage)

▪ Measured on the vertical line

Reading EKG Graph Paper

Paper divided into small squares:
▪ Width = 1 millimeter (mm)
▪ Time interval = 0.04 seconds

▪ 1 small square = 0.04 seconds

Reading EKG Graph Paper

Darker lines divide paper into every 5th
square vertically and horizontally:

▪ Large squares measure 5 mm in
height and width

▪ Represents time interval of 0.20 seconds
▪ 25 small squares in each large square

▪ 1 large square = 0.20 seconds

Interpreting EKG Rhythm Strips

▪ First and most important

▪ ASSESS YOUR PATIENT!!

▪ Read every strip from left to right, starting at the beginning of the
strip

▪ Apply the five-step systematic approach that you will learn in this
module for consistency with each strip that you interpret

Interpreting EKG Rhythm Strips
The Five Step Approach

The five-step approach, in order of application, includes analysis of
the following:

1. Heart rate
2. Heart rhythm
3. P wave
4. PR interval
5. QRS complex

Interpreting EKG Rhythm Strips
Step 1 – Heart Rate

▪ Count the number of electrical impulses as represented by PQRST
complexes conducted through the myocardium in 60 seconds (1 minute)

▪ Atrial rate: Count the number of P waves
▪ Ventricular rate: Count the number of QRS complexes

Interpreting EKG Rhythm Strips
Step 1 – Heart Rate

Methods to determine heart rate
▪ The 6 second method

▪ Denotes a 6 second interval on EKG strip
▪ Strip is marked by 3 or 6 second tick marks on the top or bottom of the graph

paper
▪ Count the number of QRS complexes occurring within the 6 second interval,

and then multiply that number by 10

▪ Using rate determination chart

▪ More accurate calculation of HR
▪ Preferred method
▪ Must use this method for the test!!

Interpreting EKG Rhythm Strips
Step 1 – Heart Rate

▪ 6 second method

Interpreting EKG Rhythm Strips
Step 1 – Heart Rate

▪ Using rate determination chart

▪ Count spaces between R to R
▪ Find number of spaces on the chart

to determine the rate

Interpreting EKG Rhythm Strips
Step 1 – Heart Rate

▪ Example:

1. Find an R to R 2. Count the small boxes between the R’s = 15 3. On the chart find “15 spaces” = 100bpm

Interpreting EKG Rhythm Strips
Step 2 – Rhythm

▪ Rhythm

▪ A sequential beating of the heart as a result of the generation of electrical
impulses

▪ Classified as:

▪ Regular pattern: Interval between the R waves is regular
▪ Irregular pattern: Interval between the R waves is not regular

Interpreting EKG Rhythm Strips
Step 2 – Rhythm

▪ Measuring a Regular Rhythm

▪ Measure the intervals between R waves (measure from R to R)

▪ If the intervals vary by less than 0.06 seconds or 1.5 small boxes, the rhythm is
considered to be regular

Interpreting EKG Rhythm Strips
Step 2 – Rhythm

▪ Measuring an Irregular Rhythm

▪ If the intervals between the R waves (from R to R) are variable by greater than
0.06 seconds or 1.5 small boxes, the rhythm is considered to be irregular

Interpreting EKG Rhythm Strips
Step 3 – P Wave

▪ P wave is produced when the left and right atria depolarize

▪ First deviation from the isoelectric line
▪ Should be rounded and upright
▪ P wave is the SA node pacing or firing at regular intervals
▪ This pattern is referred to as a sinus rhythm

Interpreting EKG Rhythm Strips
Step 3 – P Wave

▪ P wave: 5 questions to ask

1. Are P waves present?
2. Are P waves occurring regularly?
3. Is there one P wave present for every QRS complex present?
4. Are the P waves smooth, rounded, and upright in appearance, or are they

inverted?
5. Do all P waves look similar?

Interpreting EKG Rhythm Strips
Step 4 – PR Interval

▪ Measures the time interval from the
onset of atrial contraction to onset of
ventricular contraction

▪ Measured from onset of P wave to the
onset of the QRS complex

▪ Normal interval is 0.12–0.20 seconds
(3-5 small squares)

Measuring PR Interval:

Red lines indicate where calipers would be placed to measure PR interval

Interpreting EKG Rhythm Strips
Step 4 – PR Interval

▪ PR interval: 3 questions to ask

1. Are the PR intervals greater than 0.20 seconds?
2. Are the PR intervals less than 0.12 seconds?
3. Are the PR intervals consistent across the EKG strip?

Interpreting EKG Rhythm Strips
Step 5 – QRS Complex

▪ The QRS complex presents
depolarization or contraction of the
ventricles

▪ Q wave

▪ First negative or downward deflection of this
large complex

▪ R wave

▪ First upward or positive deflection following the
P wave (tallest waveform)

▪ S wave

▪ The sharp, negative or downward deflection
that follows the R wave

▪ Normal interval is 0.06-0.12 seconds
(1 ½ to 3 small boxes)

Measuring QRS complex:

Red lines indicate where calipers should be placed to measure QRS

Interpreting EKG Rhythm Strips
Step 5 – QRS Complex

▪ QRS complex: 3 questions to ask

1. Are the QRS complexes greater than 0.12 seconds (in width)?
2. Are the QRS complexes less than 0.06 seconds (in width)?
3. Are the QRS complexes similar in appearance across the EKG strip?

Interpreting EKG Rhythm Strips
Practice Strip

1. HR = # of boxes between R’s = 19 spaces = 79bpm
2. Rhythm = regular or irregular = regular (R-R’s are equal)
3. P waves = P wave for every QRS? = yes
4. PR interval = measure from beginning of P to beginning of QRS = 0.16
5. QRS = measure from start of Q to end of S = 0.08

Interpreting EKG Rhythm Strips
T Wave

▪ Produced by ventricular repolarization
or relaxation

▪ Commonly seen as the first upward or
positive deflection following the QRS
complex

Interpreting EKG Rhythm Strips
U Wave

▪ Usually not visible on EKG strips
▪ If visible, typically follows the T wave
▪ Appears much smaller than T wave,

rounded, upright, or positive deflection
is they are present
▪ Cause or origin not completely
understood
▪ May indicate hypokalemia

Interpreting EKG Rhythm Strips
Artifact

▪ EKG waveforms from sources outside the heart
▪ Interference is seen on the monitor or EKG strip
▪ 4 causes

▪ Patient movement (most common)
▪ Loose or defective electrodes (fuzzy baseline)
▪ Improper grounding (60 cycle interference)
▪ Faulty EKG apparatus

Module 3
SINUS RHYTHMS

Objectives

▪ Recognize sinus dysrhythmias on EKG and relate cause,
significance, symptoms, and treatment.

Sinus Rhythms

♥ Rhythms that originate in the sinoatrial node (SA node)

♥ 5 Common Variations of a sinus rhythm:

• Normal sinus rhythm (60 – 100 bpm)
• Sinus bradycardia (< 60 bpm)
• Sinus tachycardia ( >100 bpm)
• Sinus arrhythmia (60 – 100 bpm)
• Sinus pause/arrest

Normal Sinus Rhythm

Sinus rhythm is the normal regular rhythm of the heart set by the natural
pacemaker of the heart called the sinoatrial node. It is located in the wall of the
right atrium. Normal cardiac impulses start there and are transmitted to the
atria and down to the ventricles.

5 Steps to Identify Normal Sinus Rhythm

1. What is the rate? 60-100 beats per minute

2. What is the rhythm? Atrial rhythm regular
Ventricular rhythm regular
3. Is there a P wave before each QRS?
Are P waves upright and uniform? Yes

4. What is the length of the PR interval? Yes
0.12-0.20 seconds (3-5 small squares)

5. Do all QRS complexes look alike? Yes
What is the length of the QRS complexes? 0.06-0.12 seconds (1 ½ to 3 small squares)