HEART RHYTHM INTERPRETATION BASIC ECGS

HEART RHYTHM INTERPRETATIONBASIC ECGS

MARCH 2019

DISCLOSURES

This presentation is provided for general educational purposes only and should not be considered the exclusive source for this type of information. At all times, it is the professional responsibility of the practitioner to exercise independent clinical judgment in a particular situation.

OBJECTIVES

Correlate the normal cardiac conduction pathway to the mechanical function of the heart and to the recorded tracing on ECG paper

In a normal sinus beat, explain the normal range of a P-R interval and the width of the QRS complex

List the key characteristics of normal sinus rhythm in terms of rate, regularity, and rhythm

Describe typical rate ranges for basic arrhythmias

Analyze the rhythm of a given ECG by describing the relationship between the P wave and QRS complex and determine the regularity/irregularity

CARDIAC CONDUCTION

CARDIAC CONDUCTION

How does conduction appear on an ECG?

Cardiac conduction results in the mechanical beating of the heart. Mechanical beating is created by electrical

impulses moving throughout the conduction system

Specific waves that appear on an ECG correspond both to the mechanical and the electrical depolarization (or repolarization) of a particular area of the heart.

CARDIAC CONDUCTION: CYCLE INITIATION








ECG INTERPRETATION

LABEL THE ECG - REVIEW

P – Wave: Atrial Depolarization.

• Can be positive, biphasic, negative.

QRS Complex: Ventricular Depolarization.

• Q – Wave: 1st negative deflection wave before R-Wave.

• R – Wave: The positive deflection wave.

• S – Wave: 1st negative deflection wave after R – wave.

T – Wave: Ventricular Repolarization.

• Can be positive, biphasic, negative.

INTERVAL MEASUREMENT

Time between waves is an important characteristic in determining a normal heart rhythm (measured in milliseconds). An interval outside of the normal duration can be an indicator of heart problems.

Two key intervals in particular aid in the interpretation of ECGs.

1. PR interval: Normal is 120 – 200ms

2. QRS interval: Normal is defined as

60 – 100ms, but an interval up to

120ms can be considered clinically

normal.

READING ECG SQUARESINTERVALS & TIMING

Horizontal axis – time:

Each small square = 40 ms

Each block = 200 ms (5 each 40 ms squares)

Converting this to a rate in bpm:

1 min = 60,000 ms, so:

60,000/ms = bpm

60,000/600ms = 100 bpm

Pacemakers and ICDs calculate intervals (ms), not in rates (bpm)

CALCULATING HEART RATE

1) Measure Cycle Length (CL). 1) (# small boxes from R – R) (40ms) = CL .

2) Calculate HR• 60,000/CL = “x” BPM

(20) x (40ms) = 800ms

60,000/800 = 75 bpm

(25) x (40ms) = 1000ms

60,000/1000 = 60 bpm

(12) x (40ms) = 480ms

60,000/480 = 125 bpm

RATE – 6 SECOND RULE

1) Count the # of complexes on a 6 second strip.

2) Multiply by 10 to get approx. “bpm”

0 1 2 3 4 5 6 7

Approximately 70 bpm

Match the term on the left with the description on the right

P-R Interval

AV Node

Purkinje Network

Bundle BranchesNormally 120-200 ms

Escape rate is 40-60 bpm

Depolarizes the Ventricles

Connect His bundle to Purkinje network

KNOWLEDGE CHECKPOINT

Convert the following values to milliseconds or bpm:

50 bpm =

110 bpm =

750 ms =

857 ms =

65 bpm =

85 bpm =


ECG INTERPRETATION: OVERVIEW

ECG interpretation can be simplified if approached one step at a time.

Understanding and practicing three basic steps will aid in quickly and accurately

identifying any given rhythm.

Step 1—Calculate the RATE of an ECG tracing

Step 2—Determine the REGULARITY or irregularity of a given ECG

Step 3—Analyze the RHYTHM of a given ECG by describing the relationship between

the P waves and QRS complexes

ECG INTERPRETATION: RATE

Rate generally refers to the ventricular rate or R-waves.

Resting rate is typically 60 – 100 bpm.

Focus is placed on the QRS complex.

ECG INTERPRETATION: REGULARITY

• PR intervals should remain consistent.

• PR interval should be 120-200 ms.

• The PR interval is the time from beginning of the P-wave to the beginning of the QRS complex.

• Regularity is the consistency of the interval between each QRS complex.

ECG INTERPRETATION: RHYTHM

PR ratio is the number of P-waves compared to QRS complexes.

Every P-wave should have an associated QRS complex.


Is the rate normal or abnormal?

EXAMPLE RHYTHM STRIPS

NORMAL SINUS RHYTHM

Rate 60-100 bpm

P-P Regularity Regular

R-R Regularity Regular

P wave Present

P:QRS Ratio 1:1, associated

PR Interval Normal

QRS Width Normal

SINUS BRADYCARDIA

Rate Less than 60 bpm



P wave Present


PR Interval Normal, gradually lengthens with HR decrease

QRS Width Normal

SINUS TACHYCARDIA

Rate Greater than 100 bpm, Gradual onset



P wave Present


PR Interval Normal, gradually shortens with HR increase

QRS Width Normal

SINUS ARRHYTHMIA

Rate 60-100 bpm

P-P Regularity Irregular

R-R Regularity Irregular

P wave Present


PR Interval Normal

QRS Width Normal

SINUS PAUSE/ARREST

Rate Varies



P wave Present, except during pause


PR Interval Normal

QRS Width Normal

SINUS NODE EXIT BLOCK

Rate Varies



P wave Present, except during dropped beats


PR Interval Normal

QRS Width Normal

Rate Depends on underlying sinus rate



P wave Present, may be different morphology during PAC


PR Interval Normal, varies during PAC

QRS Width Normal

SINUS RHYTHM W/ PAC(PREMATURE ATRIAL CONTRACTION)

ATRIAL TACHYCARDIA

Rate 100-180 bpm, Sudden onset



P wave Morphology will differ from sinus p-wave


PR Interval Interval of ectopic focus will differ from sinus PR

QRS Width Normal, but can develop aberrant (wide) complexes

MULTIFOCAL ATRIAL TACHYCARDIA

Rate Greater than 100 bpm

P-P Regularity Irregularly irregular

R-R Regularity Irregularly irregular

P wave At least 3 different p-wave morphologies


PR Interval Varies

QRS Width Normal

ATRIAL FLUTTER

Atrial RateVentricular Rate

Atrial Rate commonly 250-350 bpmVentricular Rate will vary with conduction


R-R Regularity Usually regular, but may be variable

P wave “Saw-tooth” p-wave morphology

P:QRS Ratio Varies, can be 1:1, 2:1, 3:1, 4:1, etc.

PR Interval Varies

QRS Width Normal

ATRIAL FIBRILLATION

Rate Varies, ventricular response can be fast or slow

P-P Regularity Chaotic atrial activity


P wave No discernable p-waves

P:QRS Ratio None

PR Interval None

QRS Width Normal, but can develop aberrant (wide) complexes

JUNCTIONAL RHYTHM

Rate 40-60 bpm

P-P Regularity None, or Regular if antegrade or retrograde


P wave Variable (none, antegrade, or retrograde)

P:QRS Ratio None, or 1:1 if antegrade or retrograde

PR Interval None, short, or retrograde

QRS Width Normal

Rate60-100 bpm (Accelerated Junctional Rhythm)Greater than 100 bpm (Supraventricular Tachycardia)

P-P Regularity None, or Regular if antegrade or retrograde


P wave Variable (none, antegrade, or retrograde)

P:QRS Ratio None, or 1:1 if antegrade or retrograde

PR Interval None, short, or retrograde

QRS Width Normal

ACCELERATED JUNCTIONAL RHYTHMSUPRAVENTRICULAR TACHYCARDIA (SVT)

Rate Depends on underlying sinus rate



P wave No P-waves with the PVC

P:QRS Ratio No P-waves with the PVC

PR Interval None

QRS Width Wide complex (≥ 0.12 s).

SINUS RHYTHM W/ PVC(PREMATURE VENTRICULAR CONTRACTION)

VENTRICULAR RHYTHM

Rate 20-40 bpm

P-P Regularity None


P wave None

P:QRS Ratio None

PR Interval None


ACCELERATED VENTRICULAR RHYTHM

Rate 40-100 bpm

P-P Regularity None


P wave None

P:QRS Ratio None

PR Interval None


VENTRICULAR TACHYCARDIA

Rate 100-200 bpm

P-P Regularity Variable


P wave Dissociated atrial rate

P:QRS Ratio Variable

PR Interval None


FAST VT (VENTRICULAR FLUTTER)

Rate 200-300 bpm

P-P Regularity None


P wave None

P:QRS Ratio None

PR Interval None


POLYMORPHIC VT (TORSADES)

Rate 200-250 bpm

P-P Regularity None


P wave None

P:QRS Ratio None

PR Interval None

QRS Width Variable with wide complexes

VENTRICULAR FIBRILLATION

Rate Indeterminate

P-P Regularity None

R-R Regularity Chaotic Rhythm

P wave None

P:QRS Ratio None

PR Interval None

QRS Width None

SINUS RHYTHMW/ 1ST DEGREE AV BLOCK

Rate Depends on underlying rhythm



P wave Present, Normal


PR Interval Prolonged, > 0.20 s

QRS Width Normal



R-R Regularity Regularly irregular

P wave Present

P:QRS Ratio Variable; 2:1, 3:2, 4:3, etc

PR Interval Variable, gradually lengthens until dropped

QRS Width Normal

SINUS RHYTHMW/ 2ND DEGREE AV BLOCK TYPE I (WENCKEBACH)



R-R Regularity Regularly irregular

P wave Present

P:QRS Ratio Variable; 2:1, 3:2, 4:3, etc

PR Interval Normal for conducted beats

QRS Width Normal

SINUS RHYTHMW/ 2ND DEGREE AV BLOCK TYPE II

Atrial RateVentricular Rate

Atrial rate is the underlying rhythm (i.e, Sinus, Atrial Fib, etc.)Ventricular rate is from the dissociated escape rhythm



P wave Present

P:QRS Ratio Variable, dissociated

PR Interval Variable, No pattern

QRS Width Normal (Junctional escape rhythm)Wide (Ventricular escape rhythm)

SINUS RHYTHMW/ 3RD DEGREE AV BLOCK (COMPLETE HEART BLOCK)

Rate Depends on the underlying sinus rhythm



P wave Present


PR Interval Normal

QRS Width Wide (> 0.12 ms)

SINUS RHYTHM W/ BBB(BUNDLE BRANCH BLOCK)

Rate Depends on the underlying Atrial Fibrillation, Ventricular rate can be fast or slow.

P-P Regularity Chaotic atrial activity


P wave Present

P:QRS Ratio None

PR Interval None

QRS Width Wide (> 0.12 ms)

ATRIAL FIB W/ BBB(BUNDLE BRANCH BLOCK)

Identify the Rhythm:

A. Ventricular Tachycardia

B. Sinus Bradycardia

C. Complete Heart Block

D. Atrial Fibrillation

E. Ventricular Fibrillation






























PRACTICE RHYTHM STRIPS

On the following rhythm strips in subsequent slides, determine rhythm presented.

Consider the following: What is the atrial and ventricular rate? Is it normal? What is the regularity (P-P and R-R) Are any AV and/or Bundle branch blocks present? Does the rhythm have a clinical significance?

Answers can be found in the notes section of the slides.













































KEY LEARNING POINTS

Cardiac conduction results in the mechanical beating of the heart, which is created by electrical impulses moving throughout the conduction system. Specific waves that appear on an ECG correspond both to the mechanical and

electrical depolarization/repolarization of a particular area of the heart.• P-wave (atrial depolarization), QRS (ventricular depolarization), T-wave (ventricular

repolarization)

Time between waves is an important characteristic in determining a normal heart rhythm (measured in milliseconds).1. PR interval: Normal is 120 – 200ms2. QRS interval: Normal is 60 – 100ms

Understanding and practicing 3 basic steps will aid in quickly and accurately identifying any given rhythm of an ECG tracing:1. Calculate the RATE2. Determine the REGULARITY or irregularity3. Analyze the RHYTHM by describing relationship between P waves and QRS

complexes

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March 2019

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HEART RHYTHM INTERPRETATION BASIC ECGS