EKG Basics OVERVIEW OF EKG AND TELEMETRY. Outline 1. Review of the conduction system 2. EKG...

EKG BasicsEKG Basics

OVERVIEW OF EKG ANDOVERVIEW OF EKG AND

TELEMETRYTELEMETRY

OutlineOutline

1.1. Review of the conduction systemReview of the conduction system

2.2. EKG waveforms and intervalsEKG waveforms and intervals

3.3. EKG leadsEKG leads

4.4. Determining heart rateDetermining heart rate

5.5. Determining QRS axisDetermining QRS axis

The Normal Conduction SystemThe Normal Conduction System

What is an EKG?What is an EKG?

The electrocardiogram (EKG) is a The electrocardiogram (EKG) is a representation of the electrical events of the representation of the electrical events of the cardiac cycle.cardiac cycle.

Each event has a distinctive waveform, the Each event has a distinctive waveform, the study of which can lead to greater insight study of which can lead to greater insight into a patient’s cardiac pathophysiology.into a patient’s cardiac pathophysiology.

What types of pathology can we What types of pathology can we identify and study from EKGs?identify and study from EKGs?

ArrhythmiasArrhythmiasMyocardial ischemia and infarctionMyocardial ischemia and infarctionPericarditisPericarditisChamber hypertrophyChamber hypertrophyElectrolyte disturbances (i.e. Electrolyte disturbances (i.e. hyperkalemia, hypokalemia)hyperkalemia, hypokalemia)Drug toxicity (i.e. digoxin and drugs which Drug toxicity (i.e. digoxin and drugs which prolong the QT interval)prolong the QT interval)

Waveforms and IntervalsWaveforms and Intervals

EKG LeadsEKG Leads

Leads are electrodes which measure the Leads are electrodes which measure the difference in electrical potential between difference in electrical potential between either:either:

1. Two different points on the body (bipolar leads)1. Two different points on the body (bipolar leads)

2. One point on the body and a virtual reference point 2. One point on the body and a virtual reference point with zero electrical potential, located in the center of with zero electrical potential, located in the center of the heart (unipolar leads)the heart (unipolar leads)

EKG LeadsEKG Leads

The standard EKG has 12 leads:The standard EKG has 12 leads: 3 Standard Limb Leads

3 Augmented Limb Leads

6 Precordial Leads

The axis of a particular lead represents the viewpoint from The axis of a particular lead represents the viewpoint from which it looks at the heart.which it looks at the heart.

Standard Limb LeadsStandard Limb Leads

Augmented Limb LeadsAugmented Limb Leads

All Limb LeadsAll Limb Leads

Precordial LeadsPrecordial Leads

Adapted from: www.numed.co.uk/electrodepl.html

Precordial LeadsPrecordial Leads

Summary of LeadsSummary of Leads

Limb LeadsLimb Leads Precordial LeadsPrecordial Leads

BipolarBipolar I, II, IIII, II, III(standard limb leads)(standard limb leads)

--

UnipolarUnipolar aVR, aVL, aVF aVR, aVL, aVF (augmented limb leads)(augmented limb leads)

VV11-V-V66

Arrangement of Leads on the EKGArrangement of Leads on the EKG

Anatomic GroupsAnatomic Groups(Septum)(Septum)

Anatomic GroupsAnatomic Groups(Anterior Wall)(Anterior Wall)

Anatomic GroupsAnatomic Groups(Lateral Wall)(Lateral Wall)

Anatomic GroupsAnatomic Groups(Inferior Wall)(Inferior Wall)

Anatomic GroupsAnatomic Groups(Summary)(Summary)

Determining the Heart RateDetermining the Heart Rate

Rule of 300Rule of 300

10 Second Rule10 Second Rule

Rule of 300Rule of 300

Take the number of “big boxes” between Take the number of “big boxes” between neighboring QRS complexes, and divide this neighboring QRS complexes, and divide this into 300. The result will be approximately into 300. The result will be approximately equal to the rateequal to the rate

Although fast, this method only works for Although fast, this method only works for regular rhythms.regular rhythms.

What is the heart rate?What is the heart rate?

(300 / 6) = 50 bpm

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(300 / ~ 4) = ~ 75 bpm

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(300 / 1.5) = 200 bpm

The Rule of 300The Rule of 300

It may be easiest to memorize the following table:It may be easiest to memorize the following table:

# of big # of big boxesboxes

RateRate

11 300300

22 150150

33 100100

44 7575

55 6060

66 5050

10 Second Rule10 Second Rule

As most EKGs record 10 seconds of rhythm per As most EKGs record 10 seconds of rhythm per page, one can simply count the number of beats page, one can simply count the number of beats present on the EKG and multiply by 6 to get the present on the EKG and multiply by 6 to get the number of beats per 60 seconds.number of beats per 60 seconds.

This method works well for irregular rhythms.This method works well for irregular rhythms.


33 x 6 = 198 bpm

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

The QRS AxisThe QRS Axis

The QRS axis represents the net overall The QRS axis represents the net overall direction of the heart’s electrical activity.direction of the heart’s electrical activity.

Abnormalities of axis can hint at:Abnormalities of axis can hint at:

Ventricular enlargementVentricular enlargement

Conduction blocks (i.e. hemiblocks)Conduction blocks (i.e. hemiblocks)

The QRS AxisThe QRS Axis

By near-consensus, the normal QRS axis is defined as ranging from -30° to +90°.

-30° to -90° is referred to as a left axis deviation (LAD)

+90° to +180° is referred to as a right axis deviation (RAD)

Determining the AxisDetermining the Axis

The Quadrant ApproachThe Quadrant Approach

The Equiphasic ApproachThe Equiphasic Approach

Determining the AxisDetermining the Axis

Predominantly Positive

Predominantly Negative

Equiphasic

The Quadrant ApproachThe Quadrant Approach1. Examine the QRS complex in leads I and aVF to determine 1. Examine the QRS complex in leads I and aVF to determine

if they are predominantly positive or predominantly if they are predominantly positive or predominantly negative. The combination should place the axis into one negative. The combination should place the axis into one of the 4 quadrants below.of the 4 quadrants below.

The Quadrant ApproachThe Quadrant Approach2. In the event that LAD is present, examine lead II to 2. In the event that LAD is present, examine lead II to

determine if this deviation is pathologic. If the QRS in II is determine if this deviation is pathologic. If the QRS in II is predominantly positive, the LAD is non-pathologic (in other predominantly positive, the LAD is non-pathologic (in other words, the axis is normal). If it is predominantly negative, it words, the axis is normal). If it is predominantly negative, it is pathologic. is pathologic.

Quadrant Approach: Example 1Quadrant Approach: Example 1

Negative in I, positive in aVF RAD

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

Quadrant Approach: Example 2Quadrant Approach: Example 2

Positive in I, negative in aVF Predominantly positive in II

Normal Axis (non-pathologic LAD)

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

The Equiphasic ApproachThe Equiphasic Approach

1. Determine which lead contains the most equiphasic QRS 1. Determine which lead contains the most equiphasic QRS complex. The fact that the QRS complex in this lead is complex. The fact that the QRS complex in this lead is equally positive and negative indicates that the net equally positive and negative indicates that the net electrical vector (i.e. overall QRS axis) is perpendicular electrical vector (i.e. overall QRS axis) is perpendicular to the axis of this particular lead.to the axis of this particular lead.

2. Examine the QRS complex in whichever lead lies 90° 2. Examine the QRS complex in whichever lead lies 90° away from the lead identified in step 1. If the QRS away from the lead identified in step 1. If the QRS complex in this second lead is predominantly positive, complex in this second lead is predominantly positive, than the axis of this lead is approximately the same as than the axis of this lead is approximately the same as the net QRS axis. If the QRS complex is predominantly the net QRS axis. If the QRS complex is predominantly negative, than the net QRS axis lies 180° from the axis negative, than the net QRS axis lies 180° from the axis of this lead.of this lead.

Equiphasic Approach: Example 1Equiphasic Approach: Example 1

Equiphasic in aVF Predominantly positive in I QRS axis ≈ 0°


Equiphasic Approach: Example 2Equiphasic Approach: Example 2

Equiphasic in II Predominantly negative in aVL QRS axis ≈ +150°


EKG ReviewEKG Review

1. View the slide show

2. Interpret the EKGs

3. Advance slides to review findings

4. Good luck!

Recall the approachRecall the approach

1. Take a deep breath2. Analyze rate3. Analyze rhythm4. Look at axis5. Look for injury/strain/ischemic patterns6. Look for conduction defecits (RBBB, LBBB)7. Hypertrophy, meds, toxic effects8. Make your measurments (PR, QT/QTc, QRS)

Sample EKG #1. Determine rate, rhythm, diagnosis, axis

Interpretation EKG#1Interpretation EKG#1

Rate: approx 75/min

Rhythm: Baseline sinus rhythm, P:QRS is 1:1

Axis: Physiologic

Injury: ST elevation is present in the anterior, septal, and literal leads. Massive ST segment elevation is present in V2-V6, with moderate ST elevation that obscures visualization of the QRS complex in lead one. Changes are consistent with LCA occlusion.

Other: R wave progression is difficult to determine secondary to the pathological ST-T changes. No evidence of chamber enlargement or hypertrophy.

Sample EKG#2Sample EKG#2


The EKG reveals an atrial flutter at a rate of approx 100 per minute. The QRS complexes are narrow and reveal a physiological axis. There is evidence of a premature ventricular complex, readily identifiable in the lateral chest leads. No evidence of ischemia or infarction. No evidence of R or L bundle branch block. Atrial flutter is conducted at approx 3:1. (3 flutter waves to one QRS).

Sample EKG#3Sample EKG#3


The EKG reveals an irregularly irregular rhythm suggestive of atrial fibrillation. The rate is variable, with a controlled or slow ventricular response. The axis is physiologic. ST-T changes suggestive of ischemia/injury are present in leads II, III, and aVF. ST elevation of >1mm in limb leads is indicative of a possible inferior wall myocardial infarction. Reciprocal changes are seen in leads one and aVL. Early R wave progression.

EKG #4EKG #4

Interpretation of EKG #4:

This EKG reveals a baseline sinus rhythm. Rate cannot be determined definitively. The QRS is wide; V1 reveals an RSR’ pattern consistent with a right bundle branch block. The axis is physiologic but is not easy to determine because of ST elevation present in leads III and aVF (inferior wall). Other abnormal T changes are seen (T wave inversion) in leads V1-V4. ST segment depression is present in the lateral chest leads as well. No evidence of chamber enlargement. ST elevation in III and aVF with reciprocal depression in I and aVL may be consistent with an inferior wall MI (RCA lesion.)

EKG #5EKG #5

Interpretation of EKG#5:

Baseline sinus rhythm.Rate appears normal (60-100)Axis is physiologicNo evidence of block or conduction abnormalityThere is widespread ST segment elevation in all leadsGLOBAL ST elevation is consistent with pericarditis

EKG #6EKG #6

EKG #6 Interpretation:

EKG #6 reveals a baseline sinus rhythm. Rate approximately 80 bpmAxis is physiologicComplexes in V5 greater than 35 mm suggest LVHST segment depression in leads V4-V6 in the setting of LVH is suggestive of a, “strain pattern”.No evidence of bundle brnach blockST segment depression in inferior chest leads

EKG #7EKG #7


Baseline sinus rhythm.Rate of approx 80/minAxis is physiologicNo evidence of ventricular hypertrophy, but RAH is possible due to P wave in lead II >0.5 mm. Possible RBBB because of RSR’ in V1 and QRS >0.10Note pathologic Q waves in II, III, aVFPathologic Q waves are >0.04s or >1/3 the height of the R wave.Changes consistent with inferior wall myocardial infarction (old, possibly transmural). R wave progression preserved.

EKG #8

Interpretation of EKG #8:

Baseline sinus rhythm, rate approx 80. Right axis deviation, as evidenced by a primarily negative complex in lead I.Possible RAH due to large lead II P wavePossible RVH due to R>S in V1Note pervasive strain pattern due to RVH evidenced in precordial leads. The presence of RAD plus the R>S in V1 is suggestive of RVH.

Any drug toxicity? EKG#8Any drug toxicity? EKG#8

EKG Interpretation #8:

Though the picture has poor resolution, it is clear that the lateral leads reveal a pattern of digoxin toxicity. Even though rate is impossible to determine, the “cored-out” and depressed ST segments in the lateral precordial leads suggest digoxin toxicity. Furthermore, the irregular R to R intervals hint at a baseline rhythm of atrial fibrillation. Many patients take digoxin for chronic atrial fibrillation. Moderate left axis deviation.

EKG #9EKG #9

EKG #9:

This rhythm strip reveals a profound bradycardia. There is no relationship between the atria (P waves) and QRS complexes. This is consistent with complete A-V dissociation, or third degree heart block. This rhythm frequently requires emergent pacing.

EKG #10EKG #10


This EKG reveals a baseline sinus rhythm (p’s are difficult to discern.) The rhythm is a sinus tachycardia at approximately 100 per minute. Massive ST segment elevation is present in leads II, III, and aVF. Reciprocal changes (depression) in leads I and aVL. Note that the precordial chest leads (v4R to V6R) are placed on the right side of the chest. ST segment in a “right-sided” EKG likely indicates an inferior wall MI that involves the RIGHT ventricle. Be careful when giving these patients NTG. Administration of nitrates, due to the alteration of venous preload, can precipitate hypotension. Treat these MI’s with fluid first. The axis is physiologic, no evidence of chamber enlargement. R wave progression is not of value in this EKG because of the right sided chest leads.

Final Rhythm ReviewFinal Rhythm Review

Rhythm interpretation:

-The first strip reveals a prolonged PR interval, with 1:1 conduction. This rhythm is a first degree A/V block.

-The second strip is a 4:1 (or 3:1) atrial flutter.

-The third rhythm strip reveals the typical atrial fibrillation. Note the fibrillatory baseline with irregular R to R intervals.

The QT/QTc Interval: Calculation and Significance

Measurement: From the beginning of the Q wave to the end of the T wave

Parameter: Normal QT intervals range from 0.36-0.41.

Abnormalities: Hypercalcemia will shorten the QT intervaland yield measurements from 0.26-0.36s.

QTc: The QT interval varies with heart rate. Thecorrected QT interval is calculated by adjusting your measurement for the patient’s heart rate. The QT divided by thesquare root of the R to R interval typicallygives a QTc around 0.44 seconds.

Lengthening: Diseases, drugs, and toxins can prolong the QT interval and precipitate attacks oflethal ventricular arrhythmias.

Long QT syndrome, “Romano-Ward” Syndrome EKG:

The QTc, adjusted for rate, would almost certainly be greater than 0.44 seconds. You can see in this example that the QTc is approximately 0.5-0.6 seconds (almost 3 large boxes!)

Rate Cheat Sheet

Besides calculating the number of R waves in a 3 or 6 second strip and multiplying by 20 or 10 seconds, simply divide the number of small (0.04s) units

between consecutive R waves into 1500.

-The heart rate can also be calculated from the R to R interval. Simply divide the number of large boxes (0.2s) between consecutive R waves into 300.

-15 large boxes is a three second strip!

-30 large boxes represents a six second strip!

-For irregularly irregular rhythms, try to calculate rate with a decent time interval, preferably greater than a 3 second strip.

Potassium summary:

Digitalis effect summary:

In addition to a wide variety of atrial conduction defects, ventricular ectopy, and heart blocks, early digitalis toxicity manifests itself as: a shortening of the QT interval in addition to scooped-out appearing ST segments.

Precise axis calculation, anyone?

Remember that it is simply a method of addition. I+III=II. The mean QRS vector will also point 90 degrees away from the most isoelectric lead. Leads with large amplitude R waves will shift the mean QRS vector in their general direction. Remember about dropping those stubborn perpendiculars?

Chamber enlargement review:

Name that hypertrophy?

a) RVHb) LVHc) RAHd) LAH

The EKG findings are consistent with: RVH

Criteria for right ventricular hypertrophy include:-Tall R wave in lead V1 (R>S)-qR pattern in V1-Right axis deviation-T wave inversion in right to mid precordial leads possible-Commonly due to ASD! -The pattern of T wave inversion is called, “strain”and is consistent with repolarization problems in hypertrophied muscle.

For the following strips identify the QRS, QT, Heart Rate, PR, ST, intervals, and For the following strips identify the QRS, QT, Heart Rate, PR, ST, intervals, and whether or not the rhythm is normal or abnormal. Try your best to identify the whether or not the rhythm is normal or abnormal. Try your best to identify the

rhythm.rhythm.

A. Normal Sinus Rhythm

B. Atrial Fibrillation

C. Normal Sinus Rhythm with Heart Block

EKG Basics OVERVIEW OF EKG AND TELEMETRY. Outline 1. Review of the conduction system 2. EKG...

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