ekgs - students

8/13/2019 EKGs - Students

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Electrocardiograms

Cindy Chan, MD


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Electrocardiograms (EKGs or ECGs)display the electrical activity of the heart


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One electrode is placed on each arm

One electrode is placed on a leg(sometimes, one on each leg)

Six electrodes are placed across the chestwall (from right sternal border to left mid-

axillary line)


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Each lead has its own an axis (or direction) Each lead then reads the electrical current

relative to its axis Imagine that youre standing at the receiving

end of the axis, watching the current

If the current is coming toward you, the EKGdeflection is upward (ie. positive)

If the current is going away from you, the EKGdeflection is downward (ie. negative)


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So, if there is no deflection on the EKG,there are two explanations:

No currentThe current is perpendicular to the lead axis


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L R

Precordium


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1

23

Right Lef

arm ar

Up

Down


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1

23 avF

avR avL


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1

23 avF

avR avL

I nfer ior leads


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23 avF

avR

1

avL

Lateral leads


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Rate

0.04 sec (or 40 msec) = small box

0.2 sec = (small box) X 5 = large box

0.2 sec = 1/300thof minute So, if QRSs are 1 large box apart, rate is 300

If QRSs are 2 large boxes apart, rate is 150 (300/2)

If QRSs are 3 large boxes apart, rate is 100 (300/3), etc.

MEMORIZE: 300, 150, 100, 75, 60, 50

Bradycardia: (cycles/10 sec strip) X 6


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Rhythm

P before QRS


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RhythmTachyarrhythmias:

1. Sinus Tach

2. Supraventricular tachycardia (SVT) (paroxysmal atrial,junctional, or ventricular tachycardia; with or withoutblock) - rate 150-250

3. Atrial flutter - "saw-tooth", from single atrial focus, rate250-350

4. Ventricular flutter - "sine waves", rate 250-350

5. Atrial fibrillation with rapid ventricular rate (RVR) - frommultiple atrial foci, no P waves + irregular ventricularrhythm, rate 350-450

6. Ventricular Fibrillation - from multiple ventricular foci,erratic rhythm, rate 350-450


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Rhythm

Bradyarrhythmias:

1. Sick sinus syndrome - with pauses

2. 1 AVB - prolonged PR interval3. 2 AVB - ie. Wenckeback, Mobitz Type I,

gradual lengthening of PR until dropped QRS

4. 2 AVB - ie. Mobitz Type II, sporadic dropped

QRS5. 3 AVB - ie. Complete HB, complete

disassociation of P and QRS


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Axis

Normal axis is -30 to +105 degrees

Normal axis if upright in leads I and aVF

I downwards, aVF upright: RAD I downwards, aVF downwards: extreme RAD

I upright, aVF downards: LAD

LAD: left axis deviation

RAD: right axis deviation


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1

23avF

avR

avL

0

90

Normal axis

Extreme RAD

RAD

LAD


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Normal

QRS

ST

TP

P wave


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Normal

QRS

ST

TP

PR interval


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Normal

QRS

ST

TP

QRS complex


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Normal

QRS

ST

TP

QT interval


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Intervals

P wave:


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Intervalsquick method

P wave: less than 2.5 small boxes

PR interval: 3-5 small boxes

QRS: 1-2.5 small boxes

QT interval:


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Hypertrophy

1. R atrial hypertrophy: P height > 2.5 mm (right high)

2. L atrial hypertrophy: P length >0.12 sec (left long)

3. R Ventricular Hypertrophy (RVH) criteria:

RAD with widened QRS Persistent S wave in V5, V6 R > S in V1, but progressively smaller from V1-V6

4. L Ventricular Hypertrophy (LVH) criteria:

LAD with widened QRS S in V1 + R in V5 = >35 mm R in aVL > 11 mm


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Infarction

Q waves: 1 mm wide, 1/3 amplitude of QRS

Inverted T waves: ischemia

ST segment elevation: infarct

Anterior leads: V1, V2, V3, V4, V5

Lateral: 1, aVL, V6

Inferior: II, III, aVF


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Normal

QRS

ST

TP

ST segment


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Anterior

Posterior

Right Lef


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RV

LV

Anterioseptum

Inferioseptum

Inferio-Posterior

Lateral

Anterior

Anterioseptum

AnterioseptumAnterior


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LAD RCA LCx

Inferoseptum

RVRV

LVLV

AnterioseptumAnterioseptum

Inferio-PosteriorInferio-Posterior

Lateral

Inferioseptum


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LATERAL

WALL

Circumflex

LAD

ANTERIOR

WALL

RCA

POSTERIOR

WALL

Frontal plane


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LATERALWALL

Circumflex

LAD

ANTERIO

WALL

RCA

POSTERIOR

WALL

2 avF 3

1

avLavR

Leads 2, 3 and avFST

and then Q waves

inferior

Dead tissue

Frontal plane

Inferior MI


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Inferior MI

Occlusion of RCA

Significant Q waves

in 2,3 and avF


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INFERIOR

= RCA Anterior


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LAD RCA LCx

RVRV

LVLV

AnterioseptumAnterioseptum

Inferioseptum

Inferio-PosteriorInferio-Posterior

Lateral

Anterior

EKG: V1-V5 2,3,avF 1,avL,V6


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Lets look at a few

EKGs..

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