ECG Dr Osama Mahmoud

ECG

Cardiac cycle. Basic cardiac cycle (P-QRS-T) repeats itself again and again.

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EeG paper. ECG paper is a graphic divided into millimeter squares. 'lime IS measured on the horizontal axis. Each small millimeter box equals 0.04 sec, and each larger (5 mm) box equals 0.2 sec with a paper speed of 25 mm/ sec. the amplitude of any wave is measured on the vertical axis in millimeters. '-;

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P wave represents atrial depolanzation. P-R mterval represents time from initial stimulation of atria to initial stimulation of ventricles. QRS represents ventricular depolarization .S-T segment, T wave, and U wave are produced by ventricular repolarization,

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Positive and Negative Complexes. P Wave Here Is Positive (Upright), and T Wave Is Negative (Downwards). QRS Complex Is Biphasic (Partly Positive, Partly Negative) S-T Segment Is Isoelectric (Neither Positive nor Negative) rf

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Measurement of QRS width.

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Characteristics of normal S-T segment &T wave .. J junction, marks beginning ofS-T segment.

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S-T segments. Top, normal S-T segment. middle, abnormal s..T elevation. Bottom. abnormal S-T depression.

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Standardization mark. Before taking an ECG, the machine must be calibrated so that thli standardization mark, A, is 10 mm tall. Electrocardiographs can also be set at one- half standardization, B, or 2 times standardization, c. R

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Multiple chest leads give a three- dimensional VIewat cardiac electrical acnvity.

Sample ECG mounted for interpretation showing 12 standard leads.

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NORMAL CHEST LEAD PATTERNS

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Normally, the R wave in chest leads becomes relatively taller from lead VI to len chest leads.

A, Normal R wave progression with transition zone in lead V3

B. Somewhat delayed R wave progression with transition zone in lead V5. ('. Early transition woe in lead \ ' These

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Pattern of QRS in limb leads The normal pattern (the complex

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both I, A VF) =normal axis

RIGHT AXIS DEVIATION II

LEFT AXIS DEVIATION

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QRS

Left axis deviation (LAD), mean QRS axis more negative than -30°, can also be

axis more positive than + lOO°--ean be deter-.

determined by simple inspection of leads I, II, and 111 With LAD, lead 11 will show an rS complex, with the S wave of greater amplitude than the r wave.

mined by simple inspection of leads I, II, and III. With RAD, lead III will show an R wave taller than the R wave in lead II.

RIGHT AXIS DEV IATION II

III

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Example of right axis deviation. Note R waves ill leads II and III, with the R wave in lead III greater than that ill lead II. LEFT AXIS DEVIATION

Example ofleft axis deviation. Note rs complex

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P wave measurements. Normal P wave is less than 2.5 mrn tall and less than 0.12 sec wide.

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Note tall P waves. best seen here in leads II, ill, aVF, and V1. in patient with nght atrial enlarqernant (P pulmonale).

LEFT ATR 1AL ENLARGEMENT P Mitrale

(AB;-~OKMALITY)

Biphasic P waV$ in lead V1

Left atrial enlargement may produce. A. wide, humped P waves •..

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RIGHT VENTRlCULAR HYPERTROPHY " 'I.' ., \" ,:,. lit

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Note tall R wave in lead V1 (with inverted T wave caused by right ventricular strain).Also

note right axis deviation (R wave in lead III taller

than R wave in lead II). Patient had tetralogy of Fallot.

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RIGHT VENTRICULAR

HYPERTROPHY

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RV strain

Sometimes with RVH lead V1 shows tall R wave as part of qR complex. Note peaked P waves (leads II, III, and V1) because of right atrial enlargement. Also note prolonged P-R interval (O.24 sec), indicating first-degree

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AV block.

LEFT VENTRICULAR

HYPERTROPHY

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Patient with severe hypertension with left ventricular hypertrophy with strain pattern. Note tall voltage in chest leads, with strain pattern in leads I, aVL, and V4, to V6. Also note tall voltage in lead aVL, (R = 16 mrn), In addition, note pattern of left atrial enlargement, with biphasic P wave in lead VI and broad, notched P wave in lead II (P mitrale).

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+ Questions. 1. Answer these questions about the following E&G

a) What

the approximate heart rate?

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Answers:

1. a) About 100 beats/min. b) No. Notice retrograde P waves, positive in lead aVR and negative in lead II, owing to AV junctional rhythm. c) Around lead V4. d) Tall voltage in chest leads (SVl + RV6> 35 mm); tall voltage in lead aVL. (R wave> 13 mm); left ventricular strain pattern in leads I, aVL, V5, and V6. 2. a) About 75 beats/min. b) The P-R interval is prolonged (about 0.22 sec) because of firstdegree AV block. Also, the P wave in lead II is abnormally wide and notched (notice the two humps) as a result of left atrial enlargement.

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ECG SEQUENCE WITH ANTERIOR WALL INFARCTION III

A. Acute phase' S-T elevations and new Q waves. B. Evolving phase: deep T wave

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Sequential QRS and ST-T changes seen wit'" anterior wall infarction Note reciprocal ST-T changes in inferior leads (11111.and AVF).

ECG SEQUENCE WITH INFERIOR WALl

INFARCTION

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Chest leads from patient with acute anterior wall infarction. A, Note tall positive T waves (hyperacute T waves) seen in leads V2 to V5 in earliest phase of infarction. B, Recorded several hours later, shows marked S-T segment elevation in same leads (current of injury pattern) with abnormal waves in leads V1 and V2. I

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Hyperacute T waves with anterior wall infarction, of severe chest pain. Note very tall, hyperacute There is also slight S-T segment elevation depressions

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complex often seen with infarcts. In addition, T wave inversions

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Evolving anterior wall infarction. Patient sustained anterior wall infarct 1 week earlier. Note abnormal Q waves (leads I, aV1, and V2, to V5) with slight S-T segment elevations and deep T wave inversions. Left axis deviation resulting from left anterior hemi block is present as well.

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Evolving anterior wall infarction. Infarct occurred I week earlier. Note poo.· R wave progression in leads VI to V5 along wjth Q waves III leads I and a V I. T waves are slightly inverted in these leads. Right axis deviation 111 this case IS the result ofloss of lateral wall forces, with (J waves II! I ,,' d aV I.

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no rrue P waves. Veruncular (Qj{~) Jdll' I:> '/1('gU(,H RAPID ATR I AI. FIBRIL! /\ rf( 1:\J

Note coarse flbnl I atorv

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and rapid ventruula:

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thyrordism. (The commonly used term "rapui atnar nbnltauon" IS actually "mel' the word "rapid refers to [he veruncular rate, not lhe .u: ;,J! (.ilt' Ih« tor the term "slow atrial fibnll.iu.«.

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FIBRILLATIoN

Fibnllatory waves may be hard to find with rapid atrial tibnllation. A la, tl ycardia IS present WIth ventncular rate of about 140 beats I min (14 R wave cycles 0 sec) The ventricular

fate

is irregular. No P waves are seen. The rhvrhrn here

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