Joseph Brian L.

Costiniano, MD, DPCP

P WAVE
 Atrial contraction
 Upright in Lead I, II and avF
 Normal: 0.12 – 0.20 sec
PR INTERVAL
 Conduction of depolarization from SA node to AV node
 Measure in the limb lead with the longest PR interval
QRS COMPLEX
 Ventricular contraction
 Normal: <0.10 sec
 Q wave
 Lead II & avF
○ <0.04 sec wide
○ <2mm deep R

○ <25% of succeeding R wave

Q S
NORMAL R WAVE PROGRESSION
V6

V1 Poor R Wave Progression

❑R in V3 < 0.3 mV
❑R in V4 – V5 is normal V5

V3
V2 V4
ST SEGMENT
 Plateau phase of ventricular contraction
 Normally deviates between 0.5 – 1mm from baseline
 Isoelectric
QT INTERVAL
Normal :
 Male < 0.48
 Female < 0.44
QT Corrected
QT Actual
√𝑅 − 𝑅 𝐼𝑛𝑡𝑒𝑟𝑣𝑎𝑙

Normal :
 Male < 0.48
 Female < 0.44
T WAVE
 Rapid phase of repolarization
 Usually not >10mm in the precordial leads
REGULAR RHYTHM
 RATE/MIN = 1500/# of small squares

• RATE/MIN = 1500/23 = 65 beats/min

REGULAR RHYTHM
 RATE/MIN = 300/# of big squares

• RATE/MIN = 300/5 = 60 beats/min

IRREGULAR RHYTHM
 RATE/MIN = # QRS COMPLEXES X 10
 30 BIG BOXES (6 second strip)

• RATE/MIN = 12 X 10 = 120
 REGULAR SINUS RHYTHM

P to P and R to R interval are regular (Cycle length do not vary by 10%)

Rate = 60 to 100 bpm
Presence of a P wave followed by a QRS complex in a regular rate
 LEFT BUNDLE BRANCH BLOCK

Complete: QRS >0.12 sec

Broad, notched R in I, V5 and V6
Small R, deep S in V1 – V2
 RIGHT BUNDLE BRANCH BLOCK

Complete: QRS >0.12 sec

rSR pattern in V1
Wide S in V6
 SINUS ARREST/PAUSE

Sudden absence of PQRST complex

Drop beat is not in exact multiple of the preceding interval
 SINOATRIAL BLOCK

Sudden absence of PQRST complex

Drop beat is in exact multiple of the preceding interval
 FIRST DEGREE ATRIOVENTRICULAR BLOCK

Prolonged PR interval
2nd DEGREE AV BLOCK – TYPE 1 WENCKEBACH

Progressive lengthening of the PR interval

Drop beats after 3 or 4 P waves
Progressive shortening of RR interval
Cycle repeated after the drop beat
 2nd DEGREE AV BLOCK – MOBITZ TYPE II

Sudden and unexpected drop beat without changes in the preceding PR

interval
Usually 2:1 AV conduction ratio
 COMPLETE HEART BLOCK

P wave not related to QRS complex

 SINUS BRADYCARDIA

Rate < 60 bpm

Regularly occurring PQRST
 SINUS TACHYCARDIA

Regularly occurring PQRST

Rate > 100 bpm
 Supraventricular Tachycardia

Regularly occurring Narrow QRST

Absence of P-waves
 Supraventricular Tachycardia (AVNRT)

P-waves

Regularly occurring Narrow QRST

Absence of P-waves
 SINUS ARRHYTHMIA

Identical but irregularly occurring PQRST

 PREMATURE ATRIAL CONTRACTION

Prematurely occurring PQRST complex

P wave different in configuration in sinus beat
PR interval often long
QRS narrow
 ATRIAL FLUTTER

Atrial rate = 220-300

Biphasic, saw toothed flutter waves which is regular
Irregular RR interval
QRS complex narrow
 ATRIAL FIBRILLATION

No discernible P wave
Irregular R-R interval
QRS complexes usually normal
 Frequent Premature Atrial Contractions

Discernible P wave
Irregular R-R interval
QRS complexes usually normal
 VENTRICULAR TACHYCARDIA

Rapid, bizarre wide QRS complex

No P wave (ventricular impulse)
 VENTRICULAR FIBRILLATION

Associated with coarse or fine chaotic undulations

No P wave
No true QRS complexes
Indeterminate rate
 VENTRICULAR FIBRILLATION (Torsades de
Pointes)

Associated with chaotic undulations with varying amplitudes

No P wave
No true QRS complexes
Indeterminate rate
 PACEMAKER RHYTHM

No P wave (Ventricular impulse origin)

Wide QRS complex
Pacemaker spike precedes the wide QRS complex
 VENTRICULAR PREMATURE CONTRACTION

Prematurely occurring complex

Wide bizarre looking complex
Usually no preceding P wave
T wave opposite in deflection to the QRS complex
Complete compensatory pause following premature beat
 -90º

aVF
(-)

I (-)
0º
I (+)

Normal Axis

aVF
(+)

90º
Axis?
Axis
90 x aVF 90 x 5
= 50 degrees
([I] + [avF]) ([4] + [5])

If negative in I and positive in aVF (Right

axis deviation), Add 90 to the result

I aVF
 LEFT ATRIAL ABNORMALITY

Increased P terminal forces in V1 > 0.04 sec wide and 1 mm tall

Notched P wave in lead II
P wave duration >0.12 sec
 RIGHT ATRIAL ABNORMALITY

Peaked P waves in leads II, III, avF > 2.5 mm

Increased in the initial P wave in V1 > 0.08 sec
 LEFT VENTRICULAR HYPERTROPHY

Sokolow Lyon Criteria Cornell Voltage Criteria

S in V1 + R in V5-V6 >35mm Male: S in V3 + R in avL >28
R in avL > 12 Female: >20
R in avF > 20
R in I + S in III > 25
S in V1 > 24
 RIGHT VENTRICULAR HYPERTROPHY

R/S ratio in V6 < 1

R/S ratio in V1 > 1
Right axis deviation
ST depression & T wave inversion in V1 to V3
Lateral Anterior

Septal &
Posterior
Lateral

Inferior Lateral
Contiguous Leads
Leads Myocardium
II, III, AVF Inferior Wall
V1, V2 Septal Wall
V3, V4 Anterior Wall
V5, V6 Lateral Wall
I, AVL High Lateral Wall
SERIAL CHANGES IN MYOCARDIAL INFARCTION
ECG Findings in STEMI
Interpretation Q wave ST Elevation T Wave Timing

Hyperacute (-) (-/+) Peaked 0 – 6H

Acute (-/+) (++) (-/+) 6 – 24H

Recent (++) (++) Inverted 24 – 72H

Undetermined (++) (-) Inverted 72H – 6

wks
Old (++) (-) Upright > 6 weeks
 INFERIOR WALL MYOCARDIAL INFARCTION

Wide & deep Q in II, III and avF

ST segment elevation and/or T wave inversion in II, III and avF
 MYOCARDIAL ISCHEMIA

New or persistent deep T wave inversion

ST depression
Reduction of R wave voltage
Absence of significant q wave
 Early Repolarization Pattern

ST segment elevation NOT fulfilling criteria for ST-Elevation MI

 HYPERKALEMIA

Tall, narrow and peaked T waves

Intraventricular conduction defects
Decrease amplitude of p waves
 HYPOKALEMIA

Prominent u waves especially in chest leads (As tall as T in V2-V3)

T wave flattening & ST depression
Cardiac arrhythmias & AV block
 HYPERCALCEMIA

Short QT segment with early peak & gradual descent of the T wave
Best seen in chest leads
 HYPOCALCEMIA

Modest reduction: QT prolongation

Severe Reduction
Further QT prolongation
Horizontal ST segment & t wave depression
ACUTE PULMONARY EMBOLISM

S1Q3T3
 PERICARDITIS

Diffuse ST elevation (concave) with upright T waves in most leads

Absent pathologic q waves
No reciprocal changes
 PERICARDIAL EFFUSION

Electrical Alternans
Low Voltage Complexes (< 5 mm Limb Leads; < 10 mm Chest Leads)
ECG…Easy?...G?
Parameters Quick Read

1. Rate
300, 150, 100, 75, 60

2. Rhythm P-wave in Lead II? If yes, then Sinus

❑ Narrow QRS : Supraventricular/AV
Nodal
❑ Wide QRS: Ventricular
3. Axis I Up I Down
AVF Up Normal RAD
AVF LAD Extreme
Down
ECG…Easy?...G?
Parameters Quick Read
4. Chamber ❑ Peaked P waves = RAA
Enlargement ❑ Notched / Biphasic P waves = LAA
❑ RAD + Tall R in V1 = RVH
❑ S in V1 + R in V6 > 35 = LVH
5. Blocks ❑ PR > 1 big box (1st degree)
❑ Dropped beats (2nd degree)
❑ AV Dissociation (3rd degree)
❑ Rabbit ears (V1/V2 : Right; V5/V6 : Left)
❑ QRS > 3 small boxes (Complete)

6. ST-T wave Changes Ischemia

❑ ST depression > = 1 mm
Leads Myocardium
❑ Persistent Deep or New onset T wave
II, III, AVF Inferior Wall
inversions
V1, V2 Septal Wall
Infarction
V3, V4 Anterior Wall
❑ ST elevation >= 1 mm in Limb leads
V5, V6 Lateral Wall
❑ ST elevation >= 2 mm in Chest leads
I, AVL High Lateral
❑ Q waves > 25% of QRS (old infarct)