ECG INTERPRETATION

Electrocardiographic Cases
Crisbert I. Cualteros, M.D.




ECG Indications
determine cardiac rate

define cardiac rhythm

diagnose old or new MI

identify intracardiac conduction disturbances

aid in the diagnosis of IHD, pericarditis, myocarditis, electrolyte abnormalities and pacemaker malfunction
Lead Locations
V1 = 4th ICS, R sternal border
V2 = 4th ICS, L sternal border
V3 = halfway between V2 and V4
V4 = 5th ICS, L MCL
V5 = 5th ICS, anterior axillary line
V6 = 5th ICS, L mid-midaxillary line
V3R = halfway between V1 and V4R
V4R = 5th ICS, R MCL
Correspondence


RRAHIM
Components of ECG interpretation

Rate
Rhythm
Axis
Hypertrophy
Ischemia and Infarction
Miscellaneous (normal variants)






Rate
Mnemonic: 300, 150, 100, 75, 60, 50
Formula: 1500 / # of small boxes
300 / # of big boxes


Bradycardia = <60 bpm
Normal Rate = 60-100 bpm
Tachycardia = >100 bpm


Rhythm
Identify the P wave
Check relation of P wave to QRS
Normal: P wave is before QRS
SVT, heart blocks: P wave after QRS or burried
Check PR interval (0.12 - 0.20s)
Shortened: WPW
Prolonged: 1st and 2nd degree AV block


Check QRS duration (< 0.10 s)
Widened: bundle branch blocks

Check relation of R-R and P-P int
PP < RR: complete heart block
PP > RR: AV dissociation
Common Rhythm Interpretations
Sinus rhythm
Supraventricular arrhythmias
Atrial fibrillation
Atrial flutter
Supraventricular tachycardia (SVT)
Heart Blocks
First-degree AV block
Second-degree AV block
Mobitz Type I (Wenckebach)
Mobitz Type II

Third-degree AV block
Left or Right Bundle Branch Block
Complete
Incomplete

Ventricular Arrhythmias
Premature Ventricular Depolarization (PVD)
Ventricular Tachycardia (V-tach)
Sustained
Non-sustained
Ventricular fibrillation (V-fib)
Axis Determination
get the average QRS vector from the isoelectric baseline in Leads I and AVF

if the average QRS vector is above baseline → (+) QRS deflection

if the average QRS vector is below baseline
→ (-) QRS deflection
Axis


Axis
- 90 AVF

indeterminate LAD

± 180 0 I

RAD normal
(-30 to +90)
+ 90

Axis Differentials
Hypertrophy
Six Possibilities
No hypertrophy
LVH
RVH
LAE
RAE
combination
LVH criteria
3 Methods

1) S wave in V1 +
R wave in V5/6 > 35mm

2) R in AVL > 11mm

3) Romhilt and Estes Criteria (best)

RVH Criteria
RAD of ≥ +110, with any of the ff:

V1: R wave > S wave
COPD
RBBB
True posterior infarction
WPW
Deep S wave in V5-6
COPD
ST depression and T wave inversion in V1-3
LAE (p mitrale)
2 Methods

V1: wide terminal component of P wave ≥ 1 mm wide (0.04 s) and ≥ 1 mm deep

Any lead: P wave wider than 0.12s or with a ≥ 1 mm notch in the middle

RAE (p pulmonale)
2 Methods

V1: tall initial component of P wave ≥ 2mm wide and ≥ 2 mm tall

Any Lead: P wave ≥ 2.5 mm tall
RRAHIM
Components of ECG interpretation

Rate
Rhythm
Axis
Hypertrophy
Ischemia and Infarction
Miscellaneous (normal variants)
Myocardial Ischemia

1 mm ST-segment depression
Symmetrically/inverted T waves
Abnormally tall T waves
Normalization of abnormal T waves
Prolongation of QT interval
Arrhythmias, BBB, AV blocks or electrical alternans

Myocardial infarction
Criteria (any)

ST elevation
≥ 2 Chest leads: ≥ 2 mm elevation or
≥ 2 Limb leads: ≥ 1 mm elevation

Q waves ≥ 0.04s (1 small square)
Timing of MI/ECG

Differentials for ST elevation

Acute pericarditis
Ventricular aneurysm
Severe LV wall hypokinesia
Early repolarization changes
Variant (prinzmetal) angina

Q waves

never significant in aVR
not significant in V1 unless with abnormalities in other precordial leads
not significant in III unless with abnormalities in II, aVF
more reliable if associated with ST changes
Not significant in V1-V3 if (+) LBBB, but significant if (+) RBBB

Criteria for Pathologic Q waves

≥ 0.04 sec in duration
≥ 25% of the R wave amplitude


RRAHIM
Components of ECG interpretation

Rate
Rhythm
Axis
Hypertrophy
Ischemia and Infarction
Miscellaneous (normal variants)

Hypokalemia
V2, V3: u wave as tall or taller than T wave
Hyperkalemia
Chest leads: height of T wave > 10 mm
Limb leads: height of T wave > 5 mm

Hypocalcemia
Prolonged QT interval, longer than ½ the RR interval
Hypercalcemia
Shortened QT interval


Poor R wave Progression (PRWP)
Height of Rwave in V3 < 3 mm
Differentials
Old anteroseptal wall MI
LVH
Normal variant: heart rotated clockwise
LBBB
Early Repolarization Changes (ERP)
V2-V4: ST segment elevation of 2-3 mm
Normal variant, usually in males < 40y
Differentials
Acute anteroseptal wall MI
Acute pericarditis






Low-voltage QRS
QRS in all limb leads is < 5 mm

Artifacts
Irregular spikes or undulations on the ECG baseline not found in other segments
Causes
Patient movement (shivering)
Poor electrode contact
Atrial Fibrillation
Criteria
No P waves
Irregular fibrillatory waves
Irregularly irregular ventricular rhythm

Acute if < 48h

Top 5 causes of AF
(EVICT)

Ethanol (Holiday Heart Syndrome)
Valvular heart disease (MS)
IHD
Cardiomyopathy
Thyrotoxicosis





AV Nodal Blocks
First Degree AV Block

P-R interval > 0.21 sec
One-to-one AV conduction


AV Nodal Blocks
Second Degree AV Block

Sinus rhythm
Some P waves not followed by QRS complx
Mobitz I (Wenckebach)
Increasing PR interval → dropped beat

Mobitz II
PR interval prolonged but constant




Third Degree AV Block or
Complete Heart Block


AV dissociation
P waves seen marching through the QRS
PP interval < RR interval
Idioventricular rhythm


Intraventricular Blocks
Complete RBBB
QRS duration ≥ 0.12 seconds
QRS in V1 has an rsR’ configuration or is a solitary R wave

Intraventricular Blocks
Complete LBBB
QRS duration ≥ 0.12 seconds
QRS is notched and splintered
QRS has a QS or rS deflection in V1



V-Tach
Criteria
≥ 3 consecutive QRS complexes…
of uniform configuration
of ventricular origin
> 100 bpm
V-Tach Morphology
Monomorphic

Sustained VT:
> 30 s
Hemodynamic compromise
Requires intervention for termination

Non-sustained
V-Tach Morphology
Polymorphic

beat to beat variation in QRS complexes
SupraV Tach
Criteria

regular succession of QRS complexes with normal duration and configuration

rate 150 – 250 bpm

P waves not identifiable (superimposed on QRS) or preceed / succeed the QRS complex


Sinus Rhythm
Second-degree AV block, type II
Third Degree AV Block
Acute Inferior Wall MI
AF with RVR
AF with SVR
Anteroseptal Wall MI
Atrial Flutter with 2:1 conduction
Digoxin Effect
ERP
First-Degree AV block, SB
Frequent PVCs in Bigeminy
Hyperkalemia
Left Bundle Branch Block
Right Bundle Branch Block
SVT
Ventricular Fibrillation
Ventricular Tachycardia
Ventricular Tachycardia
WPW Syndrome




Thank You!