ECG Criteria

# Left Axis Deviation

## Criteria
- QRS axis between -30o and -90o
- Dominant S wave (S > R) in lead II and aVF

## Causes
- Left bundle branch block
- Left anterior fascicular block
- Left ventricular hypertrophy
- Inferior myocardial infarction
- Ostium primum atrial septal defect
- Tricuspid atresia
- WPW syndrome with right-sided accessory pathway
- Ventricular pacing
- Ventricular ectopy
- Hyperkalemia
- Mechanical shifts, such as expiration, high diaphragm (pregnancy, ascites, abdominal tumor)
- Normal variation

# Right Axis Deviation

## Criteria
- QRS axis between +90o and +180o
- Dominant S wave (S > R) in lead I and aVL

## Causes
- Right ventricular strain
- Cor pulmonale as in COPD
- Pulmonary Embolism
- Right ventricular hypertrophy
- Secundum ASD
- Lateral wall myocardial infarction
- Left posterior fascicular block
- Ventricular ectopy
- WPW syndrome with left-sided accessory pathway
- Mechanical shifts, such as inspiration and emphysema
- Normal variation in children or thin adults with a horizontally oriented heart
- Dextrocardia
- Pectus excavatum
- Reversed arm leads

# Northwest Axis (No Man's Land)

## Criteria
- QRS axis between -90o and -180o

## Causes
- Lead misplacement
- Severe right ventricular hypertrophy
- Artificial pacemaker
- Ventricular tachycardia
- Ventricular ectopy
- Accelerated idioventricular rhythm
- Hyperkalemia
- Emphysema

# Left Anterior Fascicular Block

## Criteria
- Frontal plane axis between -45 and -90.
- qR pattern in lead aVL.
- R peak time  45 ms in lead aVL.
- QRS duration < 120 ms.

# Left Posterior Fascicular Block

## Criteria
- Frontal plane axis between +90 and +180.
- Owing to the more rightward axis in children up to 16 years of age, this criterion should only be applied to them when a distinct rightward change in axis is documented.
- rS pattern in leads I and aVL.
- qR pattern in leads III and aVF.
- QRS duration < 120 ms.

# Left Bundle Branch Block

## Complete LBBB Criteria
- QRS duration  120 ms ( 100 ms in children 4 to 16 years of age;  90 ms in children < 4 years of age).
- Broad notched or slurred R wave in leads I, aVL, V5, and V6 and an occasional RS pattern in V5 and V6 attributed to displaced transition of QRS complex.
- Absence of q waves in leads I, V5, and V6 (or a narrow q wave in aVL in the absence of myocardial pathology).
- R peak time  60 ms in leads V5 and V6 but normal in leads V1, V2, and V3 (when small initial r waves can be discerned).
- ST and T waves opposite in direction of QRS deflections.

## Incomplete LBBB Criteria
- QRS duration 110 - 120 ms (90 - 100 ms in children 4 to 16 years of age; 80 - 90 ms in children < 4 years of age).
- Presence of left ventricular hypertrophy pattern.
- R peak time  60 ms in leads V4, V5, and V6.
- Absence of q wave in leads I, V5, and V6.

# Right Bundle Branch Block

## Complete RBBB Criteria
- QRS duration  120 ms ( 100 ms in children 4 to 16 years of age;  90 ms in children < 4 years of age).
- rsr', rsR', or rSR' in leads V1 or V2.
- The R' or r' deflection is usually wider than the initial R wave.
- In a minority of patients, a wide and often notched R wave pattern may be seen in lead V1 and/or V2.
- S wave of greater duration than R wave or  40 ms in leads I and V6.
- R peak time  50 ms in lead V1 but normal in leads V5 and V6.

## Incomplete RBBB Criteria
- QRS duration 110 - 120 ms (90 - 100 ms in children 4 to 16 years of age; 80 - 90 ms in children < 4 years of age).
- rsr', rsR', or rSR' in leads V1 or V2.
- S wave of greater duration than R wave or  40 ms in leads I and V6.
- R peak time  50 ms in lead V1 but normal in leads V5 and V6.

# Nonspecific or Unspecified Intraventricular Conduction Disturbance

## Criteria
- QRS duration  110 ms ( 90 ms in children 8 to 16 years of age;  80 ms in children < 8 years of age).
- Absence of criteria for LBBB or BBBB.

# Ventricular Preexcitation of Wolff-Parkinson-White Type

## Criteria
- PR interval < 120 ms during sinus rhythm assuming no intra-atrial or interatrial conduction block (or < 90 ms in children).
- Delta wave: slurring of initial portion of the QRS complex, which either interrupts the P wave or arises immediately after its termination.
- QRS duration > 120 ms (or > 90 ms in children).
- Secondary ST and T wave changes.

# Left Atrial Enlargement

## Criteria
- P wave duration  110 ms (sensitivity 62%; specificity 86%)
- Negative phase of P wave in V1  40 ms (sensitivity 20%; specificity 98%)
- P terminal force in V1  40 msec-mm (sensitivity 56%; specificity 95%)
- Negative phase of P wave in V1 > 1 mm
- Notched P wave with interpeak interval > 40 ms
- P wave/PR duration > 1.6

# Right Atrial Enlargement

## Criteria
- A tall upright P wave in lead II (> 2.5 mm), often with a peaked or pointed appearance.
- Prominent initial positivity of the P wave in V1 or V2 ( 1.5 mm).

# Left Ventricular Hypertrophy

## Criteria
- Romhilt-Estes criteria (4 points = probable, 5 points = definite):
- Largest R or S in limb leads  20 mm or S in V1 or V2  30 mm or R in V5 or V6  30 mm (3 points)
- ST displacement opposite to QRS deflection: without digoxin (3 points); with digoxin (1 point)
- LAA (3 points)
- LAD (2 points)
- QRS duration  90 ms (1 point)
- Intrinsicoid deflection (QRS onset to peak of R) in V5 or V6  50 ms (1 point)
- Sokolow-Lyon criteria:
- S in V1 + R in V5 or V6 35 mm
- R in aVL 11 mm
- Cornell criteria:
- R in aVL + S in V3 >28 mm in men or >20 mm in women
- If LAD or LAFB, S in lead III + max (R+S) in precordial leads  30 mm

# Right Ventricular Hypertrophy

## Criteria
- Increased R/S ratio in V1 (> 1)
- Tall R wave in V1 (> 6 mm)
- Deep S wave in V5 (> 10 mm) or V6 (> 3 mm)
- Drop in R/S ratio across precordium (R/S ratio in V1 > R/S ratio in V3 or V4)

# Biventricular Hypertrophy

## Criteria
- ECG criteria for LVH plus the presence of:
- Prominent S waves in V5 or V6
- Right axis deviation
- Tall biphasic R/S complexes
- Right atrial enlargement

# Pathologic Q Wave

# QT Prolongation

## Criteria
- QTc > 450 ms in males or > 460 ms in females.

## Causes
- Congenital
- Congenital long QT syndromes (K, Na, Ca channelopathies)
- Medications
- Antiarrhythmics (amiodarone, disopyramide, dronedarone, flecainide, sotalol)
- Antibiotics such as macrolides (erythromycin, clarithromycin, azithromycin) and quinolones (levofloxacin, moxifloxacin)
- Antifungals (fluconazole, ketoconazole)
- Antimotility and antiemetic agents (domperidone, granisetron, ondansetron)
- Antimalarials (quinine, chloroquine)
- Antihistamines (hydroxyzine)
- Antipsychotics (chlorpromazine, clozapine, droperidol, fluphenazine, haloperidol, olanzapine, pimozide, paliperidone, quetiapine, risperidone)
- Antidepressants (amitriptyline, citalopram, escitalopram, dosulepin, doxepin, fluoxetine, imipramine, lofepramine)
- Miscellaneous (methadone, foscarnet, sorafenib, sunitinib)
- Autonomic dysfunction
- Intracerebral hemorrhage
- Stroke
- Carotid endarterectomy
- Electrolyte imbalances
- Hypocalcemia
- Hypokalemia
- Hypomagnesemia
- Miscellaneous
- Myocardial ischemia
- Cardiomyopathy
- Bradycardia
- High-grade AVB
- Hypothyroidism
- Hypothermia
- Bundle branch block

# Poor R Wave Progression

## Criteria
- Loss of anterior forces without frank Q waves in precordial leads (decrease in R wave amplitude from V1 to V2, or V2 to V3, or V3 to V4)
- R wave in V3  3 mm

## Causes
- Prior anterior myocardial infarction
- Ventricular hypertrophy
- Left bundle branch block
- WPW syndrome
- Cardiomyopathy
- Emphysema
- Pneumothorax
- Clockwise rotation of the heart
- Lead misplacement in a cranial direction
- Normal variant

# ST Elevation

# ST Depression

# T Wave Inversion

# Low Voltage