ECG Basic

In a NORMAL ECG, what do the 12 leads look like

Lead I-III, aVF, V5,V6 are POSITIVE → Lead II should be the MOST positive

Interpret this ECG

Lead I is negative (normal = positive), aVF positive → RAD

Interpret this ECG

Lead I is positive, aVF is negative (normal is positive) → LAD

What is the normal appearance of P waves

Smooth and round → Small (less than 2.5 small boxes); positive in I,II, aVF, V2-V6, biphasic in VI, inverted in aVR

What is P mitrale

Caused by LA enlargement → Shown by broad, M shape P wave, >120 ms P wave, biphasic V1 has more negative deflection

What does this describe

M shape P wave, duration > 3 small boxes → P mitrale

What is P pulmonale

Caused by RA enlargement → Shown by tall peaked P wave in lead II, amplitude > 2.5 mm, biphasic V1 has more positive deflection

What does this describe

Tall peaked P wave in Lead II → P pulmonale

What is the appearance of the QRS complex on ECG

Q is initial negative deflection, R is first positive deflection, S is negative deflection

What is the 300 method

Regular rhythm: Count the number of large boxes between two R waves → Divide 300 by that number to get HR

What is 6 second method

For irregular rhythm: Count number of R waves in strip then multiply by 10 to get HR

What is 1500 method

More precise than 300 method; count small boxes between R waves and divide 1500 by that number to get HR

What would LVH look like in ECG

S wave in V1 + R in V5/6 >= 35 mm, R in aVL > 11 mm, ST depression and T wave inversion

What could RVH look like in ECG

R wave in V1 > S in V1, R in V1 > 7 mm; ST depression and T wave inversion

What would a RBBB look like in ECG

Wide QRS, rabbit ear or M shape in V1-V2, W shape in V5-6, I and aVL

What does this indicate

M shape in V1, W shape in lead I → RBBB

What would a LBBB look like in ECG

Wide QRS complex, dominant S wave in V1, no Q wave in V5-6, aVL

What does this indicate

Wide QRS, dominant S wave in lead V1 → LBBB

What would ECG look like for hyperkalemia

Tall peaked and narrow T wave → Tall peaked T no P wave, wide QRS

What could ECG look like for hypokalemia

T wave is flat or inverted, there are U waves, ST segment has depression

What does this indicate

Wide QRS, tall T wave → Hyperkalemia

What does this indicate

Inverted T wave, U wave present → Hypokalemia

What is PR interval

Atrial depolarization to ventricular depolarization (normal 3-5 small box) from beginning of P wave to beginning of Q wave

What is QRS duration

Ventricular depolarization (normal < 3 small boxes) → from start of Q to end of S

What is QT interval

Total ventricular repolarization (normal 360-440 ms); from Q wave to T wave

What is ST segment

Flat baseline between QRS end and T wave start; normally at baseline

What is seen in first degree AV block

Prolonged PR interval (>5 small boxes)

What does this indicate

Long PR interval → first degree AV block

What is seen in Mobitz I second degree AV block

Progressive PR prolonged until QRS

What does this indicate

Long PR until there is QRS → Mobitz I

What is seen in Mobitz II second degree AV block

Constant PR interval with sudden dropped QRS

What does this indicate

non conducted P wave without progressive prolongation of PR → Mobitz II

What is seen in third degree AV block

P and QRS complexes are independent

What does this indicate

P and QRS are independent → Third degree AV block

In RCA occlusion, ST elevation is expected in which leads

Inferior wall → II, III, aVF

In LAD occlusion, ST elevation is expected in which leads

Anterior/septal wall → lead V1-4 (V5-6 also possible)

In LCx occlusion, ST elevation is expected in which leads

Lateral wall → lead I, aVL, V5-6

What is the J point in STEMI

Where S wave terminates and ST segment begins → If higher than baseline = ST elevation

What is the characteristic of ST elevation caused by ischemia

Convex, straight up/downslope, straight horizontal

What is the characteristic ST elevation NOT caused by ischemia

Concave shaped

What are common non sinus rhythms

Afib, atrial flutter, ectopic beats, junctional rhythm, heart block

What is the sign of Afib on ECG

Irregularly irregular pattern (no pattern for RR interval), no P wave, narrow QRS

What does this indicate

No P wave, irregular R wave, QRS is narrow → Afib

What is the sign of atrial flutter on ECG

Sawtooth flutter wave (lead II, III, aVF), regular atrial rhythm (very fast but regular)

What does this indicate

Sawtooth flutter + very fast atrial rhythm → Atrial flutter

What is sign of ventricular tachycardia on ECG

Wide QRS, rapid rate and regular rhythm, AV dissociation (P and QRS do not beat together)

What is the sign of monomorphic VT

Follows all signs of VT + uniform QRS

What type of VT is this

QRS is uniform → Monomorphic

What is polymorphic VT

Follows all signs of VT + QRS is variable (all different in shape and amplitude)

What type of VT is this

QRS is not the same → Polymorphic