ECG interpretation Overview Rate Rhythm Intervals QRS STT

ECG interpretation

Overview Rate Rhythm Intervals QRS ST-T wave

ECG

P- QRS- T waves

Overview Rate Rhythm Intervals QRS ST-T wave

Rate Normal heart rate 60 -100 beats per minute Tachycardia is > 100 beats per minute Bradycardia is < 60 beats per minute

What is the heart rate?

Rate Method 1: Count squares 300 / # of big squares between QRS complexes

Rate Method 2: Count seconds 60 ÷ Seconds between QRS complexes 60 ÷ 0. 92 seconds = 65 beats per minute

Overview Rate Rhythm Intervals QRS ST-T wave

Rhythm Sinus Rhythm P wave in every lead (upright in I, III) Every P wave is followed by a QRS complex 1 p wave for every 1 QRS Are the complexes regular or irregular? Regularly irregular vs irregularly irregular

Rhythm

Rhythm

Rhythm

Overview Rate Rhythm Intervals QRS ST-T wave

Intervals

Intervals: PR interval Normal is 0. 12 -0. 20 seconds 1 st degree AV block: PR interval > 0. 20 seconds 2 nd degree AV block has 2 types Type 1: PR interval gets longer under QRS drops Type 2: PR interval doesn’t change. QRS drops suddenly 3 rd degree AV block: No association between p and QRS

st 1 degree AV block

nd 2 degree AV block

rd 3 degree AV block

Intervals

Intervals: QRS complex Normal: less than 0. 10 seconds Left bundle branch block QRS > 0. 12 seconds No q wave in V 5 and V 6 Broad notched R wave in V 5 and V 6

Intervals: QRS Right bundle branch block QRS > 0. 12 seconds Deep slurred s in leads I and V 6 “Rabbit ears” (rs. R’) in V 1 or V 2

LBBB or RBBB?

LBBB or RBBB?

Intervals: QT should be less than half of R-R interval

Overview Rate Rhythm Intervals QRS ST-T wave

QRS Is there a pathologic Q wave? (sign of previous MI) More than 1 box wide and More than 1/3 of the height of the R wave

QRS Are the QRS complexes normal, too small, or too tall? Too small (low voltages) <5 mm in leads I, III and <10 mm in leads V 1 -V 6

QRS Too tall: (left ventricular hypertrophy) Most common criteria: S in V 1 + R in V 5 or V 6 ≥ 35 mm

Overview Rate Rhythm Intervals QRS ST-T wave

ST segment-T wave Is there ST depression or elevation ? >1 mm in 2 “contiguous leads” (2 leads that are in the same area of the heart) Is there T wave inversion? What parts of the heart (leads) are involved?

What part of the heart is affected?

ST elevation

ST depression

T waves Are they inverted? (Can suggest ischemia) Are they peaked (Such as in hyperkalemia)?

Peaked T waves

Hyperkalemia Peaked T waves occurs early in hyperkalemia As hyperkalemia gets more severe PR widens QRS widens P wave disappears This is called a “sine wave”

Summary Rate Rhythm Sinus rhythm or not? Intervals PR <0. 20 seconds? QRS <0. 12 seconds? QT less than ½ of RR interval?

Summary QRS Is there a pathologic (big) Q wave? Are the QRS intervals too big/tall? R in V 1/2 + S in V 5/6 >35 mm? Are the QRS intervals too small? <5 mm in limb leads and <10 mm in V 1 -V 6 ST- T wave Is there ST elevation or depression? What part of the heart? Are the T waves inverted or peaked?

Quiz: Interpret ECG-1

Quiz: Interpret ECG-1 Rate: 150 bpm Rhythm: Sinus tachycardia Intervals: PR, QRS, QT intervals all normal QT interval looks long, but this is because HR is fast. When we calculate QT corrected for HR, it is normal. QRS: No pathologic Q waves, Normal size QRS ST-T: No ST depression/elevation, No T wave changes

Quiz: Interpret ECG-2

Quiz: Interpret ECG-2 Rate: 52 bpm Rhythm: Sinus bradycardia Intervals: PR long: 1 st degree AV block QRS normal QT long QRS: No pathologic Q wave, Normal size QRS ST-T: No ST depression/elevation. No T wave changes

Quiz: Interpret ECG-3

Quiz: Interpret ECG-3 Rate: 70 bpm Rhythm: Sinus rhythm Intervals: PR, QRS, QT all normal QRS: No pathologic Q waves. Normal size QRS ST-T: No ST depression or elevation T waves are peaked