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Electrocardiography Tips

Electrocardiography Tips
Normal P wave
• Location—before the QRS complex
• Amplitude—2 to 3 mm high
• Duration—0.06 to 0.12 second
• Configuration—usually rounded and
• Deflection—positive or upright in leads
I, II, aVF, and V2 to V6; usually positive but
may vary in leads III and aVL; negative or
inverted in lead aVR; biphasic or variable
in lead V1
Normal PR interval
• Location—from the beginning of the P
wave to the beginning of the QRS complex
• Duration—0.12 to 0.20 second
Normal QRS complex
• Location—follows the PR interval
• Amplitude—5 to 30 mm high but differs
for each lead used
• Duration—0.06 to 0.10 second, or half
the PR interval
• Configuration—consists of the Q wave,
the R wave, and the S wave
• Deflection—positive in leads I, II, III,
aVL, aVF, and V4 to V6 and negative in
leads aVR and V1 to V3
Normal ST segment
• Location—from the S wave to the beginning
of the T wave
• Deflection—usually isoelectric; may
vary from – 0.5 to + 1 mm in some precordial
Normal T wave
• Location—after the S wave
• Amplitude—0.5 mm in leads I, II, and III
and up to 10 mm in the precordial leads
• Configuration—typically round and
• Deflection—usually upright in leads I,
II, and V3 to V6; inverted in lead aVR; variable
in all other leads
Normal QT interval
• Location—from the beginning of the
QRS complex to the end of the T wave
• Duration—varies; usually lasts from
0.36 to 0.44 second
That’s a wrap!
Rhythm strip interpretation review

Normal U wave
• Location—after T wave
• Configuration—typically upright and
• Deflection—upright
Interpreting a rhythm strip: 8-step

• Step 1: Determine the rhythm
• Step 2: Determine the rate
• Step 3: Evaluate the P wave
• Step 4: Measure the PR interval
• Step 5: Determine the QRS complex
• Step 6: Examine the T waves
• Step 7: Measure the QT interval duration
• Step 8: Check for ectopic beats and
other abnormalities
Normal sinus rhythm
Normal sinus rhythm is the standard
against which all other rhythms are
• Regular rhythm
• Normal rate
• P wave for every QRS complex; all P
waves similar in size and shape
• All QRS complexes similar in size and
• Normal PR and QT intervals
• Normal T waves

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