[1] A P wave precedes each QRS complex.
[2] Rate is between 60 and 100 bpm for adults (50 - 90 bpm is probably
more realistic).
[3] P wave axis of +15 to +75 degrees. A P axis less than 0, or greater
than +90 indicates an ectopic atrial pacemaker.
[4] P wave is usually upright in leads I, II, and aVF, and inverted
in aVR. It is also usually upright in V3 - V6.
[5] P-P variation is less than 0.16 second (otherwise it is sinus arrhythmia).
Sinus Bradycardia (Chou/Knilans P. 323)
[1] Sinus rate of less than 60 bpm in an adult (50 bpm is more realistic).
[2] P wave has a normal axis, PR interval is usually greater than 0.12
second.
[3] If sinus rate is less than 40 bpm, consider 2:1 AV block.
[4] Not considered clinically significant unless less than 50 bpm.
Sinus Tachycardia (Chou/Knilans P. 324)
[1] Sinus rate greater than 100 bpm in an adult.
[2] Frequently occurs due to alcohol, caffeine, epinephrine, atropine,
fever, hypotension, hypoxia, CHF, anemia, hyperthyroidism, AV fistula,
pheochromocytoma, myocarditis, and in 1/3 of MI patients.
Atrial Fibrillation (Chou/Knilans P. 354)
[1] P waves are absent, and replaced by fibrillatory (f) waves, producing
random oscillation in the baseline.
[2] Ventricular rhythm is usually irregularly irregular.
Atrial Flutter (Chou/Knilans P. 354)
[1] Atrial deflections with a sawtooth appearance (F waves).
[2] Atrial rate usually 250 - 350 bpm.
[3] Ventricular complexes may vary in rate and regularity due to nonconduction
of some F waves through the AV node.
[4] QRS complex may be normal or abnormal, due to pre-existing disease,
or conduction abnormalities.
Right Atrial Enlargement (Chou/Knilans P. 28)
[1] Tall and peaked P wave with a height of 2.5 mm or more in leads II,
III, and aVF, with a normal duration (this is called "P pulmonale").
[2] P wave axis of +75 degrees or greater.
[3] Positive deflection of the P in lead V1 or V2 is greater than 1.5
mm.
(no examples)
Left Atrial Enlargement (Chou/Knilans P. 23)
[1] The product of (time x voltage) in the P terminal force in V1 is equal
to, or more negative than -0.04 mm-second (1 small box wide, and 1 small
box deep).
[2] P wave is notched and equal to, or wider than 0.12 second (this
is called "P mitrale").
[3] P wave axis less than +15 degrees (frequently not used in practice,
and on this website).
Right Ventricular Hypertrophy (Chou/Knilans P. 54)
QRS duration of less than 0.12 second, and one or more of the following:
[1] QRS axis of +110 degrees or greater.
[2] R/S ratio in V1 or V3R greater than 1.
[3] R wave in V1 greater than, or equal to, 7 mm.
[4] S wave in V1 less than 2 mm.
[5] qR pattern in V1.
[6] rSR' in V1 with R' greater than 10 mm.
[7] R wave in V1 plus S wave in V5 or V6 greater than 10.5 mm.
[8] R/S ratio in V5 or V6 less than, or equal to, 1.
[9] Onset of intrinsicoid deflection (downslope of R wave after the
peak) in V1 is 0.035 to 0.055 second.
(no examples)
Left Ventricular Hypertrophy (Chou/Knilans P. 37)
QRS duration less than 0.12 second, and one or more of the following:
[1] R wave in lead I plus S wave in lead III greater than 25 mm.
[2] S wave in aVR greater than 14 mm.
[3] R wave in aVL greater than 11 mm.
[4] R wave in aVF greater than 20 mm.
[5] R wave in V5 or V6 greater than 26 mm.
[6] R wave in V5 or V6 plus S wave in V1 greater than 35 mm.
[7] Largest R wave plus largest S wave in precordial leads greater
than 45 mm.
Or using the Romhilt-Estes point score (LVH present if 5 or more total
points, likely if 4 total points):
[1] 3 points
if largest R or S wave in the limb leads greater than, or equal to,
20 mm;
or S wave in V1 or V2 greater than, or equal to, 30 mm;
or R wave in V5 or V6 greater than, or equal to, 30 mm.
[2] ST-T segment changes ("LV strain" = ST-T vector shifted opposite
to QRS vector)
3 points - if without digitalis,
1 point - if with digitalis.
[3] 3 points - left atrial involvement - terminal deflection of P wave
in V1 is 1 box wide, and 1 box deep or more.
[4] 2 points - left axis deviation - QRS axis is -30 degrees or more
negative.
[5] 1 point - QRS duration greater than, or equal to, 0.09 second.
[6] 1 point - intrinsicoid deflection in V5 and V6 greater than, or
equal, to 0.05 second.
Premature Ventricular Contraction (Chou/Knilans P. 396)
[1] QRS complex occurs earlier than expected.
[2] QRS is abnormal in shape and width, with ST segment and T wave
changes.
[3] There is usually a full "compensatory" pause after the PVC.
[4] There may or may not be conduction in retrograde fashion to the
atria.
Accelerated Idioventricular Rhythm
[1] Rhythm is regular with a rate of 60 - 100 bpm.
[2] QRS complexes are abnormal in shape and duration.
[3] QRS is usually dissociated from the P waves.
[4] Ventricular capture and fusion beats can occur.
First Degree AV Block (Chou/Knilans P. 449)
[1] PR interval is greater than 0.20 second.
[2] Each P wave is followed by a QRS complex.
Third Degree AV Block (Chou/Knilans P. 455)
[1] Atrial and ventricular rhythms are independent.
[2] Atrial rate is faster than ventricular rate (if not, it is "AV
dissociation").
[3] Ventricular rhythm is either junctional or idioventricular.
Right Bundle Branch Block (Chou/Knilans P. 88)
[1] QRS duration greater than 0.12 second.
[2] rsR' or rSR' pattern in right precordial leads.
[3] Delay in the onset of the intrinsicoid deflection (downslope following
peak of the R wave) in the right precordial leads greater than 0.05 second.
[4] Wide S wave in leads I, V5, and V6.
Left Bundle Branch Block (Chou/Knilans P. 75)
[1] QRS duration greater than 0.12 second.
[2] Broad monophasic (notched or slurred) R wave in leads I, V5, and
V6.
[3] Delay in the onset of the intrinsicoid deflection (downslope following
peak of the R wave) in the V5 and V6 leads greater than 0.05 second.
[4] Displacement of the ST segment and T wave in a direction opposite
to the main deflection of the QRS complex.
Left Anterior Hemiblock (Chou/Knilans P. 101)
[1] QRS axis between -30 and -90 degrees.
[2] qR or R complex in leads I and aVL; an rS complex in leads II,
III, and aVF.
[3] Normal or slightly long QRS duration.
Left Posterior Hemiblock (Chou/Knilans P. 106)
[1] QRS axis of +90 to +180 degrees.
[2] S in lead I, a Q in lead III (S1Q3 pattern).
[3] Normal or slightly prolonged QRS duration.
Bifascicular Blocks (Chou/Knilans P. 111)
Right bundle branch block, with either left anterior hemiblock, or left
posterior hemiblock.
RBBB with LAHB (most common, Chou/Knilans P. 112)
[1] QRS duration of 0.12 second or longer.
[2] RSR' pattern in lead V1, with R' broad and slurred.
[3] Wide and slurred S waves in leads I, V5, and V6.
[4] First half or 0.06 second of QRS has an axis between -30 and -90
degrees.
[5] Initial r wave in the inferior leads.
RBBB with LPHB (Chou/Knilans P. 115)
[1] QRS duration of 0.12 second or longer.
[2] RSR' pattern in lead V1, with R' broad and slurred.
[3] Wide and slurred S waves in leads I, V5, and V6.
[4] First half or 0.06 second of QRS has an axis +90 degrees, or greater,
with an rS pattern in lead I, and qR pattern in leads II, III, and aVF.
[5] Initial r wave in the inferior leads.
Changes in Myocardial Ischemia (Chou/Knilans P. 189)
[1] Abnormally tall T waves (also occur in early MI).
[2] Symmetrically or deeply inverted T waves (also occur late in MI).
[3] ST segment depression.
[4] Nonspecific ST and T wave changes.
[5] Normalization of previously abnormal T waves.
[6] Prolongation of the QT interval.
What is an Abnormal Q Wave (Chou/Knilans P. 122)?
[1] A Q wave with a duration of greater than 0.04 second, or an amplitude
greater than 25% of the following R wave.
[2] These guidelines do not apply to leads III, aVR, and V1, where
wide and deep Q waves are found in normal patients.
[3] In lead aVL, a Q wave is abnormal if it has a duration greater
than 0.04 second, or an amplitude greater than 50% of the following R wave.
[4] A Q wave is abnormal (even if of a short duration), when seen in
leads V2, V3, and V4, which usually display an initial R wave.
Evolution of Changes in Q Wave MI (Chou/Knilans P. 124)
[1] Tall T waves.
[2] ST segment elevation (used as evidence that a MI is "acute").
[3] Abnormal Q waves.
[4] Decrease of ST elevation, with T wave inversion.
[5] Isoelectric ST segment with T wave inversion.
Anterior Q Wave Myocardial Infarction (Chou/Knilans P. 122)
rS pattern in V1, abnormal Q in one or more leads V2, V3, or V4.
Anteroseptal Q Wave Myocardial Infarction (Chou/Knilans P. 122)
QS (meaning a big Q, where you can't tell if it is really a Q or a S) pattern
in leads V1, V2, V3, or V4.
Anterolateral Q Wave Myocardial Infarction (Chou/Knilans P. 122)
Abnormal Q in leads V4, V5, V6, I, or aVL.
Inferior Q Wave Myocardial Infarction (Chou/Knilans P. 122)
Q in leads II, or III; with an abnormal Q in aVF.
Inferolateral Q Wave Myocardial Infarction (Chou/Knilans P. 122)
Q in II, III, and aVF (inferior MI) plus abnormal Q in leads V5 or V6.
Posterior Q Wave Myocardial Infarction (Chou/Knilans P. 122)
Initial R waves in leads V1, and V2 with a duration of 0.04 second or more,
with an R/S ratio of greater than 1 (in a patient 30 years or older, without
right ventricular hypertrophy).
Lateral Q Wave Myocardial Infarction (Chou/Knilans P. 122)
Abnormal Q waves in leads I and aVL.
Right Ventricular Q Wave Myocardial Infarction (Chou/Knilans P. 136)
[1] Signs of inferior or inferoposterior MI.
[2] ST segment elevation of 1 mm or more in one or more of the right
precordial leads.
[3] If you suspect a right ventricular MI, do a right-sided ECG (leads
I, II, III, aVR, aVL, avF in the usual positions; but leads V1 - V6 placed
on the right side as the mirror image of their usual left-sided positions).
Then look at lead V4R for ST elevation (88% sensitive, 78% specific for
RV MI).
(no examples)
If you would like to read more about ECG's, consider the
following books:
[1] "Rapid Interpretation of EKG's", by Dale Dubin, Cover Publishing
Company, copyright 1996. Easy reading, a very good first look at ECG's.
[2] "Basic Dysrhythmias", by Robert J. Huszar, Mosby-Year Book, Inc.,
copyright 1994. Intermediate reading, with beautiful illustrations of various
phenomena.
[3] "Electrocardiology in Clinical Practice", by Te-Chuan Chou and
Timothy K. Knilans, W.B. Saunders Company, copyright 1996. Advanced and
detailed, with complete references evaluating the usefulness of various
criteria.
Basic Criteria for Diagnosis in ECG