Anterolateral myocardial infarction
ST segment elevation in leads V2-V5 in an acute infarction
Absent R wave in V2-V5 (QS wave)
T wave inversion in leads V2-V5 in an old or evolving infarction
Q waves in leads I, aVL and V6 along with ST segment elevation in these leads is consistent with presence of additional infarction in the high anterior lateral wall

Inferior myocardial infarction
ST segment elevation in leads II, III, and aVF in an acute infarction
Q waves longer than 0.04 sec in duration in leads II, III, and aVF
T wave inversionin leads II, III, and aVF in an old or evolving infarction
Common presence of a lateral wall component in inferior wall myocardial infarction (T wave changes in leads V4-V6)

Left bundle branch block
QRS Duration Complete RBBB is > 0.13 sec. Incomplete RBBB is between 0.09 and 0.12 sec Morphology Precordial leads V1 = rsR' with CRBBB or V1 = rSr' with IRBBB V6 = qRs with CRBBB or IRBBB Limb leads Axis can be left, left, or normal Terminal 0.08 vector should be ignored when calculating axis Lead I = qRs. Orthogonal leads Lead X = qRS (with IRBBB = qrS) Lead Z = qRS (with CRBBB = qRs)
T wave always in the opposite direction from terminal S wave
Conduction abnormalities Using the usual criteria, both LAFB and LPFB can occur with RBBB Using the ususal criteria, LVH, ASMI, AMI, ACMI, and IMI can be diagnosed with RBBB. >

Left bundle branch block
QRS > 0.12 sec with mid-slurring
Variable frontal plane QRS vector variable
V1 rS along with upleft T wave
Predominantly upleft V5 and V6 along with inverted T wave
Predominantly upleft lead I along with inverted T wave

Left anterior fascicular block
QRS duration < 0.10 sec
QRS vector shows left axis deviation (LAD) in frontal plane > -30 degrees.
QRS morphology Limb leads qR in leads I and aVL. rS in leads II, III, and aVF R peaks in aVL before aVR Precordial leads Delayed R wave transition Persistent S wave in V5-V6 Normal QRS morphology when precordial leads recorded in 2-3 interspaces higher Orthogonal leads qR in lead X rS in lead Y

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LVH diastolic overload
P-wave abnormality of left atrial enlargement (LAE)
Tall, peaked T-waves in leads I, aVL, V5, and V6
Increased QRS duration Instrinsicoid deflection > .09 sec. Deep Q-waves in leads I, aVL, V5, and V6
Voltage Criteria Limb leads Lead I: R >15 mm or R >18 mm with left axis deviation (LAD) Lead aVL: R >12 mm or R >16 mm with LAD Lead II or III: R > 25 mm Precordial leads V5 > 26 mm Sum of S wave in V2 and R wave in V5 > 36 mm V6 > V5 Orthogonal leads Transverse plane mean QRS vector > 20 Frontal plane mean QRS vector > 25

Left ventricular hypertrophy; systolic overload
Abnormality of P wave due to left atrial enlargement
Increased QRS duration Intrinsicoid deflection > 0.09 sec Incomplete Left bundle branch block (ILBBB) Loss of R wave in V1 and V2
Voltage criteria Limb leads Lead I: R > 15 mm or R > 18 mm with left axis deviation (LAD) Lead aVL: R > 12 mm or R > 16 mm with LAD Lead II or III: R > 25 mm Precordial leads V5 > 26 mm Sum of S wave in V2 and R wave in V5 > 36 mm V6 > V5 Orthogonal leads Transverse plane mean QRS vector > 20 mm Frontal plane mean QRS vector > 25 mm
Secondary ST-T changes

Cor pulmonale
P wave Limb leads Vertical axis P > 3 mm in lead II or III Precordial leads Negative P in lead V1
QRS morphology Limb leads left axis deviation S > R in lead I Precordial leads R in V5 - V6 R in V2 Lead V1 rs, Rs, or rS Orthogonal leads R in lead X Tall R wave in lead II
Variable T wave