1. Standardization & Interpretation of ECG
Dr Frijo Jose A

2. Normal QRS Duration ↑with ↑ heart size
Wider - precordial > limb leads
Age- and gender-dependent
Children <4 yrs -QRS ≥90 ms prolonged
4 -16 yrs –QRS ≥ 100 ms prolonged
Adult males – N-QRS up to 110 ms
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3. Mean Frontal Plane Axis
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4. Shifts to the left with increasing age

5. Complete RBBB
QRS ≥120 ms (>16 yrs), >100 ms (4-16 yrs), >90 ms (<4 yrs)
rsr’, rsR’, or Rsr’ - V1 or V2. R’/r’ - Usually wider >R
S duration > R or >40 ms (I&V6)
Normal R peak time (V5 & V6) but >50 ms (V1)
First 3 should be present to make ∆
V1- pure dominant R wave ± notch → Criterion 4 should be satisfied
J. Am. Coll. Cardiol. 2009;53; ;

6. Incomplete RBBB QRS duration
ms (adults), ms (8 -16 yrs), ms (<8 yrs)
Other criteria - Same as for complete RBBB.
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7. Complete LBBB
1. QRS ≥120 ms (Adults),>100 ms (4-16), >90 ms ( <4) 2. Broad notched /slurred R wave - I, aVL, V5, V6 3. Absent q waves - I, V5, V6 (±q Avl) 4. R peak time > 60 ms in V5 & V6 but N in V1, V2,& V3 (when r+) 5. ST & T - Usually opposite in direction to QRS 6. + T wave with upright QRS may be N (+ concordance) 7. ↓ST and/or −T with −QRS (- concordance) -ABN
but in Avl, a narrow q may be present in the absence of myocardial pathology.. 8. LBBB may change mean frontal QRS axis to Rt, to Lt, or to suprior, in some cases in a rate-dependent manner
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8. ST↑≥0.1 mV in leads with +QRS (concordant ST)
Criteria for infarction in the presence of complete left bundle-branch block(GUSTO)
ST↑≥0.1 mV in leads with +QRS (concordant ST)
ST ↑≥ 0.5 mV in leads with −QRS (discordant ST)
ST ↓≥ 0.1 mV in V1-V3 (concordant ST)
Concordant ST changes -↑specificity but ↓ sensitivity
Discordant ST changes - ↓↓ specificity ↓↓ sensitivity
LBBB + concordant ST > 30-d mortality > LBBB + enzyme -- concordant ST changes
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9. Incomplete LBBB
1. QRS ms (adults), ms(8 -16), ms (<8)
2. Presence of LVH pattern
3. R peak time >60 ms in leads V4, V5, and V6
4. Absent q in I, V5, V6
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10. Nonspecific/Unspecified Intraventricular Conduction Disturbance
QRS >110ms (adults), >90ms (8 -16), >80ms (<8) without criteria for RBBB or LBBB
Also
RBBB criteria in precordial leads and LBBB criteria in limb leads, and vice versa
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11. Left Anterior Fascicular Block
1. Frontal plane axis -45°to -90°
2. qR pattern in aVL
3. R-peak time in aVL of ≥45 ms
4. QRS duration <120 ms
These criteria do not apply to patients with CHD in whom LAD is present in infancy
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12. Left Posterior Fascicular Block
1. Frontal plane axis +90°to 180° (adults)
2. rS pattern in I and aVL
3. qR pattern in III and aVF
4. QRS <120 ms
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13. Preexcitation of WPW Type
Whether preexcitation is full or not cannot be determined from surface ECG, but following criteria are suggestive of full preexcitation:
1. PR interval <120 ms during SR (adults) and <90 ms (children)
2. Delta wave
3. QRS >120 ms (adults) and > 90 ms (children)
4. Secondary ST and T wave changes
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14. Terms Not Recommended
Mahaim-type preexcitation -because ∆ cannot be made with certainty with surface ECG
Atypical LBBB, bilateral bundle-branch block, bifascicular block, and trifascicular block -because of great variation in anatomy and pathology producing such patterns
Recommends that each conduction defect be described separately in terms of the structure or structures involved
J. Am. Coll. Cardiol. 2009;53; ;

15. Peri-infarction block
abnormal Q wave generated by a MI in Inf/lat leads, terminal portion of QRS- wide and directed opposite to Q wave (i.e., a QR complex in the inferior or lateral leads)
J. Am. Coll. Cardiol. 2009;53; ;

16. A 59-year-old man with anterolateral pen-infarction block presented a history of
myocardial infarction in January, 1965 and was hospitalized five months later with symptoms of left ventricular
failure. The electrocardiogram demonstrates old anterior infarction. While the initial 0.04-second
QRS vector points inferiorly and posteriorly, the terminal forces point superiorly. Slurring and
notching in the early portion of the QRS complex in various leads are to be noted

17. Peri-ischemic block
transient ↑ in QRS duration accompanies the ST-segment deviation seen with acute injury
J. Am. Coll. Cardiol. 2009;53; ;

18. Primary Repolarization Abnormalities
Abn in ST & T, without changes in depolarization
Localized or diffuse
ischemia, myocarditis, drugs, toxins, electrolyte abn-esp Ca & K
Abrupt HR change, hyperventilation, body position, catecholamines, sympath stimulation or ablation of stellate ganglion, temp changes
J. Am. Coll. Cardiol. 2009;53; ;

19. Secondary Repolarization Abnormalities
Abn in ST & T →direct result of changes in sequence and/or duration of ventri depolarization
manifested as changes in QRS shape and/or duration
due to voltage gradients that are normally largely cancelled but become manifest when the changes in the sequence of depolarization alter the repolarization sequence
BBBs, preexcitation, ectopics, paced V- complexes
Primary and secondary repolarization abnormalities may
occur concurrently. For example, ventricular hypertrophy is
associated with changes in the shape and duration of the
ventricular action potential of isolated ventricular cells, particularly
on the endocardial surface (13). These changes may
contribute to ST- and T-wave changes and are independent of
the changes that are secondary to QRS-amplitude changes
and prolongation of the QRS complex. A combination of
primary and secondary repolarization abnormalities should
also be considered when T-wave polarity does not change as
anticipated by the changes in the QRS complex
J. Am. Coll. Cardiol. 2009;53; ;

20. Displacement of ST
usually measured at “J point,” and, in exercise testing 80 ms after the J point
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21. T-Wave Abnormalities T wave in I, II, aVL, and V2 - V6
Inverted −0.1 to − 0.5 Mv
Deep negative − 0.5 to − 1.0 mV
Giant negative <− 1.0 Mv
Low -amplitude <10% of R-wave in same lead
Flat to − 0.1 mV in leads I, II, aVL (with an R wave taller than 0.3 mV), and V4 to V6
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22. Classification as slight or indeterminate T-wave abnormality
Virtually impossible to develop a cause-specific classification for minor T-wave abn
Classification as slight or indeterminate T-wave abnormality
Overreader -analysis
other features
clinical condition
prior ECGs
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23. T-Wave Alternans
T-wave amplitude variations that alternate every 2nd beat
Typically microvolt T-wave alternans rarely,more pronounced
Latent instability of repolarization predictive of malign arrhythmias
Generally not present at the resting state even in high-risk patients
Stress test, requiring special equipment & analysis software- needed to provoke it
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24. The U Wave The U wave is a mechanoelectric pheno
Frequently absent in limb leads & is most evident in V2 & V3 (0.33 mv or 11% of T wave)
HR dependent
Rarely present at rates >95 bpm
Bradycardia enhances U-wave amplitude & present in 90% at HR< 65 bpm
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25. More recent information
↑ in U, usually in asso with ↓ST & a ↓in T-wave, may be due to quinidine-like effects & ↓K+ and that with more ↑ hypokalemia (<2.7), U may >T in same lead
More recent information
may be due to fusion of U with T rather than to an ↑U. Fusion of U with T also occurs in asso with an ↑ in sympath tone & in presence of a markedly ↑ QT as in LQTS
↓U(V2 - V5)→ abn(a/c ischemia/hypertension)
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26. The QT Interval QRS onset to end of T wave
Onset of QRS -occur up to 20 ms earlier in V2, V3 than limb leads
Some regard differences 50 ms up to 65 ms in QT measured in various leads being normal
This value is reported to be less in women than in men
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27. If T & U are superimposed/cannot be separated→
When QT is measured in individual leads, lead showing ↑QT should be used (usually V2/V3)
If T & U are superimposed/cannot be separated→
QT be measured in leads not showing U (aVR and aVL) or
Downslope of T be extended by drawing a tangent to the steepest proportion of downslope until it crosses TP segment
Might underestimate the QT interval
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28. QT Correction for Rate
Linear regression functions rather than Bazett’s formula be used for QT-rate correction and method used for rate correction be identified in ECG analysis reports
Rate correction of QT interval should not be attempted when RR interval variability is large, as with AF, or when identification of the end of the T wave is unreliable
Relation between QT intervals and heart rates from 40 to 120 beats/min in rest electrocardiograms of men and a simple method to adjust QT interval values
J Karjalainen, M Viitasalo, M Manttari, andV ManninenCentral Military Hospital, Helsinki, Finland.
OBJECTIVES. The aim of this study was to establish the relation between QT intervals and a wide range of rest heart rates in men. These data provided the basis of a simple method for adjusting the QT interval for heart rate. BACKGROUND. Earlier correction equations give conflicting results, especially at low and high heart rates. METHODS. The QT intervals were measured in 324 electrocardiograms of healthy young men. The sample was weighted for low and high heart rates. A curve relating QT intervals and heart rates from 40 to 120 beats/min was constructed. The QT interval at 60 beats/min was used as the reference value, and an adjusting nomogram for different heart rates was created. The reliabilities of the nomogram and three earlier QT correction equations were tested in the study group and in 396 middle-aged men. RESULTS. The nomogram method presented (QTNc = QT + correcting number) adjusted the QT interval most accurately over the whole range of heart rates on the basis of smallest mean-squared residual values between measured and predicted QT intervals. The Fridericia formula (QTFc = QT/RR1/3) gave the best correction at low, but failed at high, heart rates. The linear regression equation (QTLc = QT [1 - RR], Framingham Study) was reliable at normal, but failed at low and high, heart rates. The Bazett formula (QTc = QT/RR1/2) performed poorest at all heart rates. The relation between QT and RR intervals was determined by three linear regressions expressing the slopes for heart rates < 60 beats/min, for heart rates from 60 to 100 beats/min and for heart rates > 100 beats/min. CONCLUSIONS. The QT-RR relation over a wide range of heart rates does not permit the use of one simple adjustment equation. A nomogram providing, for every heart rate, the number of milliseconds that the QT interval must be corrected gives excellent adjustment. 
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29. Prolonged QT: women ≥460 ms; men ≥450 ms
Short QT (women & men) ≤390 ms
In ventricular conduction defects- JT interval (QT duration– QRS duration)
QT dispersion not be included in routine ECG reports
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30. Threshold Values for ST-Segment Changes
For men ≥40 - abn J-point ↑ → 0.2 mV in V2 & V3 and 0.1 mV in others
For men <40 - abn J-point ↑ → 0.25 mV in V2 & V3
For women - abn J-point ↑ → 0.15 mV in V2 & V3 and 0.1 mV in others
For men & women - abn J-point ↑ → 0.05 mV in V3R & V4R, except for males <30 →0.1
For men & women - abn J-point ↑ → 0.05 mV in V7-V9
For men & women of all ages - abn J-point ↓ → 0.05 mV in V2 & V3 and 0.1 mV in all others
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32. Criteria for Acute Myocardial Infarction
Any one of the following criteria
• Detection of ↑and/or ↓ of markers (trop) with at least 1 value above 99th percentile of URL + evidence of myo ischaemia with at least 1 of the following:
• Symptoms of ischaemia;
• ECG changes indicative of new ischaemia (new ST-T changes or new LBBB)
• Development of pathological Q waves in ECG
• Imaging evidence of new loss of viable myo or new RWMA
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33. • Sudden, unexpected cardiac death, involving cardiac arrest, often with symptoms suggestive of myo isch, and accompanied by
new ST ↑ or new LBBB,
and/or evidence of fresh thrombus by CAG and/or at autopsy, but death occurring at a time before appearance of cardiac biomarkers
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34. • Patho findings of an a/c MI
• For PCI in pts with N baseline trop, ↑of markers >99th percentile URL - peri-procedural M necrosis . By convention, ↑ of markers >3×99th percentile URL - PCI-related MI
• For CABG in pts with N baseline trop, ↑ of markers >99th percentile URL - peri-procedural M necrosis. By convention, ↑ of markers >5×99th percentile URL plus either new path Q waves or new LBBB, or angiographically documented new graft or native CA occlusion, or imaging evidence of new loss of viable myocardium - CABG-related MI
• Patho findings of an a/c MI
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35. Criteria for Prior Myocardial Infarction
Any one of the following criteria : • New patho Q waves ± symptoms • Imaging evidence of a region of loss of viable myo that is thinned & fails to contract, in absence of a non-ischaemic cause • Patho findings of a healed/healing MI
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