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Standardization & Interpretation of ECG Dr Frijo Jose A.

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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 yrs –QRS ≥ 100 ms prolonged Adult males – N-QRS up to 110 ms J. Am. Coll. Cardiol. 2009;53; ;

3 Mean Frontal Plane Axis J. Am. Coll. Cardiol. 2009;53; ;

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 ∆ o 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. J. Am. Coll. Cardiol. 2009;53; ;

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 J. Am. Coll. Cardiol. 2009;53; ;

8 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 J. Am. Coll. Cardiol. 2009;53; ;

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 J. Am. Coll. Cardiol. 2009;53; ;

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 J. Am. Coll. Cardiol. 2009;53; ;

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 J. Am. Coll. Cardiol. 2009;53; ;

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 J. Am. Coll. Cardiol. 2009;53; ;

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 J. Am. Coll. Cardiol. 2009;53; ;

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; ;

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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 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 J. Am. Coll. Cardiol. 2009;53; ;

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 J. Am. Coll. Cardiol. 2009;53; ;

22 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 J. Am. Coll. Cardiol. 2009;53; ;

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 J. Am. Coll. Cardiol. 2009;53; ;

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 J. Am. Coll. Cardiol. 2009;53; ;

25 ↑ in U, usually in asso with ↓ST & a ↓in T- wave, may be due to quinidine-like effects & ↓K+ and that with more ↑ hypokalemia ( 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) J. Am. Coll. Cardiol. 2009;53; ;

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 J. Am. Coll. Cardiol. 2009;53; ;

27 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 J. Am. Coll. Cardiol. 2009;53; ;

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 J. Am. Coll. Cardiol. 2009;53; ;

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 J. Am. Coll. Cardiol. 2009;53; ;

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 J. Am. Coll. Cardiol. 2009;53; ;

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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 99 th 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 J. Am. Coll. Cardiol. 2007;50;

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 J. Am. Coll. Cardiol. 2007;50;

34 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 J. Am. Coll. Cardiol. 2007;50;

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 J. Am. Coll. Cardiol. 2007;50;

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