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1 Folate Pool - The Role of B Vitamins in One-Carbon MetabolismThis figure depicts the pathway for folate utilization and the role of vitamins B6 and B12 in the metabolism of methyl-tetrahydrofolate and homocysteine.Folate; FolicinHEAL Open Review Collection
2 LVH - best seen in the frontal plane leads!LVH - best seen in the frontal plane leads!Knowledge Weavers ECG
3 Isochronic ventricular rhythmAn isochronic ventricular rhythm is also called an accelerated ventricular rhythm because it represents an active ventricular focus. This arrhythmia is a common reperfusion arrhythmia in acute MI patients. It often begins and ends with fusion beats and there is AV dissociation. Treatment is usuall...Knowledge Weavers ECG
4 LVH: limb lead criteriaIn this example of LVH, the precordial leads don't meet the usual voltage criteria or exhibit significant ST segment abnormalities. The frontal plane leads, however, show voltage criteria for LVH and significant ST segment depression in leads with tall R waves. The voltage criteria include 1) R in...Knowledge Weavers ECG
5 ST segment depressionST segment depression is a nonspecific abnormality that must be evaluated in the clinical context in which it occurs. In a patient with angina pectoris ST depression usually means subendocardial ischemia and, unlike ST elevation, is not localizing to a particular coronary artery lesion.Knowledge Weavers ECG
6 Rate-dependent LBBBIn this rhythm strip of sinus arrhythmia, the faster rates have a LBBB morphology. In some patients with a diseased left bundle branch, the onset of LBBB usually occurs initially as a rate-dependent block; i.e., the left bundle fails to conduct at the faster rate because of prolonged refractoriness...Knowledge Weavers ECG
7 RV vs LV PVC's - marquetteRV vs LV PVC's - marquetteKnowledge Weavers ECG
8 RBBB: Precordial leadsRBBB: Precordial leadsKnowledge Weavers ECG
9 Inferior MI and RBBBInferior MI and RBBBKnowledge Weavers ECG
10 Atrial parasystoleParasystolic rhythms involve an independent ectopic pacemaker resulting in nonfixed coupled premature beats. Parasystole may occur in the atria, as seen in this example, in the AV junction, and in the ventricles. Note the common inter-ectopic interval separating the parasystolic PAC's.Knowledge Weavers ECG
11 Digitalis intoxication: junctional tachycardia with and without exit blockIn A the rhythm is junctional tachycardia with RBBB. In B there is 2nd degree exit block with a 3:2 conduction ratio; i.e., every 3rd junctional impulse fails to reach the ventricles... at least for the first two groupings on 1.4sec.Knowledge Weavers ECG
12 LVH and many PVCsThe combination of voltage criteria (SV2 + RV6>35mm) and ST-T abnormalities in V5-6 are definitive for LVH. There may also be LAE as evidenced by the prominent negative P terminal force in lead V1. Isolated PVCs and a PVC couplet are also present.Knowledge Weavers ECG
13 Frontal plane QRS axis = +150 degrees (RAD)This is an unusual right axis deviation (RAD). Lead I is negative, which usually means RAD. Lead II is the isoelectric lead, which almost always means -30 degrees; but in this example the axis is 180 degrees away from -30, or +150 degrees.Knowledge Weavers ECG
14 Pacemaker failure to capture - marquettePacemaker failure to capture - marquetteKnowledge Weavers ECG
15 WPW type preexcitation - marquetteWPW type preexcitation - marquetteKnowledge Weavers ECG
16 Sinus pause or arrest - marquetteSinus pause or arrest - marquetteKnowledge Weavers ECG
17 SA exit block - marquetteSA exit block - marquetteKnowledge Weavers ECG
18 An interpolated PACAlthough most PACs reset the sinus node producing an incomplete compensatory pause, this PAC, indicated by the black arrow, is interpolated, i.e., sandwiched between two sinus beats. Note that the subsequent sinus P wave conducts with prolonged PR interval due to the relative refractoriness of the...Knowledge Weavers ECG
19 Incomplete AV dissociation due To 2nd degree AV block2nd degree AV block is evident from the nonconducted P waves. Junctional escapes, labled J, terminate the long pauses because that's the purpose of escape pacemakers....to protect us from too slow heart rates. All QRSs with shorter RR intervals are capture beats, labeled c. Atypical RBBB with a q...Knowledge Weavers ECG
20 Frontal plane QRS axis = +50 degrees1) lead aVL is the smallest QRS and closest to being the isoelectric lead; 2) perpendiculars to aVL are +60 and -120 degrees; 3) lead I is positive; 4) therefore, the axis is closest to being +60 degrees. Because aVL is actually slightly positive, the axis is only about +50 degrees (i.e., slightly ...Knowledge Weavers ECG
21 Atypical LBBB with primary T wave abnormalitiesPrimary T wave abnormalities in LBBB refer to T waves in the same direction as the major deflection of the QRS. These are seen in leads I, III, aVL, V2-4. Most likely diagnosis is myocardial infarction.Knowledge Weavers ECG
22 Mobitz II 2nd degree AV block with LBBBThe QRS morphology in lead V1 shows LBBB. The arrows point to two consecutive nonconducted P waves, most likely hung up in the diseased right bundle branch. This is classic Mobitz II 2nd degree AV block.Knowledge Weavers ECG
23 RBBB with primary ST-T abnormalities: Precordial leadsRBBB with primary ST-T abnormalities: Precordial leadsKnowledge Weavers ECG
24 Bifascicular block: RBBB + LAFBBifascicular block: RBBB + LAFBKnowledge Weavers ECG
25 PVC with R-on-T - marquettePVC with R-on-T - marquetteKnowledge Weavers ECG
26 PVCs - marquettePVCs - marquetteKnowledge Weavers ECG
27 Right Ventricular Hypertrophy (RVH) & Right Atrial Enlargement (RAE)In this case of severe pulmonary hypertension, RVH is recognized by the prominent anterior forces (tall R waves in V1-2), right axis deviation (+110 degrees), and P pulmonale (i.e., right atrial enlargement). RAE is best seen in the frontal plane leads; the P waves in lead II are >2.5mm in amplitud...Knowledge Weavers ECG
28 ECG intervals and wavesThe P wave represents atrial activation; the PR interval is the time from onset of atrial activation to onset of ventricular activation. The QRS complex represents ventricular activation; the QRS duration is the duration of ventricular activation. The ST-T wave represents ventricular repolarizatio...Knowledge Weavers ECG
29 Atrial flutter with 2:1 AV conductionFlutter waves are best seen in lead V1; one immediately follows the QRS and the other precedes the next QRS. The regular ventricular rate of 150 bpm should always prompt us to condider this diagnosis.Knowledge Weavers ECG
30 Left axis deviation: QRS axis = -45 degreesThere is no isoelectric, but leads aVR and II are the closest to being isoelectric, placing the axis between -30 and -60 degrees. The axis, therefore, is about -45 degrees.Knowledge Weavers ECG
31 Long QT: an ECG marker for sudden cardiac deathLong QT: an ECG marker for sudden cardiac deathKnowledge Weavers ECG
32 Frontal plane QRS axis = 0 degreesFrontal plane QRS axis = 0 degreesKnowledge Weavers ECG
33 Isolated PAC - marquetteIsolated PAC - marquetteKnowledge Weavers ECG
34 Inferolateral ST segment elevationST Segment elevation with a straight or convex upwards configuration usually means transmural ischemia (or injury) and is seen in the setting of acute myocardial infarction. This ECG finding may also be seen transiently during coronary artery spasm. Unlike ST depression, ST elevation is often loca...Knowledge Weavers ECG
35 A PAC initiates paroxysmal atrial fibrillationThe arrow indicates slight alteration of the ST-T wave by a PAC. The PAC, in turn, falls during the vulnerable period of atrial repolarization and initiates atrial fibrillation. Similar but more catastrophic events happen in the ventricles when PVC's occur during the vulnerable period, i.e. R-on-T...Knowledge Weavers ECG
36 Left Atrial Abnormality & 1st Degree AV BlockThe P-wave is notched, wider than 0.12s, and has a prominent negative (posterior) component in V1 - all criteria for left atrial abnormality or enlargement (LAE). The PR interval >0.20s. Minor ST-T wave abnormalities are also present.Knowledge Weavers ECG
37 3rd degree AV block rx'ed with a ventricular pacemakerIn A the ECG shows complete or 3rd degree AV block with a left ventricular escape rhythm, as evidenced by the upright QRS morphology. In B the artificial right ventricular pacemaker rhythm is shown.Knowledge Weavers ECG
38 Lead Error: V1 & V3 are TransposedIn this normal 12-lead ECG the V1 and V3 chest electrodes are interchanged. Experienced ECG interpreters should be able to spot this lead placement error.Knowledge Weavers ECG
39 PAC and PVC: complete vs. incomplete pausePAC and PVC: complete vs. incomplete pauseKnowledge Weavers ECG
40 Electronic atrial pacing - marquetteElectronic atrial pacing - marquetteKnowledge Weavers ECG
41 Normal sinus rhythm - marquetteNormal sinus rhythm - marquetteKnowledge Weavers ECG
42 Left ventricular PVC'sIn lead V1, these PVC's are positive or anterior in direction indicating probable LV origin with late activation of the right ventricle. The arrow points to the notch on the downstroke of the PVC making its morphology highly unlikely to be an aberrantly conducted supraventricular beat.Knowledge Weavers ECG
43 Junctional tachycardia with exit block: a manifestation of digitalis intoxicationTheladder diagramsays it all: the atria are fibrillating; there is complete heart block in the AV junction; a junctional tachycardia focus is firing at about 130 bpm, but not all junctional impulses reach the ventricles due to 2nd degree exit block.Knowledge Weavers ECG
44 Frontal plane QRS axis = +90 degrees1) Lead I is isoelectric; 2) perpendiculars to lead I are +90 and -90 degrees; 3) leads II, III, aVF are positive; 4) therefore, the axis must be +90 degrees.Knowledge Weavers ECG
45 Electrical and mechanical events diagram - marquetteElectrical and mechanical events diagram - marquetteKnowledge Weavers ECG
46 Anteroseptal MI, fully evolved: precordial leadsAnteroseptal MI, fully evolved: precordial leadsKnowledge Weavers ECG
47 Left atrial enlargement: leads II and V1Left atrial enlargement: leads II and V1Knowledge Weavers ECG
48 Fully evolved inferior MI: frontal planeFully evolved inferior MI: frontal planeKnowledge Weavers ECG
49 Frontal plane QRS axis = -75 degreesFrontal plane QRS axis = -75 degreesKnowledge Weavers ECG
50 Supernormal conduction: 2nd degree AV block with rare captures; accelerated ventricular rhythmThis complicated rhythm strip illustrates 'supernormal' conduction... a situation where conduction is better than expected. The ladder diagram shows that the accelerated ventricular rhythm prevents most of the sinus impulses from reaching the ventricles. Only appropriately timed sinus impulses rea...Knowledge Weavers ECG
51 Complete AV block, junctional escape rhythm, and ventriculophasic sinus arrhythmiaComplete AV block is seen as evidenced by the AV dissociation. A junctional escape rhythm sets the ventricular rate at 45 bpm. The PP intervals vary because of ventriculophasic sinus arrhythmia; this is defined when the PP interval that includes a QRS is shorter than a PP interval that excludes a ...Knowledge Weavers ECG
52 Junctional parasystole and pseudo-AV blockThis complicated rhythm strip shows normal sinus rhythm and a competing junctional parasystolic focus. Solid circles indicate junctional premature beats from the parasystolic focus. Open circles indicate non-conducted junctional prematures; the first open circle is a nonconducted junctional prematur...Knowledge Weavers ECG
53 Premature junctional complexes with retrograde P wavesThe ladder diagram illustrates the PJC with retrograde atrial captureKnowledge Weavers ECG
54 Left Atrial Abnormality & 1st Degree AV Block: Leads II and V1Left Atrial Abnormality & 1st Degree AV Block: Leads II and V1Knowledge Weavers ECG
55 Right Axis Deviation & RAE (P pulmonale): Leads I, II, IIIRight Axis Deviation & RAE (P pulmonale): Leads I, II, IIIKnowledge Weavers ECG
56 Ventricular bigeminy - marquetteVentricular bigeminy - marquetteKnowledge Weavers ECG
57 LBBB and 2nd degree AV block, mobitz type IMobitz II 2nd degree AV block is usually a sign of bilateral bundle branch disease. One of the two bundle branches should be completely blocked; in this example the left bundle is blocked. The nonconducted sinus P waves are most likely blocked in the right bundle which exhibits 2nd degree block. ...Knowledge Weavers ECG
58 Infero-posterior MI&RBBBDeep Q waves in II, III, aVF plus tall R waves in V1-2 are evidence for this infero-posterior MI. The wide QRS (>0.12s) and RR' complex in V1 are evidence for RBBB. Any time RBBB has an initial R in V1 equal to or greater than the R', true posterior MI must be considered. Q waves in V5-6 suggest a...Knowledge Weavers ECG
59 Extensive anterior/anterolateral MI: recentSignificant pathologic Q-waves (V2-6, I, aVL) plus marked ST segment elevation are evidence for this large anterior/anterolateral MI. The exact age of the infarction cannot be determined without clinical correlation and previous ECGs, but this is likely a recent MI.Knowledge Weavers ECG
60 Nonconducted PAC's slowing the heart rateConsecutive nonconducted PAC's, indicated by arrows, can significantly slow the heart rate. Note the distortion of the ST-T waves caused by the PAC. A hint in recognizing nonconducted PAC's is to find conducted PAC's in the same rhythm strip.Knowledge Weavers ECG
61 three fates of PAC's: 1. normal conduction; 2. aberrant conduction; 3. non-conductionthree fates of PAC's: 1. normal conduction; 2. aberrant conduction; 3. non-conductionKnowledge Weavers ECG
62 QRS axis = 0 degreesLead aVF is isoelectric; lead I is positive; therefore, the QRS axis is 0 degrees.Knowledge Weavers ECG
63 Ventricular fusion beat - marquetteVentricular fusion beat - marquetteKnowledge Weavers ECG
64 60 cycle artifact - marquette60 cycle artifact - marquetteKnowledge Weavers ECG
65 LBBB: precordial leadsLBBB: precordial leadsKnowledge Weavers ECG
66 Not all sore thumbs are ventricular in originPACs have three fates: normal conduction into ventricles, aberrant conduction in ventricles due to bundle branch or fascicular block, and non-conduction due to block in AV junction. In this example PAC 1 is normally conducted and PAC 2 is conducted with RBBB aberration. The longer preceding cycle ...Knowledge Weavers ECG
67 Acute infero-postero-lateral MIHyperacute ST segment elevation is seen in leads II, III, aVF (inferior location) and in leads V4-6 (apical lateral wall location). Hyperacute ST depression is seen in leads V1-2 (an expression of posterior wall injury). in addition there are reciprocal ST segment depression changes in leads I an...Knowledge Weavers ECG
68 Ventricular Pacemaker Rhythm: V1-3Note the small pacemaker spikes before the QRS complexes. In addition, the QRS complex in V1-3 exhibits ventricular ectopic morphology; i.e., there is a slur or notch at the beginning of the S wave, and >60ms delay from onset to QRS to nadir of S wave. This rules against a supraventricular rhythm wi...Knowledge Weavers ECG
69 Inferior MI: fully evolvedSignificant pathologic Q-waves are seen in leads II, III, aVF along with resolving ST segment elevation and symmetrical T wave inversion. This is a classic inferior MI.Knowledge Weavers ECG
70 Complete AV block (3rd degree) with junctional rhythmComplete AV block (3rd degree) with junctional rhythmKnowledge Weavers ECG
71 QRS axis = +90 degreesLead I is isoelectric; II and III are positive; the axis is +90 degrees.Knowledge Weavers ECG
72 Left bundle branch block - marquetteLeft bundle branch block - marquetteKnowledge Weavers ECG
73 Junctional escape rhythmJunctional escape rhythmKnowledge Weavers ECG
74 Diagram: AV nodal reentrant tachycardiaThe AV node often has dual pathways; in this diagram the alpha pathway is fast, but has a long refractory period; the beta pathway is conducts more slowly, but recovers faster.In sinus rhythm the faster alpha pathway is used and accounts for the normal PR interval. When a PAC occurs, however, the i...Knowledge Weavers ECG
75 Atrial parasystoleIn atrial parasystole non-fixed coupled PACs, shown by arrows, occur at a common inter-ectopic interval or at multiples of this interval. Atrial fusions, not shown here, may also occur when the PAC occurs in close temporal proximity to the sinus impulse.Knowledge Weavers ECG
76 Atrial flutter with 2:1 conduction: leads II, III, V1Atrial flutter with 2:1 conduction: leads II, III, V1Knowledge Weavers ECG
77 Pacemaker lead wire placement diagram - marquettePacemaker lead wire placement diagram - marquetteKnowledge Weavers ECG
78 Frontal and horizontal plane lead diagramFrontal and horizontal plane lead diagramKnowledge Weavers ECG
79 ST segment diagram - marquetteST segment diagram - marquetteKnowledge Weavers ECG
80 Atrial bigeminy - marquetteAtrial bigeminy - marquetteKnowledge Weavers ECG
81 Right Bundle Branch BlockRight Bundle Branch BlockKnowledge Weavers ECG
82 2nd degree AV block, type I, with accelerated junctional escapes and a ladder diagramThe ladder diagram illustrates a Wenckebach type AV block by the increasing PR intervals before the blocked P wave. After the blocked P wave, however, a rev-ed up junctional pacemaker terminates the pause. Note that the junctional beats have a slightly different QRS morphology from the sinus beats...Knowledge Weavers ECG
83 Atrial tachycardia with exit block and AV blockThe ectopic P waves, easily seen in this example,occur in groups, separated by short pauses. This is likely due to an exit block just distal to the atrial pacemaker. Because not all of the P waves make it to the ventricles, there is also 2nd degree AV block. Therefore, two levels of block are pre...Knowledge Weavers ECG
84 LVHIn this example of LVH, the precordial leads don't meet the usual voltage criteria or exhibit significant ST segment abnormalities. The frontal plane leads, however, show voltage criteria for LVH and significant ST segment depression in leads with tall R waves. The voltage criteria include 1) R in a...Knowledge Weavers ECG
85 A nonconducted PAC causes an unexpected pauseUnexpected pauses in rhythm have several causes, the most frequent being a nonconducted PAC. In this example the nonconducted PAC is seen in the ST segment of the pause. Note the change in the ST-T compared to the other ST-T waves.Knowledge Weavers ECG
86 Giant TU fusion wavesTU fusion waves are often seen in long QT syndromes. The differential diagnosis of this ECG abnormality includes electrolyte abnormalities -hypokalemia, CNS disease, e.g., subarachnoid hemorrhage; hereditary long QT syndromes, and drugs such as quinidine.Knowledge Weavers ECG
87 Left anterior fascicular block (LAFB)LAFB is the most common of the intraventricular conduction defects. It is recognized by 1) left axis deviation; 2) rS complexes in II, III, aVF; and 3) small q in I and/or aVL.Knowledge Weavers ECG
88 Atrial flutter with 2:1 AV conduction: lead V1The arrows point to two flutter waves for each QRS complex. Atrial rate = 280; ventricular rate = 140.Knowledge Weavers ECG
89 Long QT Interval and Giant Negative T WavesLong QT Interval and Giant Negative T WavesKnowledge Weavers ECG
90 Frontal plane QRS axis = -15 degreesFrontal plane QRS axis = -15 degreesKnowledge Weavers ECG
91 Ventricular pacemaker rhythmNote the small pacemaker spikes before the QRS complexes in many of the leads. In addition, the QRS complex in V1 exhibits ventricular ectopic morphology; i.e., there is a slur or notch at the beginning of the S wave, and>60ms delay from onset to QRS to nadir of S wave. This rules against a suprav...Knowledge Weavers ECG
92 Diffuse anterolateral T wave abnormalitiesDiffuse anterolateral T wave abnormalitiesT Wave AbnormalitiesKnowledge Weavers ECG
93 Frontal plane QRS axis = -45 degreesFrontal plane QRS axis = -45 degreesKnowledge Weavers ECG
94 Marked sinus arrhythmia - marquetteMarked sinus arrhythmia - marquetteKnowledge Weavers ECG
95 Muscle tremor artifact - marquetteMuscle tremor artifact - marquetteKnowledge Weavers ECG
96 RBBB + LAFB: bifascicular blockRBBB + LAFB: bifascicular blockKnowledge Weavers ECG
97 ECG of the century: A most unusual 1st degree AV blockOn Day 1, at a heart rate of 103 bpm the P waves are not clearly defined suggesting an accelerated junctional rhythm. However, on Day 2, at a slightly slower heart rate the sinus P wave suddenly appears immediately after the QRS complex. In retrospect, the sinus P wave in Day 1 was found burried i...Knowledge Weavers ECG
98 RBBB plus mobitz II 2nd degree AV blockThe classic rSR' in V1 is RBBB. Mobitz II 2nd degree AV block is present because the PR intervals are constant. Statistically speaking, the location of the 2nd degree AV block is in the left bundle branch rather than in the AV junction. The last QRS in the top strip is a junctional escape, since...Knowledge Weavers ECG
99 Left axis deviation: QRS axis = -60 degreesLead aVR is isoelectric; leads II and III are mostly negative. The QRS axis, therefore, is -60 degrees.Knowledge Weavers ECG
100 QRS axis = +30 degreesLead III is isoelectric; leads I and II are positive. The QRS axis, therefore, is +30 degrees.Knowledge Weavers ECG
101 Pacemaker failure to sense - marquettePacemaker failure to sense - marquetteKnowledge Weavers ECG
102 Pacemaker fusion beat - marquettePacemaker fusion beat - marquetteKnowledge Weavers ECG
103 RAE & RVHRAE & RVHKnowledge Weavers ECG
104 Type II, 2nd degree sino-atrial blockTwo types of 2nd degree SA block have been described. In type-I, or SA Wenckebach, the P-P interval of the pause is less than 2x the preceding P-P intervals. In type-II SA block the P-P interval of the pause is approximately 2x the normal P-P interval. The distinction between types I and II is no...Knowledge Weavers ECG
105 Bradycardia-dependent LBBB with carotid sinus massageWhen carotid sinus massage slows the heart rate in this example, the QRS widens into a LBBB. This form of rate-dependent bundle branch block is thought to be due to latent pacemakers in the bundle undergoing phase 4 depolarization; when the sinus impulse enters the partially depolarized bundle, slow...Knowledge Weavers ECG
106 Atrial tachycardia with 3:2 AV blockIn this rhythm the atrial rate from an ectopic focus is 160 bpm. Atrial activity can be seen on top of T waves, and before QRS's. Careful observation reveals a 3:2 Wenckebach relationship between P waves and QRS's. Atrial tachycardia with block is often a sign of digitalis intoxication.Knowledge Weavers ECG
107 Ventricular fusion beatsFusion beats occur when two or more activation fronts contribute to the electrical event. These may occur in the atria or in the ventricles. In this example the ventricular fusions are the result of simultaneous activation of the ventricles from two foci, the sinus node and a ventricular ectopic...Knowledge Weavers ECG
108 Diagram: digitalis effect on rhythm and conductionDiagram: digitalis effect on rhythm and conductionKnowledge Weavers ECG
109 Calibration signal - marquetteCalibration signal - marquetteKnowledge Weavers ECG
110 Old inferior MIOld inferior MIKnowledge Weavers ECG
111 Second degree AV block, type I, with 3:2 conduction ratioThere are two types of 2nd degree AV Block. In this example of Type I or Wenckebach AV block there are 3 P waves for every 2 QRSs; the PR interval increases until a P wave fails to conduct. This is an example of group beating.Knowledge Weavers ECG
112 Infero-posterior MI with RBBBThis is an unusual RBBB because the initial R wave is taller than the R wave in lead V1. This is the clue for true posterior MI. The tall initial R wave in V1 is a pathologic R wave analagous to the pathologic Q wave of an anterior MI.Knowledge Weavers ECG
113 Right Atrial Enlargement (RAE) & Right Ventricular Hypertrophy (RVH)RAE is recognized by the tall (>2.5mm) P waves in leads II, III, aVF. RVH is likely because of right axis deviation (+100 degrees) and the Qr (or rSR') complexes in V1-2.Knowledge Weavers ECG
114 Frontal plane: accelerated junctional rhythm and inferior MIFrontal plane: accelerated junctional rhythm and inferior MIKnowledge Weavers ECG
115 QRS axis = -30 degreesLead II is isoelectric; I is positive; III is negative. The axis is -30 degrees.Knowledge Weavers ECG
116 Voltage criteria for LVHVoltage criteria for LVHKnowledge Weavers ECG
117 Infero-posterior MIInfero-posterior MIKnowledge Weavers ECG
118 RBBB - marquetteRBBB - marquetteKnowledge Weavers ECG
119 Second degree AV block, type I, with bradycardia-dependent RBBBAn interesting and unusual form of rate-dependent bundle branch block. Normal sinus rhythm at 85 bpm is present with a 3:2 and 2:1 2nd degree AV block. The progressive PR prolongation in the 3:2 block makes this a type-I or Wenckebach block.Long cycles end in RBBB; short cycles have normal QRS dur...Knowledge Weavers ECG
120 Bifascicular block: RBBB + LAFBThis is the most common of the bifascicular blocks. RBBB is most easily recognized in the precordial leads by the rSR' in V1 and the wide S wave in V6 (i.e., terminal QRS forces oriented rightwards and anterior). LAFB is best seen in the frontal plane leads as evidenced by left axis deviation (-50...Knowledge Weavers ECG
121 Frontal plane lead diagramThe six frontal plane leads are illustrated with their respective positive and negative poles.When forced to intersect at a center point, the six leads inscribe a 360 degree circle. The normal frontal plane axis is from -30 degrees to + 90 degrees, shaded in grey. Left axis deviation is from -30 d...Knowledge Weavers ECG
122 Anteroseptal MI: fully evolvedThe QS complexes, resolving ST segment elevation and T wave inversions in V1-2 are evidence for a fully evolved anteroseptal MI. The inverted T waves in V3-5, I, aVL are also probably related to the MI.Knowledge Weavers ECG
123 Atrial parasystoleThe evenly spaced dots indicate ectopic atrial activity from a parasystolic atrial pacemaker. Non-fixed coupled PACs are seen having a common inter-ectopic interval. One of the PACs is nonconducted.Knowledge Weavers ECG
124 Ventricular tachycardia - marquetteVentricular tachycardia - marquetteKnowledge Weavers ECG
125 Long QT IintervalLong QT IntervalKnowledge Weavers ECG
126 ECG of the century - part II: dual AV pathwaysAn astute cardiology fellow, yours truly, went to the patient's bedside on Day 2 and massaged the right carotid sinus as indicated by the arrow. Four beats later at a slightly slower heart rate the PR interval suddenly normalized suggesting an abrupt change from a slow AV nodal pathway to a fast AV...Knowledge Weavers ECG
127 Left Atrial Enlargement & Nonspecific ST-T Wave AbnormalitiesLAE is best seen in V1 with a prominent negative (posterior) component measuring 1mm wide and 1mm deep. There are also diffuse nonspecific ST-T wave abnormalities which must be correlated with the patient's clinical status. Poor R wave progression in leads V1-V3, another nonspecific finding, is als...Knowledge Weavers ECG
128 Atrial flutter with 3:2 AV conductionThis 12-lead ECG shows a subtle bigeminal rhythm resulting from atrial flutter with a 3:2 AV conduction ratio; RR intervals alternate by a small duration. This is uncommon! The impulses from the atrial flutter conduct through the AV junction in a Wenckebach sequence; for every 3 flutter waves the s...Knowledge Weavers ECG
129 A very subtle 1st degree AV blockWhere are the P waves??? They are hiding in the T waves as indicated by the arrows. How do we know? The PVC unmasked the sinus P wave, and now it is seen in the pause following the PVC. The PR interval is, therefore, about 500 ms.Knowledge Weavers ECG
130 PAC's with and without aberrant conduction - marquettePAC's with and without aberrant conduction - marquetteKnowledge Weavers ECG
131 Ventricular fibrillation - marquetteVentricular fibrillation - marquetteKnowledge Weavers ECG
132 Nonconducted PAC - marquetteNonconducted PAC - marquetteKnowledge Weavers ECG
133 Trifascicular block: RBBB, LAFB, and mobitz II 2nd degree AV blockA nice example of trifascicular block: Lead V1 shows RBBB; Lead II is mostly negative with an rS morphology suggesting left anterior fascicular block. Since Mobitz II 2nd degree AV block is more often located in the bundle branch system, the only location left for this block is the left posterior ...Knowledge Weavers ECG
134 2nd degree AV block, type I, with junctional escapesJunctional escapes are passive, protective events whenever the heart rate slows below that of the escape mechanism. In this example of 2nd degree AV block, type I, the escapes occur following the non-conducted P waves. Arrows indicate the position of the P waves. Note that the escape beats have a...Knowledge Weavers ECG
135 Atrial flutter with 2:1 AV conductionAtrial flutter with 2:1 AV block is one of the most frequently missed ECG rhythm diagnoses because the flutter waves are often hard to find. In this example two flutter waves for each QRS are best seen in lead III and V1. The ventricular rate at 150 bpm should always prompt us to consider atrial fl...Knowledge Weavers ECG
136 Identification of PVC's and PAC'sPVC's usually stick out like sore thumbs; PAC's are often difficult to see because they are hidden in the preceding ST-T wave. The PVC in this example is mostly negative in lead V1 suggesting RV origin; i.e., most of activation is moving in posterior direction towards the left ventricle.Knowledge Weavers ECG
137 AV dissociation by defaultThe nonconducted PAC's set up a long pause which is terminated by ventricular escapes; note the wider QRS morphology of the escape beats indicating their ventricular origin. Incomplete AV dissociation occurs during the escape beats, since the atria are still under the control of the sinus node.Knowledge Weavers ECG
138 Lead error: V1 and V3 are transposed!In the precordial leads the V1 and V3 chest electrodes are interchanged. Experienced ECG interpreters should be able to spot this lead placement error.Knowledge Weavers ECG
139 Infero-posterior MI & RBBB: Frontal Plane Leads + V1Infero-posterior MI & RBBB: Frontal Plane Leads + V1Knowledge Weavers ECG
140 WPW Type Pre-excitation: Precordial LeadsWPW Type Pre-excitation: Precordial LeadsKnowledge Weavers ECG
141 Acute anterior MIAcute anterior MIKnowledge Weavers ECG
142 2nd degree AV block, type I with escapes and capturesOften in the setting of 2nd degree AV block the pauses caused by nonconducted P waves are long enough to enable escape pacemakers from the junction or ventricles to take over. This example illustrates junctional escapes, labled E and captures, labled C. Note that the PR intervals for the captures ...Knowledge Weavers ECG
143 Ventricular paced rhythm with retrograde wenckebachRetrograde atrial captures from a ventricular paced rhythm are occurring with increasing R-P intervals; i.e., retrograde Wenckebach. The ladder diagram indicates that after the blocked retrograde event, a single sinus P wave is seen dissociated from the ventricular rhythm.Wenckebach AV BlockKnowledge Weavers ECG
144 Nonconducted PAC's: an unusual bigeminyOccasionally nonconducted PAC's can create interesting rhythms. In this example every other sinus beat is followed by an early, nonconducted PAC. The resulting pause sets up a bigeminal rhythm. Note the distortion of the T waves caused by the nonconducted PAC's.Knowledge Weavers ECG
145 Atrial flutter with 2:1 AV conduction: leads II, III, V1In leads II and III, the one of the flutter waves occurs at the end of the QRS complex and might be mistaken for part of the QRS itself; i.e., the S wave. In lead V1, the two flutter waves for every QRS are more easily identified.Knowledge Weavers ECG
146 Accelerated IVR with AV dissociation - marquetteAccelerated IVR with AV dissociation - marquetteKnowledge Weavers ECG
147 Old inferior MIOld inferior MIKnowledge Weavers ECG
148 Diagram: type I vs. type II 2nd degree AV blockIn type I 2nd degree AV block the PR progressively lengthens until a nonconducted P wave occurs. The PR gets longer by smaller and smaller increments; this results in gradual shortening of the RR intervals. The RR interval of the pause is usually less than the two preceding RR intervals. The RR i...Knowledge Weavers ECG
149 PAC's with RBBB aberrationThese PAC's, indicated by arrows, enter the ventricles and find the right bundle refractory. They therefore conduct with RBBB aberrancy. In most normal hearts the right bundle recovery time is longer than the left bundle's; most aberrancy, therefore, has aRBBB morphology. In some diseased hearts t...Knowledge Weavers ECG
150 RBBB + LAFB = bifascicular blockThe RBBB is diagnosed by the wide QRS with prominent anterior (e.g., V1) and late rightward (e.g., I, V6) forces. The LAFB is recognized by the marked left axis deviation (-75 degrees) in the frontal plane, rS complexes in II, III, aVF, and the tiny q-wave in aVL.Knowledge Weavers ECG
151 Massage parlor gamesWhen unsure of the mechanism of a supraventricular tachycardia, carotid sinus massage may help make the diagnosis. In this example, carotid sinus massage causes marked AV block which permits easy recognition of the rapid, regular atrial flutter waves.Knowledge Weavers ECG
152 Wandering baseline artifact - marquetteWandering baseline artifact - marquetteKnowledge Weavers ECG
153 Frontal plane QRS axis = +15 degreesFrontal plane QRS axis = +15 degreesKnowledge Weavers ECG
154 Frontal plane QRS axis = +30 degreesFrontal plane QRS axis = +30 degreesKnowledge Weavers ECG
155 Acute inferoposterior MIAcute inferoposterior MIKnowledge Weavers ECG
156 Sinus bradycardiaSinus bradycardiaKnowledge Weavers ECG
157 2nd degree AV block, mobitz type II, with LBBBThe wide QRS complexes in lead V1 indicates LBBB. 2nd degree AV block, Mobitz II is suggested by the two fixed PR intervals prior to the nonconducted P wave. The location of the block is most likely in the right bundle, because Mobitz II is usually a sign of bilateral bundle branch disease.Knowledge Weavers ECG
158 A very subtle atrial tachycardia with 2:1 blockAlthough at first glance this looks like normal sinus rhythm at 95 bpm. On closer look, there are 2 P waves for every QRS; the atrial rate is 190 bpm. Note the hidden P in the T waves. This rhythm is likely due to digitalis intoxication, as are the GI symptoms.Knowledge Weavers ECG
159 Left atrial enlargementLeft atrial enlargement is illustrated by increased P wave duration in lead II, top ECG, and by the prominent negative P terminal force in lead V1, bottom tracing.Knowledge Weavers ECG
160 Acute postero-lateral MI: precordial leadsAcute postero-lateral MI: precordial leadsKnowledge Weavers ECG
161 Pacemaker failure to pace - marquettePacemaker failure to pace - marquetteKnowledge Weavers ECG
162 Frontal plane QRS axis = 90 degreesFrontal plane QRS axis = 90 degreesKnowledge Weavers ECG
163 Junctional tachycardia - marquetteJunctional tachycardia - marquetteKnowledge Weavers ECG
164 Diagram: frontal plane leadsDiagram: frontal plane leadsKnowledge Weavers ECG
165 Inferoposterior MIInferoposterior MIKnowledge Weavers ECG
166 Digitalis intoxication: Junctional tachycardia with and without AV blockIn a patient with longstanding atrial fibrillation being treated with digoxin, a regular tachycardia, as seen in A, with a RBBB suggests a junctional or supraventricular tachycardia. Group beating, in B, is likely due to a 2nd degree, Type 1, exit block below the ectopic junctional focus. This is h...Knowledge Weavers ECG
167 Nonconducted PACs and junctional escapesAlthough at first glance this looks like 2nd degree AV block, the P waves indicated by the arrows are premature and not sinus P waves. The pause is long enough to encourage a junctional escape focus to take over. Note the sinus P waves just before the escape beats. Had the escapes not occurred, t...Knowledge Weavers ECG
168 WPW diagramThe short PR interval is due to a bypass track, also known as the Kent pathway. By bypassing the AV node the PR shortens. The delta wave represents early activation of the ventricles from the bypass tract. The fusion QRS is the result of two activation sequences, one from the bypass tract and one...Knowledge Weavers ECG
169 PVC with venticular echoThe PVC in this example retrogradely enters the AV junction and returns, usually down a different pathway, to reactivate the ventricles....a ventricular echo. This is unlikely to be an interpolated PVC because the PR interval following the PVC is too short for the sinus impulse to have entered the ...Knowledge Weavers ECG
170 Left bundle branch block (LBBB)LBBB is recognized by 1) QRS duration>0.12s; 2) monophasic R waves in I and V6; and 3) terminal QRS forces oriented leftwards and posterior. The ST-T waves should be oriented opposite to the terminal QRS forces.Knowledge Weavers ECG
171 PAC with RBBB aberrant conductionPAC with RBBB aberrant conductionKnowledge Weavers ECG
172 Interpolated PVCs - marquetteInterpolated PVCs - marquetteKnowledge Weavers ECG
173 PVC triplet - marquettePVC triplet - marquetteKnowledge Weavers ECG
174 Ventricular tachycardia with retrograde wenckebachApproximately 50 percent of ventricular tachycardias are associated with AV dissociation. The other 50 percent have retrograde atrial capture. This example shows ventricular tachycardia with retrograde Wenckebach. The retrograde P waves are hard to find, but the arrows are of some help.Wenckebach AV BlockKnowledge Weavers ECG
175 Nonconducted and aberrantly conducted PAC'sIn A the slow sinus rhythm is actually caused by nonconducted PACs hidden in the ST segment. This is confirmed in B where some of the PACs are aberrantly conducted with LBBB, and some PACs are nonconducted.Knowledge Weavers ECG
176 Left anterior fasicular block: frontal plane leadsLeft anterior fascicular block, LAFB, is recognized by left axis deviation of -45 degrees or greater; rS complexes in II, III, aVF; and a small Q wave in I and/or aVL.Knowledge Weavers ECG
177 Right bundle branch block (RBBB)Right bundle branch block (RBBB)Knowledge Weavers ECG
178 All about premature beatsAll about premature beatsKnowledge Weavers ECG
179 Inferoposterior MIInferoposterior MIKnowledge Weavers ECG
180 Sino-atrial exit block, type I or wenckebachThis example illustrates 2nd degree sino-atrial exit block. In type 1 S-A block the conduction time between sinus firing and atrial capture progressively prolong, but this cannot be seen on the ECG tracing; type I exit block is inferred if the P-P intervals gradually shorten before the pause and if...Wenckebach AV Block; Ladder DiagramKnowledge Weavers ECG
181 Inferior & Anteroseptal MI + RBBBPathologic Q waves are seen in leads II, III, aVF (inferior MI) and in leads V1-3 (anteroseptal MI). RBBB is recognized by the wide QRS (>0.12s) and the anterior/rightwards orientation of terminal QRS forces. When an anteroseptal MI complicates RBBB (or visa versa) the rSR' complex in V1 (typical ...Knowledge Weavers ECG
182 Atrial flutter with 3:2 conduction ratio: frontal plane leadsNote the subtle bigeminy in the RR intervals. The best way to identify the flutter waves in this example is to imagine what lead III would look like if the QRS complexs disappeared; what remains is a reasonable saw-tooth pattern characteristic of atrial flutter with a flutter rate of about 300 bpm...Knowledge Weavers ECG
183 Accelerated ventricular rhythm with retrograde atrial capture and echo beatsRetrograde atrial captures from an accelerated ventricular focus are occurring with increasing R-P intervals, When the longer R-P occurs, the impulse traversing the AV junction finds a route back to the ventricles, and the result is a ventricular echo.Knowledge Weavers ECG
184 ECG components diagram - marquetteECG components diagram - marquetteKnowledge Weavers ECG
185 Postero-lateral MI: Precordial LeadsPostero-lateral MI: Precordial LeadsKnowledge Weavers ECG
186 Indeterminate frontal plane QRS axisIndeterminate frontal plane QRS axisKnowledge Weavers ECG
187 PAC couplet - marquettePAC couplet - marquetteKnowledge Weavers ECG
188 Normal variant: Early repolarizationEarly repolarization, a misnomer, describes a pattern of localized or diffuse ST segment elevation. This is especially seen in leads with prominent R waves. In this example leads I, II, V5 and V6 illustrate the early repolarization pattern. ST segments usually have a concave upwards pattern and ta...Knowledge Weavers ECG
189 AV dissociation by usurpationNormal sinus rhythm is interrupted by an accelerated ventricular rhythm whose rate is slightly faster than the sinus rhythm. Fusion QRS complexes occur whenever the sinus impulse enters the ventricles at the same time the ectopic ventricular focus initiates its depolarization.Knowledge Weavers ECG
190 Long QT mischiefThe long QT ECG has many causes: electrolyte abnormalities including hypo-K, hypo-Mg, and hypo-Ca; drugs including type I antiarrhythmics; CNS injury; and hereditary syndromes. Ventricular arrhythmias are thought to be caused by afterdepolarizations or triggered automaticity.Knowledge Weavers ECG
191 Nonconducted and conducted PAC'sThe pause in this example is the result of a nonconducted PAC, as indicated by the first arrow. The second arrow points to a conducted PAC. The most common cause of an unexpected pause in rhythm is a nonconducted PAC.Knowledge Weavers ECG
192 Atypical LBBB with Q waves in leads I and aVLIn typical LBBB, there are no initial Q waves in leads I, aVL, and V6. If Q waves are present in 2 or more of these leads, myocardial infarction is present.Knowledge Weavers ECG
193 Old inferior MI, PVCs, and atrial fibrillationOld inferior MI, PVCs, and atrial fibrillationKnowledge Weavers ECG
194 Frontal plane QRS axis = -45 degreesFrontal plane QRS axis = -45 degreesKnowledge Weavers ECG
195 LVH & PVCs: Precordial LeadsLVH & PVCs: Precordial LeadsKnowledge Weavers ECG
196 Atrial flutter with variable AV block and rate-dependent LBBBThe basic rhythm is atrial flutter with variable AV block. When 2:1 conduction ratios occur there is a rate-dependent LBBB. Don't be fooled by the wide QRS tachycardia on the bottom strip. It's not ventricular tachycardia, but atrial flutter with 2:1 conduction and LBBB. Lidocaine is not needed ...Knowledge Weavers ECG
197 three fates of PAC'sAs illustrated, PAC's can have three fates: PAC-1enters the ventricles and encounters no conduction delays, therefore causing a narrow QRS; PAC-2 occurs a little earlier and can't get through the AV junction, therefore beingnonconducted; PAC-3 seen inlead V1 makes it into the ventricles but encounte...Knowledge Weavers ECG
198 Ventricular tachycardia with AV dissociation, captures, and fusionsApproximately 50 percent of ventricular tachycardias are associated with AV dissociation. In these cases atrial impulses can enter the ventricles and either fuse with a ventricular ectopic beat or completely capture the ventricles. This ladder diagram illustrates these events.Knowledge Weavers ECG
199 Frontal plane QRS axis = +75 degreesSince there is no isoelectric lead in this ECG, the two closest leads are I and aVL. If I were isoelectric, the axis would be +90 degrees; if aVL were isoelectric, the axis would be +60 degrees. A nice compromize is +75 degrees. (The two closest leads are always 30 degrees apart.)Knowledge Weavers ECG
200 Right axis deviation: QRS axis = +130 degreesLead aVR is almost isoelectric; lead I is mostly negative, and lead III is very positive. The QRS axis, therefore, is +130 degrees. Note that the slightly more positive AVR moves the axis slightly beyond +120 degrees; i.e., closer to the + pole of the aVR lead.Knowledge Weavers ECG
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