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Imitators
- 1. Bundle Branch BlockBundle Branch Block and the Imitators of ACSand the Imitators of ACS MODULE 6MODULE 6
- 2. Bundle Branch BlockBundle Branch Block • Can be pre-existingCan be pre-existing conditioncondition • Can be caused by ACSCan be caused by ACS
- 3. Bundle Branch BlockBundle Branch Block • BBB caused by AMIBBB caused by AMI – 60%-70% association with60%-70% association with pump failurepump failure – 40%-60% mortality without40%-60% mortality without reperfusionreperfusion
- 4. Bundle Branch BlockBundle Branch Block • Can mimic ACSCan mimic ACS • Can hide evidence of ACSCan hide evidence of ACS
- 5. Bundle Branch BlockBundle Branch Block • May ProduceMay Produce – ST elevationST elevation – ST depressionST depression – Tall T wavesTall T waves – Inverted TInverted T waveswaves – Wide Q wavesWide Q waves • May HideMay Hide – ST elevationST elevation – ST depressionST depression – Tall T wavesTall T waves – Inverted TInverted T waveswaves – Wide Q wavesWide Q waves
- 6. The ProblemThe Problem • Critical to reperfuse patientsCritical to reperfuse patients with BBB produced by ACSwith BBB produced by ACS • ACS harder to identify on ECGACS harder to identify on ECG when BBB presentwhen BBB present
- 7. The SolutionThe Solution • BBB ProblemBBB Problem – New or presumably newNew or presumably new BBB is an indication forBBB is an indication for thrombolytic therapythrombolytic therapy
- 8. The SolutionThe Solution Fibrinolytic Therapy Trialists’ (FIT) Collaborative Group, 1994
- 9. BBB RecognitionBBB Recognition Forget About the Notch!Forget About the Notch!
- 10. BBB RecognitionBBB Recognition • Wide QRSWide QRS – >> 120ms120ms • Supraventricular rhythmSupraventricular rhythm
- 12. RBBB vs LBBBRBBB vs LBBB • RBBB in V1RBBB in V1
- 13. RBBB vs. LBBBRBBB vs. LBBB • LBBB in V1LBBB in V1
- 14. RBBB vs. LBBBRBBB vs. LBBB • Use V1Use V1 • Identify directionIdentify direction of terminal forceof terminal force
- 15. Bundle Branch BlockBundle Branch Block • V1V1
- 18. BBBBBB New onset BBB, or presumablyNew onset BBB, or presumably new BBB, is an indication fornew BBB, is an indication for acute reperfusion therapyacute reperfusion therapy
- 19. Ventricular RhythmsVentricular Rhythms • Paced rhythmsPaced rhythms • Idioventricular rhythmsIdioventricular rhythms • AIVRAIVR • V-TachV-Tach • PVCPVC
- 20. Ventricular RhythmsVentricular Rhythms • Can mask or mimic every ECGCan mask or mimic every ECG change suggestive of ACSchange suggestive of ACS
- 22. Left Ventricular HypertrophyLeft Ventricular Hypertrophy • Enlarged left ventricleEnlarged left ventricle – Pumping against increasedPumping against increased resistanceresistance – Chronic overfillingChronic overfilling
- 23. LVHLVH • May ProduceMay Produce – ST elevationST elevation – ST depressionST depression – Tall T wavesTall T waves – Inverted TInverted T waveswaves • May HideMay Hide – ST elevationST elevation – ST depressionST depression – Tall T wavesTall T waves – Inverted TInverted T waveswaves
- 24. LVHLVH • Does not abnormally widen QRSDoes not abnormally widen QRS • Increases height and depth of QRSIncreases height and depth of QRS – Recognized by this increaseRecognized by this increase – Three step recognition formulaThree step recognition formula
- 25. LVHLVH
- 26. LVH RecognitionLVH Recognition • Step 1Step 1 – Look in V1 and V2Look in V1 and V2 – Pick the deepest negativePick the deepest negative deflectiondeflection – Count small boxes of negativeCount small boxes of negative deflection in that leaddeflection in that lead – Remember that numberRemember that number
- 27. LVHLVH
- 28. LVH RecognitionLVH Recognition • Step 2Step 2 – Look in V5 and V6Look in V5 and V6 – Pick the tallest positivePick the tallest positive deflectiondeflection – Count small boxes ofCount small boxes of positive deflectionpositive deflection – Remember that numberRemember that number
- 30. LVH RecognitionLVH Recognition • Step 3Step 3 – Add the two numbersAdd the two numbers togethertogether – Suspect LVH if theSuspect LVH if the sum equals 35 or moresum equals 35 or more
- 31. LVHLVH
- 32. LVHLVH
- 33. Ventricular AneurysmVentricular Aneurysm • NOT Aortic AneurysmNOT Aortic Aneurysm • ““Bleb” in ventricle secondaryBleb” in ventricle secondary to infarctto infarct – Bleb is dyskineticBleb is dyskinetic – ““Pops out” when ventriclePops out” when ventricle contractscontracts
- 35. Ventricular AneurysmVentricular Aneurysm • Associated with persistentAssociated with persistent ST elevationST elevation – Often in V1-V4Often in V1-V4 – Can occur in any leadCan occur in any lead
- 37. Benign Early RepolarizationBenign Early Repolarization
- 38. Benign Early RepolarizationBenign Early Repolarization • Normal variantNormal variant • ProducesProduces – ST elevationST elevation – Tall T wavesTall T waves
- 39. Benign Early RepolarizationBenign Early Repolarization • Changes usually seen inChanges usually seen in anterior and lateral leadsanterior and lateral leads • Most often seen in malesMost often seen in males ages 20-40ages 20-40 – African-American malesAfrican-American males
- 40. Benign Early RepolarizationBenign Early Repolarization • Look for notch at J-pointLook for notch at J-point – ST segment and J-pointST segment and J-point create acreate a “fish hook”“fish hook” appearanceappearance
- 41. Benign Early RepolarizationBenign Early Repolarization
- 43. PericarditisPericarditis • May be viral, bacterial orMay be viral, bacterial or metabolicmetabolic • Clinical presentation mayClinical presentation may include chest paininclude chest pain • Often produces STOften produces ST elevation on ECGelevation on ECG
- 44. PericarditisPericarditis • Clinical presentationClinical presentation – Sharp chest painSharp chest pain – Can be localizedCan be localized – Radiates to base of neck,Radiates to base of neck, between shoulder bladesbetween shoulder blades
- 45. PericarditisPericarditis • Pain affected by movementPain affected by movement and respirationand respiration – Pain improves when patientPain improves when patient leans forwardleans forward – Pain worsens when patientPain worsens when patient supinesupine
- 46. PericarditisPericarditis • May produce ST elevationMay produce ST elevation in any leadin any lead • May be in all leadsMay be in all leads • May not be anatomicallyMay not be anatomically groupedgrouped • J-point notching oftenJ-point notching often presentpresent – Fish hookFish hook
- 47. MedicationsMedications • Some medicationsSome medications affect the ECGaffect the ECG • DigitalisDigitalis – ST depressionST depression – Characteristic sagCharacteristic sag
- 49. SummarySummary • Imitators canImitators can produceproduce STST elevation or depressionelevation or depression • Imitators canImitators can eliminateeliminate STST elevation or depressionelevation or depression
- 50. SummarySummary • Imitators canImitators can produceproduce T wave inversionT wave inversion • Imitators canImitators can hidehide T wave inversionT wave inversion
- 51. SummarySummary • Imitators can incorrectlyImitators can incorrectly place an ECG into any ofplace an ECG into any of the three categoriesthe three categories ST Elevation BBB ST Depression T wave inversion Normal Non-diagnostic
- 52. SummarySummary • Most frequent imitatorsMost frequent imitators – LVHLVH – BBBBBB – Paced rhythmsPaced rhythms
- 53. SummarySummary • If the QRS is narrowIf the QRS is narrow – Rules out BBBRules out BBB – Rules out ventricularRules out ventricular rhythmsrhythms
- 54. SummarySummary • If QRS is wideIf QRS is wide – Consider BBBConsider BBB – Consider ventricularConsider ventricular rhythmrhythm
- 55. SummarySummary • If QRS is narrowIf QRS is narrow – Consider LVHConsider LVH – Consider pericarditisConsider pericarditis – Consider early repolarizationConsider early repolarization
- 56. SummarySummary • ““Fish hooks” often seen with:Fish hooks” often seen with: – PericarditisPericarditis – BERBER • ““Fish hooks” can also beFish hooks” can also be seen with ACSseen with ACS
- 57. SummarySummary New BBB, or presumably new BBB,New BBB, or presumably new BBB, is an indication for thrombolysisis an indication for thrombolysis when accompanied by a clinicalwhen accompanied by a clinical presentation suggestive of ACSpresentation suggestive of ACS
- 58. The presence of an imitatorThe presence of an imitator DOES NOTDOES NOT rule out anrule out an Acute Coronary SyndromeAcute Coronary Syndrome
Notas del editor
- This module will again look at the three ECG categories. 1. ST elevation/BBB (new or presumably new) 2. ST depression and T wave inversion 3. Normal or non-diagnostic First discussed is the identification of bundle branch block. • Recognizing the presence of BBB • Differentiating LBBB from RBBB Next, conditions and situations are identified which may mask or mimic the criteria for ECG categorization. Some of these conditions are: LVH, BBB, pericarditis, medications and others. Finally, a real world strategy is discussed for dealing with the realities of the imitators.
- Bundle Branch Block (BBB) has a number of potential causes. BBB can be the result of a fibrosis or calcification of the ventricular conduction system. (Lev’s disease and Lenegre’s disease are examples.) People can live well for many years with the BBB caused by these conditions. Unless there is evidence of worsening conduction (syncope, dropped beats, etc) these conditions are non-emergent. BBB can also be caused by an ACS. When BBB is caused by an ACS, it identifies a very high risk patient!
- When BBB is produced by ACS it is a very poor prognostic sign that carries with it a high incidence of pump failure and death. The complications are not directly caused by the BBB, rather when an ACS produces a new BBB there is usually extensive tissue loss. It is the tissue loss that accounts for the worsened outcome.
- BBB alters depolarization (affects QRS), which alters repolarization (affects ST-T wave). Therefore, BBB can produce changes in the QRS-ST-T waves that are identical to those produced by an ACS. Conversely, BBB can hide the characteristic changes of ACS when present.
- Literally, BBB can both mask and mimic all of the ECG changes associated with ACS!
- The problem is obvious. Patients with BBB secondary to ACS need reperfusion. However, the presence of BBB makes ACS harder to identify on the ECG. Fortunately, The American Heart Association and the American College of Cardiology have provided a solution.
- The presence of a new BBB, or presumably new BBB, is an indication for thrombolytic therapy*. At the physician’s discretion, thrombolytics may be administered to patients whose BBB obscures the diagnosis of AMI on the ECG. *The 1996 ACC/AHA Guidelines for the Management of Patients with Acute Myocardial Infarction” lists BBB as a Class I indication for thrombolysis. (Definition of Class 1: Conditions for which there is evidence and/or general agreement that a given procedure or treatment is beneficial, useful, and effective)
- Using thrombolytics in the setting of BBB translates to a significant reduction in mortality. According to evidence*, BBB patients derive more benefit from thrombolytic therapy when compared to ST elevation patients. Note: Thrombolytics may be harmful to infarct patients without ST elevation. Given these facts about BBB let’s look at how to recognize it on the ECG.
- A commonly held misconception is that any notch or distortion of the QRS indicates a BBB. While BBB can cause a notch, a notch does not ensure the presence of a BBB. Therefore, other criteria for BBB recognition are needed.
- BBB widens the QRS (120ms or more). This widening is due to the fact that the ventricles are forced to contract sequentially, thus requiring more time. Other conditions widen the QRS; a common one would be ventricular rhythms either paced or spontaneous. A differentiating factor between BBB and ventricular rhythms would be the presence of an underlying supraventricular rhythm. Therefore, when a QRS of 120ms or more is produced by a supraventricular rhythm, think BBB. This rule applies in all leads.
- Example 1 underlying rhythm sinus QRS width 160ms Example 2 underlying rhythm sinus QRS width 120ms
- The “classic” pattern for RBBB in V1 is an RSR.
- The “classic” pattern of LBBB in V1 is a QS complex. There are many variations to these classic patterns, complicating the process of distinguishing RBBB from LBBB. In addition, each form of BBB produces a different set of changes in V6. Fortunately, a simplified approach does exist.
- Always remember, the following rules for differentiating RBBB from LBBB apply only to V1. We will learn to identify the terminal force of the QRS in V1, and determine if it is positive or negative. Simply stated, we will look at the tail end of the QRS complex and decide if it points up or down.
- After BBB has been determined to exist, look at lead V1. To identify the terminal force, first locate the J-point. From the J-point, back up about 40 ms into the QRS. Now determine if the terminal force (tail end) is pointing up or down.
- Have the participants review these four examples of V1 in the course guide and determine if the BBB is LBBB or RBBB.
- When the clinical presentation suggests ACS, any new or presumably new BBB is an indication for acute reperfusion therapy. Ask the patient if they have ever been told by their physician that they have a bundle branch block. Occasionally, patients have an old ECG available at home. It may be prudent in the early management of a suspected ACS patient to presume BBB is new, until proven otherwise. While BBB itself is part of the ECG categorization system, certain situations can either produce or eliminate the other elements of the ECG categorization system (ST elevation, ST depression, T wave inversion). Next we will look at some of those situations, starting with ventricular rhythms.
- Any rhythm or beat originating in the ventricles can imitate the ECG changes associated with ACS. NOTE: Sometimes caregivers are less likely to make the interpretation of a ventricular rhythm when the heart rate is greater than 60 but less than 150. Ventricular rhythms can and do occur at this “in between” rate and are referred to as accelerated idoventricular rhythms (AIVR).
- Like BBB ventricular rhythms can not only imitate an ACS but can mask the evidence as well.
- Here is an example of how ventricular rhythms can imitate changes suggestive of ACS. Remember, they can mask the changes as well.
- There are many causes of LVH. Most are the result of either the left ventricle working harder over a long period of time or the result of chronic overfilling. For ACS management, it is NOT critical to determine the cause of the LVH. Simply suspecting the presence of LVH is sufficient.
- LVH can both mask and mimic all of the ECG changes associated with ACS!
- Unlike BBB and ventricular rhythms, LVH does NOT usually widen the QRS to 120ms or more. Instead of abnormally widening the QRS, LVH increases its amplitude. There are many formulas for suspecting the presence of LVH. The three step method described here is one of the simpler means of suspecting LVH. Remember, we are not trying to identify LVH for its own sake. Rather we seek to identify LVH as a potential imitator of ACS.
- Participants review this tracing in their course guide while instructor describes method of LVH recognition.
- STEP 1 Compare V1 and V2. Determine which is the deepest negative deflection. In the deepest lead, count the millimeters of negative deflection.
- Hypertrophy often causes overlapping of ECG leads which may make counting boxes in V1 and V2 difficult.
- STEP 2 Compare V5 and V6. Determine which is the tallest. In the tallest lead, count the millimeters of positive deflection.
- STEP 3 Add the two numbers together. If their sum equals 35 or more, suspect LVH is present.
- Look again at the ECG, look to see which leads show changes suggestive of LVH. (Point out ST elevations, depressions, T wave inversions.) Could all of these changes be due to ACS? (yes) Could all of these changes be due to LVH? (yes) How would you manage such a patient? If the story suggests ACS, that is how the patient is managed.
- Ventricular aneurysm represents another situation that may produce ECG changes. An aneurysm in the left ventricle is usually the result of a previous AMI. Because of the aneurysm, ST elevation may persist indefinitely after the infarct. In other words, a complication from a previous AMI can masquerade as an ACS.
- Note the difference in systole when an aneurysm is present.
- Often the aneurysm is located in the region of the anterior wall and produces ST elevation in V1-V4. Of course changes are not limited to only those leads.
- Ventricular aneurysm is difficult to identify with certainty without previous ECG tracings. As with the other imitators, when the clinical presentation suggests ACS, treat the patient accordingly.
- Despite the obvious ECG changes seen here, this ECG was obtained from a patient with a perfectly normal heart! It is an example of a normal variant called “Benign Early Repolarization”.
- It has been theorized that the cause of BER is due to one region of myocardium repolarizing early. This produces a difference in electrical potential, and thus causes ST and T wave changes.
- Changes can occur in any lead, but are more common in the lateral and anterior chest leads (sometimes lead II and other limb leads). Anyone, male or female, of any ethnic background can have this pattern on their ECG. However, this pattern is most commonly seen in young adult African-American males.
- One ECG sign that should make you consider BER is the notched J-point, creating a fish hook like appearance of the ST segment.
- A notch at the J-point is shown here. NOTE: The presence of “fish hooks” does not rule out ACS. It is not uncommon to see J-point notching as a result of ACS. NOTE: Patients with BER often meet the voltage criteria for LVH. However, no true hypertrophy may exist.
- This ECG has ST elevations and some similarities to BER. However, in this case, BER is not present. This is an example of pericarditis.
- There are numerous causes of pericarditis. These patients often complain of chest pain, which is an indication for a 12-lead. Pericarditis is capable of producing ST changes on the ECG.
- The “classic” pericarditis presentation has some distinguishing features. The purpose of the following description is not to rule out AMI, but to help the care provider suspect the possibility of pericarditis. Classic presentation: • Sharp chest pain (meaning a stabbing nature, not meaning intense) • Pain can often be localized with one finger • Pain may radiate to the base of the neck or between the shoulder blades (trapezius area)
- Classic pericarditis presentation (continued) • Pain is affected by patient movement and respiration • Pain is affected by patient position One of the tricks to suspect pericarditis is to lean them forward and see if the pain improves. Another is to see if the pain worsens when they take a drink of fluids. Pericarditis can occur post MI and post cardiac surgery. Also have a high index of suspicion if the patient has had a recent viral or bacterial infection or IV drug abuse is suspected.
- The ST elevation of pericarditis is caused by inflammation of the epicardium secondary to inflammation of the pericardium. This process is not related to coronary artery disease and, therefore, ST changes do not tend to follow anatomical groups typically seen with ACS. Like BER, pericarditis may produce a notching of the J-point and a “fish hook” shaped ST and J-point.
- Certainly medications have the potential to affect the ECG. One of the best documented changes due to a medication is the digitalis effect.
- Digitalis depresses the ST segment and adds a characteristic “scoop” shape to it.
- Correct categorization of ECG changes can be complicated when an imitator is present. These imitators can lead to erroneous placement of a patient into the ST elevation or ST depression category. The imitators can also mask changes that would have otherwise been present on the ECG.
- Just as these conditions can affect the ST segment, they can also affect the T wave.