12 lead-lesson 3

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  • In this lesson I am going to teach you how you can uncover some things if you just dig a little.
  • In this lesson, we are going to perform the third and fourth steps of the six step method.
  • In this lesson, we will learn a few more pathologies which can be identified on a 12-lead ECG. All of these conditions listed can be identified by examining the intervals and morphologies. Lets learn how.
  • PR interval is the distance from the beginning of P wave to the beginning of QRS complex. Normal PR interval values in adults range from 0.12 to 0.20 seconds. Longer PR intervals are seen in the cases of AV block and shorter PR intervals in pre-excitation syndromes and different arrhythmias. The PR segment is the distance from the end of Pwave to the QRS onset and is usuallyisoelectric. However, with intracardiac recordings the depolarisation of His bundle may be seen. QT interval represents the sum of depolarisation(QRScomplex) and repolaisation(Stsegment and Twave). Very often, particularly in the cases of flat Twave or presence of Uwave, it is dfficult to appropriately measure the QT interval.
  • This is the atrial depolarization wave. In general, its height should not exceed 2.5 mm and its width should not exceed 0.10 seconds. Should be positively deflected in nearly every lead, may be biphasic in V1 as a normal finding.
  • The morphology of the P-wave changes depending on the site of the atrial pacemaker. Site A shows the location closes to the physiological pacemaker, the SA node. Site B shows how the pacemaker can actually be in the left atrium, and site C shows a site that could cause an inverted P-wave. If the AV junction is the primary pacemaker site, it could also cause an inverted P-wave due to retrograde conduction. Basically, the impulse is traveling in the oposite direction as it normally would, so it would be traveling away from the positive electrode, which we know will create a negative deflection on the ECG.
  • Ok, we are ready to talk about our first type of chamber enlargement, left atrial enlargement. This type of hypertrophy may be a result of left ventricular hypertrophy, or heart failure. The notched P-wave is a result of the left atrium taking longer to depolarize. The first hump is a result of the right atrium depolarizing, and the second hump is a result of the left atrium firing. A biphasic P-wave is a common finding in V1, and may be normal. However, if it is deeper than it is tall, this is clinically significant, and indicates left atrial enlargement.
  • The next type of chamber enlargement is right atrial enlargement. The pictures are an example of p-pulmonale, which is just a fancy way of saying that the right atrium is enlarged and it is usually due to right ventricular failure and enlargement which is called cor pulmonale. These tall P-waves generally have a sharper peak than the average p-wave. You may also note bi-atrial enlargement if you see this type of P-wave on a limb lead, which indicates RAE with a deep biphasic P-wave on V1 indicating LAE.
  • As I stated, V1 will commonly have a biphasic P-wave. If it isn’t deeper than it is tall, it is a sign of intra-atrial conduction delay. This just means that there is some sort of non-specific delay in conduction from the right atrium to the left atrium. As far as significant pathologies are concerned, this finding doesn’t really mean much clinically.
  • The PR-Interval lasts from the beginning of the P-wave to the beginning of the QRS complex. You may wonder, why is it called the PR-interval and not the PQ-interval, since the Q-wave is the first wave of a QRS complex. I can only guess it is because the R-wave is usually the most prominent, and often the first wave in lead II, which is the quintessential monitoring lead. The PR-interval should be bigger than 3 small boxes, but shorter than one big box.
  • WPW involves a conginital accessory pathway within the atrial wall that allows a faster path of electrical conduction from the atria to the ventricles
  • These are the classic findings for WPW. A shortened PR-Interval, widened QRS duration, and a slurring upslope of the R-wave, known as the delta wave.
  • The classic findings that indicate WPW
  • Here is an example. The baseline is altered in a few leads, but we can still try to identify any WPW findings.
  • We can see a delta wave, shortened PR-Interval and widened QRS complex all in lead 1. Keep in mind that these changes will not always be preset in every lead. Look at the other leads on this rhyhm strip and see how the morphology is different amongst them.
  • Here is another example
  • In this one, V4 seems to be the best lead to find the classic WPW findings of a shortened PR-interval, and delta wave.
  • Think FBI The drug Cardizem is contraindicated with WPW, and if administered with WPW, Cardizem could cause a lethal arrythmia that is nearly impossible to convert. Always suspect WPW with a fast, broad , and irregular arrythmia.
  • LGL has a bypass tract, called the James fiber that bypasses the AV node. Normally the AV node slows down conduction to allow the ventricles to fill. This shows up as the PR-interval on the ECG. With LGL we have a shortened PR-interval because of this bypass.
  • Here is an example. Leads V4 & V5 are the best leads on this strip to see the classic shortened PR-interval.
  • This corresponds to ventricular depolarisation. Its morphology varies in the different leads. The width should not be less than 0.10 seconds and R-wave height should not exceed 25 mm in leads V5 and V6, or 20 mm in leads I and aVL, although in aVL the height greater than 15 mm is usually abnormal. Furthermore, the Q wave must be narrow (less than 0.04 seconds) and of quick recording, and does not usually exceed 25% of the following R wave, though some exceptions exist mainly in leads III, aVL and aVF.
  • In addition to what we know about determining our QRS axis. We can use the morphology of the QRS to guide us with the rest of our 12-lead interpretation.
  • I mentioned bundle branch blocks, so what is a bundle branch block? You have two main bundle branches. The right, which consists of a single fascicle, and the left which is comprised of two fascicles, the left anterior and the left posterior. We will be using the QRS morphology to identify bundle branch blocks.
  • When you know an ECG rhythm is atrial by the presence of a P-wave, and it is greater than 120ms, or three small boxes wide, you should suspect a bundle branch block. You have three types of bundle branch block right, left, or nonspecific intraventricular conduction delay. If the right fascicle becomes blocked, you have a RBBB, if both of the left fascicles are blocked you have a LBBB, and if you are unable to differentiate between a right or left bundle branch block on the ECG it is termed a Non Specific IVCD.
  • Instead of the RBB conducting the electricity in a fast manner like normal, the individual heart cells send the conduction to each other from the left ventricle back over to the right.
  • With a LBBB the impulse travels fast through the right fascicle and then the cells conduct the impulse, slowly back to the left vetricle.
  • Lets take a look at these two QRS complexes from lead V1. Lets assume we have P-waves present so we know the rhythm is not ventricular. Lets also assume that they are obviously greater than 120ms wide.
  • To figure out whether this is a RBBB or a LBBB, we look at the last wave of the QRS. This is called the terminal deflection, and we can find it by drawing a line from the J point to close the wave off.
  • Now we can shade in the triangles to determine which type of BBB we are looking at.
  • Now look at the direction that the triangles are pointed. Almost like arrows.
  • Now think of the turn signal in your car. If you want to signal that you are turning left, you push it down, and if you are turning right, you pull it up. Well its that easy, if the terminal wave of the QRS is positive, it points up. If it points up, which is the same way you would pull your turn signal to turn right, it is a RBBB. If the terminal wave of the QRS in V1 is negative, it is pointed down, and if you want to turn left you push your lever down, so it is a LBBB.
  • Take a look at the graphic here. If the terminal wave of the QRS is positive in V1 it is a RBBB. If the terminal wave of the QRS is negative in V1 it is a LBBB. This is assuming that it is a wide atrial rhythm.
  • Now think of the turn signal in your car. If you want to signal that you are turning left, you push it down, and if you are turning right, you pull it up.
  • Here are several different possible RBBB morphologies. Most 12-lead courses would stop right there and never teach you to look for any other BBB indicators. However, there are more steps in determining BBBs appropriately.
  • Leads 1 and V6 both share very similar views of the heart. V6 will probably be a bit larger, but the morphology of the QRS should be similar.
  • A RBBB presents with a terminal R wave in V1, and a slurred S wave in lead I and V6. The slurring of the S-waves may not be as obvious as this example, and leads 1 and V6 will not be exactly the same, but similar.
  • Slurred S-waves can come in many different shapes & sizes, here are a few examples.
  • Remember how our mean vector shows up on the ECG? Take a look at this graphic again. The more the conduction flows towards the positive electrode of a lead, the more positive the QRS will be…
  • Then it makes sense that a RBBB would show up in lead 1 & 6 with an RS pattern that would have a slurred S-wave. The slurred S-wave is the vector taking longer, and heading away from the positive electrodes in lead 1 and V6 as it heads back towards the right ventricle.
  • Lets assume that we have already determined our rate, rhythm, and axis. We have moved on to morphology and intervals. We note a widened QRS duration. We confirm that this is an atrial rhythm by the presence of conducting P-waves, and we decide to determine what kind of bundle branch block we are looking at.
  • First we look at V1. On this particular 12-lead the lead names are in the middle of their lead. Lets determine if we have a terminal R wave or S wave in V1.
  • We draw our line and shade in the resulting triangle. We note that the triangle is pointing up, and since we pull up on our turn signal to turn right, we assume that this is a RBBB. Next we look at leads I and V6.
  • Do we see a slurring S-wave in these leads?
  • I sure do. So this must be a RBBB. Lets move on to LBBBs.
  • Just like with a RBBB, we must examen leads 1 and V6 to determine if we are looking at a true LBBB.
  • LBBB morphology is easier to recognize in V1. There are only a few different morphologies, here are the most common.
  • A RBBB presents with a terminal R wave in V1, and a slurred S wave in lead I and V6. The slurring of the S-waves may not be as obvious as this example, and leads 1 and V6 will not be exactly the same, but similar.
  • Lets have a look at an example. First lets identify the morphology in V1.
  • Lets draw a line from the j point and create our triangle to determine what kind of BBB we are looking at.
  • The triangle is pointing down, and since we pull down on our turn signal lever to turn left, we know this is a LBBB morphology. Lets take a look at leads I and V6 to confirm.
  • Leads 1 and v6 both have a monophasic R-wave. This means that the entire QRS complex is positive. We are in fact looking at a LBBB. Many clinicians will tell you that after determining a LBBB, you can stop interpretation because the ECG is unreadable. This is not exactly accurate, and we will return to that concept by the end of the course.
  • A RBBB presents with a terminal R wave in V1, and a slurred S wave in lead I and V6. The slurring of the S-waves may not be as obvious as this example, and leads 1 and V6 will not be exactly the same, but similar.
  • Here is a chart to make things easier.
  • Another pathology that can be discovered by examining the QRS morphology is ventricular enlargement or hypertrophy.
  • If you remember that every small box is 1mm tall, and every big box is 5mm tall, it is easy to see that the S-wave in V1 or V2 here is about 12mm deep. The R-wave in V5 or V6 here is about 20mm deep. If we add those numbers together, our result is greater than 25mm which means we are probably looking at LVH.
  • Lets take a look at a 12-lead. First, we look for the deepest S-wave in V1 or V2.
  • From the looks of it, they are about the same. I notice a particular finding with this ECG though that I will explain after we determine if it meets LVH criteria.
  • It looks like we have an S-wave in V2 of about 14 or 15mm. Lets find our tallest R-wave in V5 or V6
  • Once again, V5 and V6 look to be just about the same height. Lets measure one of the R-waves and see what we get.
  • Looks to be about 15mm, probably more.
  • Looks to be about 15mm, probably more.
  • Do you see how the tip of the S-wave is flattened in V1. This means that the ECG monitor cut off the QRS complex to keep it from interfering with other leads. This means that the QRS complex is actually deeper than it appears. This is a big indicator of hypertrophy.
  • The R-waves in V4, V5, and V6 are also cut off; which is why they appear to be the same height.
  • There are other ways to determine if a patient has LVH. Not all criteria is always present with LVH. The Deepest S-wave in v1 or v2 + the tallest r-wave in v5 or v6 rule is the most specific for LVH.
  • Remember which leads are left ventricular and which leads are right ventricular? This is a good way to remember how to differentate between left or right ventricular hypertrophy. With RVH the QRS complexes will be taller in the right ventricular leads, V2, V2, & V3. With LVH, the QRS complexes will be taller in V4, V5, and V6, which are the left ventricular leads.
  • Lets talk about the less common ventricular hypertrophy. RVH is less common as an ECG finding than LVH because RVH is usually due to RV failure which almost always results from LV failure. This means that LVH is usually presnet when RVH is, and since the LV has more mass physiologically, it usually dominates the electrical view of the heart anyhow.
  • Lets take a look at an example. Look at leads v1 and v2
  • We can easily see that V1 is taller than it is deep. This means it has an R:S ratio of > 1 and it is indicative of RVH.
  • We have talked about excessively large QRS complexes, now I want you to think about extremely small QRS complexes, as those with low voltage throughout the entire ECG.
  • the T wave is positive but with the up-slope slower than the down-slope in all leads, except VR (as the T loop is located in the negative hemifield of that lead). It is usually negative, flattened or occasionally slightly positive in V1, and sometimes may also be flattened or slightly negative in V2, and sometimes even in V3 in women and in Blacks. In III and VF, the T wave may be flattened or even slightly negative
  • A sine wave occurs when there is a straight line from the nadir, or tip of the S-wave to the peak of the T-Wave. This causes the QRS to appear wide, and the rhythm may appear ventricular. In fact if the QRS is wider than 200ms you should be very suspicious of hyperkalemia. The sine wave may only last a short while before the rhythm degrades into a ventricular rhythm. The peaked T-wave has a sharp peak, symmetrical T-wave, and is a sign of hyperkalemia as well.
  • This ECG is an example of peaked T-waves indicating hyperkalemia
  • Here is an example of a Sine Wave. Look at how it almost appears to be a straight line from the tip of the S-wave, the Nadir, to the peak of the T-Wave.
  • T-wave discordance is a normal finding with BBBs. The T-wave will be deflected in the opposite direction as the terminal or last wave of the QRS complex. With T-wave discordance, if the T-wave is positive, it is normal to find some degree of ST-Elevation. And ST-depression can be noted with a negative T-Wave discordance. Tiwave discordance is sometimes refered to as a widened QRS-T angle.
  • We can see with this RBBB example that we have appropriate T-wave discordance in every lead.
  • The QT interval measures the time from the beginning of depolarization to the end of repolarization. The image here shows, what is called Bazette’s formula; which is used to correct the QT interval based on the heart rate. The c actually stands for “corrected”. So QTc is the “corrected QT interval.
  • Luckily, the monitor will perform Bazett’s formula for us.
  • U-waves are theorized to represent the repolarization of the perkinge fibers. They can be present or not as a normal finding, but should never be prominent. Large U-waves indicate severe hypokalemia.
  • 12 lead-lesson 3

    1. 1. 12-LeadElectrocardiography a comprehensive course sson3 Le Adam Thompson, EMT-P, A.S.
    2. 2. Resourceswww.http://ecgpedia.org
    3. 3. The 6-Step Method• 1. Rate & Rhythm• 2. Axis Determination• 3. Intervals• 4. Morphology• 5. STE-Mimics• 6. Ischemia, Injury, & Infarct
    4. 4. Lesson Three• Examining Intervals and Morphologies – Bundle Branch Blocks – WPW – Chamber Enlargement – Hyperkalemia/Hypokalemia – Hypothermia – Long QT Syndrome – Digitalis Toxicity
    5. 5. Objectives• Review normal intervals & morphologies• Learn how to identify BBB’s.• Learn how to identify atrial enlargement or ventricular hypertrophy.• Learn how to identify WPW or LGL.• Learn how to identify electrolyte derangements.
    6. 6. PR-Interval • PR-Interval – > 120ms – < 200ms
    7. 7. P-Wave• Normal height < 2.5mm (2 1/2 small boxes)• Normal width < 0.10 seconds (2 1/2 small boxes
    8. 8. P-Wave
    9. 9. P-WaveII • P-Mitrale – Indicates left atrial enlargement. – A notched P-wave gretaer than 0.12 seconds.V1 – A biphasic P-wave in V1 that is deeper than it is tall.
    10. 10. P-Mitrale
    11. 11. P-Wave• P-Pulmonale – Indicates right atrial enlargement – Peaked P-wave in limb leads • Taller than 2.5mm (2 1/2 boxes)
    12. 12. P-Wave• Intra-atrial conduction delay – In V1 – Taller than it is deep – Delay in Bacchmann’s bundle
    13. 13. PR-Interval • < 200 ms • > 120 ms
    14. 14. PR-Interval • PR-Elevation – Usually indicates poor baseline • PR-Depression – May indicate pericarditis – May indicate atrial infarction
    15. 15. Short PR-Interval• Accessory Pathway – Bypasses AV node – Predisposes patients to significant re-entry tachycardias.
    16. 16. Accessory Pathway• Wolff-Parkinson-White Syndrome (WPW) – Bundle of Kent – Short PR-Interval – Delta Wave, Wide QRS• Lown-Ganong-Levine Syndrome (LGL) – James Fiber – Short PR-Interval – Normal P-wave, Normal QRS
    17. 17. WPWBundle of Kent
    18. 18. WPW• Three conduction patterns – Physiological - Normal conduction, no changes may be noted on 12-Lead – Orthodromic - Signal travels down Kent bundle and physiological pathway. • Causes shortened PR-Interval & Delta Wave. – Antidromic - From SA Node through Kent bundle to ventricles then back to atrium via AV junction. • Causes very fast wide complex tachycardias. • Looks like V-tach.
    19. 19. WPW Physiological Conduction
    20. 20. WPW Orthodromic Conduction
    21. 21. WPW Delta WaveShortened PR-Interval Widened QRS
    22. 22. WPW Antidromic Conduction
    23. 23. WPW
    24. 24. WPW
    25. 25. WPW
    26. 26. WPW
    27. 27. WPW• Fast, Broad, & Irregular (FBI) – Tachycardic, Wide QRS, Irregular rhythm – Atrial Fibrillation with WPW – Atrial Fibrillation with BBB • Always suspect WPW until proven otherwise!
    28. 28. WPWFast, Broad, & Irregular
    29. 29. LGLLown-Ganong-Levine Syndrome (LGL) » James Fiber bypasses the AV node. » Shortened PR-Interval.
    30. 30. LGL QuickTime™ and a decompressorare needed to see this picture.
    31. 31. Shortened PR-Interval• The take home message: – Recognizing the presence of an accessory pathway is much more important than the ability to differentiate between the different types of accessory pathways.
    32. 32. QRS Complex • Height & Morphology will vary, depending on the lead. • Normal Width – > 0.10 seconds – < 0.12 seconds
    33. 33. QRS Complex• Much of our 12-Lead ECG interpretation is going to be directly related to the morphology of the QRS complex.• The morphology of the QRS complex will assist us in identifying BBBs, V- tach, LVH, RVH, and infarction.
    34. 34. QRS Complex• Wide Complex Tachycardia (WCT) – Ventricular Tachycardia • Josephson’s Sign – Notching of the downslope of S-Wave • Brugada’s Sign – From behining of QRS to Nadir of S-Wave > 100ms • QRS > 140ms• Supraventricular Tachycardia (SVT) – Must have RBBB or LBBB pattern
    35. 35. QRS ComplexJosephson’s Sign
    36. 36. Bundle Branches
    37. 37. Bundle Branch Blocks• Right Bundle Branch Block (RBBB) – The single right fascicle is blocked.• Left Bundle Branch Block (LBBB) – Both left fascicles are blocked.• Non-Specific Intraventricular conduction delay (IVCD) – BBB that doesn’t meet RBBB or LBBB criteria.
    38. 38. Bundle Branch Blocks• May mimic an MI• The side that is blocked conducts last and takes longer.
    39. 39. Bundle Branch Blocks Mean vector• Normal Cardiac vector conduction 4 without a block. 1 3 3 2 2
    40. 40. Bundle Branch Blocks • With a RBBB, the right fascicle is blocked, so the left ventricle is1 conducted first and 2 then the impulse 3 returns to the right.
    41. 41. Bundle Branch Blocks • With a LBBB, the right ventricle is conducted first, and the impulse1 travels back to the left. 2 3
    42. 42. Bundle Branch BlocksV1
    43. 43. Bundle Branch Blocks V1 J-PointsThe J-point is the exact point where the QRS ends
    44. 44. Bundle Branch BlocksV1
    45. 45. Bundle Branch BlocksV1
    46. 46. Bundle Branch BlocksV1
    47. 47. Bundle Branch BlocksV1 = RBBBV1 = LBBB
    48. 48. Bundle Branch BlocksV1 LBBB RBBB
    49. 49. Right Bundle Branch Block • RBBB morphologiesV1
    50. 50. Right Bundle Branch Block• To properly differentiate between bundle branch blocks, you must also assess leads I and V6.• A slurred S-wave in leads I and V6 indicate a RBBB.
    51. 51. Right Bundle Branch Block I & V6
    52. 52. Right Bundle Branch BlockI V1 aVR V4II aVL V2 V5 V6III aVF V3
    53. 53. Right Bundle Branch Block Slurred S-Wave I & V6
    54. 54. Right Bundle Branch Block + + A B A + BMean vector moves towards positive electrode = positive QRSMean vector moves away from positive electrode = negative QRSMean vector is perpendicular to positive electrode = equiphasic QRS
    55. 55. Right Bundle Branch Block 1 2 + I & V6 3
    56. 56. Right Bundle Branch Block
    57. 57. Right Bundle Branch Block
    58. 58. Right Bundle Branch Block
    59. 59. Right Bundle Branch Block
    60. 60. Right Bundle Branch Block
    61. 61. Left Bundle Branch Block• Duration greater than 0.12 sec• Broad monomorphic R-wave in I & V6• Terminal S-wave in V1.
    62. 62. Left Bundle Branch Block V1
    63. 63. Left Bundle Branch Block I V1I aVR V4 II aVL V2 V5 V6 III aVF V3
    64. 64. Left Bundle Branch Block
    65. 65. Left Bundle Branch Block
    66. 66. Left Bundle Branch Block
    67. 67. Left Bundle Branch Block
    68. 68. Intraventricular Conduction Delay• A Non-specific IVCD is less common than a RBBB or LBBB• They are wide, atrial rhythms that usually look like a left or right BBB in V1, but do not match the criteria in I & V6.
    69. 69. Non-Specific IVCDII V1 aVR V4II aVL V2 V5 V6III aVF V3
    70. 70. Non-Specific IVCD
    71. 71. Non-Specific IVCD
    72. 72. BBB Chart RBBB LBBB IVCD V1 TERMINAL TERMINAL TERMINAL R-WAVE S-WAVE R/S-WAVEI & V6 TERMINAL TERMINAL Anything is possible S-WAVE R-WAVE
    73. 73. Ventricular Enlargement• Left Ventricular Hypertrophy (LVH) – The left ventricle is enlarged – Probably due to left-sided heart failure• Right Ventricular Hypertrophy (RVH) – The right ventricle is enlarged – Probably due to right sided heart failure – May be due to pulmonary disease
    74. 74. Ventricular Enlargement• Left Ventricular Hypertrophy (LVH) – May cause left axis deviation – May cause a left ventricular strain pattern • Often mimics an anterior MI• Right Ventricular Hypertrophy (RVH) – May cause right axis deviation – May cause a right ventrcular strain pattern • May mimic a inferior or posterior wall MI
    75. 75. LVHNormal LVH RV LV Hypertrophy
    76. 76. LVH• LVH Criteria – Large QRS complexes • Deepest S-wave in V1 or V2 • Tallest R-wave in V5 or V6 – Add them together » If the result is > 25mm = LVH• Most texts may read: – S-wave (V1/V2) + R-wave(V5/V6) > 35mm – However, tall R-waves and deep S-waves may be cut off by the monitor. – Use the 25mm criteria and examine for “strain”
    77. 77. LVH V5 or V6V1 or V2 S + R
    78. 78. LVHLets take a look at an example
    79. 79. LVHLets take a look at an example
    80. 80. LVHLets take a look at an example
    81. 81. LVHLets take a look at an example 14mm
    82. 82. LVHLets take a look at an example 14mm
    83. 83. LVH14 + 15 = 29mm 14mm 15mm
    84. 84. LVH• Since our total was 29mm, and a total of > 25mm meets LVH criteria, we can assume that this ECG is that of a patient with LVH.*LVH may look a lot like a narrow LBBB.
    85. 85. LVH • A wave that is too tall or deep may be cut off by the monitor • This is a indicator of hypertrophy
    86. 86. LVH • A wave that is too tall or deep may be cut off by the monitor • This is a indicator of hypertrophy
    87. 87. LVHAdditional LVH Criteria Any precordial > 45mm lead aVL > 11mm Lead I > 12mm aVF > 20mm
    88. 88. Ventricular Leads Right Ventricular Left Ventricular
    89. 89. RVH• Right Ventricular Hypertrophy – Criteria = R:S ration > 1 in V1/V2 • This means that the R-wave is bigger than the S-wave in V1 or V2. • The QRS complex should be narrow • P-Pulmonale may be present. • Right axis deviation is common.
    90. 90. RVHV1 or V2 R = 9mm V1/V2: R > S = RVH •QRS < 120ms (0.12 sec) S = 6mm
    91. 91. RVH
    92. 92. RVHLet’s take a look…
    93. 93. RVHLet’s take a look…
    94. 94. QRS Complex• Low Voltage – Chronic Cor Pulmonale • Progressive lung disease, leading to right-sided heart failure. – Pericardial Effusion • Fluid in the pericardial sac. – Excessive Obesity
    95. 95. T Wave • Should not be symmetrical. • Should be upright in every lead but aVR. • Height should correlate with QRS. • Should have a dull peak.
    96. 96. Symmetrical T-WaveAsymmetrical NormalSymmetrical Abnormal
    97. 97. Hyperkalemia Peaked T-Wave• Hyperkalemia = High Potassium Level – Peaked T-Waves • May mimic an acute MI – Sine Waves • Sign of lethally high potassium level Sine Wave
    98. 98. Hyperkalemia
    99. 99. Hyperkalemia
    100. 100. Hyperkalemia
    101. 101. T-Wave Discordance• Discordance means opposite. – T-Wave discordance means that the T- Wave is deflected in the opposite direction as the terminal (last) wave of the QRS. – T-Wave discordance is normal in every lead with Left or Right BBBs.
    102. 102. T-Wave Discordance
    103. 103. Digitalis Effect• Shortened QT interval• Characteristic down-sloping ST depression• Dysrhythmias – ventricular / atrial premature beats – paroxysmal atrial tachycardia with variable AV block – ventricular tachycardia and fibrillation – many others
    104. 104. Digitalis Effect
    105. 105. QT-Interval Normal QTc < 460 ms
    106. 106. QT-Interval QT QTc = RRMeasures the time from when depolarization starts to the end of repolarization.
    107. 107. QT-Interval
    108. 108. Long QT Syndrome• QTc > 460ms – Congenital • Major contributor to sudden unexplained death in children and young adults. – Drug induced • Caused by many arrhythmia medications
    109. 109. U-Wave • Usually not visible. • Should not be prominent. • Should never be bigger than T-wave
    110. 110. Osborn Waves• Sometimes called “J-Waves”• Indicates HYPOTHERMIA• May be associated with bradycardia• Extra wave at the J-Point of the QRS- complex.
    111. 111. Osborn Waves Osborn Waves
    112. 112. Lesson 3• This concludes lesson 3• Practice examining different intervals & morphologies.

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