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Basic Electrocardiography

"I do not imagine that electrocardiography is likely to find any very extensive use in the hospital. It can at most be of rare and occasional use to afford a record of some rare anomaly of cardiac action.Augustus D. WallerBarker LF: Electrocardiography and phonocardiography: A collective rev

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Basic Electrocardiography

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    1. Basic Electrocardiography Dr. Mark O’Neill Senior Lecturer and Consultant Cardiologist Imperial College Healthcare NHS Trust

    2. "I do not imagine that electrocardiography is likely to find any very extensive use in the hospital. It can at most be of rare and occasional use to afford a record of some rare anomaly of cardiac action.“ Augustus D. Waller Barker LF: Electrocardiography and phonocardiography: A collective review. Bull Johns Hopkins Hosp 1910;21:358–359 Initially, Waller had said "I do not imagine that electrocardiography is likely to find any very extensive use in the hospital. It can at most be of rare and occasional use to afford a record of some rare anomaly of cardiac action."11 No doubt, his continued usage of the modality caused him to change his mind because in 1917, just six years after expressing this sentiment, Waller presented before the Physiological Society of London a paper entitled "A Preliminary Survey of 2,000 Electrocardiograms."12 Initially, Waller had said "I do not imagine that electrocardiography is likely to find any very extensive use in the hospital. It can at most be of rare and occasional use to afford a record of some rare anomaly of cardiac action."11 No doubt, his continued usage of the modality caused him to change his mind because in 1917, just six years after expressing this sentiment, Waller presented before the Physiological Society of London a paper entitled "A Preliminary Survey of 2,000 Electrocardiograms."12

    3. Outline Common Problems with ECG recording Interpreting the 12 lead ECG Key Diagnosis using ECGs Interpreting 24 hour ECGs

    4. Problems with ECG recording Patient identity Lead position Paper speed and amplification Artifact Misinterpretation is much more common than poor recording technique.

    5. Patient Identity

    6. Lead Position There are three of these leads which are usually designated as I, II and III. They are all bipolar (i.e., they detect a change in electric potential between two points) and detect an electrical potential change in the frontal plane. Lead I is between the right arm and left arm electrodes, the left arm being positive. Lead II is between the right arm and left leg electrodes, the left leg being positive. Lead III is between the left arm and left leg electrodes, the left leg again being positive. The same three leads that form the standard leads also form the three unipolar leads known as the augmented leads. These three leads are referred to as aVR (right arm), aVL (left arm) and aVF (left leg) and also record a change in electric potential in the frontal plane. These leads are unipolar in that they measure the electric potential at one point with respect to a null point (one which doesn't register any significant variation in electric potential during contraction of the heart). This null point is obtained for each lead by adding the potential from the other two leads. For example, in lead aVR, the electric potential of the right arm is compared to a null point which is obtained by adding together the potential of lead aVL and lead aVF.There are three of these leads which are usually designated as I, II and III. They are all bipolar (i.e., they detect a change in electric potential between two points) and detect an electrical potential change in the frontal plane. Lead I is between the right arm and left arm electrodes, the left arm being positive. Lead II is between the right arm and left leg electrodes, the left leg being positive. Lead III is between the left arm and left leg electrodes, the left leg again being positive. The same three leads that form the standard leads also form the three unipolar leads known as the augmented leads. These three leads are referred to as aVR (right arm), aVL (left arm) and aVF (left leg) and also record a change in electric potential in the frontal plane. These leads are unipolar in that they measure the electric potential at one point with respect to a null point (one which doesn't register any significant variation in electric potential during contraction of the heart). This null point is obtained for each lead by adding the potential from the other two leads. For example, in lead aVR, the electric potential of the right arm is compared to a null point which is obtained by adding together the potential of lead aVL and lead aVF.

    7. Paper Speed and Amplification

    8. Paper Speed

    9. Signal Amplification

    10. Artifact

    11. Artifact

    13. Look at all the leads

    14. Interpreting the 12 lead ECG There are 2 critical types of information to be gleaned from the ECG The sequence of Cardiac Electrical Activation i.e. electrical recording reflecting electrical phenomena The anatomy/geography of the abnormality Localising conduction disturbance (accurate) Localising perfusion disturbance (less accurate, because it is not a “perfusion recording”)

    15. Cardiac Activation sequence

    16. The “poor man’s” guide

    17. Interpreting the 12 Lead ECG

    18. Key Diagnoses using 12 lead ECG Conduction Disturbance 2nd Degree AV block 3rd Degree AV block Arrhythmias Atrial fibrillation Broad Complex vs Narrow complex tachycardia Acute Myocardial ischaemia

    19. Conduction Disturbance Sinoatrial node Failure of impulse initiation Sinus node arrest Atrioventricular node Intermittent failure of impulse conduction Ist and 2nd Degree AV block Complete failure of impulse conduction 3rd Degree AV block

    20. Where is the Conduction Problem?

    21. 1st Degree AV block

    22. 2nd Degree AV block

    23. 2nd Degree AV block

    24. 2nd Degree AV block

    25. 3rd Degree AV Block

    26. Atrial Fibrillation Predominantly of left atrial origin High rate of atrial activation (>300bpm) IRREGULAR VENTRICULAR RESPONSE Filtering effect of the AV node Protects the ventricle from high atrial rates Explains why we “rate control” AF

    27. Atrial Fibrillation

    28. Atrial Fibrillation

    29. Atrial Flutter

    30. Narrow Complex Tachycardia

    31. Narrow Complex tachycardia

    32. Ventricular (Broad Complex) Tachycardia

    33. Broad Complex Tachycardia

    34. Interpreting 24 hour ECGs You have only 2 leads They are not the same as the leads recorded with a 12 lead machine Artifact is very common Morphology of ST segments counts for nothing The majority of 24h tapes are normal!

    35. Lead Positions

    37. Occasionally interesting!

    38. What is this?

    39. Summary All information is in front of you on the recording Take a logical and structured approach to the recording If in doubt, ask a colleague – it’s what I do

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