Introduction to 12 Lead ECGs

1. Introduction to 12 Lead ECGs EMS Professions Temple College

2. Topics Why 12 Lead ECGs? Critical Concepts in ACS Monitoring vs Diagnostic ECGs Acquisition & Transmission

3. Why 12 Lead ECGs? Demonstrated Advantages Rapid Identification of Infarction/Injury diagnosis made sooner in many cases Decreased Time to Reperfusion Treatment speeds preparation of & time to reperfusion therapies Increased Index of Suspicion Modification to Therapies

4. Why 12 Lead ECGs? Perceived Disadvantages Increased time spent on scene demonstrated at 0-4 min increase Cost equipment & training No clinical advantage to patient & “our transport times are short” demonstrated decrease in time to treatment compare to early notification for trauma patients Not helpful in “our system” Possibly true!

5. Why 12 Lead ECGs? American Heart Association in collaboration with International Liaison Committee on Resuscitation. Guidelines 2000 for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care: International Consensus on Science, Part 7: The Era of Reperfusion. Circulation. 2000; 102 (suppl I): I-175.

6. Critical Concepts in ACS Ischemia lack of oxygenation ST segment depression or T wave inversion Injury prolonged ischemia ST segment elevation Infarct prolonged injury results in death of tissue may or may not show Q wave This information will aid in understanding the ECG subsets in the next section. Define ischemia, injury and infarct. Note that the definitions are correlated with specific ECG criteria. Note that “injury” is also ischemia and does not imply any permanent damage or death to tissue. The term injury simply means ischemia identified by ST segment elevation. This information will aid in understanding the ECG subsets in the next section. Define ischemia, injury and infarct. Note that the definitions are correlated with specific ECG criteria. Note that “injury” is also ischemia and does not imply any permanent damage or death to tissue. The term injury simply means ischemia identified by ST segment elevation.

7. Critical Concepts in ACS ST elevation - the key to the acute reperfusion therapy subset You can’t see ST elevation without a 12-lead ECG Perform on every patient suspected of ACS Obtain early Repeat frequently While it is not always possible to identify which of the ACS a patient is experiencing, it is possible to determine if a patient can benefit from acute reperfusion therapy. The indication for acute reperfusion therapy is ST segment on the 12-lead ECG. For EMS to identify this subset of patients, a diagnostic 12-lead must be obtained . “The 12-lead ECG stands at the center of the decision making pathway in the management of patients with ischemic chest pain, and delays in obtaining the 12-lead ECG must be eliminated.” AHA, ACLS Textbook, 1997, 9-13While it is not always possible to identify which of the ACS a patient is experiencing, it is possible to determine if a patient can benefit from acute reperfusion therapy. The indication for acute reperfusion therapy is ST segment on the 12-lead ECG. For EMS to identify this subset of patients, a diagnostic 12-lead must be obtained . “The 12-lead ECG stands at the center of the decision making pathway in the management of patients with ischemic chest pain, and delays in obtaining the 12-lead ECG must be eliminated.” AHA, ACLS Textbook, 1997, 9-13

8. Critical Concepts in ACSWill Infarct Occur? Whether tissue necrosis occurs as in AMI or does not occur resulting in unstable angina is determined by the interplay of several factors. This underscores why it is usually impossible to determine which syndrome is present and why we should instead concentrate on identifying the the presence of any ACS. The issue of suspecting ACS will be addressed after a brief explanation of the terms ischemia, injury and infarction. Whether tissue necrosis occurs as in AMI or does not occur resulting in unstable angina is determined by the interplay of several factors. This underscores why it is usually impossible to determine which syndrome is present and why we should instead concentrate on identifying the the presence of any ACS. The issue of suspecting ACS will be addressed after a brief explanation of the terms ischemia, injury and infarction.

9. Critical Concepts in ACS Note treatment continuation for ST elevation or new BBB (a.k.a. acute injury pattern) subset.Note treatment continuation for ST elevation or new BBB (a.k.a. acute injury pattern) subset.

10. Critical Concepts in ACS Fibrinolytics Retaplase (rPA) Actiplase (tPA) Streptokinase (rarely used today) Percutaneous Transluminal Coronary Angioplasty (PTCA) Balloon angioplasty Stent placement Atherectomy Thrombolytics are pharmacological agents administered IV that dissolve a coronary thrombus. PTCA is an intervention that utilizes a balloon or other device, inserted through a large artery, to create a larger lumen in the offending coronary artery. Atherectomy procedures remove the occlusion by laser or cutting mechanisims. Thrombolytics are pharmacological agents administered IV that dissolve a coronary thrombus. PTCA is an intervention that utilizes a balloon or other device, inserted through a large artery, to create a larger lumen in the offending coronary artery. Atherectomy procedures remove the occlusion by laser or cutting mechanisims.

11. Critical Concepts in ACS Pain is Injury Pain-Free is the Goal Time is Muscle Door to Reperfusion Therapy Time is the issue

12. Monitoring vs Diagnostic ECGs Extra wires 3 wires vs 10 wires Are there other differences?

13. Monitoring vs Diagnostic ECGs Monitoring Quality ECG Designed to provide information needed to determine rate and underlying rhythm Designed to “filter out” artifact Reduces the amount and degree of electrical activity seen by the ECG monitor

14. Monitoring vs Diagnostic ECGs Monitor Quality The typical “3-lead” ECG was never designed to capture QRS-ST-T waveforms with complete accuracy. The 3-lead was designed to provide enough information for the user to determine cardiac rate and rhythm. Because artifact makes interpretation difficult, the 3-lead is set to “filter out” artifact by reducing the spectrum of cardiac electrical activity that it “sees”. This strategy significantly reduces artifact and still renders waveforms of sufficient quality for rate and rhythm determination. However, in doing so, the QRS-ST-T may not always be accurately represented. Therefore, do not use monitor quality for ST analysis.The typical “3-lead” ECG was never designed to capture QRS-ST-T waveforms with complete accuracy. The 3-lead was designed to provide enough information for the user to determine cardiac rate and rhythm. Because artifact makes interpretation difficult, the 3-lead is set to “filter out” artifact by reducing the spectrum of cardiac electrical activity that it “sees”. This strategy significantly reduces artifact and still renders waveforms of sufficient quality for rate and rhythm determination. However, in doing so, the QRS-ST-T may not always be accurately represented. Therefore, do not use monitor quality for ST analysis.

15. Monitoring vs Diagnostic ECGs Diagnostic Quality ECG Designed to accurately reproduce QRS, ST and T waveforms Designed to look more broadly at the cardiac electrical activity Unfortunately, may result in greater artifact being visible

16. Monitoring vs Diagnostic ECGs Diagnostic Quality The 12-lead is designed to accurately reproduce the QRS-ST-T waveforms. In order to do so the 12-lead must “look” at a broader spectrum of cardiac electrical activity. This spectrum is referred to as “frequency response” This broader spectrum is referred to as “diagnostic quality”. A diagnostic quality ECG is necessary for accurate ST segment analysis. Unfortunately, when in diagnostic quality, all 12-lead ECGs are more susceptible to more artifact than are 3-lead ECGs.The 12-lead is designed to accurately reproduce the QRS-ST-T waveforms. In order to do so the 12-lead must “look” at a broader spectrum of cardiac electrical activity. This spectrum is referred to as “frequency response” This broader spectrum is referred to as “diagnostic quality”. A diagnostic quality ECG is necessary for accurate ST segment analysis. Unfortunately, when in diagnostic quality, all 12-lead ECGs are more susceptible to more artifact than are 3-lead ECGs.

17. Monitoring vs Diagnostic ECGs Frequency Response Term used to describe the breadth of the electrical spectrum viewed by the ECG monitor Diagnostic quality is usually 0.05 Hz to 150 Hz Monitor quality is usually 0.5 Hz to 20-50 Hz Usually printed on the ECG recording strip

18. Monitoring vs Diagnostic ECGs The frequency response is printed on the ECG paper. The frequency response for diagnostic quality is 0.05Hz - 150Hz. There may be some slight variation among manufacturers and ECG models. The low end for monitor quality is often 0.5 Hz (not 0.05Hz), while the high end often is in the range of 20-50Hz. The frequency response is printed on the ECG paper. The frequency response for diagnostic quality is 0.05Hz - 150Hz. There may be some slight variation among manufacturers and ECG models. The low end for monitor quality is often 0.5 Hz (not 0.05Hz), while the high end often is in the range of 20-50Hz.

19. Acquisition & Transmission ECG quality begins with skin preparation and electrodes Hair removal Skin preparation Age & Quality of Electrodes & Cables Electrode Placement Because of the increased “window” to electrical signals, additional steps must be taken to reduce the amount of artifact produced. Removing excess hair and prepping the skin allows the electrode gel to better penetrate the skin, thus receiving a stronger signal with less artifact. First we will discuss the techniques themselves, later in the module we will look at strategies to accomplish these additional tasks quickly.Because of the increased “window” to electrical signals, additional steps must be taken to reduce the amount of artifact produced. Removing excess hair and prepping the skin allows the electrode gel to better penetrate the skin, thus receiving a stronger signal with less artifact. First we will discuss the techniques themselves, later in the module we will look at strategies to accomplish these additional tasks quickly.

20. Acquisition & Transmission Hair Removal Clipper over razor Lessens risk of cuts Quicker Disposable blade clippers available Most EMS systems use razors Excess hair presents two problems: • First, hair may prevent the electrode from adhering well. • Second, hair may inhibit gel contact and skin penetration. Some thrombolytic manufacturers recommend that clippers be used to remove chest hair. The intent is to minimize the potential for bleed sites in a patient who may receive a thrombolytic.Excess hair presents two problems: • First, hair may prevent the electrode from adhering well. • Second, hair may inhibit gel contact and skin penetration. Some thrombolytic manufacturers recommend that clippers be used to remove chest hair. The intent is to minimize the potential for bleed sites in a patient who may receive a thrombolytic.

21. Acquisition & Transmission Read the clipper manufacture’s recommendations. This is one model designed for medical applications and may be used near oxygen. In addition the head is disposable, avoiding de-contamination issues.Read the clipper manufacture’s recommendations. This is one model designed for medical applications and may be used near oxygen. In addition the head is disposable, avoiding de-contamination issues.

22. Acquisition & Transmission Skin Preparation Helps obtain a strong signal When measured from skin, heart’s electrical signal about 0.0001 - 0.003 volts Skin oils reduce adhesion of electrode and hinder penetration of electrode gel Dead, dried skin cells do not conduct well When measured from the patient’s skin, the heart’s electrical signal is extremely small, about 0.0001 to 0.003 volts. That’s as small as one-ten thousandth of a volt. Compare this with energy from a nine volt battery. Good skin prep will make the ECG signal as strong as possible, and make the artifact signals as small as possible.When measured from the patient’s skin, the heart’s electrical signal is extremely small, about 0.0001 to 0.003 volts. That’s as small as one-ten thousandth of a volt. Compare this with energy from a nine volt battery. Good skin prep will make the ECG signal as strong as possible, and make the artifact signals as small as possible.

23. Acquisition & Transmission Simply rubbing the skin with a gauze pad can have a noticeable effect on ECG clarity by: • Reducing skin oil • Removing part of the stratum corneum Simply rubbing the skin with a gauze pad can have a noticeable effect on ECG clarity by: • Reducing skin oil • Removing part of the stratum corneum

24. Acquisition & Transmission Other causes of artifact Patient movement Cable movement Vehicle movement Electromagnetic Interference (EMI) Once the skin has been prepped and the electrodes applied, there are still other sources of artifact to consider.Once the skin has been prepped and the electrodes applied, there are still other sources of artifact to consider.

25. Acquisition & Transmission Patient Movement Make patient as comfortable as possible Supine preferred Look for subtle movement toe tapping, shivering Look for muscle tension hand grasping rail, head raised to “watch” It is important to place the patient in a position of comfort. The reduction in muscle tension will help to prevent artifact. When possible, the patient should be in the supine position for a 12-lead ECG. Sometimes this is not feasible, practical or desirable. If ECG is not recording in supine position, simply note this on ECG.It is important to place the patient in a position of comfort. The reduction in muscle tension will help to prevent artifact. When possible, the patient should be in the supine position for a 12-lead ECG. Sometimes this is not feasible, practical or desirable. If ECG is not recording in supine position, simply note this on ECG.

26. Acquisition & Transmission Cable Movement Enough “slack” in cables to avoid tugging on the electrodes Many cables have clip that can attach to patient’s clothes or bed sheet It is important to place the patient in a position of comfort. The reduction in muscle tension will help to prevent artifact. When possible, the patient should be in the supine position for a 12-lead ECG. Sometimes this is not feasible, practical or desirable. If ECG is not recording in supine position, simply note this on ECG.It is important to place the patient in a position of comfort. The reduction in muscle tension will help to prevent artifact. When possible, the patient should be in the supine position for a 12-lead ECG. Sometimes this is not feasible, practical or desirable. If ECG is not recording in supine position, simply note this on ECG.

27. Acquisition & Transmission Vehicle Movement Acquisition in a moving vehicle is NOT recommended May or may not be successful Tips Pull ambulance over for 10-20 seconds during acquisition Acquire ECG while stopped at traffic light It is important to place the patient in a position of comfort. The reduction in muscle tension will help to prevent artifact. When possible, the patient should be in the supine position for a 12-lead ECG. Sometimes this is not feasible, practical or desirable. If ECG is not recording in supine position, simply note this on ECG.It is important to place the patient in a position of comfort. The reduction in muscle tension will help to prevent artifact. When possible, the patient should be in the supine position for a 12-lead ECG. Sometimes this is not feasible, practical or desirable. If ECG is not recording in supine position, simply note this on ECG.

28. Acquisition & Transmission Electromagnetic Interference (EMI) Can interfere with electronic equipment 60 cycle interference is a type of EMI Look for nearby cell phones, radios or electrical devices No contact between cables & power cords Turn off or move away from AC devices Use shielded cables; inspect for cracks It is important to place the patient in a position of comfort. The reduction in muscle tension will help to prevent artifact. When possible, the patient should be in the supine position for a 12-lead ECG. Sometimes this is not feasible, practical or desirable. If ECG is not recording in supine position, simply note this on ECG.It is important to place the patient in a position of comfort. The reduction in muscle tension will help to prevent artifact. When possible, the patient should be in the supine position for a 12-lead ECG. Sometimes this is not feasible, practical or desirable. If ECG is not recording in supine position, simply note this on ECG.

29. Acquisition & Transmission Things to look for Little or no artifact Steady baseline

30. Note how the baseline straightened out by simply repositioning the patient cables and clipping them onto the sheet. What technique(s) would you consider in order to resolve the muscle artifact?Note how the baseline straightened out by simply repositioning the patient cables and clipping them onto the sheet. What technique(s) would you consider in order to resolve the muscle artifact?

31. Acquisition & Transmission ECG Accuracy depends upon Lead placement Frequency response Calibration Paper speed All of the techniques discussed to this point have related to ECG clarity. We now need to look at what is necessary to ensure ECG accuracy.All of the techniques discussed to this point have related to ECG clarity. We now need to look at what is necessary to ensure ECG accuracy.

32. Limb Lead Placement Limb leads should be placed on the limbs. The traditional placement is near the ankles and wrists.Limb leads should be placed on the limbs. The traditional placement is near the ankles and wrists.

33. Chest Lead Placement V1: fourth intercostal space to right of sternum V2: fourth intercostal space to left of sternum V3: directly between leads V2 and V4 V4: fifth intercostal space at left midclavicular line V5: level with V4 at left anterior axillary line V6: level with V5 at left midaxillary line V1 fourth intercostal space to the right of the sternum V2 fourth intercostal space to the left of the sternum V3 directly between leads V2 and V4 V4 fifth intercostal space at left midclavicular line V5 level with lead V4 at left anterior axillary line V6 level with lead V5 at left midaxillary lineV1 fourth intercostal space to the right of the sternum V2 fourth intercostal space to the left of the sternum V3 directly between leads V2 and V4 V4 fifth intercostal space at left midclavicular line V5 level with lead V4 at left anterior axillary line V6 level with lead V5 at left midaxillary line

34. Chest Lead Placement Here is what lead placement looks like on a patient.Here is what lead placement looks like on a patient.

35. ECG Accuracy Look for: Negative aVR if aVR upright, look for reversed leads One complete cardiac cycle in each lead Diagnostic frequency response Proper calibration Appropriate speed Once a clear ECG has been obtained (free of excess artifact and has a steady baseline), it may then quickly be examined to confirm accuracy. Listed here are five items that relate the the accuracy of the ECG.Once a clear ECG has been obtained (free of excess artifact and has a steady baseline), it may then quickly be examined to confirm accuracy. Listed here are five items that relate the the accuracy of the ECG.

36. ECG Accuracy Frequency Response Display screen is non-diagnostic Use the printed ECG for ST segment analysis It is important to note that the display screen in 12-lead monitors is not in diagnostic quality. Usually a 12-lead must be printed out for accurate ST analysis. Check the 12-lead printout and confirm the correct frequency response.It is important to note that the display screen in 12-lead monitors is not in diagnostic quality. Usually a 12-lead must be printed out for accurate ST analysis. Check the 12-lead printout and confirm the correct frequency response.

37. ECG Accuracy Calibration Voltage measured vertically Each 1 mm box = 0.1 mV 1 mV = 10 mm calibration standard Confirm calibration calibration impulse should be 10 mm (2 big boxes tall) stated calibration should be “x 1.0” It is important to note that the display screen in 12-lead monitors is not in diagnostic quality. Usually a 12-lead must be printed out for accurate ST analysis. Check the 12-lead printout and confirm the correct frequency response.It is important to note that the display screen in 12-lead monitors is not in diagnostic quality. Usually a 12-lead must be printed out for accurate ST analysis. Check the 12-lead printout and confirm the correct frequency response.

38. Calibration

39. ECG Accuracy Paper Speed Standard is 25 mm/sec Faster paper speed means the rhythm will appear slower and the QRS wider Slower paper speed means the rhythm will appear faster and the QRS narrower It is important to note that the display screen in 12-lead monitors is not in diagnostic quality. Usually a 12-lead must be printed out for accurate ST analysis. Check the 12-lead printout and confirm the correct frequency response.It is important to note that the display screen in 12-lead monitors is not in diagnostic quality. Usually a 12-lead must be printed out for accurate ST analysis. Check the 12-lead printout and confirm the correct frequency response.

40. Paper Speed

41. When to Acquire These tracings show how much the ECG can change in a short time. Note the times on these ECGs. These tracings show how much the ECG can change in a short time. Note the times on these ECGs.

42. When to Acquire This excerpt from an American Heart Association algorithm shows the initial 12-lead acquisition along with the vital signs. Note treatment is concomitant and is not inordinately delayed. In later modules we will further develop the concepts relating to the dynamic nature of AMI and the 12-lead ECG. At that time it will be very apparent why early ECGs are critical. Accepting that fact necessitates a strategy for QUICK 12-lead acquisitionThis excerpt from an American Heart Association algorithm shows the initial 12-lead acquisition along with the vital signs. Note treatment is concomitant and is not inordinately delayed. In later modules we will further develop the concepts relating to the dynamic nature of AMI and the 12-lead ECG. At that time it will be very apparent why early ECGs are critical. Accepting that fact necessitates a strategy for QUICK 12-lead acquisition

43. Exposing the Chest Immediately upon suspecting ACS... Remove all clothing above the waist Or, open shirt/blouse Replace with gown (if possible) Allows for complete exam Minimizes wire entanglement Enhances quick defib if VF occurs Exposing the chest before obtaining the 12-lead is probably the single most important factor to reduce time and effort. If a gown is not available a sheet may be used, however, the gown is preferable. Exposing the chest before obtaining the 12-lead is probably the single most important factor to reduce time and effort. If a gown is not available a sheet may be used, however, the gown is preferable.

44. Transmission Transmit as soon as possible Can use patient’s land-line Many EMS systems use cell phone enroute Coordinate with ED Correlate ECG with a specific patient Early notification of AMI is key!!! Transmission protocols and strategies very tremendously from system to system. Some systems may not transmit the ECG at all. Receiving facilities may receive two 12-leads in a short period of time. Therefore, some identification mechanism must be in place to correlate the transmitted ECG to a particular EMS unit. Transmission protocols and strategies very tremendously from system to system. Some systems may not transmit the ECG at all. Receiving facilities may receive two 12-leads in a short period of time. Therefore, some identification mechanism must be in place to correlate the transmitted ECG to a particular EMS unit.