3 Introduction & Purpose Prehospital 12 Lead ECG (PHECG) is one of the fastest growing new additions to prehospital care in North America12 Lead ECG provides advantages over traditional 3 & 4 lead ECGs commonly used by prehospital providers for rhythm interpretation#1 most common reason for acquiring and interpreting 12 Lead ECG in the field is faster reperfusion for AMI patients
4 PHECG & ReperfusionAcute Myocardial Infarction (AMI) is the most frequent cause of death in the developed worldMortality is estimated at 50%AMI = coronary artery occlusion (thrombus)Problem: death of myocardium beyond thrombusModern treatment for AMI = reperfusion
5 Reperfusion for AMIReperfusion involves opening up blocked coronary artery to restore blood flow to affected myocardiumMethods of reperfusion:Pharmacological – administration of thrombolytics (fibrinolytics) that breakdown clotMechanical – balloon angioplasty referred to as Primary Percutaneous Coronary Intervention (PCI) that mechanically opens arteryPharmacological reperfusion is either referred to as thrombolysis or fibrinolysis – the terms are used interchangeably. Fibrinolysis has generally replaced thrombolysis in the medical literature as it is, in effect, more accurate. The 2 main events taking place in the development of the thrombus involve platelet aggregation and fibrin accumulation and binding. “Thrombolytics” act chiefly on breakdown of fibrin – antiplatelet therapy is normally additionally required to breakdown the thrombus.
6 Timing of Reperfusion Current model with PHECG: Patient develops signs and symptoms of ischemic chest pain/acute myocardial infarctionCall is placed to 911Crew respondsPatient is treated as acute coronary syndrome (ACS) patient including acquisition and interpretation of 12 Lead ECG and STEMI is foundED is notified of “Cardiac Alert” or “STEMI alert” and transported to ED where early reperfusion therapy is administered (either ED thrombolysis or primary PCI.IT IS ALL ABOUT STOPPING THE CLOCK ON DEATH OF MYOCARDIUM
7 Time is Muscle Survival from AMI is all about time! Regardless of method (thrombolysis or PCI), early reperfusion therapy has been demonstrated to improve survival and quality of life for AMI patients.A common phrase for simplifying the risks of AMI is to say “TIME IS MUSCLE”.Regardless of which method is used to reperfuse AMI, earlier treatment is associated with both better survival and better quality of life for survivors. Better quality of life is often under appreciated in reperfusion with focus on survival; however, patients who survive an AMI receiving earlier reperfusion are more likely to avoid CHF, reinfarction and ongoing ischemia (angina).
8 Reperfusion Delays in AMI Delays from onset of symptoms to patient recognition – 60 to 70%.Delays in out-of-hospital transport – 5%Delays in in-hospital evaluation and treatment – 25 to 30%Patient delays in seeking care for chest pain and other cardiac symptoms constitutes the single greatest obstacle to early care (60-70%). Another way of framing this is to say it is the immovable mountain, resistance to change even where significant efforts are made to improve earlier call for help. Even among patients with previous history of ischemic heart disease delays in seeking care are common. Patient and community education interventions designed to reduce delays have not been shown to improve early recognition and action by patients. However, these same education interventions have been shown to improve EMS access demonstrating the need for prehospital tools such as PH12 Lead ECG.EMS role in delays is minimal (5%). In other words, we are not part of the problem but increasingly viewed as key to the solution.Delays in in-hospital evaluation and treatment constitute 25-30% of reperfusion delays for AMI patients. It is this last element of delay that PH12 Lead ECG is targeted at reducing.
9 Prehospital Role in Reperfusion Three current strategies:PHECG + ED notification for early in-hospital thrombolysisPHECG + prehospital thrombolysisPHECG + prehospital triage to Cath lab for Primary PCIThe common factor in all 3 of the above strategies is that the prehospital 12 Lead ECG and paramedic training is required for each.PHECG + ED notification: the most common current method in North American for field recognition of STEMI, early ED notification and rapid triage for in-hospital thrombolysis. Currently used in several communities in Ontario as well as in Canada and the US. In the early days of PHECG was associated with as much as 60 minutes in improved D2N time for IHT but has more recently more commonly closer to 10 – 20 minute time savings.Prehospital thrombolysis: PHT has historically been practiced more often in Europe than North America largely due to the use of physicians in the out-of-hospital setting. In the U.S., two recent surveys of EMS systems demonstrate a low-incidence of EMS PHT. In a recent survey of US EMS providers 5.2% were delivering PHT. In the second survey of 184 of the largest EMS providers in the U.S., 84% were performing 12 Lead ECG but only 6 (3%) were delivering PHT. However the latter study noted 33% of these providers were involved in cath lab activation and 14% were transporting directly to a cath lab suggesting PHT may be under utilized in lieu of increasing access to primary PCI triage. Currently in Canada PHT programs are operating in Alberta and Nova Scotia. Save for the Ontario Air Ambulance program (ORNGE), no PHT programs are known to operate in Ontario.PCI Triage: The fastest growing method involving PH providers, PHECG and early STEMI reperfusion is PCI Triage. Primary percutaneous coronary intervention (PCI) has begun to emerge as the preferred reperfusion therapy for STEMI when it is delivered early (D2B < 90 minutes) by skilled operators.
10 PHECG & ReperfusionPrehospital 12 Lead ECG has been demonstrated to improve time to reperfusion for a select group of at risk patients – ST-elevation myocardial infarction (STEMI).Multiple published trials: PHECG in conjunction with early ED notification has been associated with improved time to ED diagnosis and early thrombolysis for STEMI from 10 – 60 minutes. (Source: see references)It is important to note that PHECG has not been demonstrated to improve time to reperfusion without a triage or notification instrument. It would be a mistake to implement PHECG without a mechanism of notification – either to ED for earlier thrombolysis or ED/cardiologist for primary PCI.
11 AHA Guidelines 2005American Heart Association recommendations on out-of-hospital 12 Lead ECG:Implementation of prehospital 12 ECGPHECG & advance notification of ED for out-of-hospital patients w/ S&S of ACSSTEMI patients: completion of a “fibrinolytic checklist”Door-to-needle time in ED of < 30 minDoor-to-balloon time in cath lab < 90 minFibrinolytic checklist, some times called a thrombolytic screen, is a checklist of contraindications patients may have to fibrinolytic therapy. These contraindications mostly include bleeding disorders or possible pathologies that may be complicated by risk of bleeding associated with “clot-buster” therapy.
12 Next Step: Prehospital Role in Reperfusion Various EMS systems in North America and Europe have evolved prehospital strategies for managing reperfusion:Prehospital Thrombolysis: the delivery of fibrinolytic agents (associated with earlier symptom to treatment time)Prehospital triage for in-hospital Primary PCIGuided by prehospital 12 Lead ECG, many EMS systems (especially in Europe) have implemented strategies to reduce time from ACS symptoms to reperfusion.These include:Prehospital Thrombolysis implemented in Edmonton, Ontario Air Ambulance and recently Nova Scotia. Involves, among current ischemia therapies such as NTG, ASA, Morphine, the addition of various antiplatlet and anticoagulant therapies.Prehospital Triage for Primary PCI (PPCI). Primary PCI is angioplasty for an acute MI rather than scheduled angioplasty to treat chronic cardiac pathologies. Prehospital triage for PPCI has taken many forms but ultimately involves EMS 12 Lead ECG diagnosis of STEMI followed by transmission to a cardiologist or ED physician for interpretation and activation of the Cath Lab (PCI suite). In some programs such as Ottawa, the paramedics diagnosis STEMI then place a single call to activate the Cath Lab team. Ottawa’s PPCI triage program has been associated with decreased door-to-balloon time and improved mortality for STEMI patients.The key point here is that none of these rapid triage and reperfusion therapies could be advanced without EMS 12 Lead ECG.
13 D2B times for direct transfer to PCI center vs referral from ED Referred directly from fieldReferred from emergency departmentp valueMedian door-to-balloon time (min)69123<0.001Door-to-balloon time less than 90 min (%)79.711.9Ottawa HI research – I’ll let Ed put in the notes here!Le May MR et al. N Engl J Med 2008; 358:
14 Ontario Base Hospital Group – Medical Advisory Committee 2007 Recommendations to MOHLTC:Prehospital 12 Lead ECG become a Provincial standard for all ambulances and paramedics.MAC supports introduction of prehospital strategies demonstrated to improve early reperfusion in STEMI:Early ED notification (i.e.: STEMI Alert)Prehospital ThrombolysisPrehospital Triage for Primary PCIMAC = Medical Advisory Committee; Makes recommendations to the Ministry of Health and Long-term Care regarding clinical issues related to paramedicine in Ontario.
16 Why 12 Lead Other than for reperfusion… The following case illustrates the importance of obtaining a 12 lead early in the patients care.Credit and thanks goes to Tim Phalen for the use of these slides
17 Case Presentation Chest Pain for 2 hours 4 on a 1-10 scale 12-lead obtained with the first vitalsOxygen and nitroglycerin givenNext 12-lead eight minutes laterCredit and thanks goes to Tim Phalen for the use of these slidesCase PresentationThis patient also presented in a classic manner.This EMS team knows that a 12-lead is critical. In fact, they not only prioritize getting a 12-lead but also strive to obtain the ECG as early as possible in the call.Following the first acquisition they leave the electrodes attached and obtain additional 12-lead during the call.
18 First 12 LeadCredit and thanks goes to Tim Phalen for the use of these slidesCompare these two 12-leads.The first shows obvious ST segment elevation. The second shows none. Putting aside the question of how that can happen, consider the implications.Had the team not done the early ECG, they would have missed the telling evidence of ST elevation. Because of the 12-lead was done early they have now documented the evidence required for immediate reperfusion.
19 8 Minutes laterCredit and thanks goes to Tim Phalen for the use of these slidesCompare these two 12-leads.The first shows obvious ST segment elevation. The second shows none. Putting aside the question of how that can happen, consider the implications.Had the team not done the early ECG, they would have missed the telling evidence of ST elevation. Because of the 12-lead was done early they have now documented the evidence required for immediate reperfusion.
20 Value of an Early ECG ECG changes from ACS are dynamic MONA treatment may mask changesST elevation = reperfusion indicationEMS is in a privileged positionEarly 12-leadDuring symptomsBefore medicationCredit and thanks goes to Tim Phalen for the use of these slidesSo, how can the ECG change so quickly? There are many possible explanations.First, we must realize that the events going on in the coronary artery can change constantly. If that’s the case then the ECG can show dynamic changes as well.Another possible explanation is that the treatment provided by EMS effected the ECG. Both nitroglycerin and oxygen have the shown capable of reducing or eliminating ST segment elevation. While this does not happen on every call, it does occur. Perhaps more frequently than we might expectTake away point: An early prehospital 12-lead may in fact be the best opportunity to capture ST segment elevation.A good approach is to prioritize the early ECG and get repeat 12-lead every 5-10 minutes.MONA = Morphine, Oxygen, Nitrates, ASANote: Other conditions such as Prinzmetal’s angina may be identified as well.
22 Lead Groups I aVR V1 V4 II aVL V2 V5 III aVF V3 V6 Limb Leads Chest Leads
23 Inferior Wall II, III, aVF Left Leg I II III aVR aVL aVF V1 V2 V3 V4 The positive electrode for leads II, III, and aVF is attached to the left leg. The ECG monitor uses this one electrode as the positive electrode for all three leads.From that perspective, these leads “look up” and “see” the inferior wall of the left ventricle.NOTE: A heart model is helpful at this juncture, particularly to remind students that the heart does not sit “straight up” in the chest.
24 Inferior Wall I II III aVR aVL aVF V1 V2 V3 V4 V5 V6 Inferior Wall NOTE: This is a posterior view of the heart.The portion of the heart that rests on the diaphragm is called the “inferior wall”.Leads II, III, and aVF, “look” up and see the inferior wall.When ST segment elevation is noted in II, III and aVF, suspect an inferior infarction.Inferior Wall
25 Lateral Wall I and aVL Left Arm I II III aVR aVL aVF V1 V2 V3 V4 V5 V6 Leads I and aVL share the positive electrode on the left arm.From the perspective of the left arm, these leads “see” the lateral wall of the left ventricle.
26 Lateral Wall V5 and V6 Left lateral chest I II III aVR aVL aVF V1 V2 V5 and V6 are positioned on the lateral wall of the left chest which is why these two leads also “see” the lateral wall of the left ventricle.
27 Lateral I, aVL, V5, V6 I II III aVR aVL aVF V1 V2 V3 V4 V5 V6 Lateral WallIIIIIIaVRaVLaVFV1V2V3V4V5V6Portions of the lateral wall are shown here from both the anterior and posterior perspective.Leads I, aVL, V5 and V6 “see” the lateral wall. When ST segment elevation is seen in these leads, consider a lateral wall infarction.
28 Anterior Wall V3, V4 Left anterior chest I II III aVR aVL aVF V1 V2 V3 The positive electrode for these two leads is placed on the anterior wall of the left chest. This correlates to their designation as anterior leads.
29 Anterior Wall V3, V4 I II III aVR aVL aVF V1 V2 V3 V4 V5 V6 Of course, ST segment elevation in V3 and V4 implies an anterior wall infarction.
30 Septal Wall V1, V2 Along sternal borders I II III aVR aVL aVF V1 V2 V3 These leads are positioned one on each side of the sternum. From that placement they “look through” the right ventricle and “see” the septal wall.NOTE: The septum is left ventricular tissue.
31 Septal V1,V2 I II III aVR aVL aVF V1 V2 V3 V4 V5 V6 V1 and V2 “look through” the right ventricle to “see” the septum.
32 AMI Localization I II III aVR aVL aVF V1 V2 V3 V4 V5 V6 Anterior: V3, V4Septal: V1, V2Inferior: II, III, AVFLateral: I, AVL, V5, V6IIIIIIaVRaVLaVFV1V2V3V4V5V6This represents the 3x4 format of the 12-lead ECG.Each box represents one lead, and the viewpoint of that lead is indicated.
33 AMI Recognition I Lateral aVR II Inferior aVL Lateral III Inferior V1 SeptalV4 AnteriorII InferioraVL LateralV2 SeptalV5 LateralIII InferioraVF InferiorEach box represents one lead, and the viewpoint of that lead is indicated.NOTE: Refer participants to their pocket card where this information is summarized as well.V3 AnteriorV6 Lateral
34 AMI Recognition Know what to look for Know where you are looking ST elevation> 1mm in limb leads> 2mm chest leadsTwo contiguous leadsKnow where you are lookingYou will soon have this memorized
35 Mnemonic for Location S = V1 (Septal) L = I (Lateral) S = V2 (Septal) Rhyme, phrase or device for remembering something“LII – LI – ASS (backwards) – ALL”S = V1 (Septal)S = V2 (Septal)A = V3 (Anterior)A = V4 (Anterior)L = V5 (Lateral)L = V6 (Lateral)L = I (Lateral)I = II (Inferior)I = III (Inferior)L = aVL (Lateral)I = aVF (Inferior)This mnemonic device may work for some learners to remember the locations of the walls of the heart in relation to the 12 Lead ECG. However, emphasize to the learners that commitment to memorizing the locations of leads is essential for fast and consistent recognition.
36 Using mnemonic on ECGYou may want to write the Letters in the corner of each Lead when interpretingLSAILSLIIAL
38 Limb Lead Placement Place leads on limbs Away from major muscles or arteriesHave patient remain still during 12 lead acquisition (to reduce artifact)
39 Limb Lead PlacementPlace electrodes on the limbs if there is a 12 lead in the patient’s future – highly preferable to torso placementLimb leads should be placed on the limbs. The traditional placement is near the ankles and wrists. Wrist placement can be complicated by some watches that create EMI. It may be acceptable to use lateral deltoid position for upper limb leads.
40 Limb Lead Placement Reasons to place on the torso? Fracture Amputation ArtifactIf Limb Leads are placed on the torso make sure to document this directly on the 12 Lead ECGA more proximal placement on the extremities is acceptable and, in fact, usually reduces movement artifact. Just be sure to keep the electrodes off the trunk. Never place the lower limb electrodes above the pelvis.The following note is included in the student manual. Please determine local policies and preferences in order to address any related questions.“The proper position for the limb electrodes is on the limbs, and that should be your technique. However, standard operating procedure in some receiving facilities is to place the electrodes on the trunk, near the limb. If this is to be done, at least make certain that the upper electrodes are near the deltoid, and the lower electrodes are below the umbilicus.”
41 Limb Leads aVR should be negative If aVR is upright, check for reversed limb leadsAVR provides the ECG Interpreter the “Square root of Squat” (to use slang). However, even then it gives you something: Because the positive electrode for aVR is located on the right arm, normal ventricular activation moves away from aVR. Thus, aVR is typically negative.If aVR is upright, it may be the result of altered conduction or it could be due to misplaced limb leads.When aVR is positive always confirm proper lead placement.
42 Precordial Chest Leads For every person, each precordial lead placed in the same relative positionV1 - 4th intercostal space, R of sternumV2 - 4th intercostal space, L of sternumV4 - 5th intercostal space, midclavicularV3 - between V2 and V4, on 5th rib or in 5th intercostal spaceV5 - 5th intercostal space, anterior axillary lineV6 - 5th intercostal space, mid-axillary
43 Chest Lead PlacementV1 fourth intercostal space to the right of the sternumV2 fourth intercostal space to the left of the sternumV3 directly between leads V2 and V4V4 fifth intercostal space at left midclavicular line. The above picture shows V4 placed almost on the nipple. This is not accurate in terms of general approach to lead placement. It is now standard & acceptable to place V4 under the Left breast in line with the midclavicular line.V5 level with lead V4 at left anterior axillary lineV6 level with lead V5 at left midaxillary line
44 Chest Lead PlacementV1 is placed in the 4th intercostal space to the right of the sternal boarderTo find the 4th intercostal space feel for the clavicleJust below the clavicle is the 2nd rib, then 3rd and 4th ribBetween the 4th rib and the 5th rib is the 4th intercostal spaceV2 is placed to the left of the sternal boarder in the 4th intercostal space
45 Chest Lead PlacementV4 is placed next in the 5th intercostal space in the mid-clavicular lineFind the half way mark on the left clavicle and move down one rib so V4 is between the 5th and 6th ribsV3 is placed after V4 and is simply placed in between V2 and V4 either on the 5th rib or in the 5th intercostal space
46 Chest Lead PlacementV5 is placed in the 5th intercostal space and the anterior axillary lineTo find the anterior axillary line lay the patient’s left arm at their side and follow the crease line in their armpit down the front of their chestV6 is placed in the 5th intercostal space in the mid-axillary line
47 Chest Lead PlacementV1V2V3V4V5V6V1: 4th intercostal space to the right of the sternumV2: 4th intercostal space to the left of the sternumV3: directly between V2 and V4V4: 5th intercostal space at the left mid-clavicular lineV5: level with V4 at the anterior axillary lineV6: level with V5 at the mid-axillary line