Presentation on theme: "A Basic Overview of How to Interpret 12 Lead EKGs and Treat a Cardiac Patient Region IV Pre-Hospital Systems Coordination Committee 12 Lead EKG 101."— Presentation transcript:
A Basic Overview of How to Interpret 12 Lead EKGs and Treat a Cardiac Patient Region IV Pre-Hospital Systems Coordination Committee 12 Lead EKG 101
The purpose of this course is to provide pre-hospital clinicians with the tools necessary to identify the basic A&P of the heart, interpret 12 Lead EKGs, localize and treat AMIs as well as recognize imposters and potential complications. Purpose:
Basic Cardiac Anatomy & Physiology Muscular pump about the size of your fist primary function is to pump oxygenated blood to the rest of the body. Made up of four chambers, right and left atria right and left ventricles The septum is a thin muscular wall that separates the right and left sides of the heart. Each contraction of the heart occurs in response to an electrical impulse that starts in the upper portion of the heart. Blood is moved in a closed circuit through the body by the pumping of the heart.
The heart contracts and pumps blood out to the body (systole) and relaxes to fill with more blood (diastole). The heart muscle itself is like all other organs in the body and requires oxygen to function. The oxygen-rich blood is circulated to the heart muscle through the coronary arteries. There are two main arteries: Right coronary artery Left main coronary artery both start at the aorta These vessels then branch off into smaller and smaller vessels along the surface of the heart. Basic Cardiac Anatomy & Physiology
In order to perform work, the heart needs oxygen and nutrients. There are two main arteries: Right coronary artery (RCA) Left coronary artery (LCA). The left coronary artery divides into: Left anterior descending (LAD) branch Left circumflex branch(LCX) The right coronary artery and the branches of the left coronary artery provide numerous smaller branches which penetrate the heart muscle, supplying it with blood. Both coronary arteries originate from the aorta and run along the surface of the heart. In the majority of human hearts, coronary circulation follows a predictable pattern.
Left Main Coronary Artery Branches quickly into the LAD & LCX. Involves almost 2/3 of the heart muscle Right Coronary Artery (RCA) The RCA supplies blood to the bottom (inferior) portion and part of the back (posterior) portion of the left ventricle. The posterior portion of the septum is also supplied with blood from the RCA. SA Node 55% AV Node 90% AV Blocks Left Anterior Descending Branch (LAD) The LAD supplies blood to the front (anterior) portion of the left ventricle, apical including most of the anterior portion of the septum separating the ventricles. Bundle Branch Block, AMI, CHF Left Circumflux Branch (LCX) The LCX supplies blood to the left side (lateral) portion and the back (posterior) portion of the left ventricle. SA Node 45% AV Node 10% Lateral & posterior MI
Sino-Atrial (SA) Node: natural cardiac pacemaker. The heartbeat starts here and spreads throughout the network of conduction fibers in the two atria causing them to contract. Normally, the heartbeat can only reach the ventricles (the two lower chambers), after it has passed through the atrioventricular (AV) node. Atrioventricular (AV) Node: slows down the electrical signal so that the atrial contractions can finish filling the ventricles completely. The AV node also prevents the lower chambers from beating too fast if the atria develops a fast rhythm (tachyarrhythmia). His Bundle, bundle branches, and the Purkinje system : The electrical signal finally passes to the ventricles causing the ventricles to contract
Anatomy of an EKG The EKG, or a measure of this electrical activity of the heart, is comprised of 3 primary parts P wave---electrical depolarization of the atria...contraction follows QRS COMPLEX---electrical depolarization of the ventricles...contraction follows T wave---electrical repolarization of the ventricles...and thus, relaxation...
P wave: Represents positive and negative deflections of atrial contraction and relaxation PR Interval: Distance between the P wave and the R wave. Should be consistent QRS Complex Q wave: First negative deflection Normal in I, aVL, V1, V6 Significant or pathologic is one box wide and/or 1/3 the height of the R wave R Wave: First positive deflection S Wave: Next negative deflection
ST Segment: Essentially isoelectric, slopes gentely upward J point: the point at which the ST Segment takes off from the QRS complex T Wave: Upright always in leads I, II, V2-V6. aVR is always negative. Leads III, aVL, aVF, and V1 can be positive or negative U Wave: Seen best in V3, same polarity as T wave, sign of hypokalemia QT Interval: One complete ventricular cycle. None are > ½ the preceding R-R
Putting the A&P with the EKG
Lead I extends from the right to the left arm Lead II extends from the right arm to the left foot Lead III extends from the left arm to the left foot Einthoven’s Triangle
This is an example a 12-lead EKG. Anatomy of a 12-Lead EKG
At the bottom of this 12- lead are rhythm strips (highlighted). Any of the 12-leads can be shown as rhythm strips. You can configure the device to show you any of the six limb leads on the rhythm strip (I, II, III, aVR, aVL or aVF). Anatomy of a 12-Lead EKG (cont.)
The format of the 12-lead EKG is very standard. While there are a few exceptions, the format you see here is typical of what you will see in most 12-lead EKGs done in North America. Anatomy of a 12 Lead EKG (cont.)
Anatomy of a 12-Lead EKG (cont.) The 12-lead can provide a computer generated interpretation. When you see “ACUTE MI SUSPECTED” the machine is right about 98% of the time. In order to attain specificity, if the computer isn’t absolutely sure that an AMI is present, it will not say anything about it. In other words YOU are the primary interpreter, the computer is your backup.
The 12-Lead is very good at measuring intervals and durations. It is better at measuring the PR-interval and the QRS width. We express these intervals and durations in seconds 12-lead expresses them in milliseconds. It is simple to convert milliseconds to seconds. Anatomy of a 12-Lead EKG (cont.)
When you use an EKG to determine the cardiac rate and rhythm, certain sampling time is required. 12-lead interpretation: Only one beat from each lead is needed to make an interpretation. Anatomy of a 12-Lead EKG (cont.)
Each lead has one positive electrode. Positive electrode is a camera. view is from the positive electrode toward the negative electrode. The portion of the left ventricle that each leads “sees” is determined by the location of that positive electrode. Different placements of the electrodes will yield different viewpoints. Anatomy of a 12-Lead EKG (cont.) There are six positive electrodes on the chest, yielding six leads. There are four electrodes on the limbs from which the EKG machine makes another six leads.
Anatomy of a 12-Lead EKG (cont.) Limb LeadsChest Leads IaVRV1V4 IIaVLV2V5 IIIaVFV3V6 Types of Leads
Anatomy of a 12-Lead EKG (cont.) View of Posterior Heart Wall Leads V1 & V2 -Tall R -ST Depression -Upright T-Wave
Leads II, III, aVFLeads II, III, aVF -Looks at inferior heart wall Anatomy of a 12-Lead EKG (cont.) View of Inferior Heart Wall -Looks from the left leg up
Leads I and aVLLeads I and aVL –Looks at lateral heart wall –Looks from the left arm toward heart Anatomy of a 12-Lead EKG (cont.) View of Lateral Heart Wall *Sometimes known as High Lateral*
Leads V5 & V6Leads V5 & V6 –Looks at lateral heart wall –Looks from the left lateral chest toward heart Anatomy of a 12-Lead EKG (cont.) View of Lateral Heart Wall *Sometimes referred to as Low Lateral or Apical view*
Leads I, aVL, V5, V6Leads I, aVL, V5, V6 - Looks at the lateral wall of the heart from two different perspectives Anatomy of a 12-Lead EKG (cont.) View of Entire Lateral Heart Wall Lateral Wall
Leads V3, V4Leads V3, V4 –Looks at anterior heart wall –Looks from the left anterior chest Anatomy of a 12-Lead EKG (cont.) View of Anterior Heart Wall
Leads V1, V2Leads V1, V2 -Looks at septal heart wall -Looks along sternal borders Anatomy of a 12-Lead EKG (cont.) View of Septal Heart Wall
I Lateral II Inferior III Inferior aVR aVL Lateral V1 Septal aVF Inferior V2 Septal V3 Anterior V4 Anterior V5 Lateral V6 Lateral Anatomy of a 12-Lead EKG (cont.)
The ST segment is normally iso- electric (baseline) neither elevated or depressed. May slope upward toward a relatively tall T wave Anatomy of a 12-Lead EKG - ST Segment The ST segment is probably the single most important element to identify on the ECG when looking for evidence of AMI.
The Three I’s Ischemia Ischemia – lack of oxygenation – ST depression or T inversion Injury Injury –prolonged ischemia –ST elevation Infarct Infarct –death of tissue –may or may not show in Q wave
Cardiac ischemia is a situation in which the blood flow within a coronary artery is limited to the point where the oxygen needs of the heart muscle cannot be met (hypoxia).coronary arteryhypoxia ( Myocardial ischemia, Ischemic heart disease, Ischemia, Myocardium ischemia, Silent ischemia ) CARDIAC ISCHEMIA
Minor episodes of cardiac ischemia tend to cause little long-term damage to the heart, but these episodes can sometimes cause serious effects in some patients: They can cause which can lead to either and They can cause arrhythmias, which can lead to either syncope or cardiac arrest and sudden cardiac death.arrhythmiassyncopecardiac arrestsudden cardiac death Severe or lengthy episodes can trigger a in myocardial infarction. Severe or lengthy episodes can trigger a result in myocardial infarction.result The collective effects of minor episodes of cardiac ischemia can potentially lead to The collective effects of minor episodes of cardiac ischemia can potentially lead to cardiomyopathy. cardiomyopathy
Symptoms of Cardiac Ischemia May be painful symptoms of cardiac ischemia, Pain, pressure or discomfort from cardiac ischemia is angina. Angina may feel like a squeezing vise or crushing pressure deep in the chest behind the sternum. May also be felt in the shoulders, arms, back, neck or jaw. angina
EKG in Acute Ischemia Tracing taken during an episode of anginal pain that occurred while the patient was at rest. Marked ST elevation in leads V2 ‑ 5 with some ST depression in aVF.
EKG after Acute Ischemia This tracing was taken 30 minutes after the initial. The patient was pain ‑ free and asymptomatic. The ST segments are isoelectric, and the ECG is normal
Evaluation after Acute Ischemia Subsequent clinical evaluation Subsequent clinical evaluation –serial ECGs –enzyme determinations, revealed no evidence of acute myocardial infarction. Disappearance of the ST elevation and the absence of clinical and electrocardiographic evidence of infarction on subsequent examinations indicate that initial ECG is representative of severe, acute, and reversible ischemia.
Epicardial Coronary Artery Lateral Wall of LV Positive Electrode Septum Left Ventricular Cavity Interior Wall of LV Well Perfused Myocardium
Epicardial Coronary Artery Lateral Wall of LV Positive Electrode Septum Left Ventricular Cavity Interior Wall of LV Ischemia
Ischemia Inadequate oxygen to tissue Inadequate oxygen to tissue Subendocardial Subendocardial Represented by ST depression or T inversion Represented by ST depression or T inversion May or may not result in infarct May or may not result in infarct
Injury Prolonged ischemia Prolonged ischemia Transmural Transmural Represented by ST elevation Represented by ST elevation Usually results in infarct Usually results in infarct
Thrombus Ischemia Injury
Infarct Death of tissue Death of tissue Represented by Q wave Represented by Q wave Not all infarcts develop Q waves Not all infarcts develop Q waves
Infarcted Area Electrically Silent Depolarization Many infarcts do not develop Q waves Infarction
Infarcted Area Electrically Silent Thrombus Depolarization Ischemia
Summary A normal ECG does NOT rule out ACS A normal ECG does NOT rule out ACS ST segment depression represents ischemia ST segment depression represents ischemia –Possible infarct ST segment elevation is evidence of AMI ST segment elevation is evidence of AMI Q wave MI may follow ST elevation or depression Q wave MI may follow ST elevation or depression
Pathophysiology of the AMI Chronic accumulation of atherosclerotic plaque in coronary vessels around the heart Fibrous plaque prone to rupture, lead to thrombytic blockage Clots form due to damaged tissue and platelets Both release chemicals causing a clot to form Forms a substance called fibren that traps cells and platelets eventually blocking and narrowing Tissue damage in AMI results from rupture of plaque on vessel walls creating a chain reaction that forms a clot in the coronary artery.
Process of an AMI Impaired blood flow: Produces varying degrees of myocardial injury Damage dependent on flow reduction and duration Tissue death progress quickly in a wave pattern Begins with endocardium Ends with epicardium Infarction becomes larger toward the surface of the heart. Ischemia – Shortage of oxygen at cellular level Injury – Diminishing supply of oxygen Infarct – cardiac cells die of anoxia.
EKG Changes from Infarction First Detectable Change in EKG Tall T-waves increase in height more symmetric may occur in the first few minutes *Known as hyper acute phase*
EKG Changes from Infarction “The Acute Phase” Signs of Myocardial Injury ST Segment Elevation Primary indication of injury Occurs in first hour to hours ST Segment Elevation in Leads 1mm or greater in limb leads 2 mm or greater in chest leads Hallmark indication of AMI *Known as Acute Phase*
EKG Changes of Infarction “Reciprocal Changes” ST elevation in contiguous leads most often represents acute infarction ST elevation in contiguous leads most often represents acute infarction ST depression in contiguous leads may represent acute ischemia ST depression in contiguous leads may represent acute ischemia In acute infarction, ST elevation in contiguous leads coupled with reciprocal ST depression in non- infarcting leads is added evidence of an AMI. In acute infarction, ST elevation in contiguous leads coupled with reciprocal ST depression in non- infarcting leads is added evidence of an AMI.
Acute ST segment elevation Reciprocal ST segment depression
EKG Changes from Infarction “T Wave Inversion” Signs of Myocardial Injury T wave inversion presence of ischemia May precede ST elevation Prominent in precordial chest leads Inversion in limb leads is pathologic T wave inversion can be caused by other things than ischemia
EKG Changes from Infarction “The Indeterminate Phase” Signs of Myocardial Infarction Pathologic Q-wave First indication of tissue death First few to several hours Q-wave ¼ size of QRS suggests infarct Represent current or past events Determine timing through ST elevation and T-wave inversion
Natural Progression of EKG in Infarction Over time: T-wave regains normal contour ST-segment returns to isometric line Q-wave remains as evidence of infarct Indicates presence of previous MI *ST segment elevation provides the strongest evidence of early recognition of AMI*
EKG Changes from Infarction (cont.) All of the changes in the previous slides are: Indicative Changes ST segment elevation is helpful in detecting an MI in its early stages Hyperacute (Tall) T-waves alone are specific enough to diagnose an MI T-wave inversion can occur with simple angina and is therefore not specific Pathological Q-wave is the most accurate recognition of an MI Not in the first few hours ST segment elevation provides the strongest evidence for early recognition of an MI
ECG Variants Coronary Spasm: “Printzmetals angina” Coronary Spasm: “Printzmetals angina” Injury pattern that resolves w/ rest, NTG,O2 etc. Early Repolarization: elevated “J” point seen best in V3,4. Key to Dx pt’s are usually young & asymptomatic Early Repolarization: elevated “J” point seen best in V3,4. Key to Dx pt’s are usually young & asymptomatic Pericarditis: ST elevation usually global associated w/ fever, pleuritic c/p. Pericarditis: ST elevation usually global associated w/ fever, pleuritic c/p.
ECG Variants due to Drugs or Electrolytes Imbalances Hypokalemia: lg U waves ( usually taller than T) seen best in precordial leads. <2.7 Hypokalemia: lg U waves ( usually taller than T) seen best in precordial leads. <2.7 Hyperkalemia: Hyperkalemia: –Tall peaked T waves > 6.0 –PR prolongs, QRS widens –P waves disappear > 8.0 Hypocalcemia: Hypocalcemia: –Prolonged QT interval Hypercalcemia: Hypercalcemia: –Shortened QT interval Digitalis effect: Digitalis effect: –ST depression- downsloping, curved ST segments. –“scooping”, “sagging”, flat or inverted T’s in lateral leads –PR prolonged –QT shortened
Bundle Branch Blocks “Turn Signal Rule” This is a simple method for differentiating right bundle branch block from left bundle branch block. V1 will be the only lead you need to view 1. Locate the terminal (last) force of the QRS complex 2. Determine if it is pointing up or down. 3. Compare to the turn signal in your car: »Up is for a right turn & RBBB »Down is for a left turn and LBBB Clinical significance: Bundle branch is a significant complication of infarction. Since the left anterior descending artery is the primary supplier of the bundle branches, BBB is considered a complication of anterior septal infarcts. When BBB is the result of MI, the incidence of pump failure is 65-70% and the in-hospital mortality rate is 40%-60%. The BBB itself is not dangerous, but the high mortality rate is due to the extensive amount of tissue death occurring when an infarct is serious enough to cause a BBB. Another manifestation of BBB is in the form of AV Block. This is why infranodal AV blocks are more serious and have wide QRS complexes.
Localizing the Area of Infarction Indicative changes are not found in every lead Only present in leads looking at the infarct Indicative changes in two or more leads looking at the same portion of the heart are anatomically contiguous leads Suspect AMI ST segment elevation in two or more leads that are not contiguous AMI not the suspected cause
Recognizing infarct: Know which part of the heart each lead looks at Localizing Infarct: Note which lead is displaying evidence and which portions of heart they are looking at *Simply knowing the changes to look for and which part of the heart each lead looks at* Recognition & Localization Leads Displaying Indicative Changes II, III, aVF V1 & V2 V3 & V4 V5, V6, I, and aVL Location of Infarct Site Inferior Septal Anterior Lateral
Anterior Wall MI Anterior Wall infarct: Occlusion of the Left Anterior Descending Artery (LAD) 2mm ST segment elevation in two or more of leads V1-V4 Reciprocal changes in leads II, III, aVF Lethal due to large myocardium involvement Possible conduction defects: Bundle Branch Block 2 nd Degree Block Type II CHB
Anterior Wall MI
Inferior Wall MI Inferior Wall MI: Occlusion of Right Coronary Artery (RCA) At least 1mm ST segment elevation in leads II, III, aVF Reciprocal ST depression in leads I & aVL or precordial leads Conduction defects: Sinus bradycardia Sinus arrest 1 st degree block Accelerated Idoventricular rhythm Complications: Bradyarrhythmias – protective mechanism, 90% of blood supply for SA & AV nodes from the RCA Hypotension – treated with fluids, consider right side involvement
Inferior Wall MI
Lateral Wall MI Lateral Wall MI: results from occlusion of the Left Circumflex Artery At least 1 mm ST segment elevation in leads I, aVL, V5 & V6 and /or 2 mm ST segment elevation in V5 & V6 Reciprocal ST depression in V1 Sometimes an extension of an Anterior or Inferior MI Conduction defects are rare
Anterior/Lateral Wall MI
Posterior Wall MI Posterior Wall MI: Occlusion of the Right Coronary Artery (RCA) or the Posterior Descending Artery No leads that look at the posterior wall Leads look at the infarct site from the opposite side(backwards) ST depression in V1 & V2 Tall R waves in V1 and/or V2 Most often associated with Inferior MI *Associated with dangerous conduction disturbances*
Posterior Wall MI
Right Ventricular MI Right Ventricular MI: caused by proximal occlusion of the Right Coronary Artery (RCA) Associated with Inferior Wall MI Can happen independently Standard 12-Lead does not assess right side of heart Infarction is significant Indicates large infarction Indicates involvement of both ventricles If the possibility of RVI exists a set of chest leads can be applied to the right side of the chest V1-6R leads look at right ventricle Lead V4R most accurate
Right Ventricular MI
Septal Wall MI Septal Wall MI: caused by septal perforation involving the LAD or the Posterior Descending Most often in the setting of an Anterior MI Loss of R-wave in leads V1, V2 or V3 May have ST segment elevation in V1 & V2 No reciprocal changes
Overview of Infarcts Location of Infarct Arterial Supply Indicative Changes Reciprocal Changes AnteriorLADV1-V4 II, III, aVF InferiorRCA I, aVL LateralCircumflex I, aVL, V5, V6 V1 Posterior Posterior Descending (RCA) None V1, V2 Septal Septal Perforating (LAD) Posterior Descending (RCA Loss of R wave in V1, V2, or V3 None
Overview of Infarcts Suspect infarction when there are indicative changes in at least two anatomically contiguous leads Indicative changes in many leads suggests larger infarct With Inferior Wall MI suspect Right Ventricular Wall Infarct Signs of possible Right Ventricular Wall Infarct: Hypotension JVD Clear lung sounds Causes of ST segment depression include digitalis, ischemia and reciprocal changes Suspect Posterior Wall Infarctions when an Inferior Wall Infarction has ST depression in Leads V1-V3
Complications of Myocardial Infarction Chest Pain: Most common complication Treatment: Oxygen and ASA (162 to 325)mg NTG initially with Morphine if pain persists Usually very effective Right Ventricular Wall Infarct: Reduces output of right ventricle decreasing left ventricular filling (decreased preload) NTG and Morphine can worsen conditions Decrease in blood pressure will worsen area of injury Presence of Inferior Wall Infarction with no EKG or clinical evidence of right side infarct does not merit any extra caution when using NTG and Morphine
Complications of Myocardial Infarction AV Block Location: indicates electrical impulse from atrium is blocked from depolarizing the ventricles Most common block is in the AV Node (nodal block) Second most common block is in the Bundle Branches (infranodal) Infarct frequently produces AV Block due to increase in parasympathetic tone Local ischemia around node can produce the block Less serious than block caused by tissue injury or death Blocks in AV node produce narrow QRS complex Bundle Branches produce wide complexes
Complications of Myocardial Infarction Determining the type of QRS presented with is a useful tool in determining the location of the block Nodal Block Infranodal Block Coronary Supply Right Coronary Artery Left Coronary Artery QR Width NarrowWide Stability Generally Stable Often Unstable Atropine Response Usually improves Often does not respond
Complications of Myocardial Infarction Hypotension: A common treatment for hypotension which is secondary to the infarct is to administer fluid boluses and inotropic drugs (dopamine) Hypotension in the setting of an inferior wall infarction is most likely secondary to right ventricular involvement. Although RV Infarcts may require significant boluses to offset loss of preload, continuously monitor the patient for signs and symptoms of developing left sided failure. Hypotension in the setting of an anterior wall infarction may not tolerate fluid boluses and may require a dopamine infusion.
Complications of Myocardial Infarction Left Coronary Artery Occlusions Right Coronary Artery Occlusions Leads Showing Indicative Changes V1-V6, I, aVL II, III, aVF, V4R-V6R Localization Septal, Anterior, Lateral, Posterior Inferior, Posterior, Right Ventricular Pain Control NTG & Morphine as appropriate NTG & Morphine used with caution if RVI present AV Block Infrequent, usually wide ORS, often unstable, Atropine may be ineffective, use standby pacing Frequent, usually narrow QRS, Generally stable, Atropine often effective, May not require treatment Hypotension cc fluid bolus, inotropic medications Vigorous fluid therapy if RVI present, inotropic medications
Clinical Pearls Suspect infarction when there are indicative changes in at least two anatomically contiguous leads Indicative changes in a greater number of contiguous leads suggests a more extensive infarction RV or Posterior infarcts should be considered in setting of Inferior Wall MI RV: ST segment elevation in rV4 Posterior: ST depression +/or Tall Rwave in V1 & V2 Other clinical signs of RV Infarct may include: Hypotension and JVD in the setting of clear lung sounds Other causes of ST segment depression besides ischemia include digitalis effects and ventricular hypertrophy Suspect Posterior Wall Infarctions when an Inferior Wall Infarction has ST depression in Leads V1-V3