12 Lead ECG PDF 2024

12 Lead ECG Foundations of Critical Care 2024 D.Freer What is an ECG? Picture of the electricity in the heart What information do we get from an ECG? Conduction system? Perfusion? To the body? To the heart? Mechanical action? Which chamber do we se...

12 Lead ECG Foundations of Critical Care 2024 D.Freer What is an ECG? Picture of the electricity in the heart What information do we get from an ECG? Conduction system? Perfusion? To the body? To the heart? Mechanical action? Which chamber do we see the most? Why? ECG When the heart depolarises, it creates an electrical current that flows through the heart The heart lies in a leftward, downward facing direction The larger mass of muscle is in the left ventricle The arms and legs are an extension of the heart’s electrical field Placing electrodes on the skin records the sum of all the electrical activity on the ECG Systematic approach Check integrity – patient details, calibration, paper speed, clinical story (Axis) – are the electrodes in the right place. R) axis… Rate & rhythm - atrial & ventricular P waves – morphology / association with QRS PR interval (blocks) Q waves QRS complexes – Narrow / Broad / Amplitude ST segment - elevated or depressed T-waves - upright, inverted, height QT interval – normal / prolonged If ischemia / injury / infarct, where is it? (Walls of the heart) Technical details Pt identifier Calibration John Smith UR: 007 DOB: 1/1/2000 Calibration Chart speed What do the leads capture? - Direction & Vectors - Axis - Leads & Walls Acute Coronary Syndrome - Coronary Arteries and walls - putting the 12-lead ECG together Acute Coronary syndrome A term that describes a spectrum of conditions including Unstable angina (UA) Non ST elevation myocardial infarction – NSTEMI ST elevation myocardial infarction – STEMI All have similar presentations Generally from plaque rupture & platelet aggregations Microcirculation / spasm The only difference is the degree of obstruction ECG criteria for STEMI Clinical symptoms consistent with ACS with ECG features including any of: ST elevation of ≥ 1mm in 2 contiguous limb leads ST elevation of ≥ 2mm in 2 contiguous chest leads New LBBB? Evolution of ECG changes Progresses through stages: 1. Ischemia: T wave inversion, ST depression Demand exceeds supply 2. Injury: ST segment elevation Cells stop functioning properly, still reversible 3. Infarction: abnormal Q wave Not reversible Ischaemia, Injury, & Infarction Myocardial Ischaemia results from an imbalance between myocardial Oxygen supply & demand If ischaemia is severe of prolonged, myocardial injury occurs and cells stop functioning normally Ischaemia & injury are reversible if blood flow is restored If ischaemia continues, the anaerobic cells eventually die and myocardial infarction occurs Infarction is irreversible Myocardial Ischaemia T wave inversion ST depression Transient & brief Reversible Myocardial Injury Hyperacute T waves Followed by ST elevation 1 mm or more in limb leads 2 mm or more in chest leads Two or more contiguous leads Within minutes Reversible ST elevation Look for: Elevation above the isoelectric line Shape Concave up normal Concave down / horizontal abnormal, more indicative of ischemia / infarction ST Depression more commonly associated with ischemia ST Elevation more commonly associated with injury / infarction (STEMI) Many other causes Pericarditis, LBBB, benign early repol, LVH, etc. Pericarditis Infarction “Tombstones” Myocardial Infarction Development of Q waves Or a loss in the height of the R wave (poor R wave progression) Q waves are pathological when: Width  0.04 sec Depth  2mm Within 1-2 hours Due to cell death Irreversible Evolved or old infarct Q waves persist ST segments return to baseline T wave become inverted May remain inverted for months May then become upright Inferior STEMI What to look for: ST elevation equal or greater than 1mm in any 2 inferior leads Which are? II, III, aVF Hyperacute T waves may precede these changes Reciprocal ST depression in aVL – true reciprocal lead What other lead may have reciprocal changes? Progressive development of Q waves in II, III, aVF Remember aVL aVL is the only lead truly reciprocal to the inferior wall, as it is the only lead facing the superior part of the ventricle. It is a sensitive marker for inferior infarction ST depression in aVL is more prevalent than STE in inferior leads Majority of “subtle” inferior STEMIs that do not meet STEMI criteria but show occlusion on PCI demonstrate ST depression in aVL Inferior injury What is the culprit artery? Dominant right coronary artery (RCA) in 80-90% of cases Dominant left circumflex (LCx) Occasionally, a “type III” or “wraparound LAD Unusual pattern of concomitant inferior ST elevation Associated features that worsen prognosis Concomitant right ventricular infarction Develop severe hypotension in response to nitrates Significant bradycardia due to second or third degree AV block Posterior infarction due to extension of infarct area Lateral STEMI What are our lateral leads? I, aVL, V5, & V6 What to look for: ST elevation greater than or equal to 1mm in lateral leads Reciprocal ST depression in the inferior leads (III and aVF) ST elevation localised to leads I and aVL is referred to as a high lateral STEMI Patterns of lateral infarction: Anterolateral STEMI due to LAD occlusion. Inferior-posterior-lateral STEMI due to LCx occlusion. Isolated lateral infarction due to occlusion of smaller branch arteries (e.g. D1, OM or ramus intermedius.) Right sided leads Record at least once in all patients with inferior MI RV leads will have negative QRS → look for ST elevation V4R is the most valuable lead in diagnosing RV infarction ST changes usually disappear within 10-12 hours RV infarction Suspected if: ST elevation in V1 (looks at the R heart) ST depression in V2 (reciprocal) ST elevation greatest in III (lead III>II) ST elevation greater than 1 mm in V4R Commonly occurs in inferior MI’s (RCA supplies inferior 80%) Place V1-6 in mirror image position on the R) side of the chest V4R is the most useful lead (ST elevation diagnostic accuracy of 83% of RV infarct) Posterior MI Diagnosis often missed No standard leads visualise this area Suspect posterior if see following changes in V1-V3 Horizontal ST depression (reciprocal of ST elevation) Tall, broad R waves (reciprocal of q waves) Leads V7-V9 are placed on the posterior chest wall in the same horizontal plane as V6 V7 – Left posterior axillary line V8 – halfway between V7 and V9 V9 – Left spinal border Isolated posterior MI is extremely rare. Why?  Practice Which wall, artery, and likely Dx? Changes & Leads Wall of the heart Culprit artery T wave inversion (TWI) V1-V4 3mm deep Q waves II, III, aVF ST depression I, aVL, V5, V6 ST elevation V1-V6, aVL “The important thing is not to stop questioning. Curiosity has its own reason for existing” - Albert Einstein Axis Deviation, R-Wave Progression, Bundle Branch Blocks and Fascicular Blocks By Sarah Della-Mina Re-capping vectors Axis deviation What is the cardiac axis? The cardiac axis is the general direction in which electricity is flowing through the heart. Axis deviation is when the electrical current deviates from the normal direction. To determine axis look at leads I and aVF, and possibly lead II  -90 180 If the lead is positive, the electrical current is running in the same direction as that lead If the lead is negative, the electrical current is running in the opposite direction as that lead Axis deviation Causes of Right Axis Deviation: Right ventricular hypertrophy -90 Most common cause as the muscle in the ventricle is thicker and therefore 180 requires a stronger electrical signal to be generated by the right side. Other causes include: WPW RV strain i.e PE Lateral MI  LEFT AXIS DEVIATION Left Axis Deviation If lead I is positive and aVF is -90 negative you need to look at lead II Normal Axis If lead II is positive axis is normal 180 If lead II is negative, you have a LAD Axis deviation Causes of Left Axis Deviation: Left ventricular hypertrophy -90 Left bundle branch block Inferior MI 180 WPW Ventricular pacing Axis deviation Extreme Axis Deviation Causes of Extreme Axis Deviation: Ventricular rhythms -90 Hyperkalaemia 180 R-wave progression How to determine an R wave? The R wave is the first upward deflection after the p wave The R wave signifies the beginning of ventricular depolarisation R-wave progression What is R-wave progression? R-wave progression is the electrical depolarization of the ventricles being seen from lead V1-V6. In normal R-wave progression the R- wave is negative in V1-V2, becomes biphasic in V3-V4 and then positive in V5-V6. Normal R-wave progression Poor R-wave progression Poor R-wave progression Poor R-wave progression can be caused by: MI: necrotic myocardium doesn’t generate electrical potentials therefore the r- wave loses amplitude (remember height = voltage) Cardiomyopathy: large amounts of myocardium mean the electrical impulse needs to be greater to get through the muscle, – thin amounts of myocardium need less electrical impulse therefore the r-waves are generally smaller. Right and Left ventricular hypertrophy Bundle branch blocks Bundle Branch Blocks Normal electrical pathway: SA node Bachmann's Bundle AV node Bundle of HIS Bundle branches Purkinje fibres Bundle Branch Blocks Right Bundle How to determine a RBBB: Wide QRS due to a delay in conduction (remember length = time) o Look at V1 and V6 R R If QRS V1 is predominantly positive o with an rSR pattern (M), you have a RBBB V6 will often have a W pattern Bundle Branch blocks Right bundle Bundle Branch Blocks Right Bundle Causes of a RBBB: - Right ventricular hypertrophy - PE - Ischemic heart disease- RBB is supplied by the LAD. New onset of chest pain and new RBBB can indicate critical occlusion of the LAD - Rheumatic heart disease - Congenital heart defects - Myocarditis - Cardiomyopathy Bundle Branch Blocks Right bundle Incomplete RBBB If rSR pattern is present in V1 but QRS is normal you have an incomplete RBBB. Bundle Branch Blocks Left Bundle How to determine a LBBB: Wide QRS due to a delay in i conduction (remember length = L time) L i Look at V1 and V6 a If QRS V1 is predominantly negative with a W shape and V6 is positive with an M, you have a LBBB Bundle Branch Blocks Left Bundle Bundle Branch Blocks Left Bundle Causes of a LBBB: Dilated Cardiomyopathy – leading cause due to the stretching of the myocardium and separation of the Purkinje fibres Aortic stenosis Ischemic heart disease Hypertension Anterior MI Hyperkalaemia Digoxin toxicity Bundle Branch Blocks i L o L R i a R o Fascicular blocks Because the left ventricle has so much more myocardium than the right, it requires more Bachmann's Bundle electrical pathways to contract the left ventricle. The left bundle branch splits into two fascicles – the left anterior fascicle, which supplies the front of the left ventricle, and the left posterior fascicle – which supples the back of the left ventricle. Occasionally one of these fascicles gets blocked causing either a LAFB or LPFB. Fascicular blocks Left Anterior Fascicular Block Left anterior fascicular block occurs when the left anterior fascicle no longer receives electrical impulses. It is characterised by: Left Axis Deviation Negative rS complex in inferior leads (II, III, aVF) Positive qS complex in lateral leads (I, aVL) Increased QRS voltage in limb leads (I, II, III, aVF, aVL, aVR) Left Anterior Fascicular Block Left Anterior Fascicular Block Left anterior fascicular block can be caused by: MI Coronary artery disease LVH Dilated cardiomyopathy Hypertrophic cardiomyopathy Degernerative disease HTN Hyperkalaemia Myocarditis and Amloydosis Fascicular blocks Left Posterior Fascicular Block Left posterior fascicular block occurs when the left posterior fascicle no longer receives electrical impulses. It is characterised by: Right Axis Deviation Negative rS complex in lateral leads (I, aVL) Positive qS complex in inferior leads (II, III, aVF) Increased QRS voltage in limb leads (I, II, III, aVF, aVL, aVR) Left Posterior Fascicular Block  Left Posterior Fascicular Block Left posterior fascicular block can be caused by: Ischemic heart disease Hyperkalemia Myocarditis Amloydosis and Cor pulmonale Bi-Fascicular and Tri-Fascicular Block Bi-Fascicular Block Causes: Bi-Fascicular Block involves two of the IHD – new onset bi-fascicular three fascicules. Either RBBB + LAFB or block with chest pain is highly RBBB + LPFB associated with LAD disease Structural heart disease Tri-Fascicular Block Tri-Fascicular Block involves all three fascicules Aortic stenosis below the AV node, resulting in bi-fascicular Anterior MI block PLUS complete heart block CHB + RBBB + LAFB or Congenital heart disease CHB + RBBB + LPFB Hyperkalaemia Digoxin toxicity Bi-Fascicular and Tri-Fascicular Block Bi-Fascicular and Tri-Fascicular Block References https://geekymedics.com/what-is-cardiac-axis/ right-bundle-branch-blocks/ https://favpng.com/png_view/practical-vector-electrocardiography-12- https://ecgwaves.com/topic/left-anterior-posterior-fascicular-block- lead-ecg-the-art-of-interpretation-3-lead-ekg-einthovens-triangle- hemiblock-ecg/ heart-png/NkCPWB1v https://litfl.com/left-anterior-fascicular-block-lafb-ecg-library/ https://litfl.com/ecg-axis-interpretation/ https://litfl.com/left-posterior-fascicular-block-lpfb-ecg-library/ https://ecgwaves.com/topic/ecg-normal-p-wave-qrs-complex-st- https://ecgwaves.com/topic/left-anterior-posterior-fascicular-block- segment-t-wave-j-point/ hemiblock-ecg/ https://litfl.com/r-wave-ecg-library/ https://litfl.com/trifascicular-block-ecg-library/ https://www.researchgate.net/figure/Repeat-12-lead-EKG-showing- https://ecgwaves.com/topic/intraventricular-conduction-delay-ecg- normal-sinus-rhythm_fig2_322504203 bundle-branch-fascicular-block/ http://www.phimaimedicine.org/2011/11/1416-poor-r-wave- https://litfl.com/bifascicular-block-ecg-library/ progression.html https://ecgwaves.com/topic/introduction-electrocardiography-ecg- book/ https://litfl.com/right-bundle-branch-block-rbbb-ecg-library/ https://en.my-ekg.com/how-read-ekg/heart-axis.html https://stock.adobe.com/be_nl/images/ecg-rbbb-right-bundle-branch- block-12-leads-ecg-paper/555156703 https://www.medicalexamprep.co.uk/bundle-branch-blocks-part-1-left-