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EKG 101 Deborah Goldstein Georgetown University Department of Internal Medicine
Steps to Interpreting an EKG Rate Rhythm Axis Intervals (PR, QRS, QTc) Hypertrophy ST segments T waves Q waves
Normal Sinus Rhythm P before every QRS –Best places to look: II, V1 QRS after each P
Axis 1. The direction of the mean electrical vector, representing the average of current flow in the frontal plane. 2. Normal axis: –30 to +90 degrees.
Look at lead I and aVF. Then find the isoelectric lead (where the QRS complex is most nearly biphasic). Then go 90 degrees perpendicular to the isoelectric lead.
Rate, Rhythm, Axis
Ddx of Axis Deviation LAD Left ventricular hypertrophy, Left anterior fascicular block, LBBB, Inferior wall MI Pregnant, ascites, short/fat RAD Right ventricular hypertrophy, Left posterior fascicular block, RBBB, lateral wall MI PE
PR Interval Normal PR = 0.12 – 0.20 seconds (3-5 little boxes) Long PR >0.20 seconds (>5 little boxes) =Delayed conduction from atria to ventricles First-degree AV block –PR>0.20 seconds –NO dropped QRS
Second Degree AV Block Wenckebach (Type 1) =block within AV node –PR interval progressively lengthens...then dropped QRS Mobitz (Type 2) =block within His-Purkinje system –Fixed PR with dropped QRS –WORSE! –Sarcoid, Lyme.... –Pacemaker!
Third Degree AV Block =Failure of conduction of any atrial impulses to get to the ventricles =Complete AV block Causes of Acute AV Block: Calcium channel blockers Acute RCA occlusion Digoxin toxicity
What kind of AV Block?
QRS Interval Normal = seconds Wide QRS = >0.12 seconds (>3 little boxes) PVC...if >3 in a row or >6/min=VTach RBBB, LBBB Left fascicular hemiblock Hyperkalemia Narrow QRS= <0.06 sec SVT ( bpm) Idiojunctional rhythm (40-60 bpm) Premature junctional complex
Chest Leads V1 V6
Bundle Branch Block V1-V2 = Right precordial leads V5-V6 = Left precordial leads LBBB Rabbit ears in V6 represent delay between depolarization from the septum to the LV RBBB Rabbit ears in V1 represent delay between depolarization from the septum to the RV
QT Interval Should be < ½ (R-R’ interval) Measure from the start of the QRS to end of T wave Varies with heart rate, so correct for RR interval Normal QTc: women=0.44, men=0.42 QTc = QT (#of small squares) x 0.04 √RR Long QT can lead to ‘R on T’ Death
Causes of Long QT **Think ‘Lytes and Meds first! Low K, Low Ca, Low Mg Macrolides, Quinolones All Antipsychotics (Haldol worst, Geodon least) SSRIs Sotalol, Quinidine, Ondansetron, Amio, TCAs Pts w/LVH or CHF are predisposed to medication- related lengthening of QT interval! –Avoid Macrolides, Quinolones in them!
Long QT: Less common causes Hypothyroid Hypothermia AV Block MI CVA Head injury Congenital long QT
Atrial Enlargement RAE P wave is tall and peaked (>2.5mm high) OR Biphasic P wave with initial positive inflection Ddx: Pulmonary HTN, COPD, PE LAE P wave is wide (>0.12 sec) and notched in the middle “M” OR Biphasic P wave with terminal negative inflection Ddx: Systemic HTN, Aortic Insufficiency, Mitral Stenosis
Which Atria is Enlarged?
LVH Criteria Sokolow + Lyon –S V1+ R V5 or V6 > 35 mm Cornell criteria (Circulation, 1987;3: ) –S V3 + R avl > 28 mm in men –S V3 + R avl > 20 mm in women Framingham criteria (Circulation,1990; 81: ) –R avl > 11mm, R V4-6 > 25mm –S V1-3 > 25 mm, S V1 or V2 + –R V5 or V6 > 35 mm, R I + S III > 25 mm Romhilt + Estes (Am Heart J, 1986:75:752-58) –Point score system (Am Heart J, 1999;37:161)
LVH “S V1+ R V5 or V6 > 35mm”
ST changes: axis + anatomy Lateral: –I, aVL –LCA, CFX Anterior: –V1, V2, V3, V4 –LAD Inferior: -II, III and aVF -RCA (or LCA) Memorize this slide
Q waves Normal Q wave: –Small septal Qs in I, aVL, V5, V6 –Isolated Qs in III, V1 Pathologic Q wave: –wider than 1 small box (0.04 sec) –OR >25% height of the R wave in that complex
Normal Q waves
Abnormal Q Waves
Non-ST Elevation MI =Severe subendocardial ischemia Marked, diffuse ST depressions in I, II, III, aVL, aVF, V2-V6
2 EKGs, several hours apart
Acute ST Elevation MI 1.Normal 2.Hyperacute T wave Elevation 3.Acute ST Elevation 4.Hours Later ST Elev, Q begins to form, T wave inverts 5.Days Later Q wave, T wave inversion 6.Weeks Later Q wave
A 55 year old man with 4 hours of "crushing" chest pain.
Acute Inferior Wall MI ST elev in II, III, AVF Reciprocal ST depression in anterior leads (V2-V4) =RCA occlusion (some LCx)
A 53 year old man with Ischemic Heart disease
Old Inferior Wall MI Pathologic Q wave in II, III, AVF: –wider than 1 small box (0.04 sec) –OR >25% height of the R wave in that complex
An 83 year old man with aortic stenosis.
LVH, LAE Romhilt-Estes LVH Point System: 3 points for Left Atrial Enlargement –M shaped P wave in II –P has prominent terminal negative component in V1 3 points for: –R wave in V5 or V6 >30mm –or S wave in V1 or V2 >30mm –or R or S in limb leads>20mm >5 points: definite LVH
A 76 year old man with breathlessness.
Afib with RVR Irregularly irregular ventricular rhythm. Must look carefully to see it is NOT regular
A 72 year old man on routine office visit
Ventricular Pacemaker Pacer spikes—hard to see! Wide QRS complexes Pacemaker starts after a long R - R interval following a blocked atrial premature beat...then NSR
A 58 year old man on hemodialysis presents with profound weakness after a weekend fishing trip.
Hyperkalemia K >8.0 Wide, tall and tented T waves Wide QRS Small or absent P waves Atrial fibrillation Shortened or absent ST segment Ventricular fibrillation
Atrial Flutter Saw tooth baseline with rate of Causes: –Ischemic heart disease –Hypertension –Mitral valve disease –Thyrotoxicosis –Cardiomyopathy
Pericarditis Evolves over hours-weeks 1.PR depression, ST elevation (concave up) in same leads, upright T 2.Normal P, normal ST, flat T 3.Normal P, normal ST, T Wave inversion 4.normal P, normal ST, upright T