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

Rate

Naming stuff P before every QRS

Normal Sinus Rhythm P before every QRS QRS after each P 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.

Axis

Axis 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.

Axis

Axis

Rate, Rhythm, Axis normal axis

Rate, Rhythm, Axis LAD

Rate, Rhythm, Axis RAD

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? 1st degree AV block

What kind of AV Block? 3rd degree

What kind of AV Block? 2nd degree AV block Mobitz—fixed PR, dropped QRS

What kind of AV Block? Type 1 Wenckebach; progressive PR progression, then dropped QRS

QRS Interval Normal = 0.06-0.10 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 (150-250 bpm) Idiojunctional rhythm (40-60 bpm) Premature junctional complex

Chest Leads V6 V1

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

Normal: V1: rS complex V6: qR complex RBBB: V1: Rabbit Ears (rSR) V1 V6 Normal: V1: rS complex V6: qR complex RBBB: V1: Rabbit Ears (rSR) V6: qRS complex LBBB: V1: wide QS complex V6: Rabbit Ears

Wide QRS—Why? RBBB: V1: wide rSR. V6: qRS complex. TWI V1-V3= secondary t wave inversions

Wide QRS—Why? LBBB: V1 has wide QRS, V6 with notched peak. Inv T in V5, V6

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 Macrolides, Quinolones **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? Right Atrial enlargement

Which Atria is Enlarged? II V1 LAE

LVH Criteria Sokolow + Lyon S V1+ R V5 or V6 > 35 mm Cornell criteria (Circulation, 1987;3: 565-72) S V3 + R avl > 28 mm in men S V3 + R avl > 20 mm in women Framingham criteria (Circulation,1990; 81:815-820) 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: Pathologic 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

nonSTelev MI w/diffuse ST depr

Non-ST Elevation MI =Severe subendocardial ischemia Marked, diffuse ST depressions in I, II, III, aVL , aVF , V2-V6

2 EKGs, several hours apart A: hyperacute T waves. B: Hours later: ST elev, Q V1/V2 (likely LAD lesion)

Acute ST Elevation MI Normal Hyperacute T wave Elevation Acute Hours Later ST Elev, Q begins to form, T wave inverts Days Later Q wave, T wave inversion Weeks Later Q wave

A 55 year old man with 4 hours of "crushing" chest pain.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    Acute inf wall MI

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 prior inf wall MI

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. LAE, LVH

LVH, LAE 3 points for: 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 RVR

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 V paced

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

Aflutter

Atrial Flutter Saw tooth baseline with rate of 250-300 Causes: Ischemic heart disease Hypertension Mitral valve disease Thyrotoxicosis Cardiomyopathy

PR depression V4-5 and I/AVL , ST elev concave up I, AVl

Pericarditis Evolves over hours-weeks PR depression, ST elevation (concave up) in same leads, upright T Normal P, normal ST, flat T Normal P, normal ST, T Wave inversion normal P, normal ST, upright T

Hypocalcemia: long Qt, inv Ts

Hypocalcemia Long QT Inverted T waves

Hyperkalemia