Ecg Essentials

ECG EssentialsSteven J. Sager, MPAS, PA-CPAC5229 - Electrocardiography

Learning Objectives

Upon satisfactory completion of the course, and in conjunction with textbooks, lecture handouts, and any recommended internet Web Sites, the student will be able to: Recognize the components of the following lists:

List #1 – Causes of regular, narrow-complex tachycardia List #2 – Causes of regular, wide-complex tachycardia List #3 – Common causes of prolonged QT interval List #4 – Common causes of ST segment depression List #5 – Common causes of a tall R wave in lead V1

List #6 – Causes of anterior ST segment depression in the setting of acute inferior infarct

Learning Objectives

Discuss the pathophysiology of dysrhythmias List the factors which determine if a patient is

hemodynamically stable List the advantages of 12-lead vs. single lead

ECGs Explain the importance of ECG comparisons Describe the benefits and limitations of ECG

interpretation by computer analysis Recognize common dysrhythmias

Six Essential Lists

List #1 – Causes of regular, narrow-complex tachycardia

List #2 – Causes of regular, wide-complex tachycardia

List #3 – Common causes of prolonged QT interval

List #4 – Common causes of ST segment depression

List #5 – Common causes of a tall R wave in lead V1

List #6 – Causes of anterior ST segment depression in the setting of acute inferior infarct

Evaluating regular, narrow-complex tachycardia

P = P waves?

Q = QRS wide or narrow?

R = Regular rhythm?

S = P waves & QRS complexes “Single”?

Hemodynamically stable?

Symptomatic? Chest pain Dyspnea/SOB Altered mental status Hypotension Shock Heart failure Pulmonary edema AMI

Causes of regular, narrow-complex tachycardia

Treatment of regular, narrow-complex tachycardia

Vagal Maneuver May transiently slow the ventricular response Will either convert PSVT to sinus rhythm or have no affect at all Types:

Carotid sinus massage Valsalva Facial submersion in ice Gagging Ocular pressure Digital rectal massage Squatting and bearing down

Adenosine “chemical Valsalva” almost immediate slowing of ventricular response

Causes of regular, wide-complex tachycardia (WCT)

Treatment of regular, WCT

Hemodynamically unstable Cardiovert (synchronized)

Hemodynamically stable Determine etiology Review prior tracings If in doubt, treat for VT

Procainamide

QT prolongation

Prolongation of the QT interval on the ECG is the major marker for Long QT Syndrome

Long QT syndrome is one of the causes of sudden death in adolescents and young adults “sudden death” = unexpected death that occurs in a

someone who is apparently healthy Long QT Syndrome is thought to be the cause when

sudden death occurs from ventricular fibrillation

QT prolongation

It most frequently occurs during sporting events and is usually attributed to a sudden, unpredictable disturbance in the rhythm of the heart. the symptoms can occur during less strenuous

activities and even on awakening from sleep may become apparent when a young person with

fainting or secondary seizures has an ECG as part of their evaluation

it is especially important to look for the syndrome when the fainting or seizures are excercise-related

Causes of QT prolongation

Ischemia

Infarction

Drugs Type IA and type III antiarrhythmic agents TCAs Phenothiazines

Causes of QT prolongation

Electrolyte deficiencies hypokalemia hypomagnesia hypocalcemia

Catastrophic CNS event CVA intracerebral hemorrhage seizures

Common causes of ST segment depression

Ischemia - symmetric

“Strain” - asymmetric

Digitalis effect – scooped or strain pattern

Hypokalemia

Hypomagnesia

ST-segment depression

Common causes of a tall R wave in lead V1

Wolff-Parkinson-White (WPW) syndrome

Right bundle branch block (RBBB)

Right ventricular hypertrophy (RVH)

Acute infero-postero-lateral infarction

Hypertrophic cardiomyopathy

Muscular dystrophy

Dextrocardia

Normal variant

Differentiate the causes of a tall R wave in lead V1

Causes QRS ECG ∆’s

W-P-W Widened Delta waves Short PR interval

RBBB Widened rSR´ in V1 Wide terminal S wave in I and V6

RVH Normal RAD R ventricular strain

Infarct Normal Changes in inferior leads

Positive “mirror test”

60 y.o. ♂ with history of heart disease.72 y.o. ♀ with history of palpitations.28 y.o. ♂ with no medical problems or heart disease.66 y.o. ♂ 2ppd smoker with history of COPD.48 y.o. ♂ with new onset chest pain.

Causes of anterior ST segment depression in the setting of acute inferior

infarct Reciprocal changes Concomitant anterior ischemia Posterior infarction

Mirror test

Combination of above

∆’s (ST depression)common in: V1, V2, and V3

Why 12-lead vs. 1-lead?

12-lead provides more information improves arrhythmia interpretation

CXR?

ABG?

60 y.o. c/o rapid heart beat.♀Denies CP. No meds.B/P = 140/90mmHg

Rate? P? Q? R? S?

50 y.o. with CAD c/o rapid heart beat. ♂Denies CP. B/P = 160/100mmHg

Rate? P? Q? R? S?

60 y.o. with COPD c/o wheezing & mild ♂dyspnea. Hx of rapid heart beats.

B/P = 130/80mmHg.

60y.o. c/o “palpitations”♂

Comparing Tracings

1. Find as many as possible2. Evaluate previous tracings

a) valid regardless of age and interval

3. Evaluate new tracing4. Compare the two most recent tracings

l systematically move from one lead to the next

l start at I and proceed through V6

l Comment on ANY and ALL differences!

Important Comparison Points to Consider

Review all available tracings request old charts look for “patterns”

Lead placement variables may alter axis, wave amplitude/morphology, etc.

Request serial ECGs when appropriate angina evolving MI interval?

Benefits of Computer Analyses

Save time Accurate calculations of:

heart rate intervals axis

Provide legible interpretations May suggest additional findings

write your interpretation first, then compare Educational

improve provider accuracy

Are Computer Analyses Accurate?

Sometimes only as good as their programming! reliably recognize sinus/normal tracings

Most accurate in computing values Routinely miss subtle infarctions Tend to overinterpret Should be used to enhance the provider’s

interpretation provide a good “second opinion”

Reviewing a Computer Analysis

√√

Intervals/durations in milliseconds

Date & time are CRITICAL! Includes patient identification

Thought for the day!

Our background and circumstances may have influenced who we are,

but only we are responsible for who we

become!

Mirror test