AMANDA HOOPER2008-2009
EKG for ACLS
Let’s start with some basics…
V1: right 4th intercostal space
V2: left 4th intercostal space
V3: halfway between V2 and V4
V4: left 5th intercostal space, mid-clavicular line
V5: horizontal to V4, anterior axillary line
V6: horizontal to V5, mid-axillar line
Conduction System of the Heart Sinus node is the pacemaker
of the heart, the dominant center of automaticity.
Generates continuous regular depolarization stimuli at a rate of 60-100 bpm
There are other potential pacemakers that can take over if SA node fails, and they have different intrinsic rates. These are in the atria, AV junction, and the ventricles.
EKG Paper
EKG machine moves at 25 mm/sec, each small box is 1 mm
Small boxes represent 0.04 sec
Large boxes represent 0.2 sec
Five large boxes equal one second
EKG Waves and Intervals
P wave: the sequential activation (depolarization) of the right and left atria
QRS complex: right and left ventricular depolarization (normally the ventricles are activated simultaneously)
ST-T wave: ventricular repolarization PR interval: time interval from onset of atrial depolarization (P
wave) to onset of ventricular depolarization (QRS complex) QRS duration: duration of ventricular muscle depolarization QT interval: duration of ventricular depolarization and repolarization
Systematic Approach to ECG Interpretation
RateRhythmAxisIntervalsHypertrophyInfarct (QRST Changes)
Determining Rate R-R interval is ventricular rate p-p interval is atrial rate. Usually the same but not always
Several ways to do this… 1) Count down the number of large boxes: 300, 150, 100, 75, 60,
50, .... Ex: this one is between 150 and 100, closer to 150 so we might say ~130-140
bpm 2) Count the number of large boxes and divide by 300
Ex: 300/2 = 150 but it is a little slower than that so we might say ~130-140 bpm
3) Count the number of small boxes between beats and divide into 1500 Ex: 1500/11 = 136 bpm
Analyzing A Rhythm Strip
Is the rhythm regular?
What is the rate?Is the QRS complex
narrow or wide?Are P waves
present?Are P waves
related to the QRS complexes?
What is the PR interval ?
Intervals PR interval
From the onset of atrial depolarization to the onset of ventricular depolarization
Normal between 0.12 and 0.20 sec—so should be less than a large box
QRS interval: Time it takes for ventricular
depolarization to occur Normal is 0.10 sec or less—so
should be less than half of a large box
QT interval From the beginning of ventricular
depolarization to the end of ventricular repolarization
Normal is les than half of a R-R interval (can’t always rely on this if rate is very tachycardic)
Atrial Flutter with 2:1 AV Block
Aflutter With Carotid Massage
Supraventricular Tachycardia (SVT)
Supraventricular rhythms start by definition at or above the AV node. If the QRS is narrow in all leads, you can almost be guaranteed the rhythm is supraventricular.
Sinus rhythm, atrial fibrillation, atrial flutter, junctional/nodal rhythms, and PSVT
PSVT is a reentry rhythm
SVT
Myocardial Infarction
Look for QRST changes in each lead Note each lead where Q waves are foundLook for R wave progression—transition
normally occurs between V2 and V4Look at ST segments and note depression or
elevation Look for T wave inversion
Q waves or T wave inversion may be a normal finding in leads III, aVF, aVL, aVR, and V1
Basic Lead Groupings
Inferior leads: II, III, aVFLateral (left-sided) leads: V4 to V6 and I, aVLSeptal leads: V1, V2Anterior leads: V2 to V4
Right coronary artery: SA node, IV septum, inferior heart, +/- posterior heart
Left coronary artery: LAD- anterior heart Left circumflex- lateral heart
12 EKG with Acute MI
Anteroseptal MI
Inferior MI with RV Infarction
From: Heart Disease 6th Edition. Braunwald E, Zipes D, and Libby P. 2001
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