EKG Technician: EKG Acquisition

lead placement

-correct limb lead placement is critical to measure the heart's electrical axis and as the reference point for the unipolar leads -makes no difference if the lead is attached distally (on wrists or ankles) or proximally (upper arm, upper thigh, or shoulder) but uniformity in placement is important to form an equilateral triangle

key responsibilities of the EKG technician include verifying:

-demographic data is accurate -leads are properly attached -the recording is clear of artifacts and ready for provider interpretation

preferred pt position for 3- or 5-lead EKG and telemetry

-depends on individual circumstance but it is important that the pt assume a comfortable relaxed position, which can be sitting, standing, or lying -can be ambulatory

sinoatrial node artery

-perfuses (supplies) the SA node -branches from the RCA -occlusion of this artery can manifest as extreme sinus bradycardia on the EKG tracing

left anterior descending artery (LAD)

-supplies the anterior wall of the left ventricle -occlusion can lead to ventricular arrhythmias and death

atrioventricular node (AV node)

-the only part of the electrical conduction system that connects the atria to the ventricles -just below the AV node is the AV junction, where the AV node and the bundle of His meet, which can act as a backup pacemaker if the SA node fails, and it fires ~40-60/min

internodal pathways

-the three pathways of the electrical conduction system found in the atria that transmit the electrical impulse from the SA node to the AV node -anterior, medial, and posterior pathways

AC interference (60 cycle interference)

-when an electronic device on or near the pt causes electrical interference -recognized as uniform sharp spikes on the EKG tracing or as flutter or P waves at a rate of 300/min

normal pathway of electrical impulses in the heart

1) electrical impulses initiated in the SA node 2) conducts through both atria and directs to the AV node 3) AV node delays or slows the transmission of the signal to the ventricles, allowing them to completely fill with blood 4) depolarization continues toward the apex of the heart through the bundle of His and left and right bundle branches, and terminates in the Purkinje fibers 5) as the electrical impulses reach the myocardium, the muscle cells depolarize and contract

right bundle branch (RBB)

carries the electrical impulse from the bundle of His to the Purkinje fibers -transmission of impulses throughout these finger-like projections causes right ventricular depolarization

pericardial sac

consists of a visceral layer that covers the heart and vessels, and an outer, strong, fibrous, parietal layer that is attached to the diaphragm and mediastinum -provides protection, stability of the structures, and lubrication between the heart and other organs in the ches

chordae tendineae

provide support to the floppy valve leaflets and prevent regurgitation of blood into other chambers of the heart -anchored to structures called papillary muscles, which are found along the inside wall of the ventricles

standard EKG grid

provides measurements for both voltage and time using small boxes that measure 1 mm tall by 1 mm wide -5 small boxes make up a larger box -thicker gridlines indicate 5 mm boxes -each mm increment on the y-axis (vertical) represents 0.1 millivolt (mV0 -each mm increment on the x-axis (horizontal) represents 40 ms or 0.04 seconds

semilunar valves

pulmonary and aortic valves -refers to the shape

4 chambers of the heart

right atrium, right ventricle, left atrium, left ventricle

bicuspid (mitral) valve

separates the left atrium from the left ventricle

tricuspid valve

separates the right atrium from the right ventricle

left circumflex artery (LCx)

supplies oxygenated blood to the posterolateral aspect of the left ventricle

preferred pt position for a 12-lead EKG

supported supine position without pillows -can use semi-Fowler's and place a pillow under head and/or knees if needed for respiratory or cardiac conditions or late stages of pregnancy

left main coronary artery (LMCA)

the 2nd of 2 main arteries that carry oxygenated blood to the myocardium -short and bifurcates into the left circumflex artery (LCx) and the left anterior descending artery (LAD)

Einthoven's triangle

the equilateral triangle with the heart in the middle formed by limb leads 1, 2, and 3

automaticity of the heart

the heart muscle can initiate its own impulse

Bachmann's bundle (interatrial tract)

the internodal pathway connecting the right and left atrium

baseline

the time between each cardiac cycle, noted as a flat line, and is a time of repolarization (relaxation)

PR interval

the time needed for an electrical impulse to travel from the SA node through the AV node to the ventricles -where the P wave ends and the Q wave begins -expected is 0.12-0.20 seconds -can increase if the AV node is not conducting impulses as expected

wandering baseline

when the recording demonstrates wavelike up-and-down movements throughout the tracing -can result from movement of the cables or leads, pt movement, loose or dry electrodes, pt's labored breathing, or improper skin preparation (traces of lotion, oils, or gel)

color-coding of leads

white: right arm black: left arm red: left leg green: right leg V1: red V2: yellow V3: green V4: blue V5: orange V6: purple

color-coding for a 3-lead EKG

white: right shoulder just below clavicle black: left shoulder just below clavicle red: below the left pectoral muscle at the apex of the heart

precordial lead locations

V1: 4th intercostal space (ICS), right of sternum V2: 4th ICS, left of sternum, directly across from V1 V3: midway between V2 and V4 V4: 5th ICS, midclavicular line V5: 5th ICS, midway between V4 and V6, at the anterior axillary line V6: 5th ICS, at the midaxillary line

Which of the following statements regarding the electrical conduction system is true? a) The AV nodes serves as the natural pacemaker of the heart b) The SA node is located in the wall of the right atrium c) The bundle of His gathers the impulse from the SA node and transmits it to the bundle branches d) The Purkinje fibers are able to initiate an impulse to cause the heart to pump at 60-80 times per minute

b) The SA node is located in the wall of the right atrium

bipolar leads

have 2 poles: one positive and one negative -standard limb leads are bipolar w the potential difference between the poles being measured and recorded on the EKG tracing

collateral circulation

if perfusion is decreased, collateral vessels can form when small arteries grow and connect to other arteries -can compensate for reduced oxygen supply so pts with coronary heart disease may not experience symptoms until the disease has progressed to advanced stages

endocardium

innermost layer of the heart -lines the chambers of the heart and forms the surface of the valves -the smooth structure protects the inner surfaces of the heart and promotes or assists in facilitating the flow of blood through the heart

In stress testing or ambulatory monitoring, what purpose does the green lead serve?

it is a ground and helps reduce artifacts

unipolar leads

leads that only have one pole -used as a reference point to create "the other end" of the lead system -WCT serves as the reference point for all unipolar leads -considered the positive end of the lead system -the precordial leads (chest leads) are unipolar in nature

atrioventricular valves

lie between the atria and ventricles -tricuspid and bicuspid

aortic valve

lies between the left ventricle and the aorta

pulmonary valve

lies between the right ventricle and pulmonary arteries

electrocardiograph machine

measures electrical energy traveling across the surface of the human body and the electrical activity of the heart -muscle tissue releases electrical energy when it depolarizes, causing a change in electrical potential across the surface of the skin -uses specialized electrodes to measure changes in electrical potential and records it on graph paper, producing an electrocardiogram

somatic tremor

muscle movement on an EKG tracing -exhibits as uneven spikes -can be caused by shivering or active seizure activity

myocardium

muscular, middle layer of the heart -consists of involuntary striated muscle tissue -responsible for physical contraction of the heart muscle -cardiac muscle fibers contract, reducing the size of the heart chambers and forcing blood out in a pumping action

placement of leads for a posterior EKG

need leads V7, V8, and V9

right coronary artery (RCA)

one of the 2 main arteries that carry oxygenated blood to the right atrium, right ventricle, part of the left atrium, and the inferior wall of the left ventricle -has a role in perfusion of the SA and AV nodes

epicardium

outer layer of the heart -made of connective tissue that forms a sac around the heart, known as the pericardium

atrioventricular node artery

perfuses the AV node -arises from the RCA in more than 90% of the population -occlusion of the AV node artery often results in high-degree heart block on the EKG

supplies and equipment needed for an EKG

-EKG machine -power source (wall outlet, internal battery) -electrodes (usually 10 per package) -leads w clips or connectors for attachment to the electrodes -EKG graph paper (unless running digitally) -alcohol wipes or electrolye pads -gauze pads or tissues (if needed for drying the skin) -scissors and/or shaving equipment (if hair removal is needed) -pillows, blankets, pt gowns as needed for privacy and comfort

ectopic beats

-an electrical impulse that initiates from outside the normal pathways -can be caused by a small area in atrial or ventricular tissue becoming irritated -can be seen on the EKG as premature atrial, junctional, or ventricular complexes

standard EKG calibration

-calibration boxes are small rectangles, typically occurring at the beginning of each lead, that indicate the paper speed and amplitude of the EKG -tracing produces a positively deflected rectangular-shaped standard marking measuring 10mm tall x 5mm wide -these measurements indicate a standard speed and amplitude of 25 mm/second and 10 mm/mV, respectively

left bundle branch (LBB)

-carries the electrical impulse from the bundle of His to the Purkinje fibers of the left ventricle, causing depolarization -located in the intraventricular septum -short and further divides into the left anterior fascicle (runs along the anterior surface of the heart) and the left posterior fascicle (runs the length of the septum and conducts impulses to the Purkinje fibers on the posterior surface of the left ventricle

augmented leads

-considered unipolar bc there is a single positive electrode referenced against the combination of the other limb leads -the 6 limb leads are the 3 augmented leads + the bipolar leads -record activity along the frontal plane relative to the heart, and are reordered as augmented voltage to the right arm (aVR), augmented voltage to the left arm (aVL), and augmented voltage to the left leg or foot (aVF)

heart blood flow

1. blood enters right atrium from superior and inferior venae cavae 2. blood in right atrium flows through right AV vale into right ventricle 3. contraction of right ventricle forces pulmonary valve open 4. blood flows through pulmonary valve into pulmonary trunk 5. blood is distributed by right and left pulmonary arteries to the lungs where it unloads CO2 and loads O2 6. blood returns from lungs via pulmonary veins into left atria 7. blood in left atrium flows through left AV valve into left ventricle 8. contraction of left ventricle (simultaneous with step 3) forces aortic valve open 9. blood flows through aortic valve into ascending aorta 10. blood in aorta is distributed to every organ in the body where it unloads O2 and loads CO2 11. blood returns to right atrium via venae cavae steps 4-6 is the pulmonary circuit steps 9-11 is the systemic circuit

standard EKG amplitude (gain)

10 mm per 1 mV -only make adjustments w provider direction and include documentation that explains the change in amplitude to avoid misinterpretation

standard EKG speed

25 mm/second -never change speed w/o direction from the provider

negative deflection

A downward curvature of waves in an EKG tracing -indicates that one or more leads is incorrectly attached

color coding for a 5-lead EKG

Option 1 white: right sternal border, 1st rib red: right sternal border, 3rd rib black: left side, anterior axillary line, 5th rib brown: left sternal border, 1st rib directly opposite the white lead green: right lower thoracic area anywhere on the rib cage Option 2 white: right chest, about 2 inches below the clavicle red: left chest, lower rib cage area black: left chest, opposite of white lead brown: right chest, 4th rib green: right lower chest, over a rib

sinoatrial node (SA node)

a cluster of cells located in the right atrial wall and functions as the primary - or natural - pacemaker of the heart -generates electrical impulses and fires approximately 60-100/min -depolarization of the r. atrium occurs first, followed closely by the left -the P wave on the EKG is a result of atrial depolarization

EKG

a graphic representation of changes in energy over time -many heart diseases result in specific changes to the EKG

Purkinje fibers

a network of wide diameter and junctional conduction pathways that travel across the surface of the ventricles and depolarize them, initiating myocardial contraction -in the absence of electrical stimulation from the SA and AV nodes, the Purkinje fibers will fire at an intrinsic rate of 20-40/min

Wilson's central terminal (WCT)

a reference point created by the three limb leads and is at the center of the Einthoven's triangle -not independent but is an average of the limb potentials -proper limb placement is critical to endure proper calculation of WCT

Bundle of His (atrioventricular bundle)

a specialized collection of cells located in the intraventricular septum that receives the electrical impulse from the AV node -transmits the impulses down the intraventricular septum, beneath the endocardium, and through the intraventricular septum

valves

control the direction of blood flow through the heart -made up of several leaflets (flaps) -extremely strong, yet floppy and require support to ensure tight closure

The recorded calibration mark is measured at 5 mm wide and 10 mm high. This demonstrates which of the following? a) There is a lead reversal b) The EKG is running at half the normal speed c) the EKG is set to record at twice the amplitude d) The universal standard is being applied

d) The universal standard is being applied

coronary circuit

delivers oxygenated blood to the heart -passive, low-pressure system -right and left coronary arteries arise from the aorta -perfused during ventricular diastole (rest of the circulatory system is perfused during ventricular systole) -during ventricular systole, the semilunar valves are closed and the ventricles fill with blood, causing pressure on the epicardium, which results in compression of the coronary vessels -as the ventricular myocardium is contracting, the surface length is shorter than during diastole, causing the coronary vessels located on the epicardium to become tortuous- attempting to perfuse these vessels would mean having to overcome high pressure, high vascular resistance, and tortuous vessels (not efficient)

interrupted baseline

demonstrated by a tracing that is not continuous -related to either broken lead wires or disconnected leads

interatrial septum

dividing wall between the 2 atria

interventricular septum

dividing wall between the 2 ventricles

3 layers of the heart wall

epicardium, myocardium, endocardium