ELECTROCARDIOGRAPHY
ELECTROCARDIOGRAPHY(ECG)ANATOMY OF THE HEART
ANATOMY OF THE HEART
3 Layers:Inner layer / Endocardium - consists of endothelial
tissue and lines the inside of the heart and valvesMiddle layer /
Myocardium - made up of muscle fibers and responsible for the
pumping action Exterior layer/ Epicardium2 Layers of
PericardiumVisceral Pericardium - adheres to the epicardiumParietal
Pericardium - a tough fibrous tissue that attaches to the great
vessels, diaphragm, sternum and vertebral column. Supports the
heart in mediastenum.
*Pericardial Space the space between two layers, filled with
30ml of fluid for lubrication of the hearts surface and reduction
of friction during systoleANATOMY OF THE HEART
Heart ChambersRight Ventricle distributes venous blood
(deoxygenated blood) to the lungs via pulmonary artery for
oxygenation.Left Ventricle distributes oxygenated blood to the
remainder of the body through the aortaRight Atrium receives blood
returning from the superior vena cava (head, neck, upper
extremities), inferior vena cava (trunk and lower extremities), and
coronary sinus (coronary circulation)Left Atrium receives
oxygentaed blood from the pulmonary circulation via the pulmonary
veins
ANATOMY OF THE HEART
Heart ValvesPermits blood to flow in only one directionComposed
of thin leaflets of fibrous tissueOpen and close in response to the
movement of bloodPressure changes within the chambers
ATRIOVENTRICULAR VALVESSeparates the atria from the
ventricleTricuspid Valve separates the right atrium from the right
ventricleMitral/Bicuspid Valve lies between the left atrium and
left venticleSEMILUNAR VALVESPulmonic Valve between the right
ventricle and pulmonary arteryAortic Valve between the left
ventricle and the aorta
CARDIAC ELECTROPHYSIOLOGYCardiac Conduction SystemGenerates and
transmits electrical impulses that stimulate contraction of the
myocardium Stimulates first the atria and then the
ventriclesSynchronization of the atrial and ventricular events fill
the ventricles completely before ventricular ejection, thus
maximizing cardiac outputSynchronization is provided by the NODAL
CELLS and PURKINJE CELLS.Automaticity: ability to initiate an
electrical impulseExcitability: ability to respond to an electrical
impulseConductivity: ability to transmit an electrical impulse from
one cell to another
CARDIAC ELECTROPHYSIOLOGYBundle of His specialized conducting
tissue where impulse is conducted.-Impulses travel through the
bundle branches until it reach the terminal point, the PURKINJE
FIBERS.PURKINJE FIBERS rapidly conducts the impulses to stimulate
the myocardial cells to cause ventricular contraction
HEART RATE is etermined by the myocardial cells with the fastest
inherent firing.SA node : 60 100 impulsesAV node : 40 60
impulses*if both malfunctioned, a pacemaker site in the ventricle
will fire at its inherent bradycardic rate of 30 to 40 impulses per
minute Sinoatrial Node -primary pacemaker of the heart-located at
the junction of the superior vena cava and the right atrium-has an
inherent firing rate of 60 100 impulses per minute
Impulses cause electrical stimulation and subsequent contraction
of the atria. Impulses are then conducted to the atrioventricular
node.
Atrioventricular Node-located in the rright atrial wall near the
tricuspid valve.- coordinates the incoming electrical impulses from
the atria and relays the impulse to the ventricles
CARDIAC CONDUCTION SYSTEM
ELECTROCARDIOGRAPHY
A diagnostic tool used in assessing the cardiovascular systemA
graphic recording of the electrical activity of the heartGraph is
obtained by placing disposable electrodes in standard positions on
the skin of the chest wall and extremitiesRecorded on a special
graph paper with 12, 15, 18 leads showing the activity from those
different reference point
ELECTROCARDIOGRAPHY12 lead ECGUsed to diagnose dysrrhytmias,
conduction abnormalities, enlarged heart chambers, and myocardial
ischemia or infarctionUsed to monitor high or low calcium and
potassium levels and the effects of some medications15 lead ECGUsed
for early diagnosis of right ventricular and posterior left
ventricular infarction18 lead ECGUseful for early detection of
myocardial ischemia and injury12 LEAD ECGWhy there are only 10
electrodes?
Its important to fully understand what the term lead actually
means. A lead is a view of the electrical activity of the heart
from a particular angle across the body. Think of a lead as a
picture of the heart and the 10 electrodes give you 12 pictures. In
other words, a lead is a picture that is captured by a group of
electrodes.
LIMB LEADS
RL - Anywhere above the ankle and below the torsoRA - Anywhere
between the shoulder and the elbowLL - Anywhere above the ankle and
below the torsoLA - Anywhere between the shoulder and the
elbowPRECORDIAL LEADSV1 - 4th Intercostal space to the right of the
sternumV2 - 4th Intercostal space to the left of the sternumV3 -
Midway between V2 and V4V4 - 5th Intercostal space at
themidclavicular lineV5 - Anterior axillary line at the same level
as V4V6 - Midaxillary lineat the same level as V4 and V5
NURSING CONSIDERATIONSPatient Positioning-Place the patient in a
supine or semi-Fowlers position. If the patient cannot tolerate
being flat, you can do the ECG in a more upright position.-Instruct
the patient to place their arms down by their side and to relax
their shoulders.-Make sure the patients legs are uncrossed.-Move
any electrical devices, such as cell phones, away from the patient
as they may interfere with the machine.Skin Preparation-Dry the
skin if its moist or diaphoretic.-Shave any hair that interferes
with electrode placement. This will ensure a better electrode
contact with the skin.-Rub an alcohol prep pad or benzoin tincture
on the skin to remove any oils and help with electrode
adhesion.Electrode Application-Check the electrodes to make sure
the gel is still moist.-Do not place the electrodes over bones.-Do
not place the electrodes over areas where there is a lot of muscle
movement.
