EKG Chapter 49
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calibration syringe
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A standardize measuring instrument used to check and adjust the volume indicator on a spriometer
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cardiac cycle
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The sequence of contraction and relaxation that makes up a complete heart beat
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deflection
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a peak or valley on an electrocardiogram
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depolarization
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The loss of polarity, or opposite charges inside and outside; The electrical impulse that initiates a chain reaction resulting in contraction
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echocardiography
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A procedure that tests the structure and function of the heart through the use of reflected sound waves, echos
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electrocardiogram (ECG)
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The tracing made by an electrocardiograph
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electrode
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Sensors that detect electrical activity
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forced vital capacity (FVC)
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The greatest volume of air that a person is able to expel when performing rapid, forced expiration
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Holter Monitor
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An electrocardiography device that includes a small portable cassette recorder worn around a patient's waist or on a shoulder strap to record the heart's electrical activity over a period of time
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hypoxemia
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Subnormal oxygenation of arterial blood, short of anoxia
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lead
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A view of a specific area of the heart on an electrocardiogram
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polarity
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The condition of having two separate poles, one of which is positive and the other, negative
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pulmonary function test
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A test that evaluates a patient's lung volume and capacity; used to detect and diagnose pulmonary problems or to monitor certain respiratory disorders and evaluate e effectiveness of treatment
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repolarization
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The process of returning to the original polar (resting) state
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sleep apnea
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A condition characterized by pauses in breathing during sleep
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spirometer
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An instrument that measures the air taken in and expelled from the lungs
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spirometry
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A test used to measure breathing capacity
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stylus
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A pen like instrument that records electrical impulses on ECG paper
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What does electrocardiography record?
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transmission, magnitude, and duration of the heart's various electrical impulses
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What are the steps of the cardiac cycle?
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Polarization, depolarization, repolarization and back to polarization
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During electrocardiograph, electrodes...
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detect and record the heart's electrical activity, including disturbances or disruptions in its rhythm
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P Wave
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small upward curve
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What does the P Wave represent?
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The SA node impulse, wave of depolarization through atria and resultant contraction
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QRS complex
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Includes Q, R, and S waves
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What does the QRS complex represent?
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Contraction (following depolarization of ventricles; larger than the P wave because ventricles are larger than atria
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Q wave
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downward deflection
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What does the Q wave represent?
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Impulse traveling down septum toward Purkinge fibers
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R Wave
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Large upward spike
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What does the R wave represent?
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Impulse going through left ventricle
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S Wave
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Downward deflection
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What does the S wave represent?
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Impulse going through both ventricles
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T Wave
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Upward curve
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What does the T wave represent?
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Recovery (repolarization of ventricles); repolarization of atria is not obvious because it occurs while ventricles are contracting and producing QRS complex
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U Wave
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Small upward curve sometimes found after T wave
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What does the U wave represent?
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Many be seen in normal individuals, in patients who experience slow recovery of Purkinge fibers, or in patients who have low potassium levels or other metabolic disturbances
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P-R Interval
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Includes the P wave and straight line connecting it to the QRS complex
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What does the P-R Interval represent?
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Time it takes for electrical impulse to travel from SA node to AV node
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Q-T Interval
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Includes QRS complex, S-T segment, and T Wave
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What does the Q-T interval represent?
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Time it takes for ventricles to contract and recover, or repolarize
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S-T segment
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Connects end of QRS complex with the beginning of T wave
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What does the S-T segment represent?
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Time between contraction of ventricles and recovery
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Standard Electrocardiograph
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12-lead, which records the electrical activity of the heart simultaneously from 12 different views
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Single Channel Electrocardiograph
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Records the electrical activity of one lead and, consequently, one view of the heart's electrical activity at a time
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Multichannel Electrocardiograph
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Record more than one lead at a time. These machines use wider paper and more than one stylus to record the leads. Some models provide a diagnosis or interpretation of the electrocardiogram
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Where to you place electrodes when preforming a routine electrocardiography?
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Right arm, left arm, right leg, left leg, and six on specific locations on the chest wall - These 10 electrodes are used to evaluate 12 different pathways of the heart's electrical activity (leads).
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What does each lead do?
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Provide an image of the heart's electrical activity from a different angle
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Bipolar leads
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Monitor 2 electrodes
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Augmented or unipolar leads
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Directly monitor only one electrode
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Precordial leads
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Or chest leads, are unipolar leads. Each lead monitors one electrode and point within the heart.
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ECG Paper
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Provided in a long, continuous roll or pad. Consists of two layers and is both heat - and pressure-sensitive
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Standardization Control
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Uses a 1-mV impulse to produce a standardization mark on the ECG paper
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Sensitivity Control
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Normally set on one - Adjusts the height of the standardization mark and tracing
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Centering Control
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Allows you to adjust the position of the stylus
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Lead Selector
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Allows you to run each lead individually, in case you need to repeat a strip containing artifacts
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Line Control
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Allows you to adjust the temperature of the stylus
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Preparing the Room and Equipment
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Make sure the room and equipment are properly setup before you being Should be quiet, private, and protected from interruptions Before using the electrocardiograph, check the date and make sure the machine is on
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Preparing the patient
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Calmly and simply explain the procedure in detail, assure of the safety of the procedure, and that it will last 10-15 minutes. Explain that the machine measures the heart's electrical activity and that no outside electricity will pass thru the body. Explain why the doctor requested the procedure, with out giving a diagnosis or prognosis. Ensure the patient's comfort.
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Artifacts
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Improper technique, poor conduction, outside interference, or improper handling of a tracing can cause these
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Wandering baseline
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Identified by a shift in the baseline from the center position for that lead. Causes include somatic interference and a variety of mechanical problems. Mechanical problems may be an inadequately warmed stylus, improper application of electrodes caused by a dangling wire, inadequate electrolyte, inadequate skin preparation, or presence of creams or lotions on the skin
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Flat line
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Typically caused by a loose or disconnected wire
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Solutions for Wandering Baseline
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Allow electrocardiograph to warm up, repeat skin prep and lead placement, reapply electrode, clean and reapply electrode/replace electrode, help patient relax and be comfortable, reposition electrode, drape wires over the patient
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Solutions for Flat line
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Reattach wires, check/change selector, check/switch wires, check/replace broken equipment, check pulse/respiration; begin CPR
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Marks not part of tracing
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Caused by careless handling, use of paper clips, wet hands, improper handling
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Solution for Marks not part of tracing
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Handle carefully, use a rubber band, ensure that hands are dry, mount properly
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Uniform, small spikes
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AC interference, improper electrode placement, inadequate grounding, dirty electrode
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Solutions for uniform, small spikes
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Turn off/unplug other electrical equipment; remove patient's watch, reapply electrode, check grounding, clean and reapply electrode
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Large, erratic spikes
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Caused by somatic interference, loose/dry electrode, electrode placed over a bone
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Solutions for large, erratic spikes
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Help patient relax and be comfortable, reapply electrode, reposition electrode
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Alternating Current (AC) Interference
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Occurs when the electrocardiograph picks up small amount of electrical current given off by another piece of electrical equipment. The tracing's line will be jagged, consisting of a series of uniform, small spikes
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Somatic interference
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Muscle movement -tensing of voluntary muscles, shifting body position, tremors, or even talking. Placing limb electrodes closer to the body's trunk - on the upper arms closer to the shoulder, and on the upper thighs - can reduce this interference. As can reducing the patient's anxiety
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Identifying the Source of Interference
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The source of interference often can be identified by checking the tracings obtained on Leads I & II - right arm, Leads I & III - left arm, and Leads II & III - left leg
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Heart rhythm
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ECG is the best way to assess. Is indicated on the ECG by regularly spaced complexes.
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Heart rate
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Can be determine by counting the number of QRS complexes in a 6-second strip of the tracing (30 squares at 25 mm per second) and multiplying by 10
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Intervals and Segments
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Variations in the length and position of the intervals and segments can indicate many heart conditions, including conduction disturbances and myocardial infarction
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Wave changes
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The direction of the waves may vary, depending on which lead is being viewed. Normally, each wave should have a similar appearance in each of the leads. Changes in the height, width, or direction of the wave my indicate a problem such as the early stages of MI (the T wave forms a large peak and then inverts and appears below the base line
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Cardiac Arrhythmias
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Irregularities in heart rhythm
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Ventricular Fibrillation (V-Fib)
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Life threatening heart condition in which the ventricles of the heart appear to quiver and there is no cardiac output. Is seen in patients experiencing a MI. The tracing is often described as a \"saw tooth\" image
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Premature Ventricular Contractions (PVCs)
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Premature heartbeats that originate from the heart's ventricles. Identified as a beat that occurs early in the cycle, followed by a pause before the next cycle. Appears on the ECG as having no P wave, a wide QRS complex, and a T wave that deflect in the opposite direction from the R wave
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Atrial Fibrillation
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Occur because of electrical disturbances in the atria and/or the AV node, which leads to fast heartbeats (tachycardia). Seen on the ECG as small, irregular, uncoordinated complexes that are difficult to interpret because the P waves cannot be identified
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Caused of Atrial Fibrillation
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MI, hypertension, heart failure, mitral valve diseases, such as MVP; overactive thyroid, pulmonary embolism, excessive alcohol consumption, emphysema, and pericarditis
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Who might have a Stress Test done?
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Patient who has had surgery or a MI to determine how the heart in functioning
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What happens in a Exercise Electrocardiography aka Stress Test?
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Patient is required to walk/run on a treadmill, pedal a stationary bike, or walk on a stair stepper why the ECG readings are taken. An ergometer measures work performed. The test continues until the patient reaches a target heart rate, experiences chest pain or fatigue, or develops complications such as tachycardia or dysrhythmia
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What safety precautions are taken during a stress test?
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Emergency medication and equipment like a defibrillator must always be present because of the potential risk of a heart attack
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Transthoracic
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Ultrasound transducer is moved around on the chest and or abdomen to produce heart images
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Transesophageal
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The transducer is passed into the esophagus, where it produces clearer images of the heart because it is closer to the heart and the sound waves do not have to penetrate the ribs
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Doppler
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Uses a special type of ultrasound to look at blood flow through the heart. The direction and speed of blood flow through the heart are assessed with this type of test, giving the physician information about coronary artery blockage and heart valve damage
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Stress Echo
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Echocardiography is done before and after exercise or injection of a drug that makes the heart work faster and harder. This is usually done in conjunction with an electrocardiogram to assess how well the heart responds to increased demand
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Ensuring the patient safety during Stress Testing
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Educate and prepare the patient Assist them during the procedure Inform the patient of what symptoms to expect during the test - fatigue, slight breathlessness, increased heart rate, increased perspiration Assure the patient that there are few risks associated with the test and that the test will ne stopped if he experiences chest pain or extreme fatigue Explain the presence of safety equipment During the test talk to and listen to the patient
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Why is a holter monitor used?
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diagnostic tool; evaluate the status of a patient who is recovering from a MI, it can indicate progress or the need to change therapy or modify the rehabilitation plan
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Patient education for a Holter Monitor
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Record all activities, emotional upsets, physical symptoms, and medications taken Wear loose fitting clothing that opens in the front while wearing Avoid getting near magnets, metal detectors, and high voltage areas and avoid using electric blankets Avoid getting the monitor wet - sponge baths Show the patient how to check the monitor to make sure it is working correctly
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Peak Flow Zones
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Green Zone: good control of asthma, with peak flow rates of 80% - 100% of the highest peak flow rate Yellow Zone: the large airways are beginning to narrow and medication is needed, 50%-80% of the highest peak flow rate Red Zone: Narrowing of the largest airways has occurred and is considered a medical emergency usually take a bronchodilator or other medication that will open the airway. Symptom include wheezing, shortness of breath, and trouble walking & talking.
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Pulse Oximetry
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A noninvasive test that measure the saturation of oxygen in the patient's arterial blood. Sensor is placed on patient's finger, earlobe, toe, or bridge of the nose.
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Speed Selector
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Allows you to adjust the speed to 50mm per second to separate the peaks and create a tracing that is easier to read when you run an ECG on an infant or child or on adults with a rapid heart beat.
