Electrophysiologic Tests Flashcards
What are electrophysiologic tests?
They use electrical activity and electrical devices to evaluate disease/injury to a specific area of the body
What are the two types of electrical impulses?
Generated spontaneously = EKG
Stimulated = EMG
What is a cardiac stress test?
Noninvasive study that provides info about a patient’s cardiac function
Heart is stressed by exercise, medicine, or pacing then heart is evaluated during the stress
Changes indicating ischemia point to coronary occlusive disease
What are the indications for a cardiac stress test?
Chest pain in patient with suspected coronary disease
Limits of safe exercise during a cardiac rehab program
Labeled or exercise-related hypertension
INtermittent claudication in patients with suspected vascular occlusive disease
Effectiveness of treatment in patients who take antianginal or anti arrhythmic medications
Effectiveness of cardiac intervention (such as bypass grafting or angioplasty)
What is the goal of the cardiac stress test stressor?
To increase the heart rate to just below maximal levels or to the “target heart rate”
What is the target heart rate?
80 to 90% of the maximal heart rate
220 - patients age
When is a cardiac stress test stopped?
If patient reaches the target heart rate or develops any symptoms or EKG changes
What is the criteria for discontinuation of an exercise stress test?
Abnormal EKG changes such as Ectopy, Flipped T waves, or ST changes
Attainment of maximal performance
Chest pain
Cyanosis
Excessive heart rate change
Excessive hypertension/hypotension
Leg claudication
Severe SOB
Syncope
What is the procedure for a cardiac stress test?
1) NPO and avoid smoking for 4 hours prior
2) Obtain protest EKG
3) Record patient’s vital signs for baseline values
4) Apply and secure appropriate EKG electrodes
5) After patient begins to exercise, adjust treadmill to apply increasing levels of stress at specific intervals
6) EKG tracing and vital signs are monitored continuously
7) Terminate test if patient becomes symptomatic
8) Testing usually takes approx. 45 min
What is the post procedure for Cardiac stress testing?
Place patient in supine position to rest after test
Monitor EKG tracing and record vital signs at post-stress intervals until recordings and values return to protest levels
Remove electrodes and paste
What is an Electrocardiography test?
Records electrical impulses that stimulate heart to contract
What are the indications for an EKG?
Evaluates: Arrhythmias Conduction defects Myocardial injury/damage Hypertrophy
Diagnoses:
Electrolyte imbalances
Drug level abnormalities
Pulmonary diseases
What are the two different planes for EKG?
Six limb leads
Six chest leads
What is the pre-procedure for EKG?
Leads are positioned as follows:
V1 in fourth intercostal space at the right sternal border
V2 in 4 ICS at the left sternal border
V3 midway between V2 and V4
V4 in 5 ICS at the midclavicular line
V5 at the left anterior auxiliary line at the level of V4 horizontally
V6 at the left midaxillary line at the level of V4 horizontally
What is an electroencephalography test?
Electrodiagnostic test performed to identify and evaluate patients with seizures, tumors, and infarction
Confirmatory test for determination of brain death
Provides graphic recording of electrical activity of the brain
Electrodes are placed on scalp overlying multiple areas of brain to detect/record electrical impulses within it
What are the indications for EEG?
Important in evaluating epileptic states which is characterized by rapid, spiking waves seen on the graph
Patients with cerebral lesions will have abnormally slow EEG waves, depending on size and location of lesion
Used to evaluate trauma, drug intoxication, and cerebral death in comatose patients
What is the pre-procedure for an EEG?
If sleep EEG will be attempted at time of testing, sleep should be shortened night before test:
Adults = no more than 4-5 hours Children = no more than 5-7 hours
Instruct patient to wash hair night before test
No oils, sprays, or lotion should be used
Some meds may need to be d/c before study but anticonvulsants should be taken unless C/I by the physician
What can alter the results of an EEG?
1) Fasting may cause hypoglycemia which could modify EEG pattern
2) Drinks containing caffeine interfere with test results
3) Body and eye movements during test can cause changes in brain wave patterns
4) Lights (especially bright or flashing) can alter test results
5) Sedatives may affect results
What is the procedure for an EEG?
1) EEG usually performed in specially constructed room shielded from outside disturbances
2) Patient placed in supine position on bed or reclining on a chair
3) 16 or more electrodes applied to scalp in a specific pattern over both sides of the head = prefrontal, frontal, temporal, parietal, and occipital areas
4) One electrode may be applied to each earlobe for grounding
5) After electrodes applied, patient is instructed to lie still with eyes closed
6) Technician continuously observes patient during recording or any movements that could alter results
7) Approx. Every 5 minutes recording is interrupted to permit the patient to move if desired
What is an Electromyography (EMG)?
Monitors electrical activity of skeletal muscle similar to EKG
Electrical activity displayed on oscilloscope as electrical waveform
Audio electrical amplifier can be added to system so that both appearance and sound of electrical potentials can be analyzed and compared simultaneously.
Performed by a psychiatrist, musculoskeletal physician, or neurologist in 30-60 min.
Small needle size helps reduce discomfort
Usually done in conjunction with nerve conduction studies
Can detect spontaneous muscle movement such as fibrillation and fasciculation
When evident, these waveforms indicate injury/disease of nerve or muscle being evaluated
Decrease in number of muscle fibers able to contract typically observes with peripheral nerve damage
What are the indications for an EMG?
Used in evaluating patients with diffuse or localized muscle weakness/atrophy
Used to detect:
Primary muscular disorders
Muscular abnormalities caused by other system such as nerve dysfunction, sarcoidosis, and paraneoplastic syndrome
What are the contraindications for EMG?
Patients receiving aggressive anticoagulant therapy as electrodes may induce intramuscular bleeding
Skin infection, as electrodes may penetrate infected skin and spread infection to muscle
What are interfering factors of EMG?
Edema
Hemorrhage
Thick SQ fat
Patients with excessive pain the precludes the patient’s ability to relax
What is the pre-procedure for EMG?
If serum enzyme tests ordered, specimen should be drawn 5-10 days afterward because penetration of muscle by electrodes may cause misleading elevations
Premedication/sedation usually avoided
What is the procedure for an EMG?
1) Patients position and position of electrode depend on muscle being studied
2) Tiny needle that acts as a reference electrode inserted into muscle being examined
3) A reference electrode is placed nearby on the skin surface
4) The patient is instructed to keep muscle at rest
5) The oscilloscope display is viewed for any evidence of spontaneous electrical activity
6) Then patient is asked to contract muscle slowly and progressively
7) Electrical waves produced examined for their number, form, and amplitude
8) A nerve innervation a particular muscle group is then simulated and resulting muscle contraction is evaluated
What disease are marked by reduced muscle electrical activity with spontaneous contraction?
Gillian-Barre Syndrome
Myasthenia Travis
Peripheral nerve injury, entrapment, or compression
Acetylcholine blockers like snake venom
Diabetic neuropathy
Anterior poliomyelitis
Muscle denervation
Amyotrophic lateral sclerosis
What primary muscle diseases are denoted by decreased electrical activity and amplitude?
Muscular dystrophy
Myopathy
Traumatic injury
Even with nerve stimulation, little or no activity is seen
What is a nerve conduction test?
Evaluates integrity of nerves and allows for detection and location of peripheral nerve injury or disease
Electrical impulse is initiated at one site of nerve and the time it takes impulse to travel to a second site of the same nerve is recorded then docnudtion velocity of the impulse in that nerve can be determined
Usually done in conjunction with an EMG
Can indicate diseases affecting either the motor or sensory nerves
Takes about 15 minutes and is performed by a psychiatrist, neurologist, or trained tech
May be uncomfortable because a mild shock is required for nerve impulse stimulation
Where are electrical impulses placed in a nerve conduction study?
For evaluating motor nerves = proximal
For evaluating sensory nerves = distal
What does a nerve conduction test evaluate?
Neuromuscular junction
Nerve axon loss
Variations in nerve recovery time
What are the indications for a nerve conduction study?
Performed to identify peripheral nerve injury in patients with:
Localized or diffuse weakness
Muscle atrophy
Dysesthesia/paresthesia
Neurogenic pain
So as to differentiate primary peripheral nerve disease from muscular injury
Documents severity of injury
Used to monitor the nerve injury and response to treatment
What is the procedure for a nerve conduction test?
1) Test can be performed in the nerve conduction lab, office setting, or a the patients bedside
2) Patients position depends on the area of suspected peripheral nerve injury or disease
3) A recording electrode is placed on the skin overlying a muscle innervated solely by the relevant nerve
4) a reference electrode is placed nearby
5) The nerve is stimulated by a shock emitting device at an adjacent location
6) FOr the evaluation of a motor nerve, the time between nerve impulse and muscular contraction is measured in ms on an EMG machine
7) The nerve is stimulated similarly at a location proximal to the area of suspected injury or disease
8) the time required for the impulse to travel from the site of initiation to muscle contraction is recorded in ms
What is Distal latency?
The time between nerve impulse and muscular contraction
What is total latency?
Time required for the impulse to travel from the site of initiation to muscle contraction
What is the distance between site of stimulation and recoding electrode measured in?
Centimeters
What is conduction velocity converted to?
Meters/second
What is the normal conduction velocity for the lower extremeties?
40-50m/sec
What cause slowing of conduction velocity?
Trauma or contusion of a nerve
Neuropathies
A conduction velocity that is greater than normal does not indicate what?
Pathologic conditions
When is no nerve conduction noted?
IN complete nerve transactions
What is a Holter monitor?
Continuous recording of electrical activity of the heart
Can be performed for up to 72 hours
EKG is recorded continuously on magnetic tape during unrestricted activity, rest, and sleep
It is equipped with a clock that permits accurate time monitoring on the EKG tape
Patient carried diary and records daily activities, as well as any cardiac symptoms that may develop during the period of monitoring
What are the indication for a Holter monitor ?
Patients who experience:
Syncope
Palpitations
Atypical Chest pains
UNexplained dyspnea
What occurs after the Holter monitor is worn for the 72 hour period?
1) Record tape is played back at a high speed
2) EKG tracing is usually interpreted by computer, which can detect any significant abnormal waveform patterns that occurred during the test
3) Computer printouts are generated
What are the two types of computer printouts that can be generated from a Holter monitor?
1) Event recording
2) Full disclosure recording
What is an event recording printout?
Representative tracings during noted events are printed out
Tracings demonstrate maximum and minimum heart rates
What is a full disclosure recording?
All the beats are printed out and are scanned by a tech who looks for aberrant waveforms
What are the clinically significant test results seen on a Holter monitor?
Cardiac arrhythmias:
Tachycardia
Bradycardia
Premature beats
Ischemic changes:
Unusual pain symptoms during a particular exercise
A monitor can be applied and that particular exercise performed
If pain occurs and associated EKG ischemic changes are noted on the monitor, the diagnosis of angina can be made even though the pain is atypical
