EKG Midterm
Query successful
An EKG technician needs to be able to identify both normal and abnormal EKG rhythms, as well as recognize changes that may signal heart problems or injury. While EKG machines often provide automatic analysis, the technician must be able to recognize abnormalities and report them to a provider.
EKG Basics
An EKG tracing is composed of essential features: the isoelectric line, waves, segments, intervals, and complexes.
Isoelectric line (baseline): The flat part of the EKG tracing.
Wave: A deflection or movement away from the isoelectric line. An upward deflection is positive, and a downward deflection is negative. The P, Q, R, S, and T waves are the most common.
Segment: The isoelectric area between two waves.
Interval: A wave plus a segment.
Complex: Several waves that are measured together.
A normal EKG tracing is called a
normal sinus rhythm (NSR). It has the following characteristics:
Rate: 60-100 beats per minute (BPM).
Rhythm: Regular, with no early or late beats.
P wave: One before each QRS complex, and they are all identical, positive, and uniform.
PR interval: Between 0.12 and 0.20 seconds.
QRS duration: Less than 0.12 seconds.
Some waves, like the
U wave, may not appear on every EKG tracing. The normal U wave is a small, rounded wave that comes after the T wave and is shorter than the T wave. A large U wave may indicate a low potassium level, while a negative or inverted U wave can be a sign of heart disease or a myocardial infarction (MI). If an EKG technician notices a concerning U wave, they should report it to the provider.
EKG Troubleshooting and Artifacts
Artifacts are errors in an EKG tracing that are caused by something other than the heart's electrical activity. Technicians need to know how to identify and avoid them. Common artifacts and their causes and solutions are listed below:
Somatic tremor: Caused by patient muscle movement. This can be from a patient being cold, having Parkinson's disease, having a seizure, or being anxious. Solutions include offering a blanket, providing a quiet environment, reassuring the patient, and encouraging slow breaths.
Wandering baseline: The EKG tracing drifts away from the center of the paper. This can be caused by a patient's breathing, tight or stretched lead wires, patient body hair, natural skin oils or grooming products, or dry electrode gel.
Broken recording (interrupted baseline): Occurs when the EKG machine can't find a signal. The stylus moves from side to side while searching for a signal. The most common cause is frayed or broken lead wires, so technicians should check the wires before each use.
Electrical (AC or 60-cycle) interference: A result of electrical equipment, fluorescent lights, or other nonmedical equipment in the area. This can be solved by moving the equipment or turning it off, or by moving the EKG machine.
An EKG technician should always double-check the electrodes and lead wires if a tracing is unclear. Errors in electrode placement, like a limb lead reversal, can also create inaccurate tracings that could be mistaken for a dangerous rhythm. A common limb lead reversal is the incorrect placement of the right and left arm electrodes. This error causes a negative deflection of QRS complexes in lead I and a positive deflection in lead aVR.
Abnormal Rhythms (Dysrhythmias)
Dysrhythmia, also called arrhythmia, means a difficult or abnormal rhythm. It includes rhythms that are too fast (tachycardia) or too slow (bradycardia), or that begin in an area of the heart other than the SA node.
Sinus rhythms: Originate in the sinoatrial (SA) node.
Atrial rhythms: Start in the atria. P waves in an atrial rhythm can be flattened, pointed, notched, biphasic, or hidden within the T wave of the preceding complex.
Junctional rhythms: Begin in the AV junction.
Ventricular rhythms: Start in the ventricles.
Ectopic focus/pacemaker: An irritable area of the heart's conduction system that generates an impulse even when the SA node is working normally.
Heart blocks (AV blocks): Caused by problems in the conduction of electrical impulses between the atria and ventricles.
Specific Rhythms
Sinus bradycardia: A slow sinus rhythm that can cause symptoms like dizziness, weakness, or fainting, and can decrease cardiac output.
Sinus tachycardia: A fast sinus rhythm that may be a side effect of medication, a response to stress, or a response to the body's need for more oxygen. It can be harmful to a patient with a history of coronary artery disease.
Idioventricular rhythm: Occurs when three or more ventricular escape beats happen in a row. The rate is very slow (20-40 BPM), and the QRS complexes are wide and bizarre. A sustained idioventricular rhythm is called agonal rhythm and can be deadly. This is a potentially lethal dysrhythmia, and the technician should take immediate emergency action.
Accelerated idioventricular rhythm (AIVR): Similar to idioventricular rhythm but with a faster rate of 40-100 BPM. The QRS complexes are wide and bizarre.
Ventricular tachycardia (VT): A very dangerous rhythm where the rate is so fast (120-250 BPM for monomorphic VT and 150-300 BPM for polymorphic VT) that the coronary arteries don't have time to fill, which reduces cardiac output. A "run" of VT is defined as three or more premature ventricular contractions in a row, and a technician should report it to the provider immediately.
Bundle branch block (BBB): A delay in the electrical impulse to part of the ventricles due to damage in a ventricular conduction pathway. All bundle branch blocks have a widened QRS complex (>0.10s), and leads V1 and V6 show noticeable changes.
ST Segment Changes and Other Indications of Injury
EKG technicians must watch for changes that may be caused by heart problems or injury, such as myocardial infarction and cardiac ischemia. Different leads on the EKG correspond to specific areas of the heart:
Inferior wall: Leads II, III, aVF.
Lateral wall: Leads I, aVL, V5, V6.
Septum: Leads V1, V2.
Anterior wall: Leads V3, V4.
Posterior wall: Leads V7, V8, V9.
The most important skill for an EKG technician is to be able to identify a normal EKG, as this makes it easier to spot and report anything abnormal.
Practice Questions
Question: A patient's EKG tracing shows a wandering baseline. What are some of the potential causes?
Answer: A wandering baseline can be caused by the patient's breathing, tight or stretched lead wires, patient body hair, natural skin oils or grooming products, or dried-out electrode gel.
Question: How does a technician troubleshoot a broken recording?
Answer: A broken recording is most often caused by frayed or broken lead wires. A technician should check the EKG machine before each use to ensure the wires are in good condition and not use them if they are frayed or broken.
Question: An EKG tracing has a wide and bizarre QRS complex with a heart rate of 30 BPM. What rhythm might this be, and what action should the technician take?
Answer: This rhythm is likely a sustained idioventricular rhythm (agonal rhythm). It is a potentially lethal dysrhythmia, so the EKG technician should take immediate emergency action according to facility policy.
Question: A patient's EKG shows a widened QRS complex and noticeable changes in leads V1 and V6. What condition might this indicate?
Answer: This indicates a bundle branch block (BBB). The technician should report it to the provider.
Question: What is the definition of a "hidden P wave" and in which category of rhythms is it commonly found?
Answer: A hidden P wave is one that cannot be seen because it is lost in the T wave of the preceding complex. This is a common variation found in atrial rhythms.
Question: A patient's EKG shows a negative deflection of the QRS complexes in lead I and a positive deflection in lead aVR. What could be the cause of this tracing?
Answer: This tracing is likely caused by the incorrect placement of the right and left arm electrodes, which is the most common limb lead reversal. The technician should check the electrode placement.