Basic ECG Interpretation
A patient calls the health care provider's office reporting dizziness and fatigue. The patient started taking a beta blocker one week ago. The patient's radial pulse is 52 bpm. Which instruction should the nurse give the patient? "Consult your health care provider about stopping the beta blocker." "Continue taking the beta blocker. Your symptoms will resolve in a week or so." "You will need to make an appointment to have a permanent pacemaker implanted." "Ask your health care provider about doubling up on your beta blocker. You need a higher dose to treat your symptoms."
"Consult your health care provider about stopping the beta blocker." Sinus bradycardia may occur in response to certain drugs, including β-blockers. If bradycardia is due to drugs, these may have to be held, discontinued, or reduced. The patient should consult the primary health care provider.
A patient presents with sinus tachycardia with a heart rate of 122. The patient also has pneumonia. Which assessment question should the nurse ask the patient first to identify the cause of the patient's symptoms? "Are you coughing up any secretions?" "What have you eaten in the last 24 hours?" "Do you find yourself sleeping in a chair at night?" "Have you taken any over-the-counter medications since you became sick?"
"Have you taken any over-the-counter medications since you became sick?" Many over-the-counter cold remedies have active ingredients (e.g., pseudoephedrine [Sudafed]) that can cause tachycardia.
A patient presents during a normal well-visit with a heart rate of 58 beats per minute. The patient is an avid runner and is currently training for a triathlon. All other vital signs are normal. Which statement indicates to the nurse the patient teaching is understood? "I need to return in 48 hours. If my heart rate is still low, I need a pacemaker." "I am sad that I have to stop running. My heart does not tolerate it anymore." "I should stop drinking coffee in the morning. This will help my heart rate increase." "I do not need to take any medications. My heart rate is expected because of my triathlon training."
"I do not need to take any medications. My heart rate is expected because of my triathlon training." Sinus bradycardia may be a normal sinus rhythm in aerobically trained athletes and in some people during sleep.
The nurse is teaching a cardiac seminar for a local community center. The nurse knows further teaching is needed if a member makes which comment about bradycardia? "If I strain with a bowel movement my heart rate may go down." "Bradycardia means my heart rate is routinely <60 beats per minute." "My heart rate may be slower if I discontinue my calcium channel blockers." "I should stop my speed walking sessions since my heart rate is 50 beats per minute."
"I should stop my speed walking sessions since my heart rate is 50 beats per minute." Sinus bradycardia may be a normal sinus rhythm in aerobically trained athletes and in some people during sleep.
List in order the pathway of the normal cardiac impulse starting at the SA node. 1. The impulse causes the atria to contract. 2. The impulse travels from the AV node through the bundle of His. 3. The impulse reaches the Purkinje fibers. 4. The impulse divides into the left and right bundle branches. 5. The ventricles contract.
1, 2, 4, 3, 5
The nurse is assessing heart rate from a patient's ECG and counts 8 R-R intervals in a 60-second stretch. The patient's heart rate is beats per minute. Use numbers only.
80 Heart rate can be calculated by counting the number of R-R intervals in a 6 second strip and multiplying by 10. In this instance a 60-second strip notes 80 R-R intervals meaning the heart rate is 80 beats per minute.
A nursing student is discussing a rhythm strip with the faculty member. Which rationale explains a shortened QT interval? A faster heart rate A slower heart rate Atrial Repolarization Firing of the sinoatrial (SA) node
A faster heart rate The QT represents the total time required for ventricular depolarization and repolarization. A shortened QT interval is associated with a quicker time for depolarization and repolarization, i.e. a faster heart rate.
A patient reports dizziness and dyspnea. On assessment, the patient's heart rate is 130 bpm. An ECG indicates normal P-wave, PR interval, and QRS complex. The patient reports that the symptoms began shortly after an injury causing acute back pain. What is the priority intervention for this patient? Repeat the ECG. Administer pain medications as prescribed. Encourage the patient to listen to the radio to help with relaxation. Obtain cardiac enzymes for evaluation of a myocardial infarction (MI).
Administer pain medications as prescribed. The ECG indicates normal findings. Sinus tachycardia is associated with physiologic and psychologic stressors such as pain. The first step is to treat the cause (medicate the patient for pain).
A nurse is gathering the history for a patient with sinus tachycardia. Which information should be expected based on the patient's condition? Fatigue Anemia Hypothyroidism Increased intraocular pressure
Anemia Sinus tachycardia is associated with anemia.
What is the path of a NORMAL cardiac impulse?
Begins in the SA node in the upper right atrium; spreads over the arterial myocardium via intertribal and internal pathways causing atrial contraction, pumping blood into the left and right ventricles; impulse then travels to the AV node through the bundle of His and down the left & right bundle branches; ending in the Purkinje fibers, which transmit the impulse to the ventricles.
An increase in the rate of cardiac impulse initiation is linked to stimulation of which component? a. Purkinje system b. Electrolyte system c. Sympathetic nervous system d. Parasympathetic nervous system
C. Sympathetic nervous system The sympathetic nervous system is responsible for increasing the rate of cardiac impulse initiation at the SA node. It also assists with node impulse conduction and cardiac contractility.
A patient asks the nurse, "Why do I need a 12-lead ECG if my heart rate is within normal limits?" The nurse responds by explaining that which heart conditions may be identified by the 12-lead ECG? Select all that apply. Cardiotoxicity Cardiac murmur Irregular rhythm Myocardial infarction Heart valve deformation
Cardiotoxicity The 12-lead ECG may show changes indicative of drug toxicity. Irregular rhythm Obtaining 12-lead ECG views of the heart is helpful in the assessment of dysrhythmias, or irregular heart rhythms. Myocardial infarction The 12-lead ECG may show changes suggesting damage to the heart including ischemia and myocardial infarction.
What methods can be used to calculate HR from an ECG?
Clouting methods: 1. count the # of QRS complexes in 1 min (most accurate, most time consuming) 2. count the # of R-R intervals in 60seconds & multiply by 10 (R wave is the first upward or (+) wave of the QRS complex) 3. count the # of small squares between one R-R interval & divide into 1500. 4. count the # of large squares between R-R interval & divide into 300. Use caliper.
Which statement describes the role of the Purkinje fibers in the pathway of the normal cardiac cycle? Origination of normal impulses Conduction of impulses from the atria to the ventricles Transmits electrical impulses from the AV node to the ventricles Conduction of impulses through the ventricles leading to ventricular muscle contraction
Conduction of impulses through the ventricles leading to ventricular muscle contraction The Purkinje fibers conduct impulses through the ventricles resulting in ventricular contraction.
Which action results in the atria after firing of the sinoatrial (SA) node? Repolarization of cardiac muscle Depolarization of cardiac muscle Contraction of the atria to move blood to the ventricles Contraction of the ventricle moving blood out to the body
Contraction of the atria to move blood to the ventricles The SA node initiates the normal cardiac cycle. The end result is the contraction of the right and left atrium as they push blood into the ventricles.
The nurse is reviewing a patient's ECG reading and notices artifact on the monitor. Which action should the nurse perform to identify the cause of the artifact? Ask the patient about any medications taken prior to the ECG Ensure that the patient's cell phone is turned off during the ECG Ask the patient about the amount of caffeine ingested prior to the ECG Determine the condition of the conductive gel on the electrodes
Determine the condition of the conductive gel on the electrodes Accurate interpretation of heart rhythm is difficult when artifact is present. If artifact occurs, check the connections in the equipment. Replace the electrodes if the conductive gel has dried out.
Characteristics of sinus tachycardia
HR 101-200 bpm and rhythm is irregular. P wave normal, precedes each QRS complex & has normal shape and duration. PR interval is normal and QRS complex has a normal shape and duration
ECG characteristics of sinus bradycardia
HR <60 bpm and rhythm is regular. P wave precedes each QRS complex & has a normal shape and duration,. PR interval is normal and QES complex has normal shape & duration.
symptomatic bradcardia
HR that is <60 bpm & is inadequate for patients condition; can cause fatigue, dizziness, chest pain, syncope
Depolarization & Repolarization
Heart cell membrane is semipermeable - allowing maintenance of a high concentration of K and low concentration of Na. Outside the cell it is opposite. Inside the cell, when at rest, or in the polarized state, is negative compared with the outside. When the cells are stimulated, the membrane changes permeability allowing Na to move rapidly into the cell making it positive compared with the outside. Slower movement of ions restores the cell to polarized state, called depolarization.
The nurse is caring for a patient with chest tightness and shortness of breath. The ECG tracing reports sinus tachycardia. Which additional finding should be expected? QRS duration 0.07 seconds Heart rate is 50 beats per minute Heart rate is 114 beats per minute Two P waves for each QRS complex
Heart rate is 114 beats per minute Characteristics of sinus tachycardia include a heart rate >100 beats per minute.
How to asses the heart rhythm:
Look for P wave, upright or inverted? is there one for every QRS complex, or more than one Evaluate atrial rhythm. regular or irregular? calculate atrial rate measure duration of PR interval. normal duration or prolonged? duration consistent before each QRS? evaluate ventricular rhythm. regular or irregular? calculate ventricular rate measure duration of QRS complex. normal duration or prolonged? Assess ST segment. isoelectric (flat), elevated or depressed? measure duration of QT interval. QT interval varies with age, gender, and changes in HR. Slower HR will cause lengthening and fast cause shortening Note T wave, upright or inverted?
review of a patient's 12-lead ECG reveals sinus bradycardia. Which information should the nurse expect to find in the patient history? Select all that apply. Hypoglycemia Hyperthyroidism Marathon training Excessive caffeine intake Increased intracranial pressure Prolonged exposure to extreme cold
Marathon training Sinus bradycardia may be a normal sinus rhythm in aerobically trained athletes, such as those training for a marathon. Increased intracranial pressure Sinus bradycardia may be caused by increased intracranial pressure. Prolonged exposure to extreme cold Sinus bradycardia may be caused by hypothermia, as may result from prolonged exposure to extreme cold.
Which physiologic process is responsible for repolarization of heart cells? Movement of sodium into the cell Movement of sodium out of the cell Movement of potassium into the cell Movement of magnesium out of the cell
Movement of sodium out of the cell When a cell or groups of cells is stimulated, the cell membrane changes its permeability. This allows sodium to move rapidly into the cell, making the inside of the cell positive compared with the outside (depolarization). A slower movement of sodium ions across the membrane restores the cell to the polarized state, called repolarization.
A patient presents with fatigue, dizziness and chest pain. On assessment, the patient's heart rate is 55 beats per minute and blood pressure is 85/60. A dopamine infusion is ineffective at reducing symptoms and returning vital signs to normal. The nurse should expect the health care provider to schedule the patient for which procedure? Echocardiogram IV atropine administration Synchronized cardioversion Placement of a permanent pacemaker
Placement of a permanent pacemaker Permanent pacemaker therapy may be necessary for a patient who does not respond to atropine or dopamine.
A patient presents with a sinus rate of 150 beats per minute and body temperature of 103 °F; the patient is otherwise clinically stable. How should the nurse prepare to manage the patient's sinus tachycardia? Prepare to administer antipyretics. Prepare to administer IV atropine. Provide the patient information on epinephrine infusion. Provide the patient information on synchronized cardioversion.
Prepare to administer antipyretics. The underlying cause of tachycardia guides the treatment. Sinus tachycardia may be caused by a high fever. Treating the patient's fever would be the first step to treating the tachycardia.
The nurse obtains an ECG for a 53-year-old patient with chest pain. The nurse palpates a heart rate of 106. Which alteration in waveform should the nurse expect to see on the ECG tracing? Inverted T wave Flattened P wave Short QT interval Narrow QRS complex
Short QT interval The nurse would expect a shortened QT interval for tachycardic patients.
Which electrolytes play key roles in polarization of the heart cells? Sodium and potassium Potassium and calcium Potassium and glucose Sodium and magnesium
Sodium and potassium The electrolytes sodium and potassium are partners in cardiac function. A higher sodium level outside the cell allows for a high potassium and low sodium level inside the cell. Potassium inside the cell is required for the conduction of impulses to achieve a polarized state.
which wave on the ECG tracing will provide the nurse more information about atrial depolarization?
The P wave demonstrates the initial firing of the SA node. The P wave can display as positive (upright), negative (inverted), or biphasic (both positive and negative).
Which ECG component would the nurse measure to identify the total time needed for ventricular depolarization and repolarization of a patient's heart?
The QT interval is the time it takes for ventricular depolarization and then repolarization. It is calculated by measuring the distance between the QRS complex and the T wave.
Excitability
ability to be electrically stimulated
Automaticity
ability to initiate an impulse spontaneously & continuously
contractility
ability to respond mechanically to an impulse
Conductivity
ability to transmit an impulse along a membrane in an order manner
sympathetic nervous system
accelerates heart rate, constricts blood verses, and raises BP
Clinical associations with sinus tachycardia
associated with physiologic and psychologic stressors such as exercise, fever, pain, hypotension, hypovolemia, anemia, hypoxia, hypoglycemia, myocardial ischemia, HF, hyperthyroidism, anxiety and fear can also be an effect of drugs such as epilepsy, noriepi, atropine, caffeine, theophylline or hydrazine.
P wave
atrial depolarization
What are the four properties of cardiac cells?
automaticity, excitability, conductivity, contractility
Treatment for sinus tachycardia include:
clinically stable patients, vagal maneuvers can be attempted. In addition, IV β-blockers (e.g., metoprolol [Lopressor]), adenosine (Adenocard), or calcium channel blockers (e.g., diltiazem [Cardizem]) can be given to reduce HR and decrease myocardial O2 consumption. In clinically unstable patients, synchronized cardioversion is used. Synchronized cardioversion uses low voltage electricity to correct the abnormal cardiac impulses that lead to extreme tachycardia.
sinus tachycardia
conduction pathway is same as NSR; discharge rate form sinus node increases because of vagal inhibition or sympathetic stimulation; sinus rater is 101-200 bpm
sinus bradycardia
conduction pathway that is the same as NSR, but SA nodes fire at a rate <60 bpm.
Treatment for sinus bradycardia include:
consists of giving IV atropine (anticholinergic drug). If atropine (AtroPen) is ineffective, transcutaneous pacing or a dopamine (Intropin) or epinephrine (Adrenalin) infusion is considered. Permanent pacemaker therapy may be needed. If bradycardia is due to drugs, these may have to be held, discontinued, or reduced.
sinus tachycardia clinical manifestations
dizziness, dyspnea, & hypotension because of decreased cardiac output. increased myocardial oxygen consumption is associated with increased HR. Angina or increase in infarction size may accompany sinus tachycardia in patients with CAD or acute MI.
Vagus nerve
either of the longest pair of cranial nerves mainly responsible for parasympathetic control over the heart and many other internal organs, including thoracic and abdominal viscera
PR segment
electrical impulse traveling the atrioventricular (AV) node
12-Lead ECG
graphic tracing of the electrical impulses produced in the heart. Wave forms on the ECG represent electrical activity produced by movement of ions across the membranes of heart cells, representing depolarization & depolarization,. Each waveform has an expected shape, length, and height. Variations of these measurements can indicate cardiac conductivity or damage to cardiac muscle.
What are common disease states associated with sinus bradycardia?
hypothyroidism, increased intracranial pressure & inferior myocardial infarction (MI).
Potassium
important to monitor in patients because even small variances above or below normal levels can cause problems with cardiac muscle condition, causing dysrhythmias.
clinical associations of sinus bradycardia
may be normal in aerobically trained athletes; carotid sinus massage, valsalva maneuver, hypothermia, increased intraocular pressure, vagal stimulation, certain drugs.
How do you correctly interpret an ECG?
measure time and voltage on the ECG paper. ECG paper consists large (heavy) and small (light) squares. Each large square consists of 25 smaller squares (5 horizaontal/5 vertical). Horizontally each small (1mm) represents 0.04 seconds. This means that one larger square = 0.20 second and that 300 large squares = 1 minute. Vertically each small square represents 0.1 millivolt (mV). This means that one large square =0.5 mV. Use these square to calculate the HR and measure time intervals for different ECG complexes.
clinical manifestations of symptomatic bradycardia include:
pale, cool skin; hypotension, weakness, angina, dizziness or syncope, confusion or disorientation and SOB
Autonomic Nervous System
part of he nervous system that regulates involuntary body functions, including the activity of the cardiac muscle, smooth muscles, & glands. It has two divisions.
repolarization
process by which the membrane potential of a neuron or muscle cell is restored to the cell's resting potential
depolarization
reduction of a membrane potential to a less negative value
QT interval
represents total time required for ventricular depolarization and depolarization
normal sinus rhythm
rhythm that starts in the SA node at a rate of 60-100 times per minute and follows the normal conduction pathway (one P wave for each QRS complex, PR interval of 0.12-0.20, a QRS duration of 0.04 to 0.10 second)
parasympathetic nervous system
slows heart rate, increases intestinal peristalsis & gland activity, and relaxes sphincters
What causes an increase in SA node firing, AV node impulse condition and cardiac contractility?
stimulation of sympathetic nerves
What causes a decreased rate of firing of the SA node & slowed impulse conduction of the AV node?
stimulation of the vagus nerve
What conditions may a 12-lead ECG show?
structural changes, conduction disturbances, damage (ischemia, infarction), electrolyte imbalance, or drug toxicity, assessment of dysrhythmias
Two divisions of the autonomic nervous system:
sympathetic and parasympathetic nervous system.
How does depolarization work in the cardiac muscle cell?
the process begins after phase 0 of the action potential and is completed by the end of phase 3. It encompasses the effective and relative refractory periods and correlates with the Q-T interval on the ECG.
QRS complex
ventricular depolarization
T wave
ventricular depolarization
