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Questions and Answers
How do you calculate heart rate from an ECG?
Count the number of QRS complexes and multiply by 10.
What are the characteristics of a normal P wave?
Which of the following are common symptoms of sinus bradycardia?
Atrial fibrillation is characterized by a regular heart rhythm.
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What is the treatment for ventricular fibrillation?
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What does it indicate if the QRS complex is prolonged?
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Match the following ECG waves with their meanings:
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What can cause artifact in an ECG reading?
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Asystole is characterized by the presence of electrical activity in the heart.
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What is the normal duration of the PR interval?
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What is the primary cause of infective endocarditis?
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How do you calculate the heart rate from an ECG strip?
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What does a regular rhythm on an ECG indicate?
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What does the P wave represent?
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The PR interval is measured from the beginning of the P wave to the beginning of the QRS complex.
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What is a normal QRS complex duration?
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What is a common treatment for sinus bradycardia?
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Which of the following is a possible cause of atrial fibrillation? (Select all that apply)
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What is assessed when ventricular tachycardia occurs?
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Ventricular fibrillation is characterized by regular waveforms on an ECG.
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What is a common diagnostic study for infective endocarditis?
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The absence of ventricular electrical activity is known as ______.
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Infective endocarditis is often associated with IV drug use.
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Study Notes
ECG Interpretation
-
Heart Rate: Count the number of QRS complexes and multiply by 10 to get beats per minute.
- Atrial rate = number of P waves.
- Ventricular rate = number of QRS complexes x 10.
-
Rhythm:
- Regular: Equal intervals between QRS complexes (R waves), varying by less than 0.06 seconds or 1.5 boxes.
- Irregular: Unequal intervals between QRS complexes (R waves), varying by more than 0.06 seconds or 1.5 boxes.
-
P Wave: Represents atrial depolarization.
- First deviation from the isoelectric line.
- Should be rounded, upright, and similar in appearance.
-
PR Interval: Measured from the beginning of the P wave to the beginning of the QRS complex.
- Represents time from atrial contraction onset to ventricular contraction onset.
- Normal interval: 0.12-0.20 seconds or 3-5 small squares.
-
QRS Complex: Represents ventricular depolarization.
- Q Wave: First negative deflection after the P wave, short and narrow, not present in all leads.
- R Wave: First positive deflection in the QRS complex.
- S Wave: First negative deflection after the R wave.
-
QRS Interval: Measured from the beginning to end of the QRS complex.
- Normal duration: less than 0.12 seconds.
- Wide QRS complexes (greater than 0.12 seconds) may indicate bundle branch block or ventricular conduction issues.
- Narrow QRS complexes (less than 0.06 seconds) can be normal, but may indicate a ventricular conduction problem.
-
QT Interval: Measured from the beginning of the QRS to the end of the T wave.
- Represents time taken for ventricular depolarization and repolarization.
- Normal duration: 0.34- 0.43 seconds.
- Prolonged QT intervals may result from drug therapy, electrolyte imbalances, or heart rate changes.
-
T Wave: Represents ventricular repolarization.
- Usually the first upward deflection following the QRS complex.
- Inverted T wave can indicate myocardial damage.
-
U Wave: Usually not visible, but if present, follows the T wave.
- Smaller than the T wave, rounded, upright, or positive deflection following the QRS complex.
- May indicate hypokalemia.
-
Artifact: EKG waves from sources outside the heart.
- Interference seen on the monitor or ECG strip.
- Causes: patient movement, muscle tremor, loose electrodes, faulty EKG apparatus.
Normal Sinus Rhythm
- Regular rhythm set by the sinoatrial (SA) node (natural pacemaker).
Sinus Bradycardia
- Regular but unusually slow heartbeat (less than 60 BPM).
- Rate: < 60 BPM.
- Rhythm: Regular.
- P wave present before each QRS, upright and uniform.
- PR interval: 0.12-0.20 seconds.
- QRS complex: 0.06-0.10 seconds.
- Causes: hypoglycemia, hypothermia, hypothyroidism, medications, MI, sick sinus syndrome.
Sinus Tachycardia
- Fast heartbeat related to rapid SA node firing.
- Rate: > 100 BPM.
- Rhythm: Regular.
- P wave present before each QRS, upright and uniform.
- PR interval: 0.12-0.20 seconds.
- QRS complex: 0.06-0.12 seconds.
- Causes: heart disease, hypertension, hyperthyroidism, fever, stress, alcohol, caffeine, nicotine, medications, pain, electrolyte imbalances.
Atrial Fibrillation
- Uncoordinated electrical signal in the atria causing them to quiver (400+ BPM) without effective contraction.
- Ventricular rate is irregular and uncontrolled.
- Decreased cardiac output due to ineffective atrial contractions.
- Thrombi may form in the atria due to blood stasis.
- Rate: 300-600 BPM.
- Rhythm: Irregular.
- No P wave.
- QRS complex: < 0.12 seconds.
- Causes: heart failure, COPD, pericarditis, heart disease, stress, alcohol, caffeine.
Atrial Flutter
- Coordinated rapid atria beating identified by recurring, regular, sawtooth-shaped flutter waves.
- Atria beat faster than ventricles (4:1 ratio).
- Rate: 200-350 BPM, ventricular rate = to 0.12 seconds
- Rhythm: Regular.
- No clear P waves (flutter waves instead).
- QRS complex: < 0.12 seconds.
- Causes: heart failure, pulmonary embolism, MI, digoxin toxicity, CAD, valve problems, drugs, hyperthyroidism, cor pulmonale, hypertension.
Premature Ventricular Contractions (PVCs)
- A contraction originating from an ectopic focus in the ventricles.
- Premature (early) occurrence of a QRS complex.
- Wide and distorted QRS complex compared to normal conduction pathways.
- Unifocal PVCs: Same shape, arising from the same focus.
- Multifocal PVCs: Arise from different foci.
- Ventricular trigeminy: PVC every other beat.
- Couplet: 2 consecutive PVCs.
- Causes: stimulants, electrolyte imbalances, heart disease, hypoxia, fever, exercise, emotional stress.
- Not harmful in patients with normal hearts, but assess for pulse deficit.
Accelerated Idioventricular Rhythm
- Ventricles try to prevent cardiac standstill when SA and AV nodes fail.
- Rate: 40-100 BPM.
- Rhythm: Regular.
- No P wave.
- Wide and distorted QRS.
- Causes: drugs, MI, metabolic imbalances, hyperkalemia, cardiomyopathy.
Ventricular Tachycardia (VT)
- 3 or more consecutive PVCs.
- Ventricle takes control as pacemaker.
- Life-threatening dysrhythmia due to decreased cardiac output and potential for ventricular fibrillation.
- Monomorphic VT: QRS complexes have the same shape, size, and direction.
- Polymorphic VT: QRS complexes gradually change shape, size, and direction.
- Torsades de Pointes (TdP): Polymorphic VT associated with prolonged QT interval.
- Hallmark finding: QRS complexes deflect upwards and downwards around the baseline.
- Rate: 150-250 BPM.
- Rhythm: Regular or irregular.
- No P wave.
- Wide and distorted QRS.
- Causes: underlying heart disease, MI, medications that prolong QT interval, electrolyte imbalance, digitalis toxicity, CHF.
Ventricular Fibrillation (VF)
- Severe heart rhythm derangement with irregular waveforms of varying shapes and amplitudes.
- Multiple ectopic foci in the ventricle.
- Ventricle quivers with no effective contraction, resulting in no cardiac output.
- Lethal dysrhythmia requiring defibrillation.
- Rate: Not measurable.
- Rhythm: Irregular.
- No P wave or measurable QRS.
- Causes: AMI, untreated VT, electrolyte imbalance, hypothermia, myocardial ischemia, drug toxicity, trauma.
Asystole
- Absence of ventricular electrical activity.
- Occasionally P waves may be seen.
- No ventricular contraction due to lack of depolarization.
- Lethal dysrhythmia requiring immediate treatment.
- Causes: advanced heart disease, severe cardiac conduction system problem, end-stage HF.
Pulseless Electrical Activity (PEA)
- Organized electrical activity on ECG, but no mechanical heart activity or pulse.
- Most common dysrhythmia after defibrillation.
- Prognosis is poor unless the underlying cause is quickly identified and addressed.
- Causes: hypovolemia, hypoxia, metabolic acidosis, hyperkalemia, hypokalemia, hypoglycemia, hypothermia, toxins, cardiac tamponade, thrombosis, tension pneumothorax, trauma.
ECG Rhythm Strip Interpretation
-
Heart Rate:
- Count QRS complexes and multiply by 10 for beats per minute (BPM).
- Atrial rate = number of P waves.
- Ventricular rate = total QRS x 10.
-
Rhythm:
- Assess for regularity of intervals between QRS (or R) waves.
- Regular: Intervals vary less than 0.06 seconds (1.5 boxes).
- Irregular: Intervals vary more than 0.06 seconds (1.5 boxes).
- Assess for regularity of intervals between QRS (or R) waves.
-
P Wave:
- First deviation from the isoelectric line, representing atrial depolarization.
- Should be rounded, upright, and occur at regular intervals.
- Normal duration: 0.06-0.12 seconds.
- Variations point to potential atrial conduction issues.
-
PR Interval:
- Measured from the P wave onset to QRS onset.
- Reflects the time from atrial contraction to ventricular contraction onset.
- Normal interval: 0.12-0.20 seconds (3-5 small squares).
- Variations suggest possible conduction issues in the AV node, bundle of His, or bundle branches.
QRS Complex
-
Q Wave:
- First negative deflection after the P wave.
- Short and narrow, often absent in several leads.
- Wide, deep Q waves can signify a myocardial infarction (MI).
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R Wave:
- First positive deflection within the QRS.
-
S Wave:
- First negative deflection after the R wave.
-
QRS Interval:
- Duration from the beginning to end of the QRS complex.
- Represents ventricular depolarization (contraction).
- Normal duration: less than 0.12 seconds.
- Variations may indicate conduction problems in the bundle branches or ventricles.
-
QT Interval:
- Measured from the beginning of the QRS to the end of the T wave.
- Represents the time for both ventricular depolarization and repolarization.
- Normal duration: 0.34-0.43 seconds.
- Variations can be caused by issues affecting repolarization, such as drugs, electrolyte imbalances, and changes in heart rate.
T Wave and U Wave
-
T Wave:
- Represents ventricular repolarization.
- Usually the first positive deflection following the QRS complex.
- Normal duration: 0.16 seconds.
- Variations may be caused by fluid or electrolyte imbalances, ischemia, or infarction.
-
U Wave:
- Not always visible on EKG strips.
- Smaller than the T wave, rounded, and upright.
- Can indicate hypokalemia (low potassium levels).
Normal Sinus Rhythm (NSR)
- Regular rhythm set by the sinoatrial node (SA node).
- All components of the EKG are normal.
Sinus Bradycardia
- Regular rhythm but slow heart rate (less than 60 BPM).
- May be normal for athletes, during sleep, or in response to a vagal maneuver.
- Causes: Hypoglycemia, hypothermia, hypothyroidism, medications, MI, sick sinus syndrome.
- Symptoms: Syncope (passing out), dizziness, shortness of breath (SOB), cool, clammy skin.
- Treatment: May involve stopping medications, holding or reducing dosages, or administration of IV atropine (anticholinergic).
Sinus Tachycardia
- Heart rate faster than 100 BPM due to rapid SA node firing.
- Requires further investigation to determine if normal for the individual.
- High heart rate correlates with high respiratory rate.
- May present with palpitations.
- Causes: Heart disease, hypertension, hyperthyroidism, fever, stress, alcohol, caffeine, nicotine, drugs, medication side effects, pain, electrolyte imbalances (potassium).
- Symptoms: Dizziness, SOB, lightheadedness, palpitations, chest pain, syncope.
- Treatment: Vagal maneuvers initially, followed by IV beta blockers (metoprolol), adenosine, or calcium channel blockers (diltiazem).
Atrial Arrhythmias
- Occur when the SA node fails to generate an impulse, resulting in other atrial tissue or internodal pathways initiating an impulse.
- Four most common types: atrial flutter, atrial fibrillation, supraventricular tachycardia, and premature atrial complexes.
Atrial Fibrillation (A-Fib)
- Uncoordinated electrical signal circles through the atria, causing quivering (400+ BPM) without effective contraction.
- Ventricles receive irregular impulses, resulting in an uncontrolled and irregular heartbeat (tachycardia).
- Decreased cardiac output (CO) due to ineffective atrial contractions ("loss of atrial kick") and/or a rapid ventricular response.
- Blood stasis can lead to thrombi forming in the atria.
- Embolized clots can travel to the brain, causing stroke.
- Patients are usually on blood thinners.
- Causes: Heart failure, COPD, pericarditis, heart disease, stress, high alcohol or caffeine consumption.
- Symptoms: Palpitations, irregular pulse, dizziness, fainting, fatigue, confusion, trouble breathing (especially while lying down), chest tightness.
- Treatment: Rate control to lower the ventricular rate to 80-100 BPM. Options include Digoxin, beta blockers, calcium channel blockers (verapamil IV for rapid rate control), antithrombotic therapy, chemical or electrical cardioversion.
Atrial Flutter (A-Flutter)
- Coordinated, but rapid beating of the atria.
- Identified by recurring, regular, sawtooth-shaped "flutter waves."
- Atria beat faster than the ventricles (often a 4:1 ratio of flutter waves to QRS complexes).
- Atrial rate can reach 350-600 BPM.
- Causes: Heart failure, pulmonary embolism, MI, digoxin toxicity, coronary artery disease (CAD), valve problems, drugs, hyperthyroidism, cor pulmonale, hypertension.
- Symptoms: Palpitations, SOB, anxiety, weakness, angina, syncope.
- Treatment: Cardioversion, antiarrhythmics (procainamide, diltiazem, verapamil, digitalis, or beta blockers) to slow the ventricular rate, heparin to reduce thrombus formation.
Ventricular Arrhythmias
- Occur when the ventricles take over as the pacemaker, often due to an ectopic focus.
- Can cause sudden and severe rhythm disturbances with a high risk of death if not quickly addressed.
- Examples: Ventricular tachycardia (VT), Ventricular fibrillation (VF), Torsades de Pointes.
- All require prompt and aggressive medical intervention.
Premature Ventricular Contractions (PVCs)
- Contraction originating from an ectopic focus in the ventricles.
- Results in a premature (early) QRS complex, appearing wide and distorted.
-
Possible types:
- Unifocal PVC: Same shape, originating from a single focus.
- Multifocal PVC: Arise from different foci, resulting in varying shapes.
- Ventricular Trigeminy: Every other beat is a PVC.
- Couplet: Two consecutive PVCs.
- Causes: Stimulants (caffeine, alcohol, nicotine, epinephrine, isoproterenol), electrolyte imbalances, heart disease, hypoxia (low oxygen), fever, exercise, emotional stress.
- Treatment: Assess the patient's hemodynamic status to determine if drug therapy is necessary. Options include beta blockers, lidocaine, or amiodarone
Accelerated Idioventricular Rhythm (AIVR)
- Ventricles attempt to maintain rhythm after SA and AV node failure.
- No P waves.
- Rate: 40-100 beats per minute.
- Cardiac output is often compromised.
- Amiodarone should not be used.
- Causes: Drugs, MI, metabolic imbalances, hyperkalemia, cardiomyopathy.
- Symptoms: Pale, cool skin, weakness, dizziness, hypotension, mental status changes.
- Treatment: Often tolerated well without specific treatment. If symptomatic (hypotension, chest pain), atropine is an option. Temporary pacing may be required.
Ventricular Tachycardia (VT)
- Run of 3 or more PVCs.
- Ventricles take control as the pacemaker due to repeated firing from an ectopic focus.
- Life-threatening due to decreased CO and potential progression to VF, which is lethal.
-
Types:
- Monomorphic VT: QRS complexes have the same shape, size, and direction.
- Polymorphic VT: QRS complexes gradually change shape, size, and direction with each beat.
- Torsades de Pointes (TdP): Polymorphic VT with a prolonged QT interval, associated with sudden upward and downward deflections of QRS complexes.
- Causes: Underlying heart disease, MI, medications (QT prolonging drugs), electrolyte imbalances, digitalis toxicity, CHF.
- Symptoms: Angina, syncope, lightheadedness/dizziness, palpitations, SOB, absent or rapid pulse, loss of consciousness, hypotension
- Treatment: If no pulse, initiate CPR. If pulse is present and patient is unstable, cardiovert and start drug therapy (amiodarone, lidocaine, antiarrhythmics). Ablation and long-term Implantable Cardioverter-Defibrillator (ICD) may be necessary.
Ventricular Fibrillation (VF)
- Severe heart rhythm disturbance.
- Characterized by irregular waves of varying shape and amplitude on EKG.
- Multiple ectopic foci fire in the ventricle, causing quivering with no effective contraction.
- No cardiac output occurs.
- Lethal dysrhythmia requiring immediate intervention.
- Causes: AMI, untreated VT, electrolyte imbalance, hypothermia, myocardial ischemia, drug toxicity, trauma.
- Symptoms: Loss of consciousness, absent pulse.
- Treatment: CPR with immediate defibrillation.
Asystole
- Absence of ventricular electrical activity.
- P waves may be seen occasionally.
- No ventricular contraction occurs (no depolarization).
- Lethal dysrhythmia requiring immediate treatment.
- Symptoms: Unresponsiveness, pulseless, apneic.
- Assessment: Always assess rhythm in multiple leads.
- Causes: End-stage heart disease, severe conduction system problem, end-stage heart failure.
- Treatment: CPR, epinephrine, and intubation. Correction of the underlying cause is crucial.
Pulseless Electrical Activity (PEA)
- Organized electrical activity present on the EKG, but no mechanical heart activity or pulse.
- Common dysrhythmia seen after defibrillation.
- Poor prognosis unless underlying cause is quickly identified and treated.
- Causes: Hypovolemia (low blood volume), hypoxia (low oxygen), metabolic acidosis, hyperkalemia, hypokalemia, hypoglycemia, hypothermia, toxins, cardiac tamponade, thrombosis, tension pneumothorax, trauma.
- Treatment: CPR, epinephrine, intubation. Correction of the underlying cause is critical.
Infective Endocarditis (IE)
- Infection of the endocardium (innermost heart layer) and heart valves.
- Associated with poor prognosis and reduced life expectancy.
- Increasing prevalence linked to increased IV drug use.
- Subacute form: Affects those with preexisting valvular disease.
- Acute form: Affects those with healthy valves.
- Most common causes: Staphylococcus aureus and Streptococcus viridans.
- Risk Factors: History of valve or heart problems (rheumatic heart disease, congenital heart disease, Marfan's syndrome), open wounds, abscesses, procedures, infected needles, prosthetic valves, prior history.
-
Stages:
- Bacteremia: Bacteria enters the bloodstream.
- Adhesion: Bacteria adheres to the valve endothelium.
- Vegetation: Masses of bacteria, fibrin, and platelets form on heart valves or endocardium, prone to embolization.
- Left-sided vegetation: Emboli can travel to the brain, kidneys, spleen, and extremities.
- Right-sided vegetation: Emboli can travel to the lungs (pulmonary embolism - PE).
- Complications: Heart failure, dysrhythmias, kidney problems, night sweats, SOB.
Clinical Manifestations of IE
- Chills
- Roth spots (on the eye)
- Malaise
- Fatigue
- Anorexia
- Splinter hemorrhages (under fingernails)
- Petechiae
- Osler's nodes (tender purple/pink nodules on fingers and/or toes)
- Janeway's lesions (painless, small, flat hemorrhages on the palms or soles)
- Fever
Diagnostic Studies for IE
- 2-3 blood cultures within 1 hour, collected from different sites.
- ESR, C-reactive protein, CBC
- Echocardiogram (echo) to visualize vegetation
Diagnosis of IE
- Requires either:
- Two major criteria and one minor criterion.
- One major criterion and three minor criteria.
- Five minor criteria.
-
Major Criteria:
- Positive blood culture.
- New valvular vegetation.
-
Minor Criteria:
- Predisposing heart condition (rheumatic heart disease) or IV drug use.
Treatment for IE
- IV antibiotics for 4-8 weeks (inpatient) after identifying the causative organism and selecting the appropriate antibiotic (usually vancomycin or penicillin).
- Repeat blood cultures every 24-48 hours until infection clears.
- Echo and inflammatory markers (blood work) at 1, 3, 6, and 12 months after antibiotic completion.
- Valve replacement may be required.
Patient Teaching for IE
- Avoid contact with people who have infections.
- Avoid stress and fatigue, plan rest periods.
- Regular dental visits.
- Importance of completing antibiotic regimen.
- Drug rehabilitation (if necessary)
Monitoring Instructions for Patients with IE
- Monitor body temperature (alternate Tylenol and ibuprofen for fever).
- Be aware of potential complications.
- Understand the nature of the disease and how to prevent reinfection.
- Stress follow-up care, good nutrition, and prompt treatment of common infections.
- Assess home setting and coping strategies.
- Assess IV lines (patient should not leave with an IV).
- Encourage compression stockings.
- Instruct on deep breathing and coughing every 2 hours.
EKG Components and Significance
- P Wave: Atrial depolarization (contraction). Problems with the P wave indicate swelling of the atria.
- QRS Complex: Depolarization of ventricles and atrial repolarization. Prolonged QRS interval suggests ventricular conduction delay.
- T Wave: Ventricular repolarization. Inverted T waves often occur after myocardial damage.
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Description
Test your knowledge on the fundamentals of ECG interpretation, including heart rate calculations, rhythm analysis, and wave identification. This quiz covers key components such as P waves, PR intervals, and QRS complexes essential for understanding cardiac function.
