Dysrhythmias and EKG Rhythm Strips Study Notes

Module Overview

  • Course: NURS 486
  • Date: February 6, 2026

Learning Objectives

  • By the end of this session, students will be able to:
    • Identify reasons for the use of 12-lead EKGs in patient care.
    • Describe the significance of the location of the various 12 leads when analyzing findings or reports.
    • Using rhythm strips, determine the following waves and intervals:
    • P wave
    • PR interval
    • QRS complex
    • ST segment
    • T wave
    • Use rhythm strips to determine:
    • Electrical heart rate
    • Rhythm
    • Nursing and medical interventions for:
      • Normal sinus rhythm
      • Tachycardia
      • Bradycardia
      • Atrial fibrillation and atrial flutter
      • Premature ventricular complexes
      • Ventricular tachycardia
      • Ventricular fibrillation
      • PEA arrest

What is an EKG?

  • EKG (Electrocardiogram, also ECG) is a test that records the electrical activity of the heart over time using electrodes placed on the skin.

The Heart’s Electrical System

  • The heart generates electrical impulses that stimulate contraction to pump blood.

Electrode Placement

  • Electrodes (stickers with conductive gel) are placed on specific points of the chest and limbs.
  • They detect tiny electrical changes occurring in the skin due to the heart muscle’s depolarization and repolarization.

Recording Electrical Activity

  • An EKG machine amplifies these electrical signals, recording them as waves on paper or a screen.
  • Each lead (view) showcases the heart’s electrical activity from a different angle.

Importance of a 12-Lead EKG

  • A 12-lead EKG provides insights into the heart's electrical activity from 12 different viewpoints.
  • EKG assists healthcare providers in:
    • Checking heart rate and rhythm.
    • Identifying arrhythmias (abnormal rhythms).
    • Detecting ischemia or infarction (lack of blood flow or heart attack).
    • Evaluating electrolyte imbalances or conduction abnormalities.
    • Monitoring effects of specific medications.

Cardiac Conduction

Key anatomical landmarks for lead placement:

  • Midclavicular line
  • Anterior Axillary line
  • Misternum
  • Trachea
  • Thyroid cartilage
  • First Rib
  • Midaxillary line
  • Posterior Axillary line
  • Suprasternal notch
  • Angle of Louis

Lead Placement

  • Standard Leads:
    • RA- (Right Arm)
    • LA (Left Arm)
    • LL (Left Leg)
    • RL (Right Leg)
    • C (Chest)

Components of the Cardiac Cycle

  • Waves and Segments:
    • P-wave: Atrial depolarization (contraction)
    • Small, upright, rounded shape.
    • PR Interval: Time from onset of atrial depolarization to onset of ventricular depolarization.
    • Signal delay at the AV node returning to the isoelectric line.
    • QRS Complex: Ventricular depolarization (contraction)
    • Characterized by tall, peaked waves.
    • ST Segment: Time from end of ventricular depolarization to beginning of repolarization.
    • Isoelectric when it joins QRS at baseline.
    • T-wave: Ventricular repolarization (resting state)
    • Typically upright.
    • U-wave: Sometimes visible with hypokalemia; positive deflection after T wave.
    • QT interval: Duration from ventricular depolarization to end of repolarization.
    • Heart rate specific.

EKG Paper and Heart Rate Calculation

Key Facts:

  • A typical EKG strip has:
    • 300 big boxes per minute.
    • Each big box = 0.2 seconds, hence: 300imes0.2=60300 imes 0.2 = 60 seconds.
    • 1500 little boxes per minute (each little box = 0.04 seconds).
    • 30 big boxes = 6 seconds.
Calculating Heart Rate:
  1. Count big boxes between QRS complexes and divide by 300 (for regular rhythm).
  2. Count little boxes between QRS complexes and divide by 1500 (for regular rhythm).
  3. For instance, if 20 little boxes between beats: 150020=75\frac{1500}{20} = 75 bpm.
  4. Hash marks on the strip generally denote a 3-second interval (15 big boxes).

Amplitude:

  • 1 big box = 0.1 millivolts (mV)
  • 5 big boxes = 0.5 mV

Rhythm Analysis Steps

  1. Regularity: Check if QRS complexes appear at regular intervals.
    • Use a blank piece of paper to mark above three successive R waves and slide along the rhythm strip.
    • If the marks do not match, the rhythm may be irregular.
  2. Identify P-waves:
    • Check for presence of P waves, their regularity, morphology, and whether there is a P wave before each QRS complex.
  3. QRS Duration:
    • Typically less than 0.120.12 seconds.
    • Prolonged QRS may indicate bundle branch block or ventricular dysrhythmia (widened QRS).
  4. PR Interval:
    • Measured from onset of P wave to onset of QRS complex.
    • Normal interval = 0.12−0.200.12-0.20 seconds (3-5 small squares).

Case Study Overview

Richard Thompson

  • Age: 68, Sex: Male
  • Medical History:
    • Coronary artery disease
    • Hypertension
    • Hyperlipidemia
    • Bilateral Knee Osteoarthritis
  • Surgical History: Elective right total knee replacement one day ago.
  • Current Medications:
    • Aspirin 81 mg PO daily
    • Atorvastatin 40 mg PO nightly
    • Metoprolol 50 mg PO BID
    • Lisinopril 10 mg PO daily
    • Acetaminophen 500 mg PRN for pain
Baseline Assessment:
  • Mental Status: Alert and oriented x3; mild surgical pain (3/10).
  • Vital Signs:
    • Temperature: 98.6°F (37°C)
    • Heart Rate: 82 bpm, normal sinus rhythm
    • Blood Pressure: 136/78 mmHg
    • Respiratory Rate: 18/min
    • Oxygen Saturation: 95% on room air
  • Cardiac Monitor: NSR
  • Physical Examination: Right knee incision with OR dressing.
Lab Results:
  • Sodium (Na+): 135 mEq/L (Normal: 135-145)
  • Potassium (K+): 3.0 mEq/L (Normal: 3.5-5.0)
  • Chloride (Cl-): 102 mEq/L (Normal: 98-106)
  • CO2 (HCO3-): 24 mEq/L (Normal: 22-28)
  • Blood Urea Nitrogen (BUN): 21 mg/dL (Normal: 8-20)
  • Creatinine: 1.1 mg/dL (Normal: 0.6-1.3)
  • Glucose: 112 mg/dL (Normal: 70-110 fasting)

Interventions and Management Strategies

When Patient Experiences "Fluttering" and Lightheadedness:

  • Priority Actions:
    • Evaluate patient's current rhythm and rate.
    • Identify if there is any artifact on the EKG monitor.
    • Use SBAR (Situation, Background, Assessment, Recommendation) to communicate patient status effectively.

After Administering Potassium and Magnesium:

  • Considerations when giving K+ IV: Never give undiluted intravenous potassium. Monitor for signs of hyperkalemia and hypokalemia.
  • If patient complains of dizziness after disconnecting from the monitor, be ready to prioritize actions such as reconnecting to telemetry, assessing vitals, and determining rhythm status.

Monitoring for Cardiac Arrest Reasons

The 6 H's and T's (Causes of Cardiac Arrest):

  1. Hypovolemia:
    • Loss of fluid volume leading to inadequate circulation.
    • Interventions include obtaining IV access and administering IV fluids (fluid challenge).
  2. Hypoxia:
    • Inadequate oxygen supply contributing to cardiac arrest.
    • Ensure open airway, adequate ventilation, and proper oxygenation.
  3. Hydrogen Ion (Acidosis):
    • Assess through arterial blood gas testing. Administer sodium bicarbonate if necessary.
  4. Hypo/Hyperkalemia:
    • Both can cause cardiac arrest. Monitor for signs:
      • High K+: taller, peaked T-waves, widening of QRS complex.
      • Low K+: flattened T-waves, prominent U-waves, widened QRS complex.
  5. Hypothermia:
    • Warm the patient, raise core temperature above 86°F and 30°C.
  6. Toxins:
    • Accidental overdose (tricyclics, digoxin, etc.). Use poison control as needed.
  7. Tamponade:
    • Fluid in pericardium causing ineffective pumping.
    • Symptoms include JVD, difficulty detecting pulse, muffled heart sounds. Pericardiocentesis may be necessary.
  8. Tension Pneumothorax:
    • Compression of thoracic structures leading to cardiovascular collapse.
    • Signs are JVD, unequal breath sounds. Needle decompression is the treatment.
  9. Thrombosis (Heart):
    • Acute myocardial infarction evidenced by ST-segment changes.
    • Treatments might include PCI or fibrinolytic therapy.
  10. Thrombosis (Lungs):
    • Massive pulmonary embolism. Signs include distended neck veins and positive D-dimer tests. Treatments might involve surgical intervention.

Critical EKG and Clinical Judgment Questions

NCLEX-style questions:

  1. Recognize cues related to atrial fibrillation (select all that apply).
  2. Analyze telemetry strip and interpret heart rhythm with provided data.
  3. Prioritize the immediate intervention for a dangerous dysrhythmia.
  4. Identify priority action when encountering a pulseless, unresponsive patient with chaotic rhythm.
  5. Recommend appropriate nursing actions for patients with atrial fibrillation.
  6. Evaluate effective treatment outcomes after administering medications.

Conclusion

  • Understanding EKG rhythms, interpretations, and clinical implications is crucial in providing effective patient care in cardiac emergencies.