chapter 25

Overview of EKG (Electrocardiogram) Interpretation

  • Introduction to EKG: necessity of understanding EKG readings for clinical practice.

  • Importance of recognizing different components of an EKG strip: P wave, QRS complex, T wave, and their meanings.

Components of an EKG

P Wave

  • Definition: Represents atrial depolarization.

  • Function: Indicates contraction of the atria.

  • Characteristics: Should be upright in certain leads (e.g., Lead II, Lead III).

  • Expected relationship with QRS: Must precede the QRS complex and be in close proximity, signaling effective conduction (no significant delay is desired).

QRS Complex

  • Definition: Represents ventricular depolarization.

  • Function: Indicates contraction of the ventricles.

  • Characteristics: Should follow the P wave closely.

  • Width considerations: Important to learn boundaries, which are detailed in telemetry courses.

T Wave

  • Definition: Represents ventricular repolarization.

  • Function: Signals the resting phase of the ventricles.

  • Characteristics: Should also be upright, indicating normal repolarization.

  • Implications of abnormalities:

    • Peaked T waves may indicate hyperkalemia (high potassium).

    • Depressed T waves can suggest ischemia.

EKG Rhythm Analysis

Isoelectric Line

  • Definition: A neutral line on the EKG strip where no electrical activity is measured.

  • Importance: Serves as a reference point to identify positive or negative deflections in the EKG.

Heart Rate Analysis

  • Normal sinus rhythm is defined as a heart rate between 60 and 100 beats per minute (bpm) with:

    • A P wave before each QRS complex.

    • A T wave present following each QRS complex.

  • Tachycardia: Identifying an increase in heart rate (>100 bpm) while still maintaining a P wave and T wave leads to classifying the rhythm as sinus tachycardia.

  • Bradycardia: Identifying a decrease in heart rate (<60 bpm) with corresponding P wave and T wave indicates sinus bradycardia.

Pulse Assessment

  • Regularity of pulse as an indicator of electrical conduction.

  • Importance of assessing radial pulse while interpreting telemetry data.

  • Symptoms associated with bradycardia: low blood pressure, fainting, syncope, and potential for shock.

Additional EKG Concepts

PR Interval and QT Interval

  • PR Interval: The time duration from the beginning of the P wave to the beginning of the QRS complex.

  • QT Interval: The time taken for the ventricles to depolarize and repolarize; should be measured carefully as prolonged QT can lead to fatal arrhythmias.

Arrhythmias and Dysrhythmias

  • Arrhythmia: Absence of rhythm (a- signifies without); refers to any irregular heart rhythm.

  • Dysrhythmia: Indicates a disturbance in rhythm, often interchangeable with arrhythmia in clinical language.

Premature Atrial Contraction (PAC)

  • Definition: An extra heartbeat originating from the atria.

  • Causes: Stress, caffeine intake, electrolyte imbalances, or may be idiopathic.

  • Significance: Can be harmless or signify underlying issues if frequent.

Atrial Flutter and Atrial Fibrillation

  • Atrial Flutter:

    • Pathophysiology: Characterized by repetitive firing of the atria, leading to sawtooth patterns on an EKG.

    • Management: Same rhythm assessment as sinus, may treat with medications (beta-blockers).

  • Atrial Fibrillation:

    • Definition: Irregular and chaotic atrial activity; characterized by lack of discernible P waves.

    • Clinical implications: Increases risk of thrombus formation and requires anticoagulation (e.g., Eliquis).

    • Medication management includes anticoagulants and potential cardioversion if unstable.

Medications in EKG Management

Atropine

  • Usage: Increases heart rate, primarily used for symptomatic bradycardia.

  • Recommended dosage: Standard initial dose of 1 mg; consider 0.5 mg for patients with pulses.

  • Mechanism: Anticholinergic agent that increases heart rate by inhibiting parasympathetic effects.

Adenosine

  • Usage: Treats paroxysmal supraventricular tachycardia (SVT).

  • Mechanism: Temporarily blocks conduction through the AV node, potentially converting the tachycardia back to normal sinus rhythm.

Cardioversion vs. Defibrillation

  • Cardioversion: Synchronized shock delivered during the QRS complex phase to restore normal rhythm (used in patients with a pulse).

  • Defibrillation: Immediate shock applied to terminate ventricular fibrillation or pulseless ventricular tachycardia (no pulse present).

Implanted Cardiac Devices

  • Definition: Devices such as pacemakers can be assessed through telemetry.

  • Pulseless Electrical Activity (PEA): Electrical conduction seen, but no mechanical contractions resulting in no pulse; CPR is initiated.

Diagnostic Assessment

  • Final assessment of an EKG must include:

    • Consistent mapping of heartbeats.

    • Monitoring rate, rhythm, and presence of PQRST waves.

    • Identifying signs of ischemia or infarction based on ST segment changes.

Conclusion

  • Continuous learning and assessments are vital in interpreting EKGs effectively for better patient outcomes in real clinical settings.