Introduction

An electrocardiogram (ECG or EKG) is a non-invasive tool that records the heart’s electrical activity. It is essential for diagnosing various cardiac conditions like arrhythmias, ischaemia, myocardial infarction, and electrolyte imbalances. Understanding ECGs is vital for identifying drug-related cardiac issues and collaborating effectively in multidisciplinary healthcare settings.

Basics of ECG Interpretation

Components of an ECG

1. P wave: Represents atrial depolarisation (electrical activation of the atria).
2. QRS complex: Represents ventricular depolarisation (electrical activation of the ventricles).
3. T wave: Represents ventricular repolarisation (recovery phase of the ventricles).
4. PR interval: The time between the start of the P wave and the start of the QRS complex, indicating impulse travel time from atria to ventricles.
5. ST segment: The flat line between the end of the QRS complex and the start of the T wave.

ECG Leads

The 12-lead ECG provides a detailed view of the heart’s electrical activity:

• Limb Leads: I, II, III, aVR, aVL, and aVF.
• Chest Leads: V1, V2, V3, V4, V5, and V6.

Common ECG Abnormalities

1. Ischaemia

Occurs when the heart muscle receives insufficient blood flow, often due to coronary artery disease.

• Key ECG Signs:
  • ST Segment Depression: Downward shift of the ST segment, indicating reduced oxygen supply.
  • T Wave Inversion: Flipped T wave, another indicator of ischaemia.

2. Arrhythmias

Abnormal heart rhythms, which may be too fast, slow, or irregular.

• Common Arrhythmias:
  • Atrial Fibrillation (AFib):
    • Irregular and rapid atrial activity.
    • ECG shows no distinct P waves with an irregularly irregular rhythm.
  • Atrial Flutter:
    • Rapid, regular atrial activity.
    • ECG shows a “sawtooth” pattern.
  • Premature Ventricular Contractions (PVCs):
    • Early ventricular beats appearing as wide QRS complexes.

3. Electrolyte Disturbances

Imbalances in potassium, calcium, and magnesium can alter the heart’s electrical activity.

• Hyperkalemia (High Potassium):
  • Tall, peaked T waves.
  • Widened QRS complex.
• Hypokalemia (Low Potassium):
  • Flattened T waves.
  • Prominent U waves.
• Hypercalcaemia (High Calcium):
  • Shortened QT interval.
• Hypocalcaemia (Low Calcium):
  • Prolonged QT interval.

Why ECG Interpretation Matters for Pharmacy Students

• Drug-Related Cardiac Issues:
  • Medications like antiarrhythmics, antipsychotics, and antibiotics can affect QT intervals and predispose patients to arrhythmias.
• Interprofessional Collaboration:
  • Recognising ECG changes helps pharmacists work with cardiologists and other healthcare professionals to optimise patient care.
• Patient Safety:
  • Early detection of ECG abnormalities can prevent adverse outcomes related to drug therapy or underlying conditions.

Conclusion

Mastering ECG interpretation will equip you with essential knowledge to recognise cardiac abnormalities such as ischaemia, arrhythmias, and electrolyte disturbances. This skill enhances your ability to manage medication-related issues and collaborate effectively within the healthcare team.

References

1. Mayo Clinic. “Electrocardiogram (EKG/ECG): What to Expect.”
2. Cleveland Clinic. “Electrocardiogram (EKG/ECG).”
3. British Heart Foundation. “ECG (Electrocardiogram).”
4. NHS Inform. “Electrocardiogram (ECG).”