T Wave on ECG: Repolarisation of the Ventricles

Introduction

The T wave is a distinct deflection on the ECG tracing that follows the QRS complex. Understanding its characteristics and significance is essential for interpreting cardiac activity.

T Wave: Repolarisation of the Ventricles

The T wave represents the repolarisation of the ventricles:

• Nature and Height: The T wave is typically higher than the P wave and represents the electrical re-polarisation of the ventricles.
• Time for Re-Polarisation: After ventricular depolarisation, the electrical sites in the ventricles require time to re-polarise before the next heartbeat.
• Mechanical Indication: In the heart, the T wave coincides with ventricular filling during diastole.

Characteristics and Interpretation

Observations and interpretations of the T wave:

• Shape: The T wave should be rounded in appearance.
• Spiky or Pointed T Wave: A T wave that is spiky, excessively tall, or pointed may indicate issues with potassium levels in the heart or other cardiac abnormalities.
• Inverted T Wave: An inverted T wave, where the wave goes below the isoelectric line, can be a sign of a heart attack, previous cardiac damage, muscle abnormalities, or incorrect lead placement.
• U Wave: In some cases, a small bump following the T wave called the U wave may be observed. It is concordant with the T wave and can be more visible in slower heart rates. An abnormal U wave may indicate arrhythmias.

Considerations and Evaluation

Key considerations for interpreting the T wave:

• Lead Placement: Check lead placement if an inverted T wave is observed.
• Patient History: Assess the patient's cardiac history and presenting symptoms to contextualise the findings.
• U Wave: Not all ECGs will display a U wave, and its presence or absence should be evaluated in the context of the patient's overall cardiac activity.

Conclusion

The T wave on an ECG signifies the repolarisation of the ventricles. Understanding its characteristics and variations is crucial for accurate interpretation and identification of potential cardiac abnormalities.