Conclusion
Differentiating causes of narrow complex tachycardia can be challenging.
Evaluation usually involves two primary components: assessment of the
patient for symptoms and signs of hemodynamic stability (or
instability), and assessment of the patient’s ECG for clues to the type
of tachycardia present. Observation of the warmup or cool down
phenomenon on ECG can help clinicians correctly identify the cause of
narrow complex tachycardia when the arrhythmia is difficult to define.