Abstract
A 63-year-old male patient with a history of hypertension, diabetes mellitus type 2, prostate cancer and class two obesity was admitted for encephalopathy. During his hospital stay he developed narrow complex tachycardia and it was difficult to definitively diagnose the underlying arrhythmia. Observation of the cool down phenomenon on telemetry strip allowed us to make the diagnosis of atrial tachycardia and elegantly rule out other causes. We report this interesting case of narrow complex tachycardia.