A 69-year-old woman with a five year history of occasional episodes of rapid palpitation, starting and ending abruptly, lasting from minutes to one hour, and accompanied by neck pulsations, weakness and dyspnea, presents to Emergency Department two hours after onset of a prolonged episode of palpitations:

• Supraventricular tachycardia, 156/min.
• AV Nodal Re-entrant Tachycardia (AVNRT)
• ST and T wave abnormality, consider inferior and anterolateral ischemia

Narrow QRS tachycardia with clinical and ECG features typical of AV nodal reentrant tachycardia:

• Abrupt onset and termination
• Rate 156/min
• P waves closely following the QRS complex, inverted in II, III and aVF, positive in aVR, aVL and V1 (pseudo-R’)

Notice ST depression and T wave inversion in the inferior and antero-lateral leads. This abnormality is often seen during and shortly after episodes of tachyarrhythmia, even in subjects with normal coronary arteries and in absence of structural heart disease.

The patient received a dose of IV adenosine, with prompt conversion to sinus rhythm and improvement of her symptoms: 

There is now normal sinus rhythm with first degree AV block (PR=220 ms).
The ST depression in the inferior and antero-lateral leads is no longer present.

The T wave abnormality has improved: flat or low-voltage, instead of inverted T (“non-specific T wave abnormality”).