ECG-Tachycardia in young female ??What is your diagnosis

A 38 year old female resident of Pondicherry, India came with chief complaints of palpitation on and off since last one year. Last episode of palpitation occur 15 days back, which were acute in onset, associated with atypical chest pain but there was no  associated nausea, vomiting, giddiness or syncope, it was of one hour duration following which patient was admitted in private hospital, diagnosed to have abnormal rhythm during ecg evaluation. Tachycardia of patient was rellived by intravenous adenosine 6 mg. Patient was referred to JIPMER hospital, Pondicherry, India for electrophysiology study and further management.

ECG 1(Click on the image to enlarge it)

Description of the ECG-Narrow QRS complex, regular tachycardia with heart rate around 210 beats per minute, Negative P wave seen in lead II, III, avF, with Pseudo R wave seen in lead V1, RP interval 60 msec, PR interval 280 msec, no significant ST-T wave changes seen, normal axis. So the ecg is suggestive of Short RP narrow complex regular tachycardia suggestive of paroxysmal supraventricular tachycardia.

ECG after giving injection Adenosine 

Normal sinus rhythm at 100 beats per minute, normal axis, no pre-excitation seen, no ST-T wave changes seen.

So on the basis of these two ecg the diagnosis of this patient is Paroxysmal supraventricular tachycardia (PSVT),most likely AVNRT. Let discuss how to approach in a patient with narrow complex regular tachycardia.

Thank you.