Inappropriate Sinus Tachycardia Mistaken for Relapse of Reentrant Supraventricular Tachycardia in a Young Woman Treated Successfully with Ivabradine

Introduction: Inappropriate Sinus Tachycardia (IST), first described in 1979, is a fast heart rhythm arising from the sinus node, the normal primary pacemaker of the heart but at an inappropriately high rate.Many treatments have been suggested for patients with IST; β-adrenergic blockers, even at high doses, generally are ineffective and tend to be associated with other symptoms.Small studies and several case reports have demonstrated the potential value of Ivabradine, the first selective sinus node If channel inhibitor, to treat IST. Case Report:We present a case of a young woman of 22 years old, treated with Ivabradine 5 mg twice a day.The patient presents episodes of tachycardia compatible with an Atrioventricular Nodal Reentry Tachycardia (AVNRT), with a maximum heart rate of 210 bpm.Many treatments were started without results.Two catheter ablations, (thermal and cryoablation) were performed.The second ablation has a good result, but one year ago, the tachycardia episodes reappeared and because the symptoms were very similar to those previously had before ablation procedure, even without seeing the ECG nodal reentrant tachycardia a new electrophysiological study was performed.With surprise, the study did not show a double nodal curve.So treatment with Ivabradine was started with a complete resolution of symptoms.The drug was effective on heart rate but it does not affect blood pressure.The control Holter monitoring shows a normal trend of heart rate with only a few episodes of sinus tachycardia during effort and no episodes at rest. Conclusion:In conclusion the last Holter monitoring does not match IST diagnosis criteria.The quality of life of the patient improved significantly.The drug as in literature reports is effective, safe and well tolerated.The patient wishes to continue the drug after one year of treatment.