We present the case of a 49-year-old woman with atrioventricular nodal re-entrant tachycardia and a severe pectus excavatum. The patient underwent an electrophysiological study and fast pathway ablation. Fast pathway ablation was not done on purpose but accidentally, likely due to the abnormal position of the heart in the chest cavity in this patient suffering from severe pectus excavatum. Some hours after the ablation, the patient developed inappropriate sinus tachycardia (IST), complaining of dyspnea and fatigue. IST has been described as a complication of fast pathway ablation in 10% of the cases. In our case it was not possible to treat IST with beta-blockers due to an important lowering of the blood pressure. Digitalis, given as second choice, was not successful. Ivabradine-the specific sinus node If current inhibitors-was used to successfully lower the heart rate with immediate relief of symptoms. A 24-hour Holter, 10 days later, showed a complete control of the heart rate without any episode of IST. The patient was completely symptom free and able to undertake her normal daily activities without any discomfort. Our case confirms the potential use of ivabradine for indications other than coronary artery disease.