We present the case of a 67-year-old woman with cardiomyopathy induced by inappropriate sinus tachycardia (IST) and a particularly high average heart rate. The patient was resistant and/or intolerant to treatment with conventional rate-slowing medications. We used ivabradine—a specific sinus node If current inhibitor—and successfully lowered the heart rate (33 beats per minute mean heart rate decrease). Symptoms, systolic function, and heart rate variability parameters recovered dramatically. No side effect was noted. We suggest that ivabradine—evaluated in trials to treat stable angina—should be considered as a second-line treatment in patients with very symptomatic and refractory IST.