Inappropriate
sinus tachycardia (IST) is characterized by
paroxysmal tachycardia originating in the sinus nodal area. IST predominately affects young, female patients. Current
antiarrhythmic drug treatment (ß-blockers,
calcium antagonists), frequently complicated by side effects, is often not successful.
Ivabradine, approved for
angina pectoris, selectively reduces heart rate by blocking the "funny current" in the sinus node. We therefore evaluated the effect of
ivabradine in patients with symptomatic IST. Ten female patients (median age 32.5 years, range 12-57) suffering from symptomatic IST who had either failed (n = 8) or refused (n = 2) conventional
therapy were analyzed. Symptoms included palpitations, pre-
syncope,
syncope,
dyspnea, and exercise intolerance. After obtaining informed consent for individual off-label
therapy, patients were treated with
ivabradine (5-7.5 mg bid) in addition to beta-blocker
therapy (n = 3) or as mono-
therapy (n = 7).
Therapy was monitored by 72-h Holter ECG and a symptoms questionnaire.
Ivabradine significantly reduced maximum and mean heart rate (baseline, maximal heart rate 176 ± 45/min, mean heart rate 84 ± 11/min;
ivabradine, maximal heart rate 137 ± 36/min, mean HR 74 ± 8/min, both p < 0.05, all values as mean ± SD). Minimum heart rate was not significantly changed. Three patients reported transient phosphene-like phenomena without discontinuation of
ivabradine while on
therapy. IST-associated symptoms were ameliorated (3 pts) or suppressed (5 pts) in all eight patients who could be contacted after a mean follow-up of 16 ± 9 months.
Ivabradine appears effective and safe in patients with symptomatic inappropriate
sinus tachycardia.