COMPARISON OF IVABRADINE AND BISOPROLOL IN THE TREATMENT OF INAPPROPRIATE SINUS TACHYCARDIA Martino Annamaria,MD; Sette A, MD; Preiti Stella, MD; Rebecchi Marco,MD; de Ruvo Ermenegildo,MD; Borrelli Alessio,MD; Scarà Antonio,MD; Fagagnini Alessandro,MD; Nuccio Francesca,MD; Sciarra Luigi,MD; Calo Leonardo,MD, FESC. Department of Cardiology, Policlinic Casilino, ASL RMB, Rome Introduction. Beta-blockers are conventionally administered for the treatment of inappropriate sinus tachycardia (IST), but are often poorly tolerated due to hypotension. Ivabradine has recently demonstrated to be effective in IST-patients (pts). The aim of our study was to compare ivabradine and bisoprolol in the treatment of IST. Methods. After performing an Holter-ECG monitoring and a stress test, consecutive IST-pts were randomized to treatment with ivabradine, started at a dosage of 5 mg bid, or bisoprolol, at an initial dose of 1.25 mg/day. After 3 months, pts underwent an Holter-ECG monitoring and a stress test during treatment. Results. Overall, 24 IST-pts (mean age 34±12 y; 23 women) symptomatic for palpitations and stress intolerance, were assigned to ivabradine or bisoprolol (12 pts for both regimens). The two subgroups were similar for Holter ECG and stress test parameters. The mean dose of ivabradine and bisoprolol administered were 5±1.3 mg bid and 2±1 mg/day respectively. After 3 months, mean Holter ECG HR lowered from 92±4.3 to 76±8 bpm with ivabradine (P<0.001) and from 91±5 to 81±12 bpm with bisoprolol (P=0.006 bisoprolol vs baseline; P=0.02 ivabradine vs bisoprolol). Ivabradine reduced maximal Holter ECG HR (from 152±16.6 to 128±18 bpm; P<0.001) and maximal HR during stress-test (from 154±12.5 bpm to 146±15.5 bpm; P=0.044). Conversely bisoprolol caused a non-significant reduction of maximal HR at Holter ECG and at stress-test. Minimal Holter ECG HR also lowered from 58±9.5 to 52±9 bpm with ivabradine (P=0.039). An increase of at least 50 Watts in the maximal step at the stress test was observed in 41.7% and 50% of individuals treated with ivabradine and bisoprolol respectively. Symptoms completely disappeared in the 89.5% and 75% of ivabradine- and bisoprolol-treated pts respectively. Phosphenes occurred in 5.3% of pts with ivabradine, whilst bisoprolol leaded to hypotension in 25% of cases. Conclusions Ivabradine and bisoprolol were effective in the treatment of IST. Ivabradine determined a better control of mean and maximal Holter-ECG HR and of maximal HR at stress test, caused a higher improvement of symptoms and provoked less side effects.