Efficacy of ivabradine administration in patients affected by inappropriate sinus tachycardia.
BACKGROUND
Inappropriate sinus tachycardia (IST) is characterized by an elevated heart rate (HR) at rest and an exaggerated HR response to physical activity or emotional stress. Beta-blockers and calcium channel blockers are the first-line therapy but sometimes are poorly tolerated due to side effects.


OBJECTIVE
The purpose of this study was to evaluate the efficacy and safety of ivabradine, a selective inhibitor of the I(f) current of the sinoatrial node, in patients affected by IST.


METHODS
Eighteen consecutive symptomatic patients (2 men and 16 women; mean age 45 +/- 15 years) affected by IST were enrolled in the study. Every patient underwent resting ECG, 24-hour Holter ECG, and exercise ECG at baseline and at 3-month and 6-month follow-up.


RESULTS
Sixteen patients (14 women; mean age 41 +/- 14 years) completed the study. Holter ECG assessment showed a significant reduction of medium HR (P <.001) and maximal HR (P <.001, basal vs 3-6 months; P = .02, 3 vs 6 months). Minimal HR slightly decreased at 3 months and then stabilized (P = .49, 3 vs 6 months) despite an increased drug dose. Stress test showed a significant decrease at rest (P <.001) and maximal HR (P <.05), suggesting an increased tolerance to physical stress, which was confirmed by a progressive increase of maximal load reached (>100 W) during stress test at 3 months (75%) and 6 months (85%). One patient was excluded because of phosphenes despite dose lowering, and another patient did not complete the protocol.


CONCLUSIONS
Ivabradine could represent an effective and safe alternative to calcium channel blockers and beta-blockers for treatment of IST.
Calò
Leonardo
L
Division of Cardiology, Policlinico Casilino, ASL RMB, Rome, Italy. leonardo.calo@tin.it
Rebecchi
Marco
M
Sette
Antonella
A
Martino
Annamaria
A
de Ruvo
Ermenegildo
E
Sciarra
Luigi
L
De Luca
Lucia
L
Zuccaro
Lorenzo Maria
LM
Giunta
Giuseppe
G
Ciccaglioni
Antonio
A
Lioy
Ernesto
E
Fedele
Francesco
F
D000284:Administration, Oral; D000328:Adult; D001552:Benzazepines / Q000008:administration & dosage / Q000627:therapeutic use*; D054815:Cyclic Nucleotide-Gated Cation Channels; D004305:Dose-Response Relationship, Drug; D015716:Electrocardiography, Ambulatory; D005260:Female; D005500:Follow-Up Studies; D006339:Heart Rate / Q000187:drug effects*; D006801:Humans; D000077550:Ivabradine; D008297:Male; D008875:Middle Aged; D013616:Tachycardia, Sinus / Q000188:drug therapy* / Q000503:physiopathology; D016896:Treatment Outcome
D001552:Benzazepines; D054815:Cyclic Nucleotide-Gated Cation Channels; D000077550:Ivabradine