Ivabradine and Inappropriate Sinus Tachycardia: A Funny Target for an Inappropriate Disease

CrossTalk opposing view: Heart rate variability as a measure of cardiac autonomic responsiveness is fundamentally flawed

“…Therefore, there is no reason to believe that the high heart rate in IST is the result of a decrease in vagal tone. Consistent with this, patients with IST are treated with ivabradine to reduce the heart rate to normal (Achike & DeAntonio, ); this suggests that the cause lies with ion channels and HCN4 in particular. HCN4 is blocked by ivabradine and is the major isoform responsible for the funny current ( I f ), arguably the most important pacemaker current in the heart (DiFrancesco, ).…”