Dobutamine is the first-line treatment for low cardiac output syndrome (LCOS) after cardiac surgery, but induces sinus tachycardia. We aimed to assess the intravenous (i.v.) ivabradine inpatients presenting LCOS with dobutamine-induced tachycardia following elective coronary artery bypass graft surgery.

In a phase 2 multicenter randomized placebo-controlled trial, i.v. ivabradine was infused inpatients presenting sinus tachycardia (heart rate (HR)>100bpm) after dobutamine initiation. Primary endpoint was the number (%) of patients having their HR reduced between 80 and 90bpm for >30minutes. Secondary endpoints were hemodynamic parameters measured by Swan-Ganz catheter.

Thirteen (93%) patients treated by ivabradine reached the primary endpoint, compared to 2 (40%) in the placebo group (P<0.05). Ivabradine significantly decreased HR [112 to 86bpm (P<0.001)] while increasing cardiac index [2.5 to 2.9L/min/m² (P<0.05)], stroke volume [38.0 to 60.0mL (P<0.001)] and systolic blood pressure [110 to 125mmHg (P<0.05)]. These parameters remained similar in the placebo group. Five (35.7%) patients developed atrial fibrillation in the ivabradine group (Table 1, Fig. 1).

Intravenous ivabradine reduced HR inpatients presenting with LCOS treated with dobutamine after CABG surgery, while improving cardiac output. This beneficial effect should be confirmed with larger trials.