Intraoperative heart rate reduction - alinidine versus metoprolol

In a double-blind randomized protocol the effectiveness of the specific bradycardic agent alinidine (0.6 mg.kg-1 i.v.) was compared to that of the betablocker metoprolol (0.035 mg.kg-1 i.v.). Twenty-four coronary artery disease patients undergoing a bypass procedure with an intraoperative heart rate increase of more than 20% were included. Patients with a concomitant intraoperative mean arterial pressure increase of more than 30% or with an intraoperative wedge pressure higher than 15 mmHg (2.0 kPa) were excluded. After application of alinidine and metoprolol, heart rate decreased significantly (P<0.01) in the alinidine group from 88 ± 19 beats per min to 72 ± 13 and in the metoprolol group from 82 ± 16 to 72 ± 12. Baseline values were not obtained. Compared to the hemodynamic changes in the metropolol group, the alterations of pulmonary capillary wedge pressure (P<0.05) (P<0.05), stroke volume index (SVI) (P<0.05), left ventricular stroke work index (LVSWI) (P<0.01) and right ventricular stroke work index (RVSWI) (P<0.05) in the alinidine group were statistically significantly different. PCWP remained unchanged after alinidine and increased in the metoprolol group (1.4 ± 0.4 to 1.6 ± 0.4 kPa). In the alinidine group LVSWI (43.1 ± 15 to 49.2 ± 18g-m.m-2), RVSWI (5.1 ± 4 to 6.6 ± 3 g-m.m-2) and SVI (37.2 ± 12.2 to 42.5 ± 12.8 ml.m-2) increased. In the metoprolol group LVSWI (44.2 ± 8 to 40.6 ± 9 g-m.m-2) and RVSWI (5.5 ± 3 to 5.3 ± 2 g-m.m-2) decreased slightly, whereas SVI was unchanged. Based on the hemodynamic data alinidine seems to be a less cardiodepressive agent than metoprolol in phases of predominant sinus tachycardia. This drug may be especially advantageous for patients with suspected or documented ischemic heart disease, those who do not tolerate betablockers well and patients who require a greater heart rate reduction than can be obtained with betablockers.