To the Editor:
We have read with interest the article of Levin et al1 in which the authors present a randomized comparison between levosimendan (LS) and dobutamine (Db) in postoperative low cardiac output syndrome. They conclude that LS is superior to Db in terms of morbidity, mortality, and length of hospital stay.
A key aspect is the fact that, of the 68 patients randomized to Db, 45 (85.3%) had received preoperative treatment with beta-blockers. As expressed in the clinical practice guidelines concerning acute heart failure,2 patients who receive treatment with beta-blockers require higher doses of Db to restore its inotropic effect. Likewise, the LIDO study,3 which demonstrates that LS brings about a greater improvement in the hemodynamic parameters in patients with severe left ventricular dysfunction than Db, concludes that treatment with beta-blockers attenuates the action of Db, but not that of LS. The statistically significant differences between LS and Db in terms of hemodynamic parameters encountered in the study of Levin et al could be due to the lower chronotropic and inotropic activity of Db, as the majority of the patients had previously received treatment with beta-blockers. These hemodynamic differences at such a crucial time as when early postoperative low cardiac output develops (initiation of inotropy 3.5 hours after the surgical intervention) can ultimately have an impact on morbidity and mortality.
In short, we can conclude that the action of LS, in contrast to that of Db, is not attenuated by treatment with beta-blockers. This aspect is important, since LS can be considered a highly appropriate treatment in cases of severe left ventricular dysfunction and as a concomitant treatment with previous beta-blockers.