Off-pump coronary artery bypass grafting involves
displacement and manipulation of heart to expose target coronary arteries, particularly obtuse marginal
and posterior descending coronary arteries. This
manipulation may be accompanied by transient annular
mitral distortion, leading to acute mitral regurgitation,
compression of pulmonary veins and/or the right
ventricle in addition to superimposed impaired cardiac
contractions due to the epicardial stabilizer. This results
in hemodynamic instability in the form of increased
filling pressures, right ventricular endâ-diastolic
pressure and transient diastolic dysfunction.[
10,
11] All
these changes are exaggerated intraoperatively in
patients with LV dysfunction, which is the main risk
factor for intra- and postoperative LCOS.[
12,
13]
The main challenge during OPCABG is to
maintain optimum hemodynamics. This can be
achieved by mechanical or pharmacological means.
Use of inotropes constitutes major pharmacological
intervention and its appropriate selection helps in
better clinical outcomes. However, conventional
inotropes such as beta-agonists and phosphodiesterase
inhibitors are associated tachycardia and arrhythmia,
leading to an increased myocardial oxygen demand.[14]
Levosimendan is a novel inotropic agent. It
also provides beneficial immunomodulatory,
cardioprotective, anti-stunning, antiâ-ischemic, antiinflammatory,
and antioxidant effects to improve
cardiac performance in the presence of ischemia.[15-18]
All these characteristics make it a near-ideal inotrope
in patients with LV dysfunction.
The IABP counter pulsation is currently the
most used mechanical assistance device for patients
with cardiogenic shock due to acute myocardial infarction. Its beneficial physiological effects have
been established. The IABP increases diastolic blood
pressure.[19,20] and, thus, it improves diastolic coronary
perfusion. Furthermore, it increases cardiac output
and stroke volume by reducing afterload. The ability
to act on diastolic pressure has a great importance in
clinical practice, since the elevated diastolic pressure
results in a redistribution of coronary blood flow
toward ischemic areas of the myocardium.[21]
A multi-center study showed that prophylactic
use of IABP improved outcomes in high-risk cardiac
patients.[22] The main disadvantages of IABP,
particularly in patients with systemic atherosclerosis,
is the development of complications associated with
instillation of the balloon including includes limb
ischemia, damage to the vessels, and bleeding.[23,24]
This study highlights the favorable hemodynamic
profile of levosimendan and IABP in terms of reduced
PCWP and improved CI after its administration. We
consistently observed higher CI in patients treated
with IABP during intra- and postoperative period,
compared to levosimendan; however, the increase
was not statistically significant. The rise in CI leads
to reduced serum lactate concentrations, indicating
improved microcirculation at peripheral tissue
level. Although data are scarce regarding the use
of levosimendan during cardiac surgery in patients
with low EF, our results are consistent with the
recent studies.[24] In a meta-analysis, Landoni et al.[21]
emphasized that the use of levosimendan contributed to
a significant reduction of mortality in cardiac patients
with favorable outcomes. In the study conducted by
Alvarez et al.,[25] they concluded that a loading dose of
levosimendan needed to be omitted in decompensated
heart failure patients to prevent hypotensive episodes.
Hence, we preferred an approach of gradually achieving
the therapeutic concentration without causing any
hypotensive episodes in our institution.
In the current study, none of the patients developed
significant hypotension, any hemodynamic instability,
and other side effects such as nausea and headache in
the preoperative period and the regime was tolerated
well. Immediate postoperative outcomes also improved
in the levosimendan group with a notably reduced
incidence of postoperative atrial fibrillation which can
be attributed to antioxidant and anti inflammatory
properties of levosimendan.[23] Although several studies
have emphasized the increased incidence of ventricular
arrythmias after administration of levosimendan, we
found no similar result in our study.
In their study, Baysal et al.[26] suggested that
levosimendan increased renal blood flow by decreasing
renal vascular resistance and increasing glomerular
filtration rate. In another study using propensity score
analysis, Lorusso et al.[27] concluded that patients with
IABP support in the preoperative period had a lower
risk of acute kidney injury. Our findings are also
consistent with the aforementioned studies, as none of
our patients developed acute kidney injury requiring
dialysis.
Furthermore, we observed a decreased incidence
of LCOS in both groups. These findings can be
attributed to favorable surgical conditions produced
by levosimendan and IABP owing to improved
myocardial contractility and reduced pulmonary
pressures which make the heart supple and easy
to operate upon. In another study, Lomivorotov et
al.[28] compared levosimendan and IABP in highâ-risk
cardiac surgery patients and concluded that the
infusion of levosimendan after anesthesia induction in
cardiac surgical patients contributed to lower cardiac
troponin I concentrations and improved hemodynamics
compared to preoperative IABP. Similarly, Severi
et al.[29] also observed a shorter ICU stay in patients
pretreated with levosimendan compared to patients
receiving prophylactic IABP. In our study, we found
a significant difference in the length of ICU and
hospital stay between the two groups. The patients in
Group B stayed in the ICU for a longer duration (mean
6.5±0.1 days) compared to the patients in Group L
(mean 4.6±0.2 days) group. Although two patients in
Group B needed an additional procedure in the form
of an embolectomy, it did not influence the total ICU
stay in the study population.
The single-center design is the main limitation
of the present study. In addition, we were unable to
consider serum-specific cardiac markers (troponin
levels) which would in detail highlight the cardiac
status of the patients in both groups. Also, the
immediate postoperative mortalities (within 48 h)
were unable to be analyzed.
In conclusion, the use of prophylactic levosimendan
is comparable to prophylactic IABP, when
hemodynamic parameters are taken into consideration.
Prophylactic levosimendan is associated with lower
hospital and ICU stay. Prophylactic levosimendan can
be considered as an alternative to prophylactic IABP
in patients with low ejection fraction in whom IABP
is contraindicated.
Declaration of conflicting interests
The authors declared no conflicts of interest with respect
to the authorship and/or publication of this article.
Funding
The authors received no financial support for the research
and/or authorship of this article.