*Corresponding Author:
Héctor Hugo Escutia-Cuevas, MD
Department of Interventional Cardiology
Regional Hospital ISSSTE Puebla
4336 Sur 14 Avenue,
Jardines de San Manuel, Puebla City, 72570, Mexico.
Tel: (+52) 55-39-38-64-01
E-mail: perseoyarista@hotmail.com
Patients undergoing a coronary artery bypass grafting (CABG) surgery
with comorbidities are considered high-risk patients (1–4). The
intra-aortic balloon pump (IABP) has been widely used to improve
coronary perfusion and prevent complications in CABG (5–7). Some recent
randomized controlled trials (RCTs) have suggested that IABP insertion
does not improve the ventricular function and does not reduce
complications in patients with cardiogenic shock after acute myocardial
infarction (AMI) (8), preoperative IABP use may prevent complications in
high-risk patients undergoing CABG (9–12). A recent meta-analysis
suggested that preoperative IABP use is associated with mortality
reduction (11), but these findings were mainly derived from small RCTs.
A new article on this field is published in this edition of Journal of
Cardiac Surgery and shows that the risk factors for in-hospital
mortality were reoperation (OR=5.07, 95% CI:1.17-21.9, p=0.03),
preoperative plasma creatinine (OR=3.2, 95% CI: 1.23-8.75, p=0.01), CPB
time (OR=1.01, 95% CI: 1.00-1.03, p=0.02) and AKI (OR=46.6, 95% CI:
5.67-383.3). On the other hand, the multivariable logistic regression
analysis shown that the risk factors for in-hospital mortality were
preoperative plasma creatinine and CABG time, OR=5.74 and OR=1.02,
respectively (p<0.05). All this data consistent with another
previous studies (11, 12, 14) thus deserving special attention.
There is still no consensus on the ideal time of insertion, since the
preoperative (prophylactic) insertion of IABP in the high risk patients
CABG was reported by many studies and the results showed that
complications and mortality rate were similar with intraoperative IABP
insertion (11, 15-17) as in this novel study only including
intraoperative IABP patients (13). Despite the existing information, the
proper use of ventricular support in CABG is still controversial. As
will be seen later, articles endorse its preoperative use and in other
studies its intraoperative use. Obtaining contradictory results in both
circumstances.
Regarding secondary endpoints, the study of Samadi et al shows that
patients with LVEF ≤35% had longer in-hospital length of stay (LOS)
compared to patients with LVEF >50% (median [IQR] 10
[8-13] days and 8 [7-10] days respectively [p=0.04]),
already seen in previous reports (9, 11, 14, 18). This outcome may be
explained by the time required for accomplish the IABP weaning as well
as the time for recovery after operation, a feature observed in almost
all similar studies, thus giving an external validation to the results
obtained in the study.
Some strengths that characterize the study by Samadi et al, and that
current and future studies evaluating the effect of IABP must have,
include the selection process with all patients individually assessed by
a Heart Team (Clinicians included cardiac anesthesiologists, cardiac
surgeons, intensivists, and cardiologists). Also, the use of
contemporary techniques and medical management based on the latest
coronary revascularization guidelines (19, 20); as well as the
comprehensive follow up of data regarding IABP management and weaning
protocol, which provides external validation to the results.
Referring to ”big data”, due to the high variability of definitions and
the heterogeneity of the methods and postoperative management, the
results reflected so far in meta-analyses have been highly contradictory
between them (9, 18). Being this one more reason to generate
homogenization in future studies evaluating the use of IABP or another
ventricular support device in CABG procedures. It would be desirable the
use of a standard definition of cardiovascular risk, since criteria for
high-risk cardiac surgery vary between reported studies. For example,
low LVEF may be considered as <35% or <40%; as
well as “significant” left main occlusion, which has not been well
defined and some studies consider >50% or
>70% occlusion; or the inclusion of previous CABG as
relevant risk factor and a defined cutoff value for “higher” EuroSCORE
(22-24).
Many experts do not continue to acknowledge the potential utility of
IABP use. An international consensus conference on mortality reduction
in cardiac anesthesia and intensive care has recently published a
consensus in this topic (25). Recognizing that there is a lack of
general agreement regarding which nonsurgical interventions can reduce
mortality in cardiac surgery, the authors sought to address this issue
with a consensus-based approach identifying 11 nonsurgical interventions
with possible survival implications for patients undergoing cardiac
surgery, the prophylactic IABP placement as one of these interventions,
suggesting its use in high-risk patients undergoing CABG might reduce
mortality.
In conclusion, it is very clear that there remains a significant lack of
true evidence related to the topic of preoperative or intraoperative
IABP use for high-risk CABG patients that can only be resolved with a
definitive RCT. This lack of evidence has resulted in the continued
variation of IABP use in these procedures. A large, multicenter RCT is
certainly required to take the next step towards more definitive
evidence, either for or against, the use of IABP in high-risk CABG.
Until then, the unanswered questions regarding this topic will remain.