Despite advances in primary angioplasty programs, coronary revascularization techniques and medical treatment, cardiogenic shock (CS) complicating acute myocardial infarction still occurs in the range from 5 to 15% and remains the leading cause of hospital mortality associated with ST-segment elevation myocardial infarction (STEMI).1–4 In this clinical setting, since 19685 intra-aortic balloon counterpulsation (IABP) has been the most widely used method for temporary mechanical circulatory support with implantation rates from 2007 to 2011 of 50,000 per year based on a national survey in the USA.6 Nevertheless, evidence supporting the benefit was based on registries with conflicting results.7

The most recent large randomized trial on the use of IABP in patients with myocardial infarction complicated with CS undergoing early revascularization (IABP-SHOCK II trial),8 showed neither benefit on 30-day mortality nor on any of the secondary endpoints. These results, in addition to the previous limited IABP evidence, led to downgrade the recommendation supporting routine use of IABP in CS in the setting of STEMI from Class IIb B from 2012 ESC guidelines9 to III A in 2014 myocardial revascularization guidelines.10

The aim of our study was to assess the impact of IABP in unselected patients presenting with STEMI complicated with CS undergoing percutaneous coronary intervention (PCI). We aimed to determine if IABP implantation could influence 30-day survival and short-term clinical outcomes during coronary care unit admission.

Between January 2009 and August 2015, 825 patients diagnosed with STEMI were admitted. Of those, 73 (8.8%) were on CS and included for the analysis. 44 (60%) were treated with IABP in addition to medical therapy (IABP group) and 29 (40%) with optimal medical therapy only (non-IABP group). Table 1 shows baseline characteristics of the patients based on the insertion of an IABP or not. Both groups were comparable on cardiovascular risk factors, prognostic scores at admission (APACHE II, GRACE, CRUSADE), hemodynamic situation, cardiopulmonary resuscitation requirement or need of inotropic agents (Table 2).

Primary PCI was the most frequent revascularization strategy (88.6% in IABP group vs. 86.2% in non-IABP group, p=0.75) with left anterior descending artery as the culprit lesion in most cases (47.7% IABP group vs. 55.2% non-IABP group, p=0.53). Of notice, 13 patients (18%) with left main disease as infarct related artery, 12 of them were treated with IABP (p=0.009). The rate of stent implantation and stent type (drug-eluting stent or bare-metal stent) was also comparable between the two groups (Table 3).

Primary and secondary end points

Cumulative 30-day mortality was similar among patients treated with IABP and those treated with conventional medical therapy only (29.5% and 27.6%, respectively; odds ratio [OR] with IABP 1.10, 95% confidence interval [CI], 0.38–3.11; p=0.85) [Table 4]. Fig. 1 shows Kaplan–Meier survival curves according to IABP use. Table 4 shows clinical outcomes of patients with and without IABP: no reinfarction or acute stent thrombosis were detected during 30-day follow-up and no differences between groups were found regarding the rate of in-hospital stroke or sepsis. There was a trend of higher bleeding events in the IABP group (11.4% and 3.4%, respectively; OR with IABP 3.6, 95% CI 0.4–32.4; p=0.22), however without reach statistical significance.

Table 4.

Clinical outcomes of patients with and without intra-aortic balloon pump.

Variable	Intra-aortic balloon pump		OR (95% CI)	Value of p
	Yes	No
30-day mortality – no./total no. (%)	13/44 (29.5)	8/29 (27.6)	1.01 (0.4–3.1)	0.85
Major Bleeding requiring transfusion – no./total no. (%)	5 (11.4)	1 (3.4)	3.6 (0.4–32.4)	0.22
Stroke in hospital – no./total no. (%)
Ischemic	1/44 (2.3)	1/29 (3.4)	1.2 (0.3–4.9)	0.76
Hemorrhagic	0	0
In hospital reinfarction	0	0
In hospital stent thrombosis	0	0
Sepsis in hospital – no./total no. (%)	10/44 (22.7)	9/29 (31)	1.2 (0.7–1.9)	0.49

OR: odds ratio; CI: confidence interval.

Figure 1.

Kaplan–Meier survival curves for patients treated with (dotted line) and without (solid line) intra-aortic balloon pump.

(0.06MB).

Similarly, no differences were found regarding data related to intensive care stay: length of time on mechanical ventilation (53% of patients received invasive mechanical ventilation), days to hemodynamic stabilization, vasoactive drug requirement and length of stay in the coronary care unit were similar in both groups (Table 5), as well as serum lactate levels (Fig. 2) and renal function at baseline and during 72h follow-up (Fig. 3).

Table 5.

Coronary care clinical outcomes.

Variable	Intra-aortic balloon pump		Value of p
	Yes (N=44)	No (N=29)
Length of stay in the coronary care unit (days) – mean (SD)	6.2 (7.0)	4.3 (4.0)	0.2
Length of time on mechanical ventilation (days) – mean (SD)	2.9 (3.7)	3.0 (3.3)	0.9
Time to hemodynamic stabilization (days) – mean (SD)	3.3 (2.6)	3.1 (2.8)	0.8
Catecholamines; n/total (%)
Dopamine	17/44 (38.6)	11/29 (37.9)	0.9
Norepinephrine	34/44 (77.3)	19/29 (65.5)	0.3
Dobutamine	42/44 (95.5)	25/29 (86.2)	0.2
Epinephrine	1/44 (2.3)	3/29 (10.3)	0.2
Catecholamine dosages (μg/kg per minute) – mean (SD)
Dopamine	6.3 (1.3)	6.6 (1.1)	0.5
Norepinephrine	0.3 (0.07)	0.3 (0.06)	0.5
Dobutamine	10.8 (1.1)	11.4 (1.6)	0.09
Epinephrine	0.3	0.2 (0.02)	0.5

Figure 2.

Serum lactate levels based on IABP treatment. *Plots showing the median and interquartile range.

(0.08MB).

Figure 3.

Creatinine clearance during 72h of follow-up based on IABP use. Creatinine clearance was calculated using the Cockcroft–Gault-formula. *Plots showing the median and interquartile.

(0.09MB).

The main finding of our real life study is that among patients with STEMI complicated with CS that received an early coronary revascularization technique (primary/rescue PCI), the use of IABP had no impact on short-term survival. Similarly, no benefit was found on short-term clinical outcomes regarding IABP use or not. Our results are consistent with the current evidence that do not recommend the routine use of IABP therapy in CS patients.

In our registry, IABP was used in up to 60% of patients with STEMI complicated with CS at admission, which implies an implantation rate significantly higher than previously reported. Recent evidence shows a significant decrease in the use of IABP in Europe. Thereby, results from the Euro Heart Survey on PCI that included 33 European countries reported an IABP use of 25%.14 Similar data were found in ALKK-PCI registry with an overall use of 25.5%.15 This significant reduction is probably a consequence of the results of previous registries16 and the meta-analysis of Sjauw et al.7 that showed no mortality benefit of IABP in patients treated with primary PCI. The largest randomized trial to date evaluating IABP use on STEMI patients complicated with CS,8 reaffirms these findings.

Our results are consistent to those previously reported.7,8,17–19 Thrombolysis within 24h of admission was performed in 12.3% of our population and when these patients are transferred to rescue PCI, the impact of IABP on 30-day mortality was similar to those who received primary PCI. In this respect, a previous meta-analysis showed benefits in terms of mortality in the subgroup of patients that received thrombolysis as revascularization strategy and treated with IABP.7 This beneficial effect on patients with CS and a previous pharmacological revascularization strategy is probably related to the diastolic augmentation with the subsequent improvement in coronary perfusion, issue of critical importance for a thrombolytic agent to effectively dissolve an occlusive coronary thrombus.20 This fact probably explains why in rescue PCI patients (revascularization modality less dependent on coronary perfusion pressure that thrombolytic therapy) the synergistic effect is lost.

Several multivariable prognostic models have been developed to predict clinical outcomes in CS patients. Classical factors associated with higher mortality from the major CS trials (SHOCK, TRIUMPH, IABP-SHOCK II)8,21,22 included older age, lower left-ventricle ejection fraction, worse renal function, signs of impaired organ perfusion, need for vasopressor support, cardiac arrest, anterior infarction during presentation among others. Similarly to previously reported, our results from multivariable modeling showed that worse renal function and known peripheral artery disease were independently associated with 30-day all cause mortality.

Previous history of diabetes mellitus was independently associated with 30-day mortality. This finding is in contrast to SHOCK trial registry23 in which after adjustment, diabetics have an in-hospital survival rate that is marginally lower than that of non-diabetics (odds ratio for death, 1.36; 95% CI 1.00–1.84; p=0.051). However, in a more recent study24 evaluating the importance of preexisting diabetes on the incidence and prognosis of CS, no difference on 30-day and 5-year mortality were found (diabetics: 30-day 63%, 5-year 91%; non diabetics: 30-day 62%, 5-year 86%; p>0.05).

Anterior wall STEMI is the most common cause of impaired LVEF in the setting of an STEMI.25 However, in the subgroup analysis from IABP-SHOCK II trial,8 patients with an anterior STEMI had similar 30-day mortality to those with non-anterior STEMI type (RR 0.81, 95% CI 0.58–1.13 vs. 1.16, 95% CI 0.85–1.57, respectively; p value for interaction 0.14). We included anterior STEMI type as a covariate in the 30-day mortality multivariate regression analysis and no differences were found. In this regard, a recent study evaluated the impact of IABP on in-hospital mortality in patients presenting with acute anterior-STEMI without cardiogenic shock26 and found similar in-hospital rate of cardiac death between the two cohorts (5.6% vs. 0%; p=0.12).

IABP improves myocardial perfusion, reduces myocardial oxygen consumption and furthermore decreases afterload and improves cardiac index,27 which are the principal variables that most be corrected in cardiogenic shock patients.25 We evaluated the impact of IABP use on the clinical course during intensive care stay and no clinical benefit in terms of hypoperfusion biomarkers (serum lactate levels), length of time on mechanical ventilation, days to hemodynamic stabilization, and length of stay in the coronary care unit were found. Our results are similar to those reported on the IABP-SHOCK II trial in which no significant differences between groups regarding process-of-care outcomes were reported.8

Our study has important limitations. First, although patients were consecutively selected, the information and analysis is retrospective and as such has many limitations including nonrandom allocation of IABP. In this setting, we remark IABP insertion in 12 of 13 patients with left main disease as culprit lesion and a trend of its placement in sickest population estimated by APACHE II score. Second, the exact moment of IABP insertion (before, during, or after PCI) was not registered so we were unable to analyze the impact of IABP timing on the clinical course of our study population, although all IABP were implanted on the catheterization laboratory. Third, the sample size is reduce and limited to a single center and as consequence our conclusions may not apply to other patient population.

In our “real life” experience, IABP use does not modify 30-day mortality neither short-term clinical outcome in STEMI patients complicated with CS undergoing an urgent percutaneous coronary revascularization. Worse renal function, known peripheral artery disease and previous history of diabetes mellitus were independent predictors of 30-day mortality.

The authors declare no conflicts of interest.