Primary percutaneous coronary intervention (PCI) and intra-aortic balloon pump counterpulsation (IABP) are established treatment modalities in acute myocardial infarction complicated by cardiogenic shock. We hypothesized that the insertion of the IABP before primary PCI might result in better survival of patients with cardiogenic shock compared to postponing the insertion to after primary PCI. We, therefore, retrospectively studied 48 patients who had undergone primary PCI with IABP because of cardiogenic shock complicating acute myocardial infarction (26 patients received the IABP before and 22 patients after primary PCI). No significant differences were present in the baseline clinical characteristics between the 2 groups. The mean number of diseased vessels was greater in the group of patients treated with the IABP before primary PCI (2.8 ± 0.5 vs 2.3 ± 0.7, p = 0.012), but the difference in the number of treated vessels was not significant. The peak creatine kinase and creatine kinase -MB levels were lower in patients treated with the IABP before primary PCI (median 1,077, interquartile range 438 to 2067 vs median 3,299, interquartile range 695 to 6,834, p = 0.047, and median 95, interquartile range 34 to 196 vs median 192, interquartile range 82 to 467, p = 0.048, respectively). In-hospital mortality and the overall incidence of major adverse cardiac and cerebrovascular events were significantly lower in the group of patients receiving the IABP before primary PCI (19% vs 59% and 23% vs 77%, p = 0.007 and p = 0.0004, respectively). Multivariate analysis identified renal failure (odds ratio 15.2, 95% confidence interval 3.13 to 73.66) and insertion of the IABP after PCI (odds ratio 5.2, 95% confidence interval 1.09 to 24.76) as the only independent predictors of in-hospital mortality. In conclusion, the results of the present study suggest that patients with cardiogenic shock complicating acute myocardial infarction who undergo primary PCI assisted by IABP have a more favorable in-hospital outcome and lower in-hospital mortality than patients who receive IABP after PCI.
A recent meta-analysis has challenged current guideline recommendations and has questioned the benefit of intra-aortic balloon pump (IABP) support in the setting of acute myocardial infarction (AMI) complicated by cardiogenic shock. Analyzing the pooled data from both randomized and observational studies, that meta-analysis did not show a significant benefit for IABP support in patients with high-risk ST-segment elevation AMI, especially in those treated with primary percutaneous coronary intervention (PCI). Debating the role of IABP in cardiogenic shock, it has so far not been considered whether it is superior to start pumping before or after primary PCI. We, therefore, conducted a retrospective study in patients with cardiogenic shock complicating AMI at our institution, investigating the implication of IABP-assisted PCI compared to postponing the insertion of IABP after primary PCI on overall clinical outcome.
Methods
This was a single-center retrospective study, including a total of 48 consecutive patients who underwent primary PCI with insertion of an IABP because of AMI complicated by cardiogenic shock from January 2005 to December 2008. Cardiogenic shock was confirmed clinically by the presence of hypotension (systolic blood pressure of <90 mm Hg for ≥30 minutes or the need for supportive measures to maintain the systolic blood pressure ≥90 mm Hg) and end organ hypoperfusion (cool extremities or a urine output <30 ml/hour) after adequate correction of preload and major arrhythmia. IABP was inserted either before or after PCI; the exact timing was dependent on the operator’s decision according to clinical and/or logistic considerations. To obtain a more homogenous population, only patients with AMI and cardiogenic shock due to left ventricular failure were included in the present analysis. Patients with mechanical complications such as ventricular rupture or acute severe mitral regurgitation, isolated right ventricular infarction, and shock, resulting from excess β blockade or calcium channel blockade or as a complication of cardiac catheterization, were excluded. Patients who did not have IABP support within 24 hours from the index PCI also were not considered. The study complied with the Declaration of Helsinki and was approved by the local ethics committee. All patients provided informed consent for the retrospective analysis of their anonymized data.
Immediately after the diagnosis of AMI, a loading dose of intravenous aspirin (500 mg) and clopidogrel (600 mg) was given to all patients. The use of platelet glycoprotein IIb/IIIa inhibitors (in the emergency room or the catheterization laboratory) was left to the physician’s discretion. Unfractionated heparin was given at 70 U/kg at initial presentation and additional heparin doses were given during PCI to maintain an activated clotting time of 250 to 300 seconds and between 200 and 250 seconds if a glycoprotein IIb/IIIa inhibitor was administered.
Cardiac catheterization was performed using the femoral route using 6Fr systems in all patients. Contrast ventriculography was routinely performed in the right anterior oblique projection. Coronary angiography and PCI were performed in a conventional manner. All patients were treated with bare metal stents, according to local institutional guidelines. The use of thrombus aspiration devices was left to the operator’s discretion.
In group A (IABP before PCI), balloon counterpulsation was always performed through the contralateral femoral artery. The patients in group B (IABP support after PCI) had the pump inserted using the same femoral artery through which cardiac catheterization and PCI had been performed. The IABP (Datascope, Hoevelaken, The Netherlands) was inserted through an 8Fr sheath and was guided into the descending aorta, approximately 2 cm from the left subclavian artery. Aortic counterpulsation was electrocardiographically triggered in all patients, and the balloon was generally left for 48 hours at a rate of 1:1. The patient was then gradually weaned off the pump during a 12-hour period before removal. Aortic counterpulsation was stopped earlier in the case of complications such as limb ischemia or hemorrhage at the access site.
Standard coronary care management was provided. After the procedure, clopidogrel was continued for 6 months (according to local institutional practice), and aspirin was prescribed indefinitely for all patients. If no contraindications were present, angiotensin-converting enzyme inhibitors/angiotensin receptor blockers, β blockers, and statins were prescribed. Vasopressor drugs were used in hemodynamically unstable patients.
The primary end point for the present analysis was in-hospital death. The secondary end points evaluated included recurrent nonfatal myocardial infarction, target vessel revascularization, the occurrence of cerebrovascular ischemic or hemorrhagic events, and the composite of major adverse cardiac and cerebrovascular events, defined as the composite of death, nonfatal reinfarction, target vessel revascularization, and cerebrovascular events during the hospital stay. In addition, the occurrence of renal failure (defined as serum creatinine ≥2.5 mg/dl) and major bleeding leading to a decrease of hemoglobin level >5 g/dl or that requiring blood transfusion were analyzed. The recurrence of myocardial infarction was defined as recurrent chest pain lasting for ≥30 minutes after the index procedure, associated with new Q waves in ≥2 leads or recurrent ST-segment elevation ≥0.1 mV in ≥2 contiguous leads, and/or re-elevation of creatine kinase-MB levels to at least twice the upper limit of normal and >50% greater than the previous value. Target vessel revascularization was defined as repeat PCI or surgical bypass grafting of any segment of the target vessel.
Data evaluation was performed using a statistical software package (Minitab, version 13.1). Continuous variables are expressed as the mean ± SD or the median and interquartile range and were analyzed using the Student t test or Mann-Whitney U test, as appropriate. Discrete variables are presented as counts and percentages and were analyzed using the Pearson chi-square test or Fisher’s exact test, as appropriate. A multivariate analysis using a logistic regression model with a backward elimination procedure was performed to detect independent predictors of in-hospital mortality. p Value <0.05 was considered statistically significant.
Results
The patients’ data were analyzed using their clinical status at initial admission to the hospital. According to the treatment they received, we divided the patient population into 2 groups: group A included 26 patients who had the IABP inserted before PCI, and group B included 22 patients who had the IABP inserted and pumping started after PCI.
No statistically significant differences were found in the risk factors for coronary artery disease or the baseline clinical characteristics between the 2 groups ( Table 1 ). However, significant differences were present in the mean values of the cardiac enzymes at presentation and the maximal levels reached during hospitalization. The mean creatine kinase and creatine kinase-MB levels at presentation were significantly greater in group B than in group A, and the mean values of the maximal levels of cardiac enzymes were also significantly greater in group B than those in group A ( Table 1 ). The mean number of diseased vessels was greater in group A than in group B; no significant difference was found in the mean number of treated vessels per patient, localization of the infarct territory, or the postprocedural Thrombolysis In Myocardial Infarction flow. Also, no significant differences were found in the management offered to the 2 groups regarding the administration of glycoprotein IIb/IIIa inhibitors, the need for high-dose vasopressor drugs (≥2 different drugs or >3 times the usual dose) or the mean number of stents used ( Table 2 ).
| Variable | Insertion of IABP Before PCI (n = 26) | Insertion of IABP After PCI (n = 22) | p Value |
|---|---|---|---|
| Women | 3 (12%) | 6 (27%) | 0.27 |
| Age (years) | 70 ± 10 | 71 ± 11 | 0.80 |
| Diabetes mellitus | 13 (50%) | 10 (45%) | 0.78 |
| Arterial hypertension | 18 (69%) | 14 (64%) | 0.76 |
| Hyperlipidemia (total cholesterol >200 mg/dl) | 15 (58%) | 12 (55%) | 1.0 |
| Current smokers | 11 (42%) | 9 (41%) | 1.0 |
| Peripheral arterial disease | 2 (8%) | 4 (18%) | 0.39 |
| Previous myocardial infarction | 9 (35%) | 9 (41%) | 0.77 |
| Previous coronary bypass | 4 (15%) | 5 (23%) | 0.71 |
| Atrial fibrillation | 5 (19%) | 8 (36%) | 0.21 |
| Ejection fraction (%) | 23.5 ± 10.6 | 23.2 ± 8.7 | 0.92 |
| Systolic blood pressure (mm Hg) | 109 ± 10 | 105 ± 14 | 0.36 |
| Diastolic blood pressure (mm Hg) | 60 ± 10 | 62 ± 13 | 0.60 |
| ST-segment elevation myocardial infarction | 15 (58) | 16 (73) | 0.37 |
| Creatine kinase at admission (U/L) | 325 (175–510) | 644 (247–1764) | 0.028 |
| Peak creatine kinase (U/L) | 1,077 (438–2067) | 3,299 (695–6,834) | 0.047 |
| Creatine kinase-MB at admission (U/L) | 58 (27–77) | 93 (42–197) | 0.031 |
| Peak creatine kinase-MB (U/L) | 95 (34–196) | 192 (82–467) | 0.048 |
| Variable | Insertion of IABP Before PCI (n = 26) | Insertion of IABP After PCI (n = 22) | p Value |
|---|---|---|---|
| Number of diseased vessels | 2.8 ± 0.5 | 2.3 ± 0.7 | 0.012 |
| Number of treated vessels | 1.5 ± 0.5 | 1.4 ± 0.5 | 0.54 |
| Left anterior descending as culprit vessel | 12 (46%) | 10 (45%) | 0.71 |
| Number of stents implanted per patient | 2 (1–3) | 1.5 (1–2.25) | 0.22 |
| Length of stents implanted (mm) | 34 (18–64) | 23 (15–46) | 0.18 |
| Use of glycoprotein IIb/IIIa inhibitors | 14 (54%) | 17 (77%) | 0.13 |
| Postprocedure Thrombolysis In Myocardial Infarction flow | 2.7 ± 0.9 | 2.3 ± 1.2 | 0.13 |
| Door-to-needle interval (min) | 115 (50–240) | 80 (33–499) | 0.45 |
| Procedural duration (min) | 88 ± 26 | 85 ± 34 | 0.76 |
| Duration of intra-aortic balloon support (hours) | 43 ± 35 | 47 ± 37 | 0.79 |
| Need for high-dose vasopressor agents | 9 (35%) | 11 (50%) | 0.38 |
| Need for renal dialysis | 2 (8%) | 3 (14%) | 0.65 |
| Need for mechanical ventilation | 13 (50%) | 16 (72%) | 0.12 |
| Duration of mechanical ventilation (days) | 0.5 (0–4.25) | 2.5 (1–9) | 0.059 |
| Duration of intensive care stay (days) | 6.5 (1.9–10) | 7 (2.5–15.8) | 0.70 |
| Duration of hospital stay (days) | 16 (9.5–25) | 12 (2.8–25) | 0.34 |
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