Abstract: Background. We present the indications for use, temporal trends, complications, and 1-year clinical outcomes after single-access percutaneous mechanical circulatory support device placement from years 2009-2015 at our institution. Methods and Results. Patients with an intraaortic balloon pump (IABP) or Impella device placed in the catheterization suite between January 1, 2009 and December 31, 2015 were included. There were a total of 778 patients in this study. The mean number of devices placed per year was 111. There was no statistically significant trend in total number of devices placed overall, but the rate of Impella placement declined over time (P=.02). There was a significant trend toward less use before high-risk percutaneous coronary intervention (PCI) (P=.04). The composite secondary endpoint occurred in 59.4% of patients, with no significant difference between patients treated with an IABP or Impella (P=.66). There were 37 device-related complications, which occurred more commonly with the Impella (12.5%) than with the IABP (3.7%; P<.01). Conclusions. There was no significant overall change in the total number of devices placed per year, but we did observe a decreased use of Impella support. There was a significant decrease in the utilization of percutaneous mechanical circulatory support prior to high-risk PCI, driven primarily by a decreased usage of the IABP. There were more complications related to the Impella device vs the IABP, with no improvement in the composite outcome.
J INVASIVE CARDIOL 2017;29(9):309-313. Epub 2017 July 15.
Key words: intraaortic balloon pump, high-risk PCI, left ventricular device support
Intraaortic balloon pump (IABP) counterpulsation was first described by Kantrowitz et al in 1968 as a minimally invasive mechanism to support the failing left ventricle.1,2 The IABP has since become the most widely used mechanical circulatory support device, with approximately 50,000 IABPs placed per year in the United States.3,4 Beneficial hemodynamic effects of the IABP include improvements in mean arterial pressure, cardiac output, myocardial blood flow, and decrease in ventricular afterload.5 The Impella device (Abiomed, Inc) is a percutaneously inserted left ventricular assist device (LVAD) using a continuous axial-flow rotary pump that is positioned in the left ventricle. It is able to increase cardiac output by up to 2.5 L/min (Impella 2.5) or 3.7 L/min (Impella CP). Studies have shown improved hemodynamic parameters with the Impella device compared with the IABP, but no improvement in clinical outcomes to date.6-9 Despite a lack of clinical evidence supporting their use, there has been a national trend toward increased utilization of the Impella device with mixed reported trends in IABP utilization.3,4,10 Given the national trends in device usage, the aim of this observational study was to review indication for use, temporal trends, and early outcomes after single-access percutaneous mechanical circulatory support device (IABP and Impella 2.5/CP) placement in the cardiac catheterization laboratory from 2009-2015 at our institution. We tested the hypothesis that device usage changed during the observation period and that this in turn would be associated with changes in clinical outcomes.
This study was performed using data of patients treated at Mayo Clinic St. Mary’s Hospital (Rochester, Minnesota) after Institutional Review Board approval. The cardiac catheterization laboratory procedure database was used to identify cases in which an IABP or Impella 2.5/CP was placed between January 1, 2009 and December 31, 2015. Inclusion criteria were age ≥18 years and device insertion in the catheterization laboratory. Exclusion criteria were age <18 years, device placement during cardiac surgery, device placement outside of the catheterization laboratory (eg, operating room or bedside insertion), and patients referred to our facility with a device already in place.
The primary measure was yearly rate of device placement by specific indication. Secondary outcomes included a composite of in-hospital mortality rate, 1-year mortality rate, and 1-year readmission rate, as well as each component individually, and renal failure requiring hemodialysis. The primary safety outcome was device-related complications including vascular injury requiring surgical intervention or causing limb ischemia, bleeding requiring transfusion or device removal, localized infection or bacteremia, and device malfunction.
We considered 6 indications for device placement: acute myocardial infarction with cardiogenic shock; preoperative coronary artery bypass graft (CABG)/valve surgery; in preparation for surgical LVAD implantation; high-risk percutaneous coronary intervention (PCI); hemodynamic support following complications of PCI; and other.
Definitions. Acute myocardial infarction was defined by a characteristic rise and fall of cardiac biomarkers (troponin T) with 1 or more of the following: ischemic chest pain or anginal equivalent (left arm, neck, jaw pain, or shortness of breath) lasting >30 min; ischemic electrocardiographic changes (ST elevation, depression, or T-wave inversion); pathologic Q-waves; or prehospital cardiac arrest.11 Cardiogenic shock diagnosis was based on clinical features including systolic blood pressure (SBP) <90 mm Hg for >30 min despite adequate fluid resuscitation, SBP <100 mm Hg despite vasopressors or inotropic therapy, and evidence of end-organ hypoperfusion (hypoxia, altered mental status, oliguria [<30 mL/hr], or cool, clammy skin).12
Patients without cardiogenic shock who had a device placed prior to undergoing CABG/valve surgeries were included in the preoperative CABG/valve group. Similarly, if a device was placed prior to surgical LVAD implantation, they were included in the preoperative LVAD cohort. For both of these indications, a portion of the groups had a device placed in an elective fashion prior to a planned procedure. In other cases, the device was placed to stabilize the patient prior to making a decision to go to the operating room.
High-risk PCI was defined as left ventricular ejection fraction <30%, left main coronary artery intervention, last remaining patent vessel intervention, or triple-vessel coronary artery intervention.13 PCI complications included coronary artery dissection, perforation, embolization, or no-reflow phenomenon. All other indications for use were categorized as other.
Statistical analysis. Continuous variables are reported as mean ± standard deviation and categorical variables are reported as absolute values with percentages. Trend analysis was performed using linear regression analysis of the number of devices placed per year. Continuous variables were analyzed with the Student’s t-test and categorical variables with the Chi2 test. Factors were considered statistically significant if the P-value was <.05.
A total of 778 cases in which an IABP or an Impella was inserted in the catheterization laboratory were identified. Of these cases, 682 were with an IABP and 96 were with an Impella. The most common reason for IABP placement was acute myocardial infarction with cardiogenic shock (34.8%), followed by preoperative CABG/valve surgery (24.6%) and preoperative LVAD (17.7%). The most common indication for Impella placement was high-risk PCI (44.8%) followed by other (28.1%), and acute myocardial infarction with cardiogenic shock (26.0%) (Table 1). Patient characteristics are shown in Table 2. The mean age of those included was 66.1 ± 13.4 years, and 69.5% were male. The number of device implants per year varied, from a low of 94 in 2015 to a high of 161 in 2011, with a mean of 111.1 cases/year. There was no significant trend in overall device usage during this 7-year period (P=.43, or P=.45 when adjusted for PCI case volume). In addition, there was no significant trend in the number of IABPs placed per year (P=.63), but there was a significant decline in the number of Impella devices that were utilized per year (P=.02) (Figure 1).
When the trend analysis was performed looking at the specific indications, there was no significant change in the number of devices placed for acute myocardial infarction with cardiogenic shock (P=.91), preoperative CABG/valve surgery (P=.52), preoperative LVAD surgery (P=.63), or other (P=.80). There was a significant trend toward less frequent device usage before high-risk PCI (P=.04). This was driven primarily by a decreased utilization of the IABP (P=.04) rather than Impella (P=.13). There was also a decrease in the use of devices to manage complications of PCI (P=.02) (Figure 2).
The composite secondary endpoint occurred in 462 patients (59.4%). There was no significant difference in rates of the composite endpoint between patients with an IABP (59.6%) or an Impella (57.3%; P=.66). However, there was a significant difference in the individual components. The in-hospital mortality rate was higher with the Impella (30.2%) compared with the IABP (18.5%; P=.01), as was the 1-year mortality rate (40.6% vs 27.3%; P<.01). This was offset by the higher 1-year readmission rate for patients treated with an IABP compared with the Impella (45.0% vs 28.4%, respectively; P=.08). There were 86 patients (11.1%) who required hemodialysis during their hospitalization, but there was no difference between the IABP and Impella (10.6% vs 14.6%; P=.26) (Table 3).
Device-related complications occurred in 37 patients (4.8%). Complications were more likely to occur with an Impella (12.5%) compared with the IABP (3.7%; P<.01). The most common complications observed were vascular injury,11 followed by bleeding requiring transfusion,9 infection (access site or bacteremia),8 and device malfunction.8
The primary results of this single-center analysis of single-access percutaneous mechanical circulatory support devices over a 7-year observation period are: (1) overall usage of these devices did not change over time, but a trend toward less utilization of the Impella was observed; (2) fewer high-risk PCI procedures were performed with single-access mechanical circulatory support, primarily driven by a reduction in procedures with an IABP; and (3) higher rates of complications and in-hospital mortality occurred in patients receiving an Impella device compared with IABP, although these groups had different baseline characteristics.
Recent reports from national databases contrast with our single-center experience. Stretch et al reported usage of short-term mechanical circulatory support devices from 2004-2011 using the National Inpatient Sample.3 These authors observed no significant change in the use of IABP counterpulsation, with a marked increase in utilization of other percutaneous mechanical circulatory support devices from 2007-2011. A separate study by Khera et al using the National Inpatient Sample from 2007-2012 showed a similar marked increase in the use of other percutaneous mechanical circulatory support devices, but a trend toward less use of IABP counterpulsation.4 The most recent report by Sandhu et al using the National Cardiovascular Data Registry cathPCI database from 2009-2013 evaluating the use of mechanical circulatory support in patients with acute myocardial infarction complicated by cardiogenic shock found decreased usage of IABP counterpulsation without a concurrent increase in the use of other mechanical circulatory support devices.14
The 2011 American College of Cardiology Foundation/American Heart Association PCI guidelines give a class IIb (level of evidence, C) recommendation for the use of an appropriate percutaneous mechanical support device as an adjunct to PCI in selected high-risk patients.15 Despite these recommendations, we observed a decrease in the overall usage of mechanical circulatory support before high-risk PCI. This change was driven primarily by a decrease in utilization of IABP counterpulsation, which likely reflects literature that was published during the observation period. The BCIS-1 study published in 2010 showed no early survival benefit with the use of IABP for support during high-risk PCI, although a survival benefit appeared to develop during prolonged follow-up.12,16 The PROTECT II study, which compared the Impella 2.5 to IABP counterpulsation for hemodynamic support during high-risk PCI, failed to show any difference in mortality at 30 days.9 Although it was underpowered to assess for 90-day outcomes, there was a trend toward improvement with use of the Impella 2.5 at 90 days. This favorable data may have contributed to the observed usage of the Impella for hemodynamic support during high-risk PCI.
There was no difference in the composite outcome of in-hospital mortality, 1-year mortality, or 1-year readmission rates between those patients treated with an IABP or Impella. There was, however, a significant difference in the individual components of the composite outcome. Patients treated with an Impella had higher in-hospital and 1-year mortality rates despite having similar baseline characteristics compared with those treated with an IABP. It is likely that unmeasured confounding variables that led the providers to select an Impella as opposed to an IABP contributed to the increased mortality rates.
We observed an overall complication rate of 4.8% with the use of percutaneous mechanical circulatory devices. Complications were less common in the IABP group (3.7%) compared with the Impella group (12.5%). These complication rates are lower than those previously published. Valente et al reported a 2.1% incidence of major limb ischemia and a 6.9% incidence of severe bleeding from an IABP, although a large proportion of the bleeding was non-specific and possibly unrelated to the IABP.17 In the Impella-EUROSHOCK registry, the incidence of bleeding requiring transfusion associated with the Impella 2.5 was 24.2%, with 4.2% requiring surgery.7 In this registry, 7.5% of the patients had significant hemolysis secondary to the Impella device; we did not measure this outcome in the present study.
Despite the limited data and controversies regarding mechanical circulatory support with either the IABP or Impella, the 2015 expert consensus statement on percutaneous mechanical circulatory support devices continues to endorse their use while ongoing studies are being conducted.18
Study limitations. This is a retrospective, single-center study of single-access percutaneous mechanical circulatory support devices placed in the catheterization laboratory for any hemodynamic instability indication, and has all the well-documented inherent biases for retrospective studies. The overall number of devices placed was relatively modest, limiting our statistical power for subgroup trends and subgroup analyses. The decision to place a device was at the discretion of the interventional cardiologist.
We observed a decrease in prophylactic device usage in the high-risk PCI population, which was a small subset of the overall group (10% of the total population). We cannot statistically exclude that this observation was a chance finding.
During the 7 years studied, there was no significant change in the total number of circulatory support devices placed per year, despite decreased usage of the Impella device. There was a significant decrease in utilization of percutaneous mechanical circulatory support for patient undergoing high-risk PCI, driven primarily by decreased usage of the IABP. There were more complications and higher mortality in patients who received an Impella compared with an IABP, but this observation could be explained by selection bias, with the sicker patients receiving an Impella device.
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From the 1Department of Cardiovascular Diseases and the 2Division of Pulmonary and Critical Care Medicine, Department of Medicine, Mayo Clinic Rochester, Rochester, Minnesota.
Disclosures: The authors have completed and returned the ICMJE Form for Disclosure of Potential Conflicts of Interest. The authors report no financial relationships or conflicts of interest regarding the content herein.
Manuscript submitted March 14, 2017 and accepted March 24, 2017.
Address for correspondence: Gregory W. Barsness, MD, Mayo Clinic Rochester, 200 First Street SW, Rochester, MN 55905. Email: Barsness.Gregory@mayo.edu