Initiation of Extracorporeal Membrane Oxygenation in the Cardiac Catheterization Laboratory: The Mayo Clinic Experience

Abstract: Introduction. Extracorporeal membrane oxygenation (ECMO) support is indicated for the management of patients with cardiogenic shock or refractory cardiac arrest in the cardiac catheterization laboratory. The aim of this study was to review the outcomes of patients initiated on ECMO support in the cardiac catheterization laboratory. Methods. We performed a retrospective analysis of adult patients (>18 years old) initiated on ECMO support in the cardiac catheterization laboratory from 2010-2017. Baseline demographics, clinical characteristics, procedural details, and indication for ECMO support were reviewed. The outcomes assessed included 30-day mortality, blood product transfusion, vascular injury, prolonged respiratory failure, stroke, ischemic bowel, renal failure requiring hemodialysis, and compartment syndrome. Results. Between January 1, 2010 and December 31, 2017, a total of 25 patients were cannulated for ECMO in the cardiac catheterization laboratory. The mean age was 61 years and 56% of patients were men. Cardiac arrest was the most frequent indication for ECMO support (64%), followed by cardiogenic shock (28%). The 30-day mortality rate was 40%. The most frequent complications associated with ECMO were the need for vascular surgery (52%) and renal failure requiring hemodialysis (36%). The univariate predictors of 30-day mortality were age (P=.02; unit odds ratio [OR], 1.08; 95% confidence interval [CI], 1.01-1.15), history of tobacco use (P=.04; OR, 6; 95% CI, 1.01-35.91), and Apache IV score (P=.02; unit OR, 1.02; 95% CI, 1.01-1.09). Conclusions. ECMO should be considered early during the resuscitation attempts of selected patients with ongoing cardiopulmonary resuscitation or refractory cardiogenic shock in the cardiac catheterization laboratory.

Key words: cardiac arrest, cardiogenic shock, extracorporeal membrane oxygenation

The utilization of percutaneous mechanical circulatory support devices for patients with cardiogenic shock (CS) or refractory cardiac arrest has drawn significant controversy over recent years. The intra-aortic balloon pump (IABP) had been the only available percutaneous device for many years; however, studies in patients with an acute myocardial infarction (AMI) and CS have failed to show an improvement in mortality for patients treated with an IABP compared with medical therapy alone at 30 days or 1 year.^1,2 The current American College of Cardiology Foundation/American Heart Association guidelines give a class IIa (level of evidence B) recommendation for IABP insertion in patients with an acute myocardial infarction and CS, while the European Society of Cardiology/European Association for Cardio-Thoracic Surgery guidelines give it a class III (level of evidence A) recommendation.^3,4 Devices such as Impella (Abiomed) or TandemHeart (CardiacAssist) have been shown to have superior hemodynamic effects compared with the IABP, but the initial small studies failed to show an improvement in outcomes.^5,6 The most recent studies of the Impella CP device have shown that with a standardized approach combined with early initiation of support, patients with an AMI and CS can achieve a 76% hospital survival rate, as opposed to the 50%-60% hospital survival reported in other studies.^7-9 Despite the significant hemodynamic support these devices are able to provide, they are unlikely to be sufficient in patients with profound CS, biventricular failure, or refractory cardiac arrest. Extracorporeal membrane oxygenation (ECMO) can be rapidly deployed in the cardiac catheterization laboratory and is able to achieve full cardiopulmonary support in these situations. The aim of this study is to review the outcomes of patients initiated on ECMO support in the cardiac catheterization laboratory.

Methods

After obtaining institutional review board approval, all consecutive patients cannulated for venoarterial ECMO in the cardiac catheterization laboratory at Mayo Clinic in Rochester, Minnesota between January 1, 2010 and December 31, 2017 were identified. A total of 25 patients were included in this analysis. Demographic, clinical, and procedural data were recorded and adverse events/outcomes data were obtained by reviewing patient medical records. Our ECMO team consisted of a cardiac anesthesiologist-intensivist, an interventional cardiologist, a cardiovascular surgeon, a perfusionist, and a trained nurse or respiratory therapist (ECMO specialist). As per institutional protocol, an assembled and primed system was available around the clock for use in the catheterization laboratory. Patient triage for eligibility was performed by the on-call ECMO physician. Mobilization of the ECMO team and the primed ECMO machine occurred rapidly once patient eligibility was confirmed. Cannulation was performed by the interventional cardiologist or cardiovascular surgeon as circumstances allowed. Anticoagulation was achieved with heparin or bivalirudin, and titrated to achieve either an activated clotting time in the range of 140-170 seconds or activated partial thromboplastin time in the range of 50-80 seconds. ECMO circuit flow was maintained at a cardiac index of 2.0-2.4 L/min/m² as allowed by the cannula size and the patient’s volume status, with an aim to keep mixed venous saturation >60%. After ECMO initiation, if left atrial hypertension-pulmonary edema persisted due to profound residual left ventricular dysfunction, left ventricular decompression was considered. Vasopressor administration was titrated to maintain a mean arterial pressure of 60-65 mm Hg. 

Routine monitoring by clinical examination, pulse oximetry, and ultrasound assessment of the limbs was carried out to identify possible limb ischemia in the setting of femoral arterial cannulation. Follow-up echocardiograms, chest x-ray, and electrocardiography were performed to monitor myocardial recovery. Weaning of ECMO support was based upon the clinical and investigative evidence of recovery of cardiac function. Successful weaning was defined as separation from ECMO without reinsertion. Withdrawal of ECMO support was based upon evidence of prolonged multiple organ failure, no recovery of cardiac function, massive uncontrollable bleeding, documented brain death, or family decision.

The outcomes assessed included in-hospital mortality, blood product transfusion, vascular surgery, prolonged respiratory failure, stroke, ischemic bowel, renal failure requiring hemodialysis, and compartment syndrome. We assessed blood product administration during ECMO support to include packed red blood cells, fresh frozen plasma, cryoprecipitate, and platelet transfusion. The need for vascular surgery was defined by bleeding at the cannulation site requiring cannula manipulation with vascular repair, limb ischemia requiring cannula revision/removal, or conversion to central cannulation. Routine vascular repair upon decannulation was not included. Prolonged respiratory failure was defined as mechanical ventilation for >14 days or tracheostomy placement. A stroke was confirmed if there was evidence of a neurological deficit and imaging (computed tomography or magnetic resonance imaging) confirmed an ischemic or hemorrhagic infarct. Ischemic bowel required direct operative confirmation with inspection of the small bowel and resection due to ischemia. Renal failure was defined as the need for renal replacement therapy during ECMO support. A diagnosis of compartment syndrome required an elevated creatine kinase, evidence of elevated compartment pressures, and a requirement for fasciotomy.

Statistical analysis. Continuous variables are reported as mean ± standard deviation and categorical variables are reported as percentages. Survivors and non-survivors were compared using Fisher’s Exact test for categorical variables and the Wilcoxon rank-sum test for continuous variables. Predictors of 30-day mortality were determined using univariate analysis and reported as unit odds ratio (OR) and 95% confidence interval (CI). All tests were two sided and P-values ≤.05 were considered statistically significant. All statistical analyses were performed using JMP, version 14.1.0 (SAS Institute).

Results

Between January 1, 2010 and December 31, 2017, a total of 25 patients were initiated on ECMO in the cardiac catheterization laboratory. Mean patient age was 61 ± 14.1 years and 14 patients (56%) were men. Echocardiographic examination revealed a mean left ventricular ejection fraction of 27% with moderate right ventricular dysfunction (Table 1). 

Of the 25 patients cannulated for ECMO, a total of 17 patients (68%) underwent attempted percutaneous coronary intervention (PCI); of these, fifteen (88%) presented with an acute coronary syndrome and 12 (71%) had ST-segment elevation myocardial infarction. The left anterior descending artery was treated most frequently (59%), and multivessel PCI was attempted in 41% of cases. At least 1 attempted PCI was performed in 76% of these patients prior to ECMO initiation. PCI was successful in restoring TIMI 3 flow in all epicardial coronary vessels in 76% of treated patients. 

Of the additional 8 non-PCI patients cannulated for ECMO, 3 patients (12%) underwent a percutaneous mitral valve replacement, 2 patients (8%) had massive pulmonary emboli, 2 patients (8%) had ventricular tachycardia storm, and 1 patient (4%) had an anaphylactic reaction (Table 2). In total, 84% of patients had a cardiac arrest in the catheterization laboratory with a mean duration of cardiopulmonary resuscitation (CPR) prior to ECMO initiation of 36 minutes. The initial cardiac rhythm during the resuscitation was pulseless electrical activity/asystole in 66% and pulseless ventricular tachycardia/ventricular fibrillation in 33%. Eight patients (32%) had another percutaneous mechanical circulatory support device placed prior to the initiation of ECMO. 

At the time of ECMO cannulation, 16 patients (64%) were undergoing active CPR (extracorporeal life support), 7 patients (28%) had refractory cardiogenic shock, and 2 patients (8%) were placed on ECMO to support a high-risk procedure (Table 3). Peripheral cannulation was performed in 96% of cases. Only 1 patient (4%) received a distal perfusion catheter and 5 patients (20%) required a left ventricular vent for unloading of the left ventricle. The mean Apache IV score was 113, which correlates to a predicted mortality of 73%. 

The 30-day mortality rate of patients cannulated for ECMO in the cardiac catheterization laboratory was 40%. Of the 15 patients that survived, 12 (80%) were bridged to recovery and 3 (20%) were bridged to cardiac replacement therapy (left ventricular assist device or orthotopic heart transplantation). Blood product administration was frequent; the mean packed red blood cell product requirement was 21 units, fresh frozen plasma requirement was 8 units, cryoprecipitate requirement was 2 units, and platelet requirement was 4 units. The most common complication observed was the need for vascular surgery in 13 patients (52%); 9 patients had lower-extremity ischemia, 3 had a vascular injury due to cannulation, and 3 had significant bleeding. Renal failure requiring hemodialysis occurred in 9 patients (36%) (Table 4). The mean duration of ECMO support was 89 hours and the average length of hospitalization was 23 days. 

The univariate predictors of 30-day mortality were age (P=.02; unit OR, 1.08; 95% CI, 1.01-1.15), history of tobacco use (P=.04; OR, 6; 95% CI, 1.01-35.91), and Apache IV score (P=.02; unit OR, 1.02; 95% CI, 1.01-1.09). Complications associated with ECMO were not associated with increased 30-day mortality; however, the duration of ECMO support was much shorter in the non-survivors (48 hours vs 116 hours in the survivors; P=.07).

Discussion

In this study, we report the outcomes and complications associated with ECMO use in the cardiac catheterization laboratory. Despite the majority of patients (84%) suffering a prolonged cardiac arrest (36 minutes) in the catheterization laboratory, the 30-day survival rate was 60%. Cardiac recovery occurred in 80% of these patients, with 3 (20%) requiring cardiac replacement therapy. The complications associated with ECMO support continue to remain high, with frequent vascular complications associated with large-bore peripheral cannulas. 

The patients included in our study were placed on ECMO due to profound CS (28%) or during CPR (64%). Eight patients had either an IABP or an Impella placed prior to the initiation of ECMO support. The use of mechanical circulatory support devices for patients with CS has been a major topic of debate over the past decade, with multiple studies showing no benefit of these devices.^1,2,5,6,8 It is well known that the cardiac output augmentation provided by the IABP (0.3-0.5 L/min) is insufficient to provide meaningful support to a patient in profound CS or to stabilize a patient with ongoing CPR.¹⁰ Despite this, it remains the “standard of care” and all clinical trials studying additional mechanical circulatory support devices are compared to this. 

The Impella was developed to provide greater hemodynamic support. Depending on the device deployed, the cardiac output augmentation can be 2.5 L/min, 3.8 L/min, or 5.0 L/min. However, the early studies with the Impella 2.5 and Impella CP have failed to show a survival benefit in patients with an AMI complicated by CS.^5,8,11 There are some data supporting the use of the Impella CP prior to PCI in patients presenting with an AMI and CS.^7,12 The rationale for early Impella placement in these patients is that it is able to restore systemic hemodynamics early and prevent deterioration to multiorgan failure, which is a major complication of CS. Unfortunately, despite the increased hemodynamic support generated by the Impella, it remains insufficient in cases of profound CS, biventricular failure, or ongoing cardiac arrest. 

Veno-arterial ECMO circuits include an oxygenating membrane and provide robust hemodynamic support (up to 5 L/min), conferring a distinct advantage over the other support devices. In the setting of refractory out-of-hospital ventricular fibrillatory arrest, ECMO support can be rapidly deployed during ongoing CPR after arrival to the catheterization laboratory and is associated with improved outcomes when compared with historical cohorts.^13,14 These studies build on previous observational studies that showed improved outcomes in patients treated with veno-arterial ECMO for profound CS or refractory ventricular arrhythmias.^15-18 

With the advancement and ongoing miniaturization of transcatheter technology, increasingly complex procedures can now be performed in the catheterization laboratory with enhanced safety and equivalent effectiveness to open surgery. Such procedures include multivessel/complex PCI, transcatheter aortic valve replacement, transcatheter mitral valve repair/replacement, and transcatheter tricuspid valve repair/replacement. The decision to pursue catheter-directed therapy as opposed to standard surgical intervention in these patients is often related to the elevated surgical risk. However, these patients remain at high risk of hemodynamic collapse during catheter-directed procedures and consideration is given to prophylactic support. 

Both the IABP and Impella have been studied in the setting of hemodynamic support prior to high-risk PCI. In the short-term studies, there did not appear to be a benefit associated with hemodynamic support; however, longer-term follow-up studies did appear to show a benefit.^19-21 The long-term benefit observed in these studies has been attributed to the more complete coronary revascularization achieved with supported procedures. There are clinical situations when either the IABP or Impella are not deemed to be sufficient for hemodynamic support during high-risk percutaneous procedures. In these scenarios, ECMO support should be considered. Currently there are only small retrospective studies describing the use of ECMO prior to high-risk PCI or high-risk transcatheter aortic valve implantation, with good outcomes observed.^22-24

Study limitations. This single-center study has the inherent biases that limit interpretation of all retrospective studies. Despite reviewing the previous 8 years, we had relatively few cases (25) in which ECMO was initiated in the cardiac catheterization laboratory. There was a wide variety of procedures and indications for the initiation of ECMO, which can limit the ability to define the subgroup of patients who will benefit from ECMO support. Due to the nature of this report, we were not able to identify the cases in which ECMO was considered but was not initiated to determine if there would have been a difference in outcomes. In the future, larger, multicenter, randomized studies will be needed to determine whether there is a benefit from ECMO support and, if so, which patients will derive the benefit. 

Conclusion 

Despite having a very high predicted mortality (73%) based on the Apache IV score, patients initiated on ECMO in the cardiac catheterization laboratory had a 30-day survival rate of 60%. ECMO should be considered early during the resuscitation attempts of selected patients with ongoing CPR or refractory CS in the cardiac catheterization laboratory.

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From the ¹Division of Cardiovascular Medicine, University of Wisconsin – Madison, Madison, Wisconsin; ²Department of Cardiovascular Medicine, Mayo Clinic, Rochester, Minnesota; and ³Department of Anesthesia, Critical Care Medicine, and ECMO Services, Mayo Clinic, Rochester, Minnesota.

Disclosure: The authors have completed and returned the ICMJE Form for Disclosure of Potential Conflicts of Interest. The authors report no conflicts of interest regarding the content herein.

Manuscript submitted August 8, 2019, provisional acceptance given August 14, 2019, final version accepted August 19, 2019.

Address for correspondence: Bradley Ternus, MD, UW Health University Hospital, 600 Highland Avenue, Madison, WI 53792. Email: bwternus@medicine.wisc.edu