Author + information
- Published online May 1, 2017.
- Courtney E. Bennett, DO∗ (, )
- Marysia S. Tweet, MD,
- Hector I. Michelena, MD,
- Gregory J. Schears, MD and
- Sharon L. Mulvagh, MD
- ↵∗Division of Pulmonary and Critical Care, Critical Care Department, Mayo Clinic, 200 First Street SW, Rochester, Minnesota 55905
Transthoracic echocardiography and transesophageal echocardiography (TEE) are valuable for patients on extracorporeal membrane oxygenation (ECMO). These tools are used to perform “turn down” assessments, evaluate for cannula placement/position, and guide management. ECMO is a form of mechanical circulatory support using a pump and circuit for oxygenation and cardiac output. The multiple chest tubes, surgical incisions, mechanical ventilation, and restricted positioning required for ECMO patients can limit echocardiography quality. Even TEE images can be obscured by post-operative changes to the mediastinal structures and cardiac chambers.
Contrast echocardiography (CE) with perflutren microbubbles has been validated as a safe and effective method to evaluate cardiac chamber function and to rule out cardiac masses or thrombi in technically difficult studies (1). There is limited information on the utility and safety of CE in patients receiving ECMO (2). Potential issues include accelerated destruction of contrast microbubbles by the ECMO circuit (3) and concern for circuit interference because the systems are designed to detect bubbles (4). The purpose of this report is to evaluate our experience with the safety and feasibility of CE use in patients on ECMO.
We retrospectively reviewed the records of patients from our institution that received CE while on ECMO support from September 2001 to March 2016. Patients were identified by searching the Echo Information Management System for “ECMO” and “contrast.” There were a total of 1,996 studies of patients on ECMO and 4 (<1%) of these studies included CE. The commercially available contrast agent, Definity (Lantheus Medical Imaging, Billerica, Massachusetts), was used in all 4 cases, according to the institutional protocol (Mayo Clinic Echocardiography Laboratory Contrast Administration protocol) and the American Society of Echocardiography guidelines (1,5).
Of the 4 patients studied, 2 were during transthoracic echocardiography and 2 during TEE. Three patients were on venoarterial ECMO and 1 was on venovenous ECMO. All 4 patients were on a CARDIOHELP machine (Maquet Getinge Group, Wayne, New Jersey). Three of these studies were indicated for the assessment of possible mass or thrombus and 1 was to define the left ventricular function. CE answered the clinical question in all cases, and in 2 cases, resulted in a change in management. The findings in 1 case assisted in the titration of the ECMO settings. Another case demonstrated left atrial thrombus prompting emergent cardiac surgery. Two cases resulted in resolution of clinical concern for mass or thrombus. No complications related to CE are reported in the records. In our most recent case the integrated detector for air bubbles or thrombi alarmed, indicating engagement of the “zero-flow” mode and imminent pump shut down. Fortunately, the perfusionist was present at the bedside and had purposefully suspended the intervention. The ECMO circuit continued to function without complications. In the literature, alarms triggered by contrast microbubbles with resultant shutdown of the ECMO circuit and hemodynamic consequences have been reported in 2 patients (4). In our series, there are a few possibilities that may explain why only 1 event occurred. The interventions may have been pre-emptively suspended and/or the volume may not have been sufficient enough to trigger the alarms. Finally, if the right ventricular function is adequate, then no contrast may have entered the circuit.
In summary, we have successfully used CE to assess 4 ECMO patients without deleterious effects and with positive impact on management. However, microbubbles can result in acute, potentially catastrophic hemodynamic effects in these patients when detected as air bubbles by the ECMO circuit and trigger pump shutdown. We suggest creating a CE protocol specifically for ECMO patients. This protocol should focus on minimizing dosing and healthcare personnel communication, with requisite presence of a perfusionist or ECMO specialist at the time of CE performance. High mechanical index may be utilized to destroy the microbubbles if they persist in the circulation once the CE is complete.
Please note: The authors acknowledge Amy Dichak, RDCS, for her contribution to data collection. Dr. Mulvagh has received research grants from Lantheus Medical Imaging, Bracco Diagnostics Inc., and GE Healthcare; and has served as a consultant for Lantheus Medical Imaging and Bracco Diagnostics Inc. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose.
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