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Initial Experience of Transaortic Catheter Venting in Patients with Venoarterial Extracorporeal Membrane Oxygenation for Cardiogenic Shock

Hong, Tae Hee; Byun, Joung Hun; Lee, Hee Moon; Kim, Yong Hwan; Kang, Gu-Hyun; Oh, Ju Hyeon; Hwang, Sang Won; Kim, Han Yong; Park, Jae Hong

doi: 10.1097/MAT.0000000000000327
Adult Circulatory Support

Extracorporeal membrane oxygenation (ECMO) has become one of the often applied mechanical support for acute cardiogenic shock. During venoarterial (VA) ECMO support, left heart decompression should be considered when left ventricular (LV) distension develops with pulmonary edema and LV dysfunction. The aim of this study was to report the results of transaortic catheter venting (TACV), as an alternative venting method, performed during VA-ECMO in patients with acute cardiogenic shock. We retrospectively reviewed the records of seven patients who underwent both ECMO and TACV between February 2013 and February 2014. Extracorporeal membrane oxygenation was performed uneventfully, and TACV was introduced under transthoracic echocardiographic guidance in all cases. Hemodynamic parameters, LV ejection fraction, and LV end-diastolic dimension (LVEDD) were measured 24 hours after initiating TACV in survivors. There were no procedure-related complications. Four of the seven patients (58%) survived. Transaortic catheter venting led to an increase in mean blood pressure in all patients (p = 0.050). There was a significant difference between pre- and post-TACV-LVEDD (59 ± 14 vs. 50 ± 12 mm, p = 0.044), with a 10–23% reduction in LVEDD in survivors. Transaortic catheter venting might be an acceptable alternative to venting procedures and useful for LV recovery during VA-ECMO in patients with severe LV dysfunction.

From the *Department of Thoracic and Cardiovascular Surgery, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, South Korea; Department of Emergency Medicine, Samsung Changwon Hospital, Sungkyunkwan University School of Medicine, Changwon, South Korea; Department of Cardiology, Samsung Changwon Hospital, Sungkyunkwan University School of Medicine, Changwon, South Korea; §Department of Thoracic and Cardiovascular Surgery, Samsung Changwon Hospital, Sungkyunkwan University School of Medicine, Changwon, South Korea and Present address: Department of Thoracic and Cardiovascular Surgery, Changwon Hospital, Gyeongsang National University School of Medicine, Changwon, South Korea.

Submitted for consideration May 2015; accepted for publication in revised form December 2015.

Disclosure: The authors have no conflicts of interest to report.

Correspondence: Joung Hun Byun, Department of Thoracic and Cardiovascular Surgery, Changwon Hospital, Gyeongsang National University School of Medicine, 11, Samjeongja-ro, Seongsan-gu, Changwon-si 51472, South Korea. Email: jhunikr@naver.com.

Cardiogenic shock is still an extremely fatal condition, and its mortality rate (50–80%) remains unacceptably high.1,2 In refractory cardiogenic shock, venoarterial extracorporeal membrane oxygenation (VA-ECMO) is an established treatment option because it can rapidly unload both ventricles and maintain end-organ perfusion. During VA-ECMO support, especially in the peripheral type, left ventricular (LV) distension can develop, resulting in pulmonary edema and LV dysfunction. Various methods for left heart decompression are known, but there is no consensus about the appropriate method and timing of decompression.3,4

Current practices widely used for decompression include transseptal approaches and surgical venting. However, these are not always applicable in clinical situations with various constraints, such as sudden hemodynamic collapse or limited resources of the particular institution. In addition, it is reasonable to suppose that direct ventricular decompression would be preferred more than atrial decompression in patients with severe LV dysfunction or LV asystole.

Several groups have reported the possibility of transaortic catheter venting (TACV), which can directly unload LV without surgical manipulation.5,6 However, evidence regarding the effectiveness of TACV is limited. Prior reports have involved animal experiments or case reports. Here, we evaluated our institutional experience with TACV during VA-ECMO in seven patients with severe LV dysfunction in the setting of acute cardiogenic shock.

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Methods

Study Design and Patient Characteristics

This retrospective study was reviewed and approved by the Institutional Ethical Committee of Sungkyunkwan University, Samsung Changwon Hospital (Approval number 2014-SCMC-026-01). Patient consent was waived based on the nature of this study. Baseline characteristics of patients are presented in Table 1. Records of seven consecutive patients who underwent both VA-ECMO and TACV between February 2013 and February 2014 were reviewed. Two of the seven patients were female. The mean age was 39.9 ± 13.6 years (range 22–60 years). The underlying pathology included acute myocardial infarction, pulmonary thromboembolism, and decompensated heart failure in dilated cardiomyopathy. None of the patients had a medical history of underlying lung disease, such as emphysema, chronic pulmonary infection, or interstitial lung disease. All patients had experienced acute cardiogenic shock, and four patients (1, 2, 3, and 6) underwent extracorporeal cardiopulmonary resuscitation because of acute cardiogenic shock with cardiac arrest.

Table 1

Table 1

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Installation and Management of VA-ECMO and TACV

Venoarterial ECMO (MAQUET Cardiopulmonary AG, Hirrlingen, Germany) was established peripherally through both a femoral artery and a femoral vein using a RMI 15–17 Fr arterial cannula (Edwards Lifescience LLC, Irvine, CA) and a DLP 21–22 Fr venous cannula (Medtronic Inc., Minneapolis, MN). All cannulation procedures were performed percutaneously in the emergency room or intensive care unit (ICU). Detailed ECMO data are presented in Table 2. The target ECMO flow was 2.5 L/min/m2 body surface area. The criteria for the application of percutaneous TACV for LV decompression were severe LV dysfunction (LV ejection fraction [LVEF], <25%), with persistent pulmonary edema on chest x-ray (criterion A) or LV asystole with/without mitral insufficiency on transthoracic echocardiography (TTE) (criterion B). All seven patients met criterion A, whereas patients 5 and 7 also met criterion B. After confirmation of severe LV dysfunction or asystole by TTE, a 5–6 Fr pigtail TACV catheter (PIG performa; Merit Medical, South Jordan, UT) was inserted directly into the LV cavity across the aortic valve (AV) using a transfemoral approach (Figure 1). In Korea, only the 5–6 Fr pigtail used in this study has the length necessary to reach the LV (at least 1 m long). The procedure was performed under TTE guidance. The TACV catheter was connected to the venous limb of the ECMO circuit (Figure 2).

Table 2

Table 2

Figure 1

Figure 1

Figure 2

Figure 2

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Postprocedural Management and Weaning of Transaortic Catheter Venting

The flow patency of the TACV catheter was checked hourly using Doppler ultrasound. Electrocardiogram (EKG) tracings and arterial and central venous pressures were continuously monitored. TTEs were checked daily after initiating ECMO and TACV. Post-TACV-LVEF and post-TACV-LV end-diastolic dimension (LVEDD) were measured 24 hours after initiating TACV in surviving patients. Normothermia and mean arterial pressure >60 mm Hg were maintained in all patients after TACV initiation. Blood gas analysis from the TACV catheter was measured hourly to assess improvement in pulmonary function. To prevent differential hypoxia, mechanical ventilation was set to maintain a PaO2 >70 mm Hg based on the results of blood gas analysis from the TACV catheter. An intra-aortic balloon pump was inserted in patient 5 as a bridge therapy. Weaning from the TACV was considered when the chest x-ray revealed improved pulmonary edema, blood gas analysis through the TACV catheter showed improved oxygenation (especially a ratio of arterial oxygen partial pressure to fractional inspired oxygen [PaO2/FiO2] > 100 to 150), LV asystole was resolved on TTE (opening of AV), and an arterial pulse waveform with greater than 20 mm Hg pulse pressure was maintained for more than 12 hours.

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Statistical Analysis

For statistical analysis, continuous data are presented as the mean ± standard deviation. Differences between the survival and the death groups were compared using Student’s t-tests. The effect of TACV was determined using Wilcoxon’s signed rank tests. A p value <0.05 was considered statistically significant. Data were analyzed using SPSS Statistics 21.0 (IBM, New York, NY).

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Results

Transaortic catheter venting catheters were introduced without any procedure-related complications, including damage to the LV wall, AV, or aortic wall. Four of the seven (58%) patients survived. Patients 4, 5, 6, and 7 were discharged and successfully weaned from ECMO and mechanical ventilation without complications. In the surviving patients, mean ECMO support duration was 5.8 ± 3.1 days. In the nonsurvivors, mean ECMO support duration was 6.6 ± 8.1 days. The mean cumulative ICU stay and mean hospital stay were 8.3 ± 3.8 days and 30.3 ± 17.3 days, respectively. Patients 1 and 3 died from excessive upper gastrointestinal bleeding, and patient 2 died from sepsis. There was a significant difference in ECMO flow rates between patients who survived and those who did not (2.76 ± 0.23 vs. 1.92 ± 0.20 L/min, p = 0.011; Table 2).

The effect of TACV during ECMO is shown in Table 3. In surviving patients, pre- and post-TACV-LVEF were 18.3 ± 7% and 38.3 ± 16.5%, respectively (p = 0.094). There was a significant 10–23% reduction in LVEDD after insertion of a TACV (59 ± 14 vs. 50 ± 12 mm; p = 0.044). After insertion of a TACV catheter, the mean arterial blood pressure increased in the surviving patients (p = 0.050; Table 4).

Table 3

Table 3

Table 4

Table 4

Although they did not reach statistical significance, lactate level and dopamine requirement also decreased after the application of TACV (p = 0.052 and p = 0.056, respectively). Chest x-ray revealed improved pulmonary edema after TACV insertion (Figure 3, A and B). In patients 5 and 7, who showed asystole on TTE before TACV insertion, restoration of the arterial blood pressure waveform and heart rhythm on EKG tracing were evident immediately after TACV insertion.

Figure 3

Figure 3

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Discussion

In 1971, Hill et al. 6 reported the first successful use of VA-ECMO in a 24 year-old polytrauma patient with a ruptured aorta. Various types of ECMO pumps and oxygenators have been subsequently developed, enabling the majority of the patients to be stabilized through ECMO support. Thus, VA-ECMO support could reasonably increase mid- to long-term outcome of severe cardiogenic shock, with reported survival rates of 28–42%.7–9 The Extracorporeal Life Support Organization Registry indicates an average survival rate of 41% for adult patients with cardiogenic shock.10

Extracorporeal membrane oxygenation support provides wall tension control and ventricular unloading, as well as ensuring the tissue perfusion.11 However, LV distension occurs and can be aggravated during VA-ECMO by the afterload induced by ECMO on a failing LV, suboptimal venous return with right heart recovery, heavy bronchial and Thebesian blood flow, and aortic insufficiency.11

Inadequate LV decompression during VA-ECMO causes increased LV end-diastolic volume and myocardial wall stress, which lead to increased myocardial oxygen demand and potential ischemic damage to the myocardium.12 Also, elevated left atrial pressure produces pulmonary edema and hemoptysis. Furthermore, there is an increased risk of intracardiac thrombus formation in the distended left heart chamber that shows severe akinesia and a closed AV.13

For these reasons, left heart decompression is of paramount importance during VA-ECMO. However, there is no consensus about the appropriate method or timing of left heart decompression. Although the indication to vent the left heart is still controversial, it is also reasonable to insert a vent prophylactically. Indeed, some centers routinely perform venting before the development of signs of LV distension (e.g., narrow pulse pressure and failure of AV opening in TTE), especially in pediatric patients whose myocardium is extremely vulnerable to distension. Hacking et al. 14 recently reported that prophylactic (elective) left heart decompression in pediatric patients at the time of initiation of VA-ECMO was not associated with improved ECMO survival. According to previous studies on left heart venting, left heart decompression is usually considered in cases of LA/LV dilatation with LV dysfunction or uncontrolled pulmonary edema13,15

There are various methods of venting, including surgical ventricular venting or percutaneous methods of venting. Surgical techniques to directly vent the LV include direct pulmonary venous cannulation and transapical cannulation.13 A number of percutaneous techniques have also been described, including intra-aortic balloon pump, blade or balloon septostomy, axial flow pumps (Impella, Abiomed, Danvers, MA), and a percutaneous transpulmonic approach.13

According to recent articles on percutaneous techniques of venting, the percutaneous transseptal approach is represented to be a more practical and safer method compared with other techniques.16,17 However, left heart decompression using transseptal approaches risks septal injury or possible left-to-right shunt formation. In addition, LA decompression can prevent pulmonary edema but has no direct unloading effect on the LV in the absence of mitral insufficiency, especially in asystole of the LV. Transaortic catheter venting might be advantageous under these conditions because it can directly decompress the LV.

Transaortic catheter venting can be performed percutaneously with TTE, eliminating the need for surgical manipulation, which is associated with bleeding risk and surgical complications. Furthermore, this technique is available at bedside in the ICU, without the need to move critically ill patients. Timely intervention might be impossible if required to be performed in an operating room or catheterization laboratory because LV distension can progress to LV asystole in a few minutes. According to a report by Aiyagari et al.,16 the median procedural time to place the left atrial drain was 51 minutes (range 42–145 minutes). The average duration of the TACV procedure is less than 20 minutes, which is much shorter than that of other techniques. Prompt management of critical patients is possible because of the timely introduction of TACV, which might contribute to better clinical outcome. It is also less expensive than surgical and transseptal approaches.

The TACV catheter can be used to perform blood gas analysis. This allows for early detection of differential hypoxia (especially coronary or cerebral hypoxemia) caused by poor lung function. We performed hourly blood gas analysis from TACV catheter samples. Consequently, we successfully maintained adequate oxygenation in blood ejected from the LV, which is critical for the recovery of damaged myocardium.

There have been several reports about TACV for left heart decompression. In 1997, Kurihara et al. 18,22 reported the effect of TACV on LV function during ECMO. They suggested that TACV might be an adjunctive technique to VA-ECMO for patients with LV failure. However, the study was performed in an adult dog. Whether the results are completely relevant to humans is unclear. Several subsequent human case reports of TACV have been published.5,19 However, no study has addressed the effectiveness of TACV in multiple patients.

To our knowledge, this is the first study regarding the effectiveness of TACV including multiple patients. In addition, we measured the degree of LV decompression using LVEDD as a quantified parameter. The values correlated well with hemodynamic values and clinical resolution of symptoms, such as disappearance of pulmonary edema. In 2014, Weymann et al. 20 reported on the LV unloading effect of central VA-ECMO combined with surgical LV venting in 12 patients. They reported an overall survival rate of 58.3% but did not measure actual hemodynamic parameters of LV decompression. Although we included the small number of patients, the clinical outcomes regarding survival rate and complication rate were notable. Four patients had undergone cardiopulmonary resuscitation before cannulation, which means the underlying pathological process was fulminant. In the previously mentioned setting, four of the seven patients (57%) survived, showing a comparable outcome to previous reports with similar settings. We performed ECMO with TACV without procedure-related complications.

There were some limitations to the current study. First, this was a retrospective study without a control group and included a small number of patients. Consequently, the study has weak statistical power. Further comparison between the TACV and the transseptal approaches will be required. Second, left ventricular end diastolic pressure (LVEDP) is widely used in echocardiographic evaluation of diastolic dysfunction and might be a more accurate index of LV decompression.21 In our study, LVEDD was used as an index of LV decompression in place of LVEDP. However, we were able to confirm a decrease in LVEDP in one case (patient 7) by connecting TACV to a pressure monitoring line. In the future, we will measure LVEDP using a continuous pressure monitor on TACV. Third, we were unable to collect TTE data (e.g., pre-TACV-LVEDD) from deceased patients (patients 1, 2, and 3) because of hemodynamic instability. Last, we could not determine the correct flow through the vent catheter. We could only check the flow patency of the TACV catheter using Doppler ultrasound. Instead, we had to predict the effect of venting as LVEDD according to TTE before and after the procedure.

In conclusion, TACV is an easy, rapid, and safe method for direct LV decompression. It is useful especially in emergency cases in which surgical venting or complex procedures are not possible. Transaortic catheter venting is a feasible option for LV venting, especially in patients with LV distension with asystole or severe LV dysfunction.

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References

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Keywords:

extracorporeal membrane oxygenation; decompression; left ventricular dysfunction

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