Predictivity of Each Readiness-to-Explant Criterion for Successful Venoarterial Extracorporeal Membrane Oxygenation Explantation

Abstract

Background: The use of temporary mechanical circulatory support (tMCS) has revolutionized the management of cardiogenic shock (CS). However, standardized readiness-to-explant criteria for venoarterial extracorporeal membrane oxygenation (VA-ECMO) have not been established.

Methods and Results: We performed a retrospective analysis of 37 patients with CS who were explanted from VA-ECMO at Okayama University Hospital from December 2018 to May 2024 to evaluate the diagnostic performance of each readiness-to-explant criterion for explant success or failure. Explant success was defined as 30-day survival without re-insertion of MCS. Hemodynamic parameters were assessed at explant, weaning (1.0 to 1.5 L/min), and the off test (5 min). We assessed the predictive performance among parameters in successful or unsuccessful explantation of VA-ECMO using receiver operative characteristic curve analysis. The pulmonary artery catheter (PAC) criteria (pulmonary artery wedge pressure ≤18 mmHg, central venous pressure ≤12 mmHg, and cardiac index ≥2.2 L/min/m²) at the off test showed the highest predictability for successful explantation of VA-ECMO (area under the receiver operating characteristics curve 0.83; 95% confidence interval 0.71–0.96). The sensitivity, specificity, positive predictive value, and negative predictive value of the PAC criteria were 67%, 100%, 100%, and 38%, respectively.

Conclusions: Our results suggest that the PAC criteria at the off test may be the most appropriate algorithm for predicting successful explantation of VA-ECMO. Further prospective studies are needed to validate the present findings and to establish standardized VA-ECMO explantation practices.

Central Figure

Cardiogenic shock (CS) is a life-threatening condition characterized by end-organ hypoperfusion, which can result from a variety of etiologies, including acute myocardial infarction and heart failure.¹ The use of temporary mechanical circulatory support (tMCS) devices has become increasingly prevalent in clinical practice,^2–5 and recent trials have demonstrated the efficacy of tMCS for CS.⁶ As tMCS devices are approved for use for periods ranging from approximately 6 h to 30 days, depending on the device type, tMCS is intended to serve as a bridge to the next level of care.⁷ This may include a bridge to recovery or a bridge to the decision of heart transplantation, a durable continuous-flow left ventricular assist device, or withdrawal of care. In accordance with the prevailing adult heart allocation policy for heart transplantation, individuals are deemed eligible for transplantation if they have demonstrated dependence on tMCS through attempted device weaning trials.^8,9 However, there is currently no standardised protocol for the evaluation of tMCS dependence, and optimal strategies for tMCS de-escalation remain poorly defined.^10–12

The tMCS de-escalation process encompasses 2 key procedures: weaning and explantation.¹³ Weaning refers to the reduction of device support, whereas explantation denotes the removal of the tMCS device. It is of great importance that protocols and explant criteria for the evaluation of tMCS explantation readiness are established, as this will advise of tMCS dependence of patients supported with tMCS and facilitate the selection of appropriate treatment. Previous studies have evaluated predictors of the composite outcomes of weaning and explantation process in the venoarterial extracorporeal membrane oxygenation (VA-ECMO) population;^14–17 however, most of these studies did not exclusively assess predictors of post-explant outcomes. Furthermore, some readiness-to-explant criteria according to hemodynamic parameters was suggested for the de-escalation process in tMCS.¹³ However, a lack of studies evaluating the safety and efficacy of tMCS explant protocols and no standardized approach for tMCS weaning and explantation still remain.

To assess the validity of suggesting readiness-to-explant criteria in previous studies, the present study sought to evaluate the predictive performance of each hemodynamic parameter for successful explant VA-ECMO wean and off tests using a single-center cohort.

Methods

Participants and Study Design

The present study is a single-center, retrospective observational study. A retrospective medical record review was conducted for patients who underwent VA-ECMO treatment between December 2018 and May 2024 at the Department of Cardiology in Okayama University Hospital. The analysis included only those patients who underwent VA-ECMO explantation. The study cohort was divided into 2 groups: those who experienced explant success, and those who did not. The term ‘explant success’ was defined as survival without reintroduction of mechanical circulatory support (MCS) due to refractory CS or cardiac arrest within 30 days.¹⁸ Conversely, ‘explant failure’ was defined as death or reintroduction of MCS within the same timeframe. The study was conducted in accordance with the principles set forth in the Declaration of Helsinki. The institutional ethics committee approved this study (approval no. 2209-028; approval date August 26, 2022), and a waiver of informed consent was obtained due to the retrospective nature of the study.

Wean and Off Test Protocol

Given the retrospective observational nature of the present study, the clinical management and decision-making processes were at the discretion of the treating physician. In principle, the management of VA-ECMO was performed in accordance with the relevant guidelines, namely the Japanese Circulation Society (JCS), the International Society for Heart and Lung Transplantation (ISHLT), and the Extracorporeal Life Support Organization (ELSO) guidelines.^10–12 A weaning procedure was initiated when the patient was deemed hemodynamically stable and had demonstrated sufficient cardiac recovery. The determination of hemodynamic status and sufficient cardiac recovery was conducted by physicians through the assessment of various physiological parameters, including mean arterial blood pressure (BP), heart rate, pulse pressure, left ventricular ejection fraction (LVEF), pulmonary artery catheter (PAC) parameters, lactate levels, end-organ function, and the use of vasoactive agents. In the event that the patient was deemed to be hemodynamically stable and to have undergone sufficient cardiac recovery, the ECMO flow was decreased by 0.5 L/min, and a further evaluation of hemodynamic stability was conducted. In the event of an unstable hemodynamic status, the ECMO flow was returned to the initial rate and the procedure was terminated. Following a reduction in ECMO flow to a rate of 1.5–2.0 L/min, which was deemed to be hemodynamically stable, a wean test and off test were considered. A wean test entailed the reduction of the ECMO flow to a rate of 1.0–1.5 L/min for a minimum of 5 min, after which the physician evaluated the patient’s readiness for explantation based on clinical and hemodynamic parameters. Once the patient was deemed suitable for explantation following the wean test, the off test was initiated. During this phase, the VA-ECMO circuit was clamped for a period of 5 min, after which the physician reassessed the patient’s condition based on clinical and hemodynamic parameters. In the present study, wean and off tests conducted within 24 h prior to VA-ECMO explantation were used for analysis.

Readiness-to-Explant Criteria

In the present study, as previously reported,⁹ each readiness-to-explant criterion was defined as follows: the LVEF criterion is defined as LVEF ≥25%; the vital criterion as mean BP ≥65 mmHg and heart rate <100 beats/min; the pulse pressure criterion as pulse pressure ≥60 mmHg; the lactate criterion as lactate <2.0 mmol/L; the PAC criterion as pulmonary artery wedge pressure (PAWP) ≤18 mmHg and central venous pressure (CVP) ≤12 mmHg; and the cardiac index ≥2.2 L/min/m².

Covariates

All covariates were obtained from medical records. The following data for patient characteristics, laboratory tests, and echocardiography were collected within 24 h before VA-ECMO explantation: complete blood count, albumin, bilirubin, aspartate aminotransferase, alanine aminotransferase, C-reactive protein, creatinine, LVEF, left ventricular end-diastolic dimension (LVEDD), and left ventricular end-systolic dimension (LVESD). The estimated glomerular filtration rate (eGFR) was calculated using the modified isotope dilution mass spectrometry-traceable 4-variable Modification of Diet in Renal Disease Study equation, which was modified for the Japanese population, resulting in the following equation: (4 ÷ serum creatinine [mg/dL]) − (1.094 ÷ age [years]) − (0.287 ÷ 0.739 [if female]).¹⁹ This equation has previously been validated in the Japanese population. Chronic kidney disease was defined according to eGFR criteria, with a value of <60 mL/min/1.73 m² indicating presence of the condition. A PAC was introduced into the body through an internal jugular vein or a femoral vein. The following hemodynamic parameters were measured just before VA-ECMO explantation, at the wean test, and at the off test: heart rate, systolic arterial BP, diastolic arterial BP, mean arterial BP, PAWP, and systolic pulmonary artery pressure (PAP). Additionally, the following parameters were monitored: arterial pressure (AP), diastolic arterial pressure (DAP), mean arterial pressure (MAP), CVP or right atrial pressure (RAP), lactate, ratio of the partial pressure of arterial oxygen to the fraction of inspired oxygen (P/F ratio), and cardiac index, which was calculated using the Fick method to estimate oxygen uptake.^20,21

Statistical Analysis

All statistical analyses were conducted using the R statistical computing environment (version 4.1.2) and the ‘pROC’ package (version 1.18.0). Continuous variables are presented as medians with 25th and 75th percentiles, and categorical variables are presented as numbers and percentages. For comparison between participants with explant success and those with failure, continuous and categorical variables were tested using the Mann-Whitney U and Chi-squared tests, respectively. The capacity of each variable to differentiate between the 2 groups was assessed using receiver operating characteristic (ROC) curve analysis. The area under the ROC curve (AUC) with 95% confidence interval is provided. As an explanatory analysis, each ROC curve was compared using DeLong’s method without multiple testing corrections. Statistical significance was set at 2-tailed P<0.05.

Results

Baseline Characteristics

A total of 72 patients diagnosed with CS was treated with VA-ECMO at Okayama University Hospital between December 2018 and May 2024. After excluding 27 patients who did not undergo explantation of the VA-ECMO device and 8 patients who did not undergo wean or off tests, a total of 37 patients was included in the subsequent analysis (Figure). Wean and off tests were conducted in 37 (29 of whom had PAC) and 21 (18 of whom had PAC) patients, respectively. The median age was 59 years (interquartile range [IQR] 53–69 years), and 28 (76%) patients were male. The etiologies of heart disease are as follows: 23 (62%) patients had acute coronary syndrome, 1 (3%) patient had ischemic heart disease other than acute coronary syndrome, 5 (14%) patients had myocarditis, 4 (11%) patients had dilated cardiomyopathy, 3 (8%) patients had idiopathic ventricular fibrillation, 1 (3%) patient had cancer therapy-related cardiac dysfunction, and 1 (3%) patient had takotsubo syndrome. The patients were divided into 2 groups based on whether they achieved explant success or failure (Table 1). No significant differences were observed in the patient characteristics between the 2 groups.

Figure.

Study flow chart showing patient enrolment and exclusion, and clinical outcomes. Explant failure was defined as death, or reinitiation of any mechanical circulatory support within 30 days of VA-ECMO explantation. LVAD, left ventricular assist device; PAC, pulmonary artery catheter; VA-ECMO, venoarterial extracorporeal membrane oxygenation.

Table 1.

Characteristics of Patients in the Explant Success and Failure Groups

	Overall (n=37)	Failure (n=8)	Success (n=29)	P value
Age (years)	59 [53–69]	59 [52–66]	59 [53–69]	0.81
Sex, male	28 (76)	7 (88)	21 (72)	0.68
BSA (m2)	1.72 [1.61–1.78]	1.81 [1.56–2.03]	1.72 [1.61–1.76]	0.44
BMI	22.8 [20.0–27.0]	25.6 [21.0–30.7]	22.4 [19.6–26.1]	0.32
Etiology				0.74
ACS	23 (62)	7 (88)	16 (52)
ICM (non-ACS)	1 (3)	0 (0)	1 (3)
Myocarditis	5 (14)	1 (13)	4 (14)
DCM	4 (11)	0 (0)	4 (14)
iVF	3 (8)	0 (0)	3 (10)
CTRCD	1 (3)	0 (0)	1 (3)
TTS	1 (3)	0 (0)	1 (3)
History of hypertension	14 (38)	5 (63)	9 (31)	0.23
History of diabetes	11 (30)	4 (50)	9 (31)	0.56
History of myocardial infarction	4 (11)	2 (25)	2 (7)	0.41
History of heart failure	3 (8)	0 (0)	3 (10)	0.83
History of CKD	5 (14)	2 (25)	3 (10)	0.63
Cardiac arrest before VA-ECMO initiation	26 (70)	7 (88)	19 (66)	0.44
Ventilation	37 (100)	8 (100)	29 (100)	NA
Renal replacement therapy	13 (35)	4 (50)	9 (31)	0.56
Duration of ECMO	6 [3–13]	6 [2–14]	6 [4–12]	0.70
Central ECMO	2 (5)	0 (0)	2 (7)	1.00
IABP	8 (22)	2 (25)	6 (21)	1.00
pVAD	23 (62)	4 (50)	19 (66)	0.70
ECMO flow at explant (L/min)	1.3 [1.0–1.5]	1.5 [1.0–1.5]	1.2 [1.2–1.5]	0.89
Inotrope at explant	19 (51)	7 (88)	12 (41)	0.06
Vasopressor at explant	19 (51)	5 (63)	14 (48)	0.75
WBC	9,290 [6,580–9,900]	8,120 [6,830–10,520]	9,440 [6,580–14,030]	0.48
Hb (g/dL)	9.3 [8.8–9.9]	8.9 [8.6–9.4]	9.3 [8.9–9.9]	0.22
Platelets (104/mcL)	7.5 [5.6–11.4]	7.1 [5.3–11.2]	7.5 [5.9–11.4]	0.77
Albumin (g/dL)	2.7 [2.6–3.1]	2.5 [2.4–2.8]	2.7 [2.6–3.1]	0.12
Bilirubin (mg/dL)	0.95 [0.68–1.39]	1.08 [0.75–1.44]	0.92 [0.68–1.39]	0.99
AST (U/L)	83 [49–138]	93 [61–127]	79 [47–138]	0.51
ALT (U/L)	43 [26–57]	40 [28–47]	48 [25–61]	0.73
Creatinine (mg/dL)	1.17 [0.78–1.68]	1.56 [1.13–2.88]	1.11 [0.74–1.58]	0.09
CRP (mg/dL)	10.10 [5.47–15.37]	10.80 [8.96–12.71]	8.89 [5.36–17.21]	0.71
LVEF (%)	39 [30–50]	36 [23–46]	39 [30–50]	0.38
LVEDD (mm)	47 [43–50]	50 [46–52]	45 [42–50]	0.13
LVESD (mm)	37 [32–42]	40 [34–45]	37 [30–41]	0.18

Values are presented as n (%), or median [Q1–Q3], unless otherwise indicated. ACS, acute coronary syndrome; ALT, alanine aminotransferase; AST, aspartate aminotransferase; BMI, body mass index; BSA, body surface area; CKD, chronic kidney disease; CRP, C-reactive protein; CTRCD, cancer therapy-related cardiac dysfunction; DCM, dilated cardiomyopathy; ECMO, extracorporeal membrane oxygenation; IABP, intra-aortic balloon pumping; ICM, ischemic cardiomyopathy; iVF, idiopathic ventricular fibrillation; LVEDD, left ventricular end-diastolic dimension; LVEF, left ventricular ejection fraction; LVESD, left ventricular end-systolic dimension; pVAD, percutaneous ventricular assist device; TTS, takotsubo syndrome; VA-ECMO, venoarterial extracorporeal membrane oxygenation; WBC, white blood cell.

Clinical Parameters During Wean and Off Tests

No significant differences were observed between the explant success and failure groups with respect to the clinical parameters at the time of weaning (Table 2). However, at the time of the off test, the PAWP and diastolic PAP were significantly higher in the explant failure group compared with the explant success group (P=0.02 and P=0.04, respectively).

Table 2.

Clinical and Hemodynamic Parameters at the Wean and Off Tests

	Overall	Failure	Success	P value
Wean test (n)	37	8	29
Heart rate (beats/min)	79 [73–89]	81 [75–91]	78 [73–88]	0.41
Systolic BP (mmHg)	106 [92–118]	104 [87–119]	106 [94–118]	0.51
Diastolic BP (mmHg)	65 [57–75]	64 [53–67]	65 [59–75]	0.25
Mean BP (mmHg)	78 [71–87]	75 [69–81]	81 [72–87]	0.40
Lactate (mmol/L)	0.9 [0.7–1.2]	1.0 [0.9–1.3]	0.9 [0.7–1.1]	0.23
P/F ratio (mmHg)	287 [189–380]	257 [178–325]	295 [194–380]	0.63
Wean test with PAC (n)	29	5	24
PAWP (mmHg)	13 [11–15]	18 [16–21]	13 [11–15]	0.08
Systolic PAP (mmHg)	31 [27–37]	37 [28–41]	31 [27–37]	0.36
Diastolic PAP (mmHg)	16 [13–20]	18 [16–21]	16 [13–19]	0.27
Mean PAP (mmHg)	21 [19–26]	24 [21–29]	21 [18–26]	0.25
CVP (mmHg)	11 [8–13]	13 [11–14]	11 [8–12]	0.24
Cardiac index (L/min/m2)	2.73 [2.38–3.55]	3.02 [2.66–3.34]	2.71 [2.37–3.66]	0.58
SvO2 (%)	68.3 [62.7–70.8]	64.6 [62.7–70.3]	68.9 [62.8–73.2]	0.51
Cardiac power output (W)	0.50 [0.45–0.59]	0.54 [0.47–0.55]	0.50 [0.45–0.64]	0.91
Off test (n)	21	3	18
Heart rate (beats/min)	81 [76–94]	80 [80–89]	82 [75–93]	0.69
Systolic BP (mmHg)	97 [87–113]	95 [86–101]	99 [87–114]	0.37
Diastolic BP (mmHg)	60 [54–69]	59 [50–60]	60 [55–71]	0.48
Mean BP (mmHg)	74 [65–79]	70 [68–74]	75 [66–81]	0.62
Lactate (mmol/L)	0.9 [0.8–1.1]	0.9 [0.80–1.1]	0.9 [0.8–1.1]	0.84
P/F ratio (mmHg)	301 [217–430]	301 [212–388]	317 [224–428]	0.69
Off test with PAC (n)	18	3	15
PAWP (mmHg)	16 [12–18]	20 [20–22]	15 [12–16]	0.02
Systolic PAP (mmHg)	33 [30–41]	42 [37–45]	33 [29–37]	0.14
Diastolic PAP (mmHg)	17 [15–20]	20 [20–22]	15 [15–18]	0.04
Mean PAP (mmHg)	24 [20–27]	29 [26–31]	23 [20–26]	0.07
CVP (mmHg)	11 [9–13]	13 [11–14]	10 [9–13]	0.44
Cardiac index (L/min/m2)	2.96 [2.46–3.72]	2.45 [2.27–4.22]	3.00 [2.54–3.62]	0.72
SvO2 (%)	69.7 [64.6–73.9]	57.0 [56.4–70.9]	70.4 [65.1–73.2]	0.52
Cardiac power output (W)	0.46 [0.36–0.66]	0.35 [0.33–0.70]	0.47 [0.42–0.62]	0.77

Values are presented as n (%), or median [Q1–Q3], unless otherwise indicated. BP, blood pressure; CVP, central venous pressure; PAC, pulmonary artery catheter; PAP, pulmonary artery pressure; PAWP, pulmonary artery wedge pressure; P/F ratio, the ratio of the partial pressure of arterial oxygen to the fraction of inspired oxygen; SvO₂, mixed venous blood oxygen saturation.

Predictive Performance of Each Readiness-to-Explant Criterion

Table 3 delineates the proportion of patients who met the readiness-to-explant criteria in both the explant success and failure groups. For prediction of successful explantation, among the readiness-to-explant criteria, the PAC criteria at off test showed the highest AUC (0.83; 95% confidence interval 0.71–0.96), with a sensitivity of 67%, specificity of 100%, positive predictive value of 100%, and negative predictive value of 38% (Table 4).

Table 3.

Proportions of Patients Who Fulfil Readiness-to-Explant Criteria in the Explant Success and Failure Groups

Readiness-to-explant criteria	Overall	Failure	Success	P value
All (n)	37	8	29
LVEF	32 (87)	6 (75)	26 (90)	0.63
Wean test (n)	37	8	29
Vital	32 (87)	7 (88)	25 (86)	1.00
PP	6 (16)	3 (38)	3 (10)	0.19
Lactate	36 (97)	8 (100)	28 (97)	1.00
Wean test with PAC (n)	29	5	24
PAC	16 (55)	1 (20)	15 (63)	0.21
Off test (n)	21	3	18
Vital	17 (81)	3 (100)	14 (78)	0.91
PP	3 (14)	1 (33)	2 (11)	0.90
Lactate	20 (95)	3 (100)	17 (94)	1.00
Off test with PAC (n)	18	3	15
PAC	10 (56)	0 (0)	10 (67)	0.14

Values are presented as n (%). LVEF, left ventricular ejection fraction; PAC, pulmonary artery catheter; PP, pulse pressure.

Table 4.

Predictivity of Each Readiness-to-Explant Criterion

Readiness-to-explant criteria	AUC	95% CI	Se (%)	Sp (%)	PPV (%)	NPV (%)
LVEF	0.57	0.40–0.74	90	25	81	40
Wean test
Vital	0.49	0.36–0.63	86	13	78	20
PP	0.36	0.18–0.55	10	63	50	16
Lactate	0.48	0.45–0.52	97	0	78	0
PAC	0.71	0.49–0.93	63	80	94	31
Off test
Vital	0.39	0.29–0.49	78	0	82	0
PP	0.39	0.05–0.72	11	67	67	11
Lactate	0.47	0.42–0.53	94	0	85	0
PAC	0.83	0.71–0.96	67	100	100	38

Predictability of the following criteria are described: LVEF criterion – LVEF ≥25%; vital criterion – mean blood pressure ≥65 mmHg and heart rate <100 beats/min; PP criterion – PP ≥60 mmHg; lactate criterion – lactate <2.0 mmol/L; PAC criterion – PAWP ≤18 mmHg, central venous pressure ≤12 mmHg and cardiac index ≥2.2 L/min/m². AUC, area under curve; CI, confidence interval; LVEF, left ventricular ejection fraction; NPV, negative predictive value; PAC, pulmonary artery catheter; PAWP, pulmonary artery wedge pressure; PP, pulse pressure; PPV, positive predictive value; Se, sensitivity; Sp, specificity.

Discussion

This single-center, observational study demonstrated the highest predictive performance for successful explantation of VA-ECMO in the PAC criteria at the off test (PAWP ≤18 mmHg, CVP ≤12 mmHg and cardiac index ≥2.2 L/min/m²) compared with the other criteria (sensitivity 67%, specificity 100%, positive predictive value 100%, and negative predictive value 38%). Furthermore, the results of the explanatory analysis indicated that PAC criteria at the off test and at the wean test exhibited a higher AUC than the other criteria.

Explant failure is a rare but devastating outcome of the tMCS de-escalation process. Durable LVAD or transplant should be considered instead of tMCS explantation when pre-explant evaluation indicates the risk of an unsuccessful outcome. Therefore, it is critical to accurately predict whether tMCS can be extricated or not in the management of tMCS. Although previous reports proposed several algorithms for de-escalation in the VA-ECMO population,^10–12 there are no validated criteria or metrics to determine readiness for successful explantation. In previous studies on the de-escalation process in patients with VA-ECMO, compared with unsuccessfully de-escalated patients, successfully de-escalated patients had LVEF ≥25%, left ventricular outflow tract velocity time integral >10 cm, tissue Doppler Sa 6 cm/s,¹⁵ no history of hypertension, low serum creatinine, low serum lactate, high platelet count,¹⁶ systolic BP >120 mmHg, and length of ECMO support ≤7 days.¹³ However, these previous studies evaluated the entire de-escalation process, which included both weaning and explantation, but studies to evaluate the predictors of successful explantation among VA-ECMO population are lacking.

In the present study, for head-to-head comparisons, we assessed each readiness-to-explant criteria at the wean and off tests that were recently proposed as readiness-to-explant criteria for tMCS,¹³ suggesting the PAC criteria at the off test may be the most reliable criteria to predict successful explantation of VA-ECMO. As CS is a cardiac pump failure with hypoperfusion and congestion due to both or either of the left or right ventricle, it may be reasonable that the PAC criteria, which can directly measure the status of hypoperfusion and congestion, was the most reliable indicator. Among the hemodynamic parameters measured using PAC, the present study demonstrated a significant difference in PAWP between successful or unsuccessful tMCS explant. In contrast, other parameters including the cardiac index and RAP were not associated with successful tMCS. Cardiac power output and mixed venous oxygen saturation, which were recommended as treatment targets for managing CS in a recently published statement from the Japan Critical Care Cardiology Committee,²² were also not associated with successful tMCS. These findings suggest congestion in the left heart system may be more sensitive to successful or unsuccessful tMCS explant compared with total circulatory flow and congestion in the right heart system.

Study Limitations

The present study had several potential limitations. First, the present study was a single center, retrospective study that included a limited study population. Therefore, the results of the present study should be interpreted as exploratory in nature. Second, the present study included only Japanese patients (East Asian population), and therefore the generalizability of the results to other racial populations is limited. Third, since the protocols and criteria in the present study relied on daily clinical practice, several algorithms based on previous trials for VA-ECMO explantation (e.g., the pump-controlled retrograde trial off [PCRTO]) was not evaluated in the present study.²³ Fourth, as the present study was not designed to examine echocardiographic parameters, including left ventricular outflow tract velocity time integral (LVOT-VTI), we did not collect such parameters. Therefore, we are not able to assess the impact of LVOT-VTI in the prediction of successful explant for VA ECMO. Fifth, the number of patients who underwent the off test was low (18/37; 49%). As the nature of a retrospective study is to review medical records, the decision to perform the wean test or the off test was made by the attending physician, and the rationale behind this decision was not readily apparent. Last, selection bias and information bias are inevitable in this type of observational study. It is difficult to fully achieve the primary objective of validating the proposed readiness-to-explant criteria in this study due to these limitations. To overcome these potential limitations, a further multi-center prospective study is warranted.

Conclusions

In patients who underwent VA-ECMO explantation, the PAC criteria (PAWP ≤18 mmHg, CVP ≤12 mmHg and cardiac index ≥2.2 L/min/m²) at off test showed the highest predictability for successful explantation of VA-ECMO compared with other hemodynamic parameters, suggesting such PAC criteria may be an appropriate algorithm in the de-escalation process of VA-ECMO. Further prospective studies are needed to validate the present findings and establish standardized VA-ECMO explantation practices.

Acknowledgments

The authors appreciate the members of Okayama University Hospital for their contributions to VA-ECMO management.

Disclosures

K.N. is a member of Circulation Reports’ Editorial Team.

IRB Information

The institutional ethics committee approved this study (approval no. 2209-028; approval date August 26, 2022).

Data Availability

The deidentified participant data will not be shared.

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