Clinical Outcomes and Reduced Pulmonary Artery Pressure With Intra-Aortic Balloon Pump During Central Extracorporeal Life Support

Left Ventricular Unloading in Extracorporeal Membrane Oxygenation: A Clinical Perspective Derived from Basic Cardiovascular Physiology

PURPOSE OF REVIEW

To present an abridged overview of the literature and pathophysiological background of adjunct interventional left ventricular unloading strategies during veno-arterial extracorporeal membrane oxygenation (V-A ECMO). From a clinical perspective, the mechanistic complexity of such combined mechanical circulatory support often requires in-depth physiological reasoning at the bedside, which remains a cornerstone of daily practice for optimal patient-specific V-A ECMO care.

RECENT FINDINGS

Recent conventional clinical trials have not convincingly shown the superiority of V-A ECMO in acute myocardial infarction complicated by cardiogenic shock as compared with medical therapy alone. Though, it has repeatedly been reported that the addition of interventional left ventricular unloading to V-A ECMO may improve clinical outcome. Novel approaches such as registry-based adaptive platform trials and computational physiological modeling are now introduced to inform clinicians by aiming to better account for patient-specific variation and complexity inherent to V-A ECMO and have raised a widespread interest. To provide modern high-quality V-A ECMO care, it remains essential to understand the patient's pathophysiology and the intricate interaction of an individual patient with extracorporeal circulatory support devices. Innovative clinical trial design and computational modeling approaches carry great potential towards advanced clinical decision support in ECMO and related critical care.

Venting during venoarterial extracorporeal membrane oxygenation

Cardiogenic shock and cardiac arrest contribute pre-dominantly to mortality in acute cardiovascular care. Here, veno-arterial extracorporeal membrane oxygenation (VA-ECMO) has emerged as an established therapeutic option for patients suffering from these life-threatening entities. VA-ECMO provides temporary circulatory support until causative treatments are effective and enables recovery or serves as a bridging strategy to surgical ventricular assist devices, heart transplantation or decision-making. However, in-hospital mortality rate in this treatment population is still around 60%. In the recently published ARREST trial, VA-ECMO treatment lowered mortality rate in patients with ongoing cardiac arrest due to therapy refractory ventricular fibrillation compared to standard advanced cardiac life support in selected patients. Whether VA-ECMO can reduce mortality compared to standard of care in cardiogenic shock has to be evaluated in the ongoing prospective randomized studies EURO-SHOCK (NCT03813134) and ECLS-SHOCK (NCT03637205). As an innate drawback of VA-ECMO treatment, the retrograde aortic flow could lead to an elevation of left ventricular (LV) afterload, increase in LV filling pressure, mitral regurgitation, and elevated left atrial pressure. This may compromise myocardial function and recovery, pulmonary hemodynamics—possibly with concomitant pulmonary congestion and even lung failure—and contribute to poor outcomes in a relevant proportion of treated patients. To overcome these detrimental effects, a multitude of venting strategies are currently engaged for both preventive and emergent unloading. This review aims to provide a comprehensive and structured synopsis of existing venting modalities and their specific hemodynamic characteristics. We discuss in detail the available data on outcome categories and complication rates related to the respective venting option.

Graphical abstract

Extracorporeal Life Support for Cardiogenic Shock With Either a Percutaneous Ventricular Assist Device or an Intra-Aortic Balloon Pump

Extracorporeal life support (ECLS) can result in complications due to increased left ventricular (LV) afterload. The percutaneous ventricular assist device (PVAD) and intra-aortic balloon pump (IABP) are both considered to be effective means of LV unloading. This study describes the efficacy of LV unloading and related outcomes with PVAD or IABP during ECLS. From January 2010 to April 2018, all cardiogenic shock patients who underwent ECLS plus simultaneous PVAD or IABP were analyzed. Forty-nine patients received ECLS + PVAD, while 91 received ECLS + IABP. At 48 hours, mean pulmonary artery pressure was significantly reduced in both groups [34 mm Hg to 22, p < 0.01; 32 mm Hg to 21, p < 0.01; ECLS + PVAD and ECLS + IABP group, respectively]. The two groups had similar 30 day survival rates [19 patients (39%) vs. 35 (39%), p = 0.56]. The ECLS + PVAD group had higher incidences of bleeding at the insertion site [11 (22%) vs. 0, p < 0.01] and major hemolysis [9 (18%) vs. 0, p < 0.01]. Both groups had improvement in LV end-diastolic dimension (61 ± 12 mm to 54 ± 12, p = 0.03; 60 ± 12 mm to 47 ± 10, p < 0.01), and LV ejection fraction (16 ± 7% to 22 ± 10, p < 0.01; 22 ± 12% to 29 ± 15, p = 0.01). Both ECLS + PVAD and ECLS + IABP effectively reduced pulmonary artery pressure and improved LV function. Bleeding at the PVAD or IABP insertion site occurred more frequently in the ECLS + PVAD group than the ECLS + IABP group (p < 0.01). Nine patients (18%) in the ECLS + PVAD group experienced major hemolysis, while there was no hemolysis in the ECLS + IABP group (p < 0.01). Careful considerations are required before selecting an additional support to ECLS.

The hemodynamic effect of different left ventricular unloading techniques during veno-arterial extracorporeal life support: a systematic review and meta-analysis

Background:

Pulmonary edema and left ventricular thrombosis may arise during veno-arterial extracorporeal life support due to an increase in cardiac load. This mechanical stress can be reduced through different left ventricular unloading techniques. We set out to quantitatively summarize the hemodynamic effects of available methods in patients treated with veno-arterial extracorporeal life support.

Methods:

Literature was systematically searched for studies reporting left ventricular unloading during veno-arterial extracorporeal life support as reflected by changes in left atrial pressure, pulmonary capillary wedge pressure, diastolic pulmonary artery pressure, or left ventricular end-diastolic pressure. For studies including ⩾10 patients per group, changes in these parameters were pooled using (1) standardized mean differences and (2) ratio of means. Assessment of potential bias was performed for all studies.

Results:

Eight studies met the inclusion criteria. Reported techniques included use of intra-aortic balloon pump (n = 1), micro-axial blood pump (Impella®, n = 2), left ventricular venting (n = 1), and atrial septostomy (n = 4). Overall, left ventricular unloading was associated with a statistically significant reduction in preload parameters (standardized mean differences = −1.05 (95% confidence interval = −1.24 to −0.86) and ratio of means = 0.60 (0.47 to 0.76)). Effect sizes were strongest for micro-axial blood pump and atrial septostomy (standardized mean differences = −1.11 (−1.55 to −0.68) and −1.22 (−1.47 to −0.96), and ratio of means = 0.58 (0.39 to 0.86) and 0.54 (0.36 to 0.83), respectively).

Conclusion:

Left ventricular unloading was associated with a significant reduction in left ventricular preload parameters in the setting of veno-arterial extracorporeal life support. This effect may be most pronounced for micro-axial blood pump and atrial septostomy.

Optimal Strategy and Timing of Left Ventricular Venting During Veno-Arterial Extracorporeal Life Support for Adults in Cardiogenic Shock

Background:

Veno-arterial extracorporeal life support (VA-ECLS) is widely used to treat refractory cardiogenic shock. However, increased left ventricular (LV) afterload in VA-ECLS can worsen pulmonary congestion and compromise myocardial recovery. Our objectives were to explore the efficacy, safety, and optimal timing of adjunctive LV venting strategies.

Methods:

A systematic search was performed on Medline, EMBASE, PubMed, CDSR, CCRCT, CINAHL, ClinicalTrials.Gov, and WHO ICTRP from inception until January 2019 for all relevant studies, including LV venting. Data were analyzed for mortality and weaning from VA-ECLS on the basis of timing of LV venting, along with adverse complications.

Results:

A total of 7995 patients were included from 62 observational studies, wherein 3458 patients had LV venting during VA-ECLS. LV venting significantly improved weaning from VA-ECLS (odds ratio, 0.62 [95% CI, 0.47–0.83]; P =0.001) and reduced short-term (30 day; risk ratio [RR], 0.86 [95% CI, 0.77–0.96]; P =0.008) but not in-hospital (RR, 0.92 [95% CI, 0.83–1.01] P =0.09) or long-term (6 months; RR, 0.96 [95% CI, 0.90–1.03]; P =0.27) mortality. Early (<12 hours; RR, 0.86 [95% CI, 0.75–0.99]; P =0.03) but not late (≥12 hours; RR, 0.99 [95% CI, 0.71–1.38]; P =0.93) LV venting significantly reduced short-term mortality. Patients with LV venting spent more time on VA-ECLS (3.6 versus 2.8 days, P <0.001), and mechanical ventilation (7.1 versus 4.6 days, P =0.013). With the exception of hemolysis (RR, 2.18 [95% CI, 1.58–3.01]; P <0.00001), overall adverse events did not differ.

Conclusions:

LV venting, especially if done early (<12 hours), appears to be associated with an increased success of weaning and reduced short-term mortality. Future studies are required to delineate the importance of any or early LV venting adjuncts on mortality and morbidity outcomes.