The source of coronary perfusion during partial bypass for extracorporeal membrane oxygenation (ECMO)

Central extracorporeal membrane oxygenation with left-ventricular vent for fulminant myocarditis: a retrospective study

PURPOSE

Fulminant myocarditis presents as acute severe heart failure and requires mechanical cardiocirculatory support. Left-ventricular (LV) decompression is necessary for the successful recovery of these patients. This retrospective study aimed to evaluate the functional outcomes of providing central extracorporeal membrane oxygenation (ECMO) with LV decompression for the treatment of refractory fulminant myocarditis.

METHODS

Between January 2015 and February 2021, seven consecutive fulminant myocarditis patients (mean age: 41.1 ± 26.1 years) received central ECMO support with transapical LV decompression, with an 18 French cannula integrated into the ECMO circuit in a Y-fashion. The baseline characteristics and postoperative outcomes of the patients were collected.

RESULTS

On admission, all patients received prior peripheral ECMO, and 85.7% (6/7) of patients received prior intra-aortic balloon pumping. However, all patients had refractory cardiogenic shock that failed prior to decompression. Six patients recovered successfully after a mean ECMO support of 20.0 ± 11.5 days and five patients had no recurrence of cardiac decompensation. The mean ICU and mean hospital stays were 36.7 ± 23.5 days and 60.6 ± 24.9 days, respectively. Hospital mortality was 28.6% (2/7). Two patients died due to sepsis and stroke during hospitalization.

CONCLUSIONS

Central ECMO with an LV vent was effective for fulminant myocarditis refractory to percutaneous cardiopulmonary support therapy and other therapies.

Watershed phenomena during extracorporeal life support and their clinical impact: a systematic in vitro investigation

Aims

Extracorporeal life support (ECLS) during acute cardiac failure restores haemodynamic stability and provides life‐saving cardiopulmonary support. Unfortunately, all common cannulation strategies and remaining pulmonary blood flow increase left‐ventricular afterload and may favour pulmonary congestion. The resulting disturbed pulmonary gas exchange and a residual left‐ventricular action can contribute to an inhomogeneous distribution of oxygenated blood into end organs. These complex flow interactions between native and artificial circulation cannot be investigated at the bedside: only an in vitro simulation can reveal the underlying activities. Using an in vitro mock circulation loop, we systematically investigated the impact of heart failure, extracorporeal support, and cannulation routes on the formation of flow phenomena and flow distribution in the arterial tree.

Methods and results

The mock circulation loop consisted of two flexible life‐sized vascular models (aorta and vena cava) driven by two paracorporeal assist devices, resistance elements, and compliance reservoirs to mimic the circulatory system. Several large‐bore antegrade and retrograde access ports allowed connection to an ECLS system for extracorporeal support. With four degrees of extracorporeal support—that for cardiac failure, early recovery, late recovery, and weaning—we investigated aortic blood flow velocity, blood flow, and mixing zones using colour‐coded Doppler ultrasound in the aorta and its corresponding branches. Full retrograde extracorporeal support (3–4 L/min) perfused major portions of the aorta but did not reach the supra‐aortic branches and ascending aorta, resulting in an area in the thoracic aorta demonstrating nearly stagnant blood flow velocities during cardiogenic shock and early recovery (0 ± 4 cm/s; −10 ± 15 cm/s, respectively) confined by two watersheds at the aortic isthmus and renal artery origin. Even increased ECLS flow was unable to shift the watershed towards the aortic arch. Antegrade support resulted in homogeneous flow distribution during all stages of cardiac failure but created a markedly negative flow vector in the ascending aorta during cardiogenic shock and early recovery with increased afterload.

Conclusions

Our systematic fluid‐mechanical analysis confirms the clinical assumption that despite restoring haemodynamic stability, extracorporeal support generates an inhomogeneous distribution of oxygenated blood with an inadequate supply to end organs and increased left‐ventricular afterload with absent ventricular unloading. End‐organ supply may be monitored by near‐infrared spectroscopy, but an obviously non‐controllable watershed emphasizes the need for additional measures: pre‐pulmonary oxygenation with a veno‐arterial‐venous ECLS configuration can allow a transpulmonary passage of oxygenated blood, providing improved end‐organ supply.

Extracorporeal life support with left ventricular decompression-improved survival in severe cardiogenic shock: results from a retrospective study

Objective

Extracorporeal life support (ECLS) is a life-saving procedure used in the treatment of severe cardiogenic shock. Within this retrospective single centre study, we examined our experience in this critically ill patient cohort to assess outcomes and clinical parameters by comparison of ECLS with or without selective left ventricular decompression.

Methods

Between 2004 and 2014 we evaluated 48 adult patients with INTERMACS level 1 heart failure (age 49.7 ± 19.5 years), who received either central ECLS with (n = 20, 41.7%) or ECLS without (n = 28, 58.3%, including 10 peripheral ECLS) integrated left ventricular vent in our retrospective single centre trial.

Results

Follow up was 100% with a mean of 0.83 ± 1.85 years. Bridge to ventricular assist device was feasible in 29.2% (n = 14), bridge to transplant in 10.4% (n = 5) and bridge to recovery in 8.3% (n = 4). Overall 30-day survival was 37.5%, 6-month survival 27.1% and 1-year survival 25.0%. ECLS support with left ventricular decompression showed favourable 30-day survival compared to ECLS without left ventricular decompression (p = 0.034). Thirty-day as well as long-term survival did not differ between the subgroups (central ECLS with vent, ECLS without vent and peripheral ECLS without vent). Multivariate logistic regression adjusted for age and gender revealed ECLS without vent as independent factor influencing 30-day survival.

Conclusion

ECLS is an established therapy for patients in severe cardiogenic shock. Independent of the ECLS approach, 30-day mortality is still high but with superior 30-day survival for patients with ECLS and left ventricular venting. Moreover, by unloading the ventricle, left ventricular decompression may provide an important time window for recovery or further treatment, such as bridge to bridge or bridge to transplant.

Extracorporeal life support with an integrated left ventricular vent in children with a low cardiac output

BACKGROUND

The aim of this study was to evaluate our experience in central extracorporeal life support with an integrated left ventricular vent in children with cardiac failure.

METHODS

Eight children acquired extracorporeal life support with a left ventricular vent, either after cardiac surgery (n = 4) or during an acute cardiac illness (n = 4). The ascending aorta and right atrium were cannulated. The left ventricular vent was inserted through the right superior pulmonary vein and connected to the venous line on the extracorporeal life support such that active left heart decompression was achieved.

RESULTS

No patient died while on support, seven patients were successfully weaned from it and one patient was transitioned to a biventricular assist device. The median length of support was 6 days (range 5-10 days). One patient died while in the hospital, despite successful weaning from extracorporeal life support. No intra-cardiac thrombus or embolic stroke was observed. No patient developed relevant intracranial bleeding resulting in neurological dysfunction during and after extracorporeal life support.

CONCLUSIONS

In case of a low cardiac output and an insufficient inter-atrial shunt, additional left ventricular decompression via a vent could help avoid left heart distension and might promote myocardial recovery. In pulmonary dysfunction, separate blood gas analyses from the venous cannula and the left ventricular vent help detect possible coronary hypoxia when the left ventricle begins to recover. We recommend the use of central extracorporeal life support with an integrated left ventricular vent in children with intractable cardiac failure.

Central extracorporeal life support with left ventricular decompression for the treatment of refractory cardiogenic shock and lung failure

BACKGROUND

The purpose of this prospective study was to evaluate the effects and functional outcome of central extracorporeal life support (ECLS) with left ventricular decompression for the treatment of refractory cardiogenic shock and lung failure.

METHODS

Between August 2010 and August 2013, 12 consecutive patients (2 female) with a mean age of 31.6 ± 15.1 years received central ECLS with left ventricular decompression for the treatment of refractory cardiogenic shock and lung failure. Underlying disease was acute cardiac decompensation due to dilated cardiomyopathy (n = 3, 25%), coronary artery disease with acute myocardial infarction (AMI) (n = 3, 25%), and acute myocarditis (n = 6, 50%). We routinely implemented ECLS by cannulating the ascending aorta, right atrium and inserting a left ventricular decompression cannula vent via the right superior pulmonary vein.

RESULTS

All patients were successfully bridged to either recovery (n = 3, 25%), long-term biventricular support (n = 6, 50%) or cardiac transplantation (n = 3, 25%). Seven patients (58.3%) were discharged after a mean hospital stay of 42 ± 11.9 days. The overall survival from ECLS implantation to the end of the study was 58.3%. The cumulative ICU stay was 23.1 ± 9.6 days. The length of support was 8.0 ± 4.3 days (range 3-17 days).

CONCLUSIONS

We strongly recommend left ventricular decompression in refractory cardiogenic shock and lung failure to avoid pulmonary edema, left heart distension and facilitate myocardial recovery.

ECMO cannulation controversies and complications

Advances in extracorporeal life support have expanded indications for use extending beyond patients undergoing cardiac surgery. The approach to cannulation in patients requiring extracorporeal membrane oxygenation should be individualized and based on the specific clinical scenario in which the need arises. Adherence to proper techniques of vessel visualization, exposure, and cannulation along with accurate placement of cannulae will optimize flows and minimize complications in this setting. Patients in need of mechanical circulatory support require input from a multidisciplinary team approach with systematic clinical evaluation to optimize outcome. If hemodynamics do not initially permit the successful separation from mechanical support, then a systematic search for potentially reversible patient and/ or pump related factors should be undertaken. The success of this therapy is predicated on patient selection, a multidisciplinary team approach in the intensive care unit, adherence to precise technical principles, and repeated patient evaluation.

Extracorporeal life support

Extracorporeal life support (ECLS) denotes the use of prolonged extracorporeal cardiopulmonary bypass in patients with acute, reversible cardiac or respiratory failure. As technology has advanced, organ support functions other than gas exchange, such as liver, renal, and cardiac support, have been provided by ECLS, and others, such as immunologic support, will be developed. The future of ECLS will include improvements in devices accompanied by circuit simplification and auto-regulation. Such enhancements in technology will allow application of ECLS to populations currently excluded from such support; for example, thromboresistant circuits will eliminate the need for systemic anticoagulation and lead to the use of this technique in premature newborns. As the ECLS technique becomes safer and simpler, and as morbidity and mortality are minimized, criteria for application of ECLS will be relaxed. New approaches to ECLS, such as pumpless arteriovenous bypass, the artificial placenta, arteriovenous CO(2) removal (AVCO(2)R), and intravenous oxygenators (IVOX), will become more commonly applied. Such advances in technology will allow broader and more routine application of ECLS for lung and other organ system failure.

Mechanical cardiac support in the young. Short-term support: ECMO

Although based on technology developed several decades ago, extracorporeal membrane oxygenation (ECMO) retains great clinical relevance in the management of advanced pediatric cardiorespiratory disease. Largely because of its widespread use in pediatric patients with respiratory failure, familiarity with this technology has established ECMO as the most commonly used form of mechanical circulatory support in children. Clinical applications and technical aspects of ECMO support continue to evolve, ensuring the ongoing importance of this modality for pediatric circulatory support.

Mechanical circulatory support for infants and children with cardiac disease

Mechanical circulatory support is assuming an expanding role in the practice of congenital cardiac surgery. Extracorporeal membrane oxygenation and centrifugal ventricular assist devices are still the mainstay of mechanical circulatory support for children; however, newly developed pulsatile, paracorporeal ventricular assist devices designed for pediatric applications are achieving increased utilization. In addition, several new, continuous flow devices that are under development as fully implantable systems for adults, ultimately may be useful for pediatric patients.

Left ventricular dysfunction during extracorporeal membrane oxygenation in a hypoxemic swine model

BACKGROUND

Perfusion of the coronary circulation with hypoxemic blood from the left ventricle has been postulated to cause myocardial dysfunction during venoarterial extracorporeal membrane oxygenation for respiratory support.

METHODS

We investigated this hypothesis in 10 anesthetized open-chest piglets (7 to 9 kg) undergoing venoarterial extracorporeal membrane oxygenation after placement of minor-axis sonomicrometry crystals and left ventricular micromanometer. The left atrial partial pressure of oxygen was made hypoxemic (25 to 40 mm Hg) after initiation of extracorporeal membrane oxygenation by ventilation with a hypoxic gas mixture. Left ventricular contractile function, including peak LV pressure, shortening fraction, maximum rate of increase of left ventricular pressure, velocity of circumferential fiber shortening, end-systolic pressure-minor axis dimension relationship, and preload recruitable dimensional stroke work, was measured or calculated on extracorporeal membrane oxygenation before (baseline) and at 4 and 6 hours after rendering the left atrial blood hypoxemic.

RESULTS

Left ventricular shortening fraction and velocity of circumferential fiber shortening were significantly lower (p < 0.05) at 4 and 6 hours when compared with baseline. The slope of the end-systolic pressure-minor axis dimension relationship decreased but was not significantly different at 4 and 6 hours when compared with baseline owing to poor linear correlation (r = 0.30 to 0.93). The preload recruitable dimensional stroke work was more linear (r = 0.87 to 0.99), and the slope was significantly lower (p < 0.01) at 4 and 6 hours when compared with baseline.

CONCLUSIONS

Hypoxemic cardiac output from the left ventricle during venoarterial extracorporeal membrane oxygenation is associated with depression of left ventricular systolic function in this animal model. Current use of venoarterial extracorporeal membrane oxygenation for respiratory support may not provide adequate oxygen supply to the myocardium.

The effect of left-to-right shunting on coronary oxygenation during extracorporeal membrane oxygenation

BACKGROUND/PURPOSE

Blood perfusion to the coronary artery (CA) during venoarterial (VA) extracorporeal membrane oxygenation (ECMO) was examined to determine whether it was receiving highly oxygenated ECMO blood or desaturated blood from the pulmonary circulation of diseased lungs.

METHODS

In the first experiment, left ventricle output and oxygen saturation in the left ventricle (LV) and CA were measured in dogs placed on VA ECMO. In the second experiment, dogs with an artificial subclavian-pulmonary artery shunt were placed on VA ECMO at 100 mL/kg/min, and oxygen saturation was measured as the shunt flow increased.

RESULTS

Without an artificial shunt, a substantial portion of coronary perfusion was found to be supplied by the left ventricle (54 + 30%), even at a high ECMO flow rate of 100 mL/kg/min and low LV output (22+/-17%) relative to ECMO flow. With a shunt, oxygen saturation in the CA was more than 95%, even when shunt flow was only 7.5% of ECMO flow and output from the left ventricle was less than 25% of the ECMO flow rate.

CONCLUSIONS

These results suggest that an excessive "lung rest" strategy during VA ECMO may produce suboptimal coronary oxygenation possibly leading to myocardial damage. The presence of a small left-to-right shunt may prevent coronary hypoxia.

Regional blood flow distribution from the proximal arterial cannula during veno-arterial extracorporeal membrane oxygenation in neonatal dog

Extracorporeal membrane oxygenation (ECMO) is frequently used for treatment of patients with severe hypoxemia due to life-threatening respiratory failure. Due to this hypoxemia, the myocardium of these patients is insufficiently provided with oxygen, and consequently their cardiac function commonly deteriorates. But veno-arterial (V-A) ECMO provides oxygenated blood to the coronary arteries from ECMO circuit insufficiently. To increase the coronary blood flow distributed from ECMO, we placed the arterial cannula 1 cm above the aortic valve and evaluated the regional blood from the proximal arterial cannula in comparison with the distal cannula. Eight neonatal dogs weighting 1.8-2.5 kg were supported by V-A ECMO. The regional blood flow from the arterial cannula was measured by injection of colored microspheres into ECMO circuit. The site of the arterial cannula was changed under fluoroscopy. The bypass flow was maintained at either 50 or 100 ml/min/kg. We found that the coronary blood flow distributed from the proximal arterial cannula was significantly higher than that from the distal cannula. The proximal arterial cannula appears necessary to provide sufficient oxygenated blood to the coronary circulation during V-A ECMO. Therefore, it is expected that the increased cardiac function may improved, and that the survival rate of the patients with retarded cardiac function due to severe hypoxemia may increase by proximal placement of the arterial cannula during V-A ECMO.

Oxygenation of the cerebral and coronary circulation with right axillary artery perfusion during venoarterial bypass in primates

The effectiveness of right axillary artery perform in delivering oxygenated blood to the cerebral and coronary circulation during venoarterial bypass in primates was studied. Both right and left common carotid flow measurements and arterial gas measurements revealed high flows and elevated PO2 levels. Incomplete mixing in the ascending aorta was observed from cineangiograms taken at various pump oxygenator flows in 1 animal. The results demonstrated that the brain receives excellent oxygenation at all bypass levels. However, the coronary circulation is perfused primarily by blood ejected from the left ventricle and receives only minimal contribution of well-oxygenated blood from the pump oxygenator circuit. Therefore, the heart may suffer prolonged hypoxemia during long-term venoarterial bypass for acute respiratory insufficiency.