Extracorporeal membrane oxygenation (ECMO) and other forms of mechanical circulatory support (MCS) have a place in COVID-19 management for acute respiratory distress syndrome (ARDS) as well as for cardiogenic shock involving only the heart. However, COVID-19 patients with direct viral-induced or cytokine-mediated myocardial dysfunction in the setting of concomitant advanced respiratory failure have a very poor prognosis and are unlikely to benefit from advanced circulatory support.
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So advised Edward Soltesz, MD, MPH, Surgical Director of Cleveland Clinic’s Kaufman Center for Heart Failure and Recovery, in a recent Tall Rounds online CME activity from Cleveland Clinic covering COVID-19 and the heart.
“Evidence thus far indicates that ECMO, Impella and other devices may help COVID-19 patients with single-organ involvement,” says Dr. Soltesz. “But multiorgan failure from cytokine storm is associated with poor outcomes, and mechanical circulatory support is generally not recommended.”
VV-ECMO for ARDS
According to guidance from the Extracorporeal Life Support Organization, patients with ARDS brought on by COVID-19 who have failed conventional management should be considered for venovenous ECMO (VV-ECMO) based on their ratio of arterial oxygen partial pressure to fractional inspired oxygen (PaO2:FiO2) in tandem with other factors:
- For those with PaO2:FiO2 ≥ 150 mmHg, VV-ECMO is indicated with a pH < 7.25 with PaCO2 ≥ 60 mmHg for > 6 hours.
- For those with PaO2:FiO2 < 150 mmHg, VV-ECMO is indicated if any of the following criteria are met: (1) PaO2:FiO2 < 80 mmHg for > 6 hours; (2) PaO2:FiO2 < 50 mmHg for > 3 hours; or (3) pH < 7.25 with PaCO2 >60 mmHg for > 6 hours.
For other patients, management should consist of prone positioning, neuromuscular blockade and a high positive end-expiratory pressure strategy, and possibly inhaled pulmonary vasodilators and recruitment maneuvers.
General contraindications to ECMO apply, as do those specific to COVID-19 patients, including older age, mechanical ventilation for more than 7 days and multisystem organ failure.
Several VV-ECMO challenges are unique to patients with COVID-19 and include risk of the following:
- Slow recovery of lung function, often requiring 2 to 3 weeks on ECMO support
- A prothrombotic state caused by systemic inflammation, necessitating high heparin dosages and possibly bivalirudin
- Exacerbation of COVID-19severity by ECMO itself, leading to compromise of additional organs
Options for managing cardiogenic shock
Myocardial involvement occurs in about 22% of critically ill COVID-19 patients. “The best candidates for device support for cardiogenic shock are patients with single-organ myocardial involvement,” emphasizes Dr. Soltesz. “This can arise rarely as virus-induced primary fulminant myocardial involvement, and more often from exacerbation of existing cardiovascular disease.”
Patients with multiorgan failure — i.e., myocardial involvement secondary to advanced respiratory failure and cytokine storm — tend to have poor outcomes, he adds, limiting the role for any type of MCS.
As for all patients requiring emergency MCS, the goals are to restore adequate end-organ perfusion and break the shock spiral, unload the injured ventricle and allow a safe bridge to recovery, transplant or a permanent device. In the setting of COVID-19, an additional goal is to maintain safety for caregivers.
Veno-arterial ECMO (VA-ECMO) has several advantages in a crisis. It is minimally invasive, can be rapidly initiated at the bedside and offers full cardiopulmonary biventricular support. Caregiver risk is also relatively low compared with use of other surgical devices. However, its lack of left ventricular unloading limits recovery and predisposes an already at-risk patient to lung injury. In addition, the prothrombotic state of COVID-19 can exacerbate the likelihood of a left ventricular or aortic thrombus, as well as hemolysis. Another disadvantage is the inability to decouple the left and right ventricles, making it difficult to understand future needs. Furthermore, most configurations of ECMO preclude ambulation, hampering recovery.
The Impella pump offers an important advantage for COVID-19 in that it completely unloads the left ventricle, protecting the lungs. Support can range from days to months with the larger devices. It is associated with a low rate of hemolysis, and ambulation is possible with surgically placed axillary cannulation (Impella 5.0 or 5.5 device). However, although the CP and 2.5 models are percutaneous, the surgically implanted devices put caregivers at a higher risk due to the need for open surgery and the use of transesophageal echocardiography for placement.
Temporary right-ventricular assist devices (RVADs), including the ProtekDuo/TandemHeart, CentriMag and Impella RP products, are routinely used to support the right ventricle. An oxygenator can be spliced in to provide an oxy-RVAD configuration.
Cardiogenic shock strategy
For a patient presenting with cardiogenic shock with cardiovascular collapse, Dr. Soltesz notes, the typical management strategy is guided by a multidisciplinary discussion with Cleveland Clinic’s Miller Family Heart, Vascular & Thoracic Institute shock team and usually involves rapid percutaneous placement of VA-ECMO, with use of a reperfusion sheath to provide distal limb perfusion. Over the next hours, management is tailored to a ventricle-specific unloading strategy that allows patient ambulation. This often consists of the use of an endovascular, transvavular flow pump (Impella) in the axillary position for left ventricular support.
In the setting of COVID-19, Dr. Soltesz adds, venous-arterio-venous ECMO (VAV-ECMO) may be useful in certain patients who are not in cardiogenic shock but have signs of impending right or left ventricular dysfunction. Indications for VAV-ECMO include low ejection fraction, increasing need for inotropes and rising troponin levels.
“The importance of a shock team — including heart failure surgeons and medical specialists, cardiac interventionalists, anesthesiologists, specialty nurses, social workers and perfusionists— cannot be overemphasized,” Dr. Soltesz concludes. “They identify the endpoint, select the initial device, tailor the device daily and continuously reevaluate the endpoint.”
An additional perspective
“ECMO and other MCS devices have saved the lives of tens of thousands of patients with pulmonary and cardiac disease worldwide over decades,” adds cardiothoracic surgeon Kenneth McCurry, MD, Surgical Director of Cleveland Clinic’s Respiratory ECMO Program. “Given current knowledge of COVID-19-related disease and the outcomes noted thus far, the use of such devices for COVID-19 should generally be limited to ARDS without multisystem organ failure and potentially to myocardial dysfunction in the absence of significant pulmonary disease. Access to resources and an individual hospital’s capacity during a surge may necessarily alter inclusion or exclusion criteria.”