Patients with advanced heart or pulmonary failure may require mechanical assistance, either temporarily or permanently, to supplement or replace the action of their failing heart or lungs. Mechanical circulatory support (MCS) is an umbrella term that describes both temporary and more durable devices that are used in this patient population. However, the use of these devices and interventions comes with its own set of risks, including potentially life-threatening hemostatic events such as pump thrombosis, stroke, and bleeding. Although thrombotic complications can be treated with anticoagulation and antiplatelet medications, these agents may increase the risk of bleeding. Acquired von Willebrand syndrome, along with other hematologic changes, can also affect the risk of hemorrhage. Therefore, to help manage hematologic complications associated with the use of MCS, hematologists must be part of a patient’s MCS management team.
In a new review paper published in the American Society of Hematology Education Book, the different types of MCS devices, some of their effects on the hematologic system, and their management were described.
“The most important take home message for patient management is that MCS causes activation of all aspects of the hematologic system,” said Lisa M Baumann Kreuziger, MD, MS, associate medical director at the BloodCenter of Wisconsin, assistant professor at the Medical College of Wisconsin in Milwaukee, and the paper’s coauthor, in an interview with Hematology Advisor. “Anticoagulation and antiplatelet medications are used to counteract that activation.”
She emphasized that “one of the largest challenges for hematologists is to understand the terminology used to describe MCS devices. It is important to understand which device is in place to know the degree of activation of the hematologic system [as well as] how long the device is anticipated to be in place.”
Understanding the terminology used to describe MCS devices would allow for better communication, but facilitating this process is tricky; many different words are used to describe MCS devices, type of ﬂow, and indication for device implantation. To further complicate matters, the terminology continues to evolve, which can be confusing for physicians working outside of specialties such as cardiology, critical care medicine, or cardiothoracic surgery.
Devices are usually described as being “full support” if the device ﬂow replaces the entire cardiac output and “partial support” if the ﬂow only augments the heart.
Extracorporeal membrane oxygenation (ECMO) provides respiratory (venovenous ECMO [VV-ECMO]) or respiratory and cardiac support (venoarterial ECMO [VA-ECMO] and can serve as a “bridge” to recovery or organ transplant for patients with cardiac or pulmonary failure who are refractory to medical therapy.
However, ECMO can cause serious complications in patients after 10 days to 20 days of use, such as vasomotor instability, capillary leak syndrome, bleeding, and multisystem organ failure. ECMO is contraindicated in patients with end-stage primary disease, severe neurologic injury or intracranial bleeding, and uncontrolled visceral bleeding. It is also contraindicated in premature infants and infants weighing less than 2 kg.
Another temporary device is TandemHeart (CardiacAssist), an extracorporeal centrifugal peripherally inserted ventricular assist device (VAD) that can support patients for up to 2 weeks. Depending on the catheter size, it can support blood flow of up to 5 L/min and can be used with an oxygenator in an ECMO system.
A third device is the Impella pump (Abiomed), a temporary percutaneous continuous ﬂow axillary device that is approved by the US Food and Drug Administration (FDA) for use in patients undergoing high-risk percutaneous coronary interventions or in cardiogenic shock. This pump is meant for very short-term use as it typically supports a patient for several hours to days.