via a transseptal puncture through the intra‐atrial septum from the right atrium to left atrium where oxygenated blood is aspirated. A second outflow cannula is placed that returns the blood to the femoral artery. Advantages compared to the IABP and transaortic intraventricular pump are improved unloading of the left ventricle with improved cardiac output. This pump also bypasses the left ventricle and aortic valve and can therefore be useful for patients with left ventricular thrombus or aortic stenosis [8]. Like the transaortic intraventricular pump, this device results in improved hemodynamic profiles but with less certain short‐term mortality benefits. The disadvantage of this extracorporeal centrifugal pump is the transseptal puncture, requiring a surgeon or experienced interventional cardiologist for placement. This approach also increases complications associated with potential iatrogenic cardiac injury [8]. Similar to other devices, an understanding of how to troubleshoot this device and manage the complications is imperative for safe transport.
Extracorporeal membrane oxygenation
ECMO devices provide prolonged mechanical support by pumping blood and by exchanging oxygen and carbon dioxide in the blood prior to its return to the patient. Thus, ECMO may be helpful during both circulatory failure and pulmonary failure. There are two main types of ECMO support, venoarterial (VA) and venovenous (VV). VA ECMO drains venous blood via a venous cannula, oxygenates the blood in the ECMO circuit, and pumps the oxygenated blood into a large artery via an arterial cannula, bypassing both the heart and lungs. VA ECMO is used for both cardiac and pulmonary failure. VV ECMO oxygenates the blood and returns it to the body to be circulated by the heart, requiring adequate function of the both the right and left heart. VV ECMO is used during respiratory failure.
Cannulation for VA and VV ECMO differs in both their locations of access and who generally performs the procedure. For VA ECMO the venous cannula can be inserted into the right atrium via the internal jugular vein, or less commonly, via a femoral vein to the inferior vena cava and then right atrium. Venous cannulation can be performed via open incision, but it can also be placed via Seldinger technique. The arterial cannulation for VA ECMO can be performed via the right carotid artery, the femoral artery, or via a transthoracic approach by directly cannulating the aorta. There are benefits and downsides to each location, for example leg ischemia in femoral cannulation or neurologic compromise in carotid cannulation. VV ECMO cannulation usually involves the right internal jugular vein or femoral veins and may involve anywhere from one to multiple sites of cannulation for venous drainage. There are cannulas that can be placed in the right internal jugular vein with multiple lumens that can drain deoxygenated blood and return oxygenated blood from a single cannulation point.
Indications for ECMO include acute, reversible, severe respiratory or cardiac failure unresponsive to conventional management. A few examples for VV ECMO include neonates with respiratory failure following meconium aspiration, severe influenza‐associated acute respiratory distress syndrome, and near‐drowning with inability to oxygenate the patient. Some examples for VA ECMO include drug overdoses, massive pulmonary embolism, and witnessed cardiac arrest with refractory ventricular arrhythmias. Absolute contraindications to ECMO include patients with advanced, untreatable, or irreversible disease like advanced malignancy, nonrecoverable cardiac disease (and not transplant candidates), or irreversible brain injury. Some relative contraindications may include elderly patients, multiorgan failure, and bleeding diathesis.
EMS physicians may encounter ECMO devices in the setting of critical care transport. Some medical centers are able to cannulate patients but are unable to provide additional services they may require once on ECMO, necessitating transport. Other hospitals do not have ECMO cannulation capabilities, and surgeons or intensivists with training in ECMO cannulation are sometimes transported to the outlying hospital to cannulate the patient prior to transport.
ECMO has been initiated in the prehospital setting as a treatment of refractory cardiac arrest, one of the most notable cases being at The Louvre in Paris [9]. Pilot projects are being conducted to determine the feasibility of implementing systematic initiation of ECMO in the field for cases of refractory cardiac arrest. Such efforts require substantial investments in developing the necessary multidisciplined team to conduct the resuscitation, cannulate the patient, and manage the technology.
Transporting ECMO patients is a complex undertaking that requires planning [10]. Specialized equipment, as well as equipment mounts, may be required depending on the mode of travel [10]. The size and composition of the transport team should also be determined in advance. Some ECMO programs include a cannulation team that goes out ahead of the transport team. Transport teams may include a perfusionist to manage the ECMO device and a physician to provide direct medical oversight. Conversations between the transport team and the referring and receiving institutions should occur prior to patient contact to arrange for needed supplies and equipment in order to prevent delays. Without question, these are resource‐intensive cases.
Long‐term mechanical circulatory support devices
Ventricular assist devices
Ventricular assist devices (VAD) commonly refer to surgically implanted pumps that are intended to assist one or both ventricles of the heart. They are most often placed in patients with severe congestive heart failure. Devices include left ventricular assist devices (LVADs), right ventricular assist devices (RVADs), and biventricular assist devices. The most common is the LVAD, with a cannula placed in the apex of the left ventricle, blood flow to the pump, and flow back through a cannula into the ascending aorta. Thus, the device assists the ventricle in moving blood through the circulatory system [3].
VADs were first developed in the 1960s. Technological advances made them more portable, but the patient was still confined to the hospital. In the 1990s, fully portable devices were developed that allowed VAD patients to be discharged from the hospital [11, 12]. VADs are most commonly used as a bridge to cardiac transplantation, but they also may be used as a bridge during a reversible cardiac condition or as a permanent destination therapy. There are two types of VAD patients. There are those with nonportable devices who require critical care transport with a perfusionist. Alternatively, those with portable VADs may be living at home where prehospital EMS clinicians may be called.
Currently, there are four generations of VADs with features that vary (Box 11.1). First‐generation devices mimic the pumping action of the left ventricle via the use of diaphragms or pusher plates that cause blood to be sucked into the left ventricle and expelled into the aorta. This mechanism results in pulsatile blood flow. The patient will have a pulse and blood pressure that can be measured [12]. The pumps are powered by electricity and can be either electromechanical or pneumatic. Electromechanical pumps use an electromagnetic pusher plate to drive the blood, whereas pneumatic devices use air pressure to move the blood. Pneumatic devices may come with a hand pump to be used in the event of device or power failure [11].
Second‐generation LVADs have continuous‐flow rotary pumps. If the device only assists with the work of the left ventricle, the underlying heart function may result in a palpable pulse. If the LVAD is fully replacing the function of the ventricle, there may not be a palpable pulse. As with other technological advances, these devices offer advantages in size, ease of implantation, and durability. The number of moving parts has been reduced to one: the impeller. Second‐generation LVADs are subdivided into devices with axial pumps and those with radial (centrifugal) pumps [11] (Figure 11.2).
Box 11.1 Examples of LVADs by generation
First generation (pulsatile blood flow)
Berlin Heart ECXOR (Berlin Heart AG)
HeartMate XVE (Abbott Laboratories)
Thoratec PVAD (Abbott)
Second generation (continuous flow)
HeartMate