(A) TandemHeart pump. (B) TandemHeart system. Courtesy of CardiacAssist, Inc., Pittsburg, PA; with permission. 

Context in source publication

Context 1

... TandemHeartTM (CardiacAssist, Inc., Pittsburgh, PA) is a percutaneous centrifugal pump ( Figure 2) that houses a 6-blade rotor which can generate up to 5.0 L/min at 7500 rpm. The inflow cannula is a 21-Fr polyurethane tube with an end hole and multiple side holes that are inserted through the femoral vein into the left atrium via a transseptal puncture approach. Blood is returned to patients by the outflow cannula (either one 17-Fr cannula or two 15-Fr cannulas connected to a Y catheter) in the contralateral femoral artery, although insertion via the axillary artery and vein has also been reported. 13 Complications associated with the transseptal puncture include perforation of the aortic root, coronary sinus, or posterior right atrial free wall. 14 Long-term disposition of the transseptal puncture is unknown, but the majority of echocardiographic studies have not shown any significant left- to-right shunting after removal of the transseptal catheter. 15 Widespread use of the TandemHeart has been limited by the need for transseptal placement of the inflow catheter, which, if not done during cardiovascular surgery, requires the expertise of trans-septal puncture by an electrophysiologist or interventional cardiologist. 9 The TandemHeart is contraindicated in patients with large ventricular septal defects due to the risk of hypoxemia caused by right-to-left shunting with LV unloading. Severe peripheral vascular disease may prevent TandemHeart insertion. 16 The intended use of the TandemHeart left ventricular assist device (LVAD) is to provide temporary mechanical support and complete unloading of the left heart. The device provides short-term support from a few hours up to 14 days, until the heart can be bridged to recovery or a more permanent LVAD. 17 Additionally, the TandemHeart can be used in a temporary fashion during high-risk cardiac catheterization procedures including high-risk percutaneous coronary intervention, and it can also be used as a temporary right ventricular assist device and is placed percutaneously as well. 18 In venoarterial extracorporeal membrane oxygenation (VA ECMO), the drainage cannula is commonly placed in the inferior vena cava (IVC) or right atrium (RA). This can be done either via a sternotomy or percutaneously by inserting the cannula through the internal jugular or the femoral vein. Blood is returned to the patient through a cannula inserted in either the ascending aorta (central ECMO, inserted surgically) or the femoral artery (peripheral ECMO, inserted either surgically or percutaneously). Central ECMO is a preferred option when used immediately after cardiopulmonary bypass (CPB) as the location of the cannulae is similar to the ones used during surgery and the chest is open for easy access and cannulation. VA ECMO support decreases cardiac work and reduces cardiac oxygen consumption. It also provides adequate systemic organ perfusion with oxygenated blood because the oxygen present in the ECMO circuit provides adequate tissue oxygenation regardless of the underlying lung function. If cardiac recovery is expected, it is important to reduce distension of the ventricles; VA ECMO can achieve this if the left ventricle continues to eject or a drainage catheter is inserted directly into the left ventricle. Whether a peripheral or central ECMO, these circuits are usually placed in patients who are in extremis or undergoing cardiopulmonary resuscitation. The peripheral VA ECMO circuit is the one that can be placed the most quickly. However, with the drawbacks of leg ischemia and inability to unload the left ventricle, it is intended to be a short-term acute device and often requires transition to another temporary device in profoundly ill patients who are unlikely to recover cardiac function. Another commonly used indication for ECMO support is in patients who have undergone a recent cardiac surgery and have developed post-cardiotomy shock. Because the chest is still open, the transition to a central ECMO is easily done, and a left- ventricular vent can also be placed to unload the left ventricle. The goal of central ECMO in this setting is to allow time for the patient’s heart to recover and thus allow explantation of the central device. However, as in other indications of ECMO placement, patients who do not recover their cardiac function may need to be bridged to another temporary or more permanent device. The CentriMag ® pump (Thoratec Corporation, Pleasanton, CA) (Figure 3 A) and the BPX-80 Bio-Pump ® Plus centrifugal pump (Medtronic, Inc., Minneapolis, MN) are surgically implanted centrifugal pumps with a bearingless, magnetically levitated rotor. These pumps are specifically designed for extracorporeal circulatory support applications, such as CPB or used as an ECMO circuit, or for a temporary ventricular assist device. 19 The pump has no contact between the impeller and the rest of the pump components; therefore, it creates a frictionless motor that does not generate heat or wear of the components, which leads to lower rates of hemolysis and pump thrombosis. 7 The pump can provide up to 10 L/min of flow and is intended for up to 14 days of support. 9 A console displays the pump’s rotational speed and flow rate (Figure 3 B). Although insertion is usually via a sternotomy, peripheral cannulation through the femoral artery and vein has also been reported. 20 If full cardiopulmonary support is needed, an oxygenator can be added to the circuit to adapt it for ECMO. 21 Both of these centrifugal pumps can provide right-ventricular or left-ventricular support depending on the cannulation involved. They can be used together for biventricular support as well, using the combination of left and right heart cannulation strategies. Since these devices commonly require a sternotomy, and patients often undergo delayed sternal closure, there is always a risk of bleeding and infection. Other concerns regarding use of these extracorporeal pumps are the effects on the patient’s coagulation cascade, rate of hemolysis, and platelet dysfunction. ...