Left Ventricular Unloading in v-a ECLS Patients

*Gaik Nersesian, Daniel Lewin, Pia Lanmüller, Sascha Ott and Evgenij Potapov*

### **Abstract**

The v-a ECLS is an effective approach for mechanical circulatory support, however, it is associated with several disadvantages. An increased afterload generated by a pump outflow leads to a left ventricular (LV) distension, pulmonary congestion, and lung edema on one hand and impairs myocardial perfusion on the other. In this chapter, we will discuss the rationality as well as different techniques for LV unloading during v-a ECLS support.

**Keywords:** ECLS, LV unloading, ECMELLA, Impella, IABP, venting

### **1. Introduction**

V-a ECLS represents an effective rescue therapy in patients suffering circulatory failure. The mechanical circulatory support (MCS) with a v-a ECLS can be rapidly established, achieving a blood flow of up to 9.9 L/min and simultaneous blood oxygenation and decarboxylation [1]. Uncomplicated placement, reasonable costs, and the possibility to implant a v-a ECLS during an ongoing cardiopulmonary resuscitation (eCPR) have made it a widely used mobile tool for first-line MCS [2].

Despite these alluring benefits v-a ECLS is an invasive approach and has its side effects, which have to be taken into consideration [2]. One of the significant disadvantages of the system is an increased afterload of the LV generated by the pump outflow [3]. In patients with severely impaired cardiac function, this can cause LV distention and ballooning, increasing the myocardial oxygen consumption, and impairing the coronary perfusion at the same time [2]. In addition, increased left heart enddiastolic pressure leads to pulmonary congestion and edema, with the consequence of respiratory failure [3]. All these factors limit the potential benefits of the v-a ECLS and complicate circulatory weaning [3]. Temporary MCS with v-a ECLS can impair ventricular recovery regardless of the severity of myocardial damage [4].

In order to prevent an LV distention on v-a ECLS, several approaches can be established: LV unloading via passive LV venting, creation of an ASD, or with a microaxial catheter-based Impella pump. Alternatively, LV afterload can be decreased by using a combination of ECLS with an intra-aortic balloon counterpulsation (IABP).

## **2. Passive venting**

LV venting can be achieved through the placement of an additional inflow cannula draining the left atrium or LV into the venous side of the ECLS. In the case of postcardiotomy patients, the venting cannula is usually placed in the left ventricle via the right superior pulmonary vein and then connected by a Y-tubing to the venous drainage line of the ECLS circuit [5]. Alternatively, the venting cannula may be directly placed into LV via the left ventricular apex, with a subsequent subxiphoid tunneling and externalization [5]. Another possibility is the direct placement of the cannula into the pulmonary artery [3].

In rare cases, an iatrogenic atrial septal defect (ASD) can be created in order to achieve passive drainage of the left atrium (LA) via a venous cannula placed in the right atrium [6]. This approach can be performed both surgically or by a percutaneous blade and balloon atrioseptostomy and is considered more as rescue therapy rather than a standard approach [6].

## **3. Percutaneous venting**

Alternatively, in patients with a closed chest on peripheral v-a ECLS left ventricular apical cannulation can be performed through a left anterolateral thoracotomy. This approach requires high surgical expertise due to potential LV damage, coronary injury, and a high risk of bleeding [5].

Furthermore, percutaneous approaches for LV unloading are available [5]. The TandemHeart system (LivaNova PLC, London, UK) uses a single-stage cannula, which can be placed percutaneously in the LA through an atrial septal puncture providing LV unloading on mechanical circulatory support [7].

The specially designed Bio-Medicus NextGen two-stage cannula (Medtronic PLC., Dublin, Ireland) can be applied in order to obtain both left-sided venting and venous drainage simultaneously. For this approach, the cannula is placed via a femoral vein with its tip advanced into the LA; the venous drainage is achieved by a second inflow positioned in the inferior vena cava [7]. The cannulation in both cases is performed in a catheterization lab or hybrid operation room under fluoroscopic and/or echocardiographic guidance. The major drawback of this method is ASD remains after decannulation. In the vast majority of cases, the iatrogenic ASD has no hemodynamic influence, however, can become relevant in patients undergoing a LVAD implantation [7].
