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ORIGINAL ARTICLE |
Department of Cardiothoracic Surgery Henri Mondor Hospital Créteil, France
Hiroshi Sugiki, PhD, Tel: +33 0149812111, Fax: +33 0149812199, Email: Hsugiki{at}aol.com, Department of Cardiothoracic Surgery, Henri Mondor Hospital, 51 Avenue du Mal de Lattre de Tassigny, 94010 Créteil Cedex, France.
ABSTRACT
Post-cardiotomy right ventricular failure is a serious complication that frequently results in adverse outcomes. We reviewed our experience with the Impella Recover RD (Impella Cardiosystems GMbH, Aachen, Germany). From January 2007 to December 2007, 7 patients (5 males, 54 +7 years old) had this device implanted for temporary support after heart transplantation in 4, after repeat mitral valve replacement in 2, and with a left ventricular assist device in 1. Devices were implanted during initial operation (n =5) or shortly thereafter (n =2). Six patients underwent implantation without cardiopulmonary bypass. Effective support with pump flows of 4.0–4.5 L · min–1 and adequate unloading (central venous pressure decreased from 15.3 ± 1.4 to 9.4 ± 1.2 mm Hg) was achieved in all patients. Patients were assisted for a mean duration of 4.9 ± 4.5 days. Three patients could be weaned after 7.0 ± 5.6 days of support and underwent device explantation without cardiopulmonary bypass. One of these patients died of recurrent right ventricular failure, 2 remained stable but died later of sepsis. The patient with a left ventricular assist device was switched to an alternative device for prolonged support. Two patients experienced pump dysfunction. Our preliminary experience shows that the Impella Recover RD is an effective device that can be easily implanted and explanted. However, its mechanical reliability needs to be improved.
Key Words: Ventricle-assist devices • Right ventricular dysfunction • Postcardiotomy cardiac dysfunction
INTRODUCTION
Right ventricular (RV) failure is a serious complication that may occur after conventional cardiac procedures, cardiac transplantation, or left ventricular assist device (LVAD) implantation, which frequently has an adverse outcome.1–4 It occurs in approximately 0.1% of patients after conventional cardiac procedures, but it accounts for 50% of all complications and 19% of early deaths after orthotopic cardiac transplantation.5,6 It is also observed in 9%–30% of LVAD recipients and is associated with a mortality rate of 43%.7 Although some patients recover successfully on inotropic drugs in conjunction with pulmonary vasodilators, others require temporary mechanical circulatory support.8,9 Several devices have been evaluated for this indication. Some groups advocate the use of veno-arterial extracorporeal life support, while others use extra-, para- or intra-corporeal pulsatile devices.10–12 We have previously evaluated axial flow pumps for RV failure.13–15 Recently, several new devices designed specifically for RV support have been developed.16–19 We report our initial experience with one of the latest generation, the Impella Recover RD (Impella Cardiosystems GMbH, Aachen, Germany).
PATIENTS AND METHODS
The Impella Recover RD is a partially implantable device, specifically designed for temporary RV support, with a recommended maximum use of approximately 10 days. The system consists of 3 parts: a pump, a mobile console, and a purger (Figure 1
). The pump is a micro-axial blood pump with an outer diameter of 11.5–12.3 mm. The pump is located within the right atrial inflow cannula, connected to the outflow cannula by a ring-reinforced polytetrafluoroethylene (PTFE) flexible vascular prosthesis. It is connected to the mobile console by a drive line. All pump parameters can be monitored continuously on the mobile console. Flow can be adjusted by variation of the rotational speed. A flow rate of 5 L min–1 can be achieved at a maximal speed of 32,000 revolutions per minute. The pump is also connected to the Impella purger by the same drive line. The purger continuously delivers heparinized rinsing fluid (20%–40% glucose solution and 2,500 IU heparin; 200–600 IU h–1 of heparin) from a 50-mL syringe to the micro-axial blood pump. This allows in-situ anticoagulation of the system and reduces the need for systemic anticoagulation. Thus no specific biological monitoring of anticoagulation by heparinemia or activated clotting time is required.
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). RV dysfunction was diagnosed by direct observation of RV contractility during the operation, or by hemodynamic parameters (central venous pressure 
20 mm Hg) or transesophageal echocardiography. Prior to implantation, the patients received inotropic support with dobutamine (5–15 µg kg–1 min–1) in 6 patients, and epinephrine (1.5–5 mg h–1) in all 7. Nitric oxide was administered in all patients directly into the endotracheal tube at a dose of 40–50 ppm. Five patients had the device implanted during their initial operation; one was still under cardiopulmonary bypass (CPB) and 4 received the device after termination of CPB. The other 2 patients returned to the operating room 2 and 46 h after termination of the initial operation and had the device implanted without CPB. The mean delay between aortic crossclamp removal at the initial operation and initiation of RV support was 8.3 ± 6.6 h (range, 1–48 h). The Impella Recover RD device was implanted directly into the right atrium and pulmonary artery, using double-purse string sutures with short snares. The sewing rings of the inflow and outflow cannulas were fixed at the cannulation site using several interrupted sutures (Figure 2). The sternum could be closed after implantation in all patients, with the drive line exiting through the lower part of the medium sternotomy. The decision on weaning and explantation was taken after serial echocardiography (transthoracic or transesophageal) performed in the intensive care unit. When improved RV contractility suggested recovery, the pump flow was progressively decreased to 1.5 L min–1. Pump explantation was decided when hemodynamic, clinical, and echocardiographic parameters remained stable during this weaning period.
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Categorical data are presented as percentages. Continuous data are expressed as mean ± standard deviation. Pre-and postoperative values were compared using the paired t test. A p value < 0.05 was considered statistically significant.
RESULTS
Patients had RV assist for a mean duration of 4.9 ± 4.5 days (range, 1–13 days). Three patients died of multiple organ dysfunction during support of 1–3 days. Another 3 patients were weaned after 3–13 days and underwent device explantation without CPB. One of these died of recurrent RV failure on postoperative day (POD) 16, the other 2 remained hemodynamically stable, but both died later of pulmonary infection on POD 24 and 25. The LVAD recipient was assisted successfully with the Impella Recover RD and could be extubated during RV support on POD 3. However, his RV function did not recover sufficiently and he was switched to a right Thoratec p-VAD for prolonged hybrid support on POD 8. He subsequently underwent successful transplantation 41 days after implantation of the Impella Recover RD. Thus, overall survival to explantation of the device was 57% (4/7), but survival to discharge was only 14% (1/7). Effective RV support was achieved in all patients with pump flows ranging from 4.0 to 4.5 L min–1. Central venous pressure decreased significantly after RV support initiation (Table 2 and Figure 3). Hepatic transaminases and bilirubin levels were only moderately elevated prior to support and did not increase after implantation. Moreover, glutamate pyruvate transaminase normalized progressively after implantation (Table 2 and Figure 4).
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DISCUSSION
Our preliminary experience shows that the Impella Recover RD is an effective and easy-to-use device for RV support, providing acceptable survival-to-explantation rates. The Impella Recover RD has several distinctive advantages over other devices, although its mechanical reliability needs to be improved. In recent studies on RV support devices, 12%–54% of the patients could be successfully weaned.11,12,20 Our experience compares favorably with those results, although overall mortality remains sobering high.
The implantation technique for this device is rapid and simple; it requires no additional cutaneous incisions for cannulas, drive lines, or an internal pocket for the pump. Furthermore, it can be implanted without CPB.17 These aspects greatly facilitate a rapid decision on implantation. Indeed, early decisions within 2 hours after aortic crossclamp removal in most of our patients probably prevented the occurrence of liver shock. The Impella Pump is small and flexible, it fits into the pericardial space without compressing the RV, and the chest can be closed easily. Consequently, patients do not need to remain sedated and some can even be extubated. In addition, the very small drive line of the Impella Recover RD can be brought out through the lower part of sternotomy. Although the device itself is designed for short-term support, this may reduce the risk of infection inherent to the larger percutaneous cannulas or drive lines of other systems. On the other hand, the very small size of the purging line carries a risk of occlusion. Indeed, the definitive pump stop reported above was attributed to crystallization of the glucose solution within the purger line. Thus, we decided to use a 10% glucose solution (instead of 30%) as the rinsing solution.
Implantation or explantation of this system still requires opening the chest. From this perspective, the new RV assist device described by Wirtz and colleagues16 provides a major improvement. It can be easily introduced percutaneously through the jugular vein without sternotomy, and it does not require reopening for explantation. However, it is not clear whether this device is effective for longer durations of support because it has only been evaluated for very short-term support during off-pump coronary artery bypass grafting. Bleeding is one of the most frequent complications after VAD implantation.10,11 Most of the currently available devices require full-dose systemic anticoagulation. In contrast, with the Impella Recover RD system, heparin is delivered directly within the pump. Although some heparin unavoidably reaches the systemic circulation, systemic heparin level remains low. However, in patients who require systemic anticoagulation for other reasons, such as a mechanical heart valve or LVAD, the dose of heparin from the Impella purger should be added to the total dose administered systemically, otherwise over-anticoagulation may occur. We think that it probably contributed to the diffuse bleeding we described in one of our patients. Although the Impella Recover RD allowed effective temporary RV support, 2 patients experienced pump dysfunction. This suggests that some improvement should be made regarding the reliability of this device.
REFERENCES
Asian Cardiovasc Thorac Ann 2009;
17:395-400
© 2009 by SAGE Publications
DOI: 10.1177/0218492309338121
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