Continuous-flow left ventricular assist devices (LVADs) are being increasingly used for refractory end-stage heart failure in appropriate candidates.1,2 Proper LVAD function relies on blood supply from the forward flow generated from right ventricle (RV). Thus, right ventricular dysfunction (RVD) is a critical event leading to increased morbidity and mortality.3,4 Treatment options for managing RVD include inotropes, inhaled NO2 or use of an oral phosphodiesterase inhibitor, or a temporary right ventricular assist device (RVAD).5 The planned use of temporary mechanical assist support in these situations has been reported as a better means of managingRVD.6
For nearly a decade, our center has been using a new-generation extracorporeal membrane oxygenation (ECMO) system (ROTAFLOW; MAQUET Gmbh & Co. KG, Rastatt, Germany) as our preferred tool for temporary RV mechanical circulatory support. This device has a spiral housing containing a spinning rotor with logarithmically curved flow channels that impart a rotary motion on the incoming blood, directing it toward the outlet. These features have been shown to allow improved continuous laminar flow, with fewer areas of stagnant flow or high shear stress.7–9 In addition, the ROTAFLOW’s permanent, stable radial magnetic field and low-friction, one-point sapphire bearing allow for reduced heat generation within the pump.7,8 Recent data suggest that this device is much more durable than systems from prior generations, which may translate to an improvement in patient care.10 The ROTAFLOW and custom tubing pack are coated with a synthetic immobilized recombinant albumin coating (Safeline; MAQUET Cardiopulmonary AG, Hirrlingen, Germany). The purpose of this study was to determine the outcomes associated with using the ROTAFLOW system as a temporary RVAD in patients with RVD after the implantation of a HeartMate (HM) II LVAD (Thoratec Corporation, Pleasanton, CA).
A retrospective chart review was conducted on all patients who had undergone implantation of a HM II LVAD at our institution. Patients who required temporary RV support at the time of HM II implantation were identified and constitute the basis for this study. Medical records and clinic notes were additionally used to collect demographics, pre- and postoperative echocardiographic reports, hemodynamic variables, blood chemistries, length of RV support, length of stay, postoperative complications, and midterm outcomes. This study was conducted after the written approval of the Cleveland Clinic’s Institutional Review Board.
ROTAFLOW Implantation Technique for RV Support
Indications for RV support are largely based on the inability to transition from cardiopulmonary bypass to full HM II support due to RV dysfunction, despite maximal medical therapy, which included epinephrine, milrinone, or inhaled nitric oxide. The technique by which we placed a patient on temporary RV support has been previously described.11 In brief, a pulmonary arteriotomy is performed, and a 10 mm nonring reinforced Hemashield graft (Maquet, Inc, Wayne, NJ) is sutured to the artery in a continuous fashion using running PROLENE (Johnson & Johnson Medical Ltd.; Livingston, West Lothian, United Kingdom) suture. The graft is exited through a small thoracotomy in the left chest and is mated to the outflow line of the ROTAFLOW circuit with tie bands. For venous drainage, the femoral vein is cannulated with an 18–28 Fr long venous cannula (Duraflo Coating; Edwards Lifesciences LLC; Irvine, CA), with percutaneous technique reaching the right atrium over a wire, and this is attached to the inflow line of the ROTAFLOW. In our cases, the ROTAFLOW centrifugal pump does not involve an in-line membrane gas exchange. The average flow after initiation of RV support is 3.5 L/min. The central venous pressure (average) before RV support is 13 mm Hg; immediately after ROTAFLOW initiation, it decreases significantly reflecting adequate RV decompression. In all cases, the chest was closed, and the patient was transferred to the cardiovascular intensive care unit (CVICU).
Systemic anticoagulation for the ROTAFLOW was undertaken in the form of a heparin infusion, which is typically initiated 24 hours postoperatively, and only when all bleeding associated with the procedure has subsided. For appropriate anticoagulation, we monitored partial thromboplastin time and set a goal of 45–60 seconds.
Technique of Weaning and Explant
Right ventricular function was assessed daily during rounds by way of catheter-based hemodynamic monitoring. A patient was deemed eligible for weaning once inotropic support was minimal, and the patient was able to maintain good hemodynamics with the flow rate of the ROTAFLOW at 1 L/min. All procedures were performed in the operating room with transesophageal echocardiographic guidance. The pulmonary graft was exposed through a small left thoracotomy. It was clamped and ligated at the level of the lung. The femoral cannula was simply withdrawn and pressure applied to the groin for hemostasis.
Predictive Models for RV Dysfunction or the Need for RVAD
Five different predictive models were applied to this patient case series to document the preoperative risk of RV dysfunction or the need for RVAD after HM II implantation. A patient was determined to be at risk if the calculated score was ≥ 50 points as reported by Fitzpatrick et al.,5 an odds ratio (OR) of ≥2.8 as reported by Matthews et al.,9 a score of ≥ 5.5 points as reported by Drakos et al.,10 an OR of ≥ 2.1 based on Kormos et al.,3 or an RV stroke work index of < 300 based on Ochiai et al.11 (Appendix 1).
Continuous variables are expressed as mean and ranges, and categorical data are given as proportions. Kaplan-Meier methodology was used to calculate the overall survival for the group.
Demographics and Baseline Variables
Between October 2009 and September 2011, 194 patients were implanted with a HM II LVAD at our institution. Of these, 12 (6.2%) patients received temporary RV support in the form of a ROTAFLOW at the time of HM II implantation. Demographics of this patient group are shown in Table 1. Most patients were men, with an average age of 51.4 years (range, 24–69 years). The most common etiology leading to heart failure was nonischemic cardiomyopathy, and LVADs were commonly implanted as a bridge to transplantation. Nearly half of the patients in this group were either INTERMACS level I or II. Preoperatively, all patients had depressed ventricular function. Estimated left ventricular ejection fraction was < 25% for all patients, and 10 (83.7%) of 12 patients had moderate-to-severe RV function.
Table 2 depicts the risk scores for RVD or the need for an RVAD for each patient in this case series based on five recently published models.4,6,12–14 Based on these, the model proposed by Drakos et al.10 would have predicted RVD/RVAD in 10 of the 12 patients in this study. Conversely, the RV stroke work index published by Ochiai et al.11 would have predicted three of the 12 patients having a similar problem.
The mean CVICU and hospital length of stay for this group were 19 days (range, 15–22 days) and 73 days (range, 15–92 days), respectively. Four patients (36%) underwent an operation for bleeding related to generalized coagulopathy and HM II placement. The mean duration of RV support was 8 days (range, 3–18 days). Two patients (18%) developed acute renal failure requiring dialysis; however, both patients recovered normal renal function before discharge. Five patients (45%) developed respiratory failure requiring a tracheostomy. One patient with ischemic cardiomyopathy developed “blue toes,” presumably as a result of atherosclerotic embolization from a diseased aorta. There were no strokes or infections reported in the postoperative period. One (8.3%) patient died on postoperative day 10 due to multisystem organ failure.
Overall, 1 year survival by Kaplan-Meier analysis was 91.7% (Figure 1). Of the 11 patients who survived until discharge, two (16.6 %) patients underwent transplantation at a mean of 126 days after VAD implantation. The remaining nine patients had a functioning HM II LVAD at a mean follow-up of 12.2 months.
Follow-up echocardiogram showed improved RV function in comparison with the pre- and perioperative echocardiogram on all patients supported with an LVAD. None of the patients had required further mechanical RV support since their initial wean and discharge from hospital.
There have been four patient readmissions since discharge. In one case, a planned readmission occurred for a scheduled LVAD explant in a patient with myocardial recovery. A second patient was admitted for the treatment of pneumonia. A third patient who had developed toe gangrene was admitted for elective toe amputations. Finally, a fourth patient had an unplanned readmission due to acute renal failure, which was successfully managed medically without the need for hemodialysis.
There were no complications due to retained pulmonary artery outflow grafts. Specifically, there was no reported case of infection, graft pseudoaneurysms, or pulmonary embolism from retained outflow grafts. In addition, there were no VAD-associated readmissions in this case series.
This article adds to the growing literature demonstrating the feasibility and safety of using new-generation temporary mechanical circulatory support systems to aid in bridging to recovery patients with RVD after HM II implantation.
Right ventricular dysfunction continues to be a significant cause of morbidity and mortality after the implantation of long-term implantable LVADs. In a recent study, Dang et al.4 showed that patients who had RVD after LVAD implantation RVF not only had a higher mortality compared with those who did not but also had greater lengths of stay, more reoperations for bleeding, and a higher risk for renal failure. Similar findings have been reported by others.15
These data have led to the creation of several risk stratification models that attempt to identify patients at risk of developing RVAD, who may benefit from earlier interventions.4,6,12–14 Some of these therapeutic strategies may include altering the surgical plan from the use of univentricular support to that of biventricular support or even the use of temporary RV support systems to bridge the RV to recovery.16,17
The choices for temporary mechanical RV support have varied over the years from the large and bulky ABIOMED (Danvers, MA) system to the much more smaller and versatile CentriMag (Thoratec Corporation). The pros and cons of each of these devices have been previously highlighted.16
The introduction of the ROTAFLOW to the surgeon’s armamentarium provides yet another tool to aid in the management of this difficult patient population. In our experience, the ROTAFLOW was used exclusively as a temporary RVAD with good results. The ROTAFLOW has several advantages over older devices. These include ease of priming, implantation, and explantation. In addition, because of its size, it may allow for easier patient transportation not only within the hospital setting but also between referring and accepting institutions in a hub-and-spoke system. One of the other advantages has been its design. Similar to the CentriMag, the ROTAFLOW has a magnetically levitated rotor, and because of the lack of bearings or seals, there is much less trauma to blood elements, causing less hemolysis than older generation devices. Furthermore, the device can be configured to ECMO in cases of refractory respiratory failure by simply inserting an oxygenator into the system.18 Finally, although the ROTAFLOW’s engineering may be similar to that of the CentriMag, it has been suggested that it can be used at a fraction of the cost.19
Currently, there are no randomized trials comparing tem-porary mechanical support devices. We believe that despite the increasing number of devices in the marketplace, no single device may be superior and that the results are largely based on the experience of the user. It is important to underscore that surgeons and practitioners alike should select the device with which they feel most comfortable. Our study shows that early temporary mechanical support of the RV with the ROTAFLOW system using a convenient cannulation system is effective and should be considered when faced with RVD at the time of HM II implantation.
The important limitations of this study are its retrospective nature, the small sample size, and the lack of a control.
Right ventricular dysfunction can be successfully managed with the use of the ROTAFLOW, and good outcomes can be expected with its application.
The authors thank Kelli R. Trungale, MLS, ELS, for editorial assistance.
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HeartMate II; ROTAFLOW; RVAD; right ventricular dysfunction