Right ventricular failure (RVF) remains a common complication during left ventricular assist device (LVAD) implantation.1 Incidence ranges from 20% to 50% in smaller studies2,3 and is reported at 0.49 events per 100 patient months by Interagency registry for Mechanically Assisted Circulatory Support (INTERMACS) in the most recent era.4 The occurrence of RVF is associated with worse outcome and patients may require prolonged postoperative ventilation and may develop renal failure, multi-organ failure, or gastrointestinal ischemia.2–4 Right ventricular failure may be caused by geometric changes from the opening of the pericardium or by a leftward shift of the interventricular septum from the LVAD suction. It may be aggravated by the increased cardiac output by the LVAD, overwhelming the right ventricle (RV) by increasing its preload. Also, it may be induced by a hypervolemic perioperative state.5–7 Existing RV dilatation and tricuspid valve (TV) regurgitation may further increase the risk for RVF. Therapeutic strategies including intraoperative pharmacological RV afterload optimization with pulmonary vasodilators and maintenance of euvolemia with volume and diuretics are widely accepted.8 Surgical approaches of concomitant TV procedures showed ambiguous outcome data. Although certain reports describe a benefit from TV repair or replacement, other authors assume an impairment of the RV from TV procedures because of an increase in afterload with consecutive worse early postoperative outcomes.8–10
Our approach to minimize RVF starts with a minimally invasive implant procedure, which maintains the RV-supporting pericardial geometry and fully spares the sternum. Although deemed appropriate for perioperative RVF in contemporary state-of-the-art reviews,1 we believe that aggressive perioperative inotrope use may actually contribute to postoperative morbidity and should be avoided. On the other side, the use of a temporary right ventricular assist device (RVAD) is widely regarded as a failure during LVAD implantation. Temporary RV support is described with a 30 day mortality between 12% and 20%.11,12 We, however, use RVAD support with a lower threshold as a temporary strategy which ensures stable early postoperative hemodynamics, offers real RV unloading, and also reduces inotrope and pressor requirements. With our minimally invasive implant technique for the RVAD, we still preserve the pericardial geometry as well as the sternum. We herein report outcomes of minimally invasive RVAD implantation (MI-t-RVAD) for RVF during minimally invasive LVAD (MI-LVAD) implantation as an alternative approach to aggressive inotropic therapy.
All patients receiving MI-t-RVAD support during MI-LVAD implantation between January 2012 and April 2016 were retrospectively reviewed. Data were retrieved from our hospital database. Patient selection for LVAD implantation was according to current international recommendations and required consensus of the local dedicated heart team, consisting of cardiac surgeons, cardiologists, intensive care physicians, anesthesiologists, and specialized psychologists.13,14 Written informed consent was obtained from all patients before the procedure (when INTERMACS profile ≥2 and no preoperative mechanical ventilation existed).
Definition of RV Failure
Diagnosis of RVF at the end of the LVAD implant procedure was conducted according to INTERMACS adverse event definitions.15 A combination of intraoperative right atrial pressure >16 mm Hg, dilated inferior vena cava with no inspiratory variation on transesophageal echocardiography, cardiac index <2.5 L/min/m2, all refractory to moderate administration of inotropes and inhaled nitric oxide, led to the intraoperative decision for temporary RVAD support.
Ventricular Assist Device Implantation
Minimally invasive LVAD and temporary RVAD implantation was performed as previously described16: HVAD (HeartWare, Framingham, MA) implantation was performed through bilateral mini-thoracotomy incisions, providing access to the left ventricle (LV) apex and the aorta with support of femoro-femoral cardiopulmonary bypass (CPB). For implantation of temporary RVAD, a left-sided mini-thoracotomy incision was performed in the second intercostal space adjacent to the sternal border (Figure 1A). The pulmonary artery (PA) anastomosis was performed with 4–0 polypropylene suture using a side-biting clamp and a beveled 10 mm Gelweave graft (Vascutek, Renfrewshire, Scotland) as RVAD outflow. At this point, accurate tailoring of the graft is of particular importance to protect against possible kinking within the subcutaneous tunnel. Subsequently, the graft was externalized through a puncture wound in the sixth intercostal space and cannulated with a 22 Fr aortic cannula (Medtronic, Minneapolis, MN) (Figure 1B). Right ventricular assist device inflow was achieved using a 25 Fr venous multistage femoral cannula (Medtronic) (Figure 1C). A Centrimag (Levitronix, Zurich, Switzerland) or Deltastream (Medos, Stolberg, Germany) was used as temporary extracorporeal assist system in all cases.
Right ventricular assist device support was maintained until all pressors and inotropes were weaned off and the patient was extubated and mobilized on our specialized cardiac surgery intensive care unit. Weaning from RVAD support was performed by reducing the flow by 0.5 L/min/day under transthoracic echocardiography (TTE) monitoring and daily control of laboratory markers for RV failure such as lactate, glutamate oxalacetate transaminase/glutamat-pyruvat-transaminase, and creatinine. When laboratory findings were constant and TTE did not present RV dilatation or a significantly dilated inferior vena cava, RVAD weaning was continued until a minimum support of 2 L/min was achieved. Then, RVAD explantation was scheduled.
Right ventricular assist device explantation was performed in an operating room on an awake patient using local anesthesia only. The PA graft was accessed through a small skin incision 2–3 cm cranial of the skin exit, ligated, cut, and retained in place. The venous cannula was pulled and mild compression was applied (Figure 2).
Baseline, intraprocedural and follow-up data were collected and entered into a dedicated standardized database. Clinical endpoints were death or unsuccessful RVAD weaning. Data are presented as absolute numbers and percentages for categorical variables and mean values and standard deviation for continuous variables unless stated otherwise.
Overall, 10 out of 74 consecutive LVAD patients (90% male, mean age 49.6 ± 14.8) received MI-t-RVAD implantation for acute RVF during MI-LVAD surgery. Of those, five patients (50%) fulfilled clinical requirements for INTERMACS level 1 or 2 and were in need for preoperative temporary mechanical circulatory support consisting of two extracorporeal membrane oxygenations (ECMO), two Impella systems (Abiomed, Danvers, MA), and one intra-aortic balloon pump (IABP; Abiomed, Danvers, MA).
Detailed patient demographics are summarized in Table 1.
Preoperative Laboratory, Echocardiography and Right Heart Catheterization Findings
Preoperatively, patients presented with signs of end-organ damage in advanced heart failure with a mean creatinine value of 2.2 ± 1.0 mg/dl, an Aspartate Aminotransferase of 348.3 ± 714.6, and an Alanine transaminase of 204.6 ± 297.9 unit/l.
Echocardiography revealed a preoperative left ventricular ejection fraction of 14.5 ± 7.9% and precursors of impaired RV function. Tricuspid insufficiency ≥ moderate was present in 4/10 patients (40%).
Right heart catheterization presented a mean central venous pressure of 10.6 ± 5.8 mm Hg, a mean PA pressure of 19.8 ± 9.3 mm Hg, and a pulmonary capillary wedge pressure of 23.2 ± 9.3 mm Hg.
Detailed preoperative laboratory and echocardiography findings are summarized in Table 2.
Mean operation time was 411.6 ± 78.6 min with use of CPB in all cases. In no case a concomitant valve procedure was performed. In 9/10 patients (90%), the HVAD outflow graft was anastomosed to the ascending aorta and in 1 patient (10%) to the descending aorta. In one case, a hemisternotomy was performed because of inconvenient location of the ascending aorta.
Postoperatively, dilative tracheostomy was performed in two cases caused by prolonged ventilation. Dialysis was necessary in 4/10 patients (40%) because of acute renal failure with a mean duration of 3.3 ± 4.6 days.
Clinical Outcome Data
There were no pump thromboses or major gastrointestinal bleedings. In four patients (40%), re-thoracotomy had to be performed because of increased postoperative hemorrhage. In no patient conversion to median sternotomy was necessary.
Shortest duration of temporary RVAD support was 3 days and longest duration was 35 days. Weaning from the temporary RVAD systems was successful in all cases with subsequent unproblematic explantation.
Thirty day survival was 80% with two deaths on postoperative day 11 and 12 at ICU, respectively. One patient died from intracranial hemorrhage because of inadequate International normalized ratio increase after phenprocoumon administration. Post-mortem computed tomography showed massive hemorrhage with concomitant edema and midline shift. Another patient with history of recurrent ventricular arrhythmias, who already had an implanted implantable cardioverter defibrillator died from intractable ventricular tachycardia resistant to medical and electrical cardioversion. This patient had recovered well from surgery, had MI-t-RVAD explanted, and showed adequate RV function in the last follow-up echo. All other patients were stable on isolated LVAD support with a mean follow-up of 273.8 ± 179.2 days. One patient received heart transplantation on postoperative day 365.
In the entire LVAD cohort of 74 patients, 11 more patients were provided with LVAD and a temporary RVAD via sternotomy. Here, 30 day survival was 45.5%.
For detailed clinical outcome data, see Table 3.
Minimally invasive temporary right ventricular assist device support for acute RVF during MI-LVAD implantation is feasible and safe. There were no complications attributed to the RVAD. Major advantages of our strategy are the stable early postoperative hemodynamics on biventricular VAD support, the maintenance of the pericardial geometry which may facilitate RV recovery or adaption, and the noninvasive explant procedure not requiring sedation. In addition, our approach provides a safe and feasible access to the LV apex, the ascending aorta, and the PA in redo scenarios because only few adhesions have to be dissected.
Contrary to percutaneous RV support systems, our technique combines the advantages of early mobilization (with venous femoral cannula in place), possibility of using the system more than two weeks and the feasibility of a bed-side explantation procedure. Percutaneous systems either do not provide experience with mobilization on the system (right-side Impella [Abiomed Inc., Danvers, MA]) or are only approved for clinical use up to 6 days by the FDA (TandemHeart plus ProtekDuo cannula [CardiacAssist Inc., Pittsburgh, PA]).17,18
In cases where RVAD requirement was unexpected, successful weaning rates of only 50% were reported. In these cases RVAD was initiated when severe RVF occurred intraoperatively.19 Although, we herein also describe unplanned temporary RVAD implants, our threshold for implantation was lower. We achieved a successful weaning rate of 100%, which substantiates the capacity of this approach to achieve RV recovery or adaptation. Although the described patient cohort consists of only 10 patients, these outcomes show at least noninferiority compared with inotropic therapy for RVF alone.11,20 Our minimally invasive implant technique may have contributed to the successful weaning in all patients. The pericardium surrounding the RV was left intact, which has been suggested to be beneficial in animal models and may be also advantageous in humans.21
In 2010, Kormos and colleagues described the general misconception that the RVAD system itself contributes to the inferior outcomes of patients requiring RVAD support after LVAD implantation.22 Furthermore, the INTERMACS definition of RVF includes the usage of RVAD support (Appendix A, available at www.uab.edu/medicine/intermacs). Because of this misperception, there is a persistent reluctance in the field for early RVAD implantation, which may lead to disastrous outcomes when RVAD implantation is postponed until frank RVF has developed. For this patient subgroup, Fitzpatrick and colleagues reported an in-hospital mortality of 71%.23 A more liberal and planned usage of MI-t-RVAD systems for RVF may help reduce weaning failure and can protect an already impaired RV against sudden hemodynamic alterations intra- or early postoperatively.24 It is known that early RVF in LVAD patients causes inferior outcomes compared with patients not developing RVF.25 Moreover, it is known that patients who require an RVAD later after LVAD implantation have significantly worse outcomes than patients receiving an RVAD simultaneously with LVAD implantation, suggesting that RVF is more difficult to treat than to prevent.26 Our liberal approach in combination with an entire minimally invasive technique may have substantially contributed to protect against early severe RVF and enabled a weaning rate of 100% in the current study.
Another main advantage of the herein described procedure is the awake explantation method for the temporary RVAD. It is known that general anesthesia, and especially use of propofol significantly changes the inotropic state of the RV, particularly in terms of a decrease in RV ejection fraction.27 Moreover volatile anesthetics lead to a decrease in myocardial perfusion and pharmacological vasodilatation to fluid administration, which may lead to volume overload of the RV.28 By omitting general anesthesia, not only the RV can be protected against further functional deterioration, but also reliable assessment of the RV can be performed right before explantation by echocardiography.
Typical limitations for a retrospective, single-center study with limited patient numbers apply: no patient was randomly assigned to specific treatment and the conclusion is limited by the small patient number of the study group. Especially, the heterogeneity of the patients included, in terms of different LVAD implantation strategies (bridge-to-transplantation, destination therapy, etc.) may have biased the results. Furthermore, conclusions on adequate mechanical support as well as long-term sufficient native RV function have to be interpreted with caution because of the mean follow-up time of 273 days. Therefore, implications will have to be confirmed in larger patient cohorts for further clinical evaluation and before general recommendations can be made.
There is still a misperception in the field that RVAD support is a failure of LVAD therapy. Also, there is another misperception that avoidance of RVAD implants reflects the nonoccurrence of RVF. In this first series, we could demonstrate that temporary RVADs are safe and when implanted with a reasonably low threshold before severe RVF develops, successful weaning is possible with good early results. We thus advocate for a wider use of this technology, as we believe it could potentially be advantageous compared to “aggressive inotrope use”.
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