Effect of Timing of RVAD Insertion on Outcomes
Twenty-six patients underwent concomitant RVAD insertion while 14 underwent delayed RVAD insertion (median delay of 3 days after LVAD implantation, range 1–66 days). Baseline characteristics were similar between groups, except for the body mass index. Median duration of RVAD support was 13 days (range, 1–103 days) in the concomitant RVAD group versus 25 days (range, 5–104 days) in the delayed RVAD group (p = 0.41). Of patients who underwent concomitant RVAD insertion, 3 (12%) underwent successful transplant during a temporary RVAD support, and 14 (53%) successfully weaned off RVAD support. Of the 14 patients who underwent delayed RVAD insertion, 4 (29%) had successful transplant during a temporary RVAD support, and 6 (43%) were successfully weaned off RVAD support. In-hospital mortality was similar between groups (50% for the delayed group vs. 46% for the concomitant group, p = 0.82). The 1-year actuarial survival was 42% in the concomitant RVAD group and 36% in the delayed group (p = 0.42, Figure 2).
Outcomes According to the Era
To investigate the impact of the era on outcomes, the cohort was divided into 2 groups: 2000–2004 (Era 1, n = 101) and 2005–2010 (Era 2, n = 181). Preoperative patient’s status significantly varied across the era. Patients in Era 1 were significantly sicker than those in Era 2 with lower ejection fraction (16 ± 5.9% vs. 18 ± 6.2%, p = 0.0013), lower sodium (131 ± 6.7 mmol/L vs. 133 ± 4.4 mmol/L, p = 0.032), higher BUN (42 ± 23 mg/dl vs. 36 ± 18 mg/dl, p = 0.0022) and creatinine (1.8 ± 0.73 mg/dl vs. 1.5 ± 0.58 mg/dl, p = 0.0004), higher AST (131 ± 288 IU/L vs. 51 ± 109 IU/L, p = 0.0013), and lower total protein (5.9 ± 1.6 g/dl vs. 6.6 ± 1.0 g/dl, p < 0.0001). The 1-year survival rate increased significantly from Era 1 (67.2%) to Era 2 (79.7%) (p = 0.0059). Era 1 included 15 patients who required RVAD support and Era 2 included 25. Survival rate at 1 year for RVAD group was 27% in Era 1 and 48% in Era 2, respectively (p = 0.029, Figure 3).
Impact of Device Type on Outcomes
Incidence of severe RV failure requiring RVAD support was significantly lower in patients with HeartMate II (5.3%) compared with those with HeartMate I (20%) (p = 0.0004). Outcomes were compared according to the type of RV support device either with pulsatile flow device (Thoratec PVAD or Abiomed 5000, n = 27) or continuous flow device (Centrimag, n = 13). The 1-year survival rate was not statistically different between pulsatile (41%) and Centrimag (54%) group (p = 0.28).
Effect of RVAD Insertion on End-Organ Function
Table 3 demonstrated the time course of hepatic and renal function after RVAD insertion according to in-hospital mortality. In nonsurvivors, hepatic and renal functional marker levels, including AST, ALT, and creatinine, deteriorated with time. However, in survivors, hepatic and renal functions were likely to recover on postoperative day 3. Creatinine levels on postoperative day 3 showed a statistically prominent difference between survivors and nonsurvivors.
The major findings of this study are that the development of RV failure that requires RVAD support in LVAD recipients is associated with high mortality irrespective of the timing of device insertion.
The use of LVAD has become standard care for heart failure patients with mild inotrops as a bridge to transplantation or as destination therapy.16,17 However, there are still two major limiting factors for further success with LVAD. One is device-related complications such as thromboembolism, infection, and bleeding. Another is the RV failure after LVAD implantation. The recent innovation of technology could dramatically improve device-related complications.17 Furthermore, some studies implied that the continuous flow LVAD might decrease the incidence of RV failure compared with pulsatile flow devices.2,18 Indeed, our study showed that the use of HeartMate II had significantly reduced the postoperative need for RVAD. However, simultaneously, all these studies, including ours, confirmed that the RV failure after LVAD remains problematic in terms of outcomes.
In the current study, 1-year survival rate was 82% for the non-RVAD group and 40% for the RVAD group. The recent data from the Interagency Registry for Mechanically Assisted Circulatory Support (INTERMACS) showed 6-month survival rate was 86% for the LVAD group and 56% for the BiVAD group.7 Compared with this registry data, present data showed worse survival for the RVAD group. This is explained by the fact that our cohort included old series since 2000. Patient’s selection for device insertion has significantly changed during the study period, resulting in improving outcomes in the latter half of period. Furthermore, our RVAD cohort only included patients who required “unplanned” RVAD support after LVAD insertion. A previous study showed that “planned” BiVAD implantation improved outcomes compared with delayed conversion.6 This might also influence the outcomes.
Multiple studies have attempted to identify the risk factors for the development of RV failure after LVAD placement.2–6 Like these studies, our study identified preoperative CVP as a risk factor for RVAD implantation. However, in the clinical setting, we cannot precisely predict which patients would newly develop RV failure after LVAD implantation because the etiology of RV failure is multifactorial. Proposed underlying mechanisms include intrinsic myocardial dysfunction, leftward ventricular septum shifting, and insufficient RV afterload reduction.2,19,20 It is important to keep in mind numerous other potential complications after LVAD surgery such as renal failure, infection, and bleeding, which might predispose patients to RV failure. Intra- and perioperative strategies to avoid these complications as well as preoperative optimization to reduce CVP should be made as much as possible to reduce the incidence of RV failure.
Timing of mechanical support for RV failure remains controversial issue. The insertion of RVAD is mandatory before the end-organ malperfusion progresses, as hospital survivors adequately restored end-organ function after RVAD support in contrast to nonsurvivors. However, our results suggest that no benefits are gained by placing RVAD prophylactically in high-risk patients of RV failure after LVAD insertion. Most recently, Aissaoui et al.8 showed results similar to ours. They reported similar 6-month survival between the early RVAD group (50%) and the delayed RVAD group (44%). On the contrary, some reports recommend simultaneous establishment of RVAD with LVAD insertion. Fitzpatrick et al.6 showed superior 1-year survival in the planned BiVAD group (51%) versus in the unplanned RVAD group (29%). However, their series consisted of patients in the old era from 1995. Their long duration of study period undoubtedly have an effect on outcomes similar to ours. Our unplanned RVAD group in Era 2 showed comparable survival (48%) to their planned BiVAD group. Kormos et al.2 reported most comprehensive data regarding RV failure after contemporary continuous flow device insertion. They included 30 patients who required RVAD support. Within this group, patients who received an RVAD within the first 24 hours had better 6-month survival compared with those who received an RVAD later (77% vs. 39%). However, there were only eight patients in the later group. Further studies including larger population would be necessary to draw a conclusion. Loforte et al.14 also described better outcome for simultaneous temporary RVAD insertion. They reported higher in-hospital mortality associated with multiple end-organ failure in the delayed RVAD group. Importantly, patients requiring mechanical RV support already had a great degree of hemodynamic compromise and end-organ malperfusion; therefore, these patients had increased major adverse events and in-hospital mortality rates. One reason explaining our result as opposed to them is that degree of end-organ dysfunction and hemodynamic indices was similar between two groups, suggesting that RVAD was inserted without significant delay once it was clinically necessary. Therefore, from these results, patient status at the timing of RVAD insertion is more likely to be the key determinants affecting survival.
The data from the INTERMACS demonstrated no difference in survival between durable LVAD/durable RVAD and the durable LVAD/temporary RVAD configurations.7 However, our study showed that approximately half of the patients could be weaned from RVAD support with a median duration of 13 days. Recent studies also support our findings with a 20–70% chance of RV recovery, after which RVAD can be removed.8–11,13,14 Furthermore, temporary RVAD with devices such as CentriMag (Levitronix, LLC., Waltham, MA) is easy to implant and explant.11–14 These findings again make surgeons consider prophylactic RVAD insertion in patients at high risk for RV failure.2,14 However, further studies are required to justify this strategy because it could generate unnecessary device insertion and device-related complications. Currently, we only use temporary RVAD for refractory RV failure after LVAD insertion. The use of isolated continuous flow LVAD after optimization of RV status is our first-line strategy.
There are several limitations in this study. This is a retrospective analysis from a single-center experience. HeartMate II was only used in 40% of patients. Furthermore, various type of device was used for RVAD support. Further studies including larger population will be useful to determine the impact of contemporary continuous flow devices on the outcomes. The number of patients receiving RVAD support was relatively low, therefore limiting statistical power. The timing of RVAD insertion was based on the clinical picture of each patient. No definite criteria were used to decide RVAD insertion.
In conclusion, severe RV failure requiring temporary RVAD support after LVAD implantation is associated with poor outcomes. The timing of RVAD insertion does not affect overall outcomes. Preoperative patient status including hemodynamic indices and end-organ function is the key determinants affecting survival. Appropriate pre-, intra-, and postoperative management for RV failure is mandatory to improve outcomes.
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Keywords:Copyright © 2013 by the American Society for Artificial Internal Organs
right ventricle; heart failure; ventricular assist device