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Ann Thorac Surg 2004;77:859-863
© 2004 The Society of Thoracic Surgeons

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Original article: cardiovascular

Is severe right ventricular failure in left ventricular assist device recipients a risk factor for unsuccessful bridging to transplant and post-transplant mortality

^a Department of Surgery, Division of Cardiothoracic Surgery, College of Physicians and Surgeons, Columbia University, New York, New York, USA

Accepted for publication September 10, 2003.

^* Address reprint requests to Dr Morgan, Columbia University, College of Physicians and Surgeons, 177 Fort Washington Ave, Milstein Hospital 7GN-435, New York, NY 10032, USA.
e-mail: jm2240{at}columbia.edu

	Abstract

Top Abstract Introduction Patients and methods Results Comment Acknowledgments References

 
BACKGROUND: Bridging to transplant with a left ventricular assist device (LVAD) can be limited by severe right ventricular failure (RVF). The focus of this study was to ascertain whether early implantation (< 24 hours) of a right ventricular assist device (RVAD) in patients with severe RVF improved survival and whether severe RVF adversely affected post-transplant survival.

METHODS: We conducted a 10-year review of our bridge to transplant experience using the Heartmate device (Thoratec, Pleasanton, CA, USA), studying patients who required an Abiomed RVAD (Abiomed, Danvers, MA, USA).

RESULTS: There were 243 patients who underwent LVAD implantation, of which 17 (7.0%) required an RVAD. Ten patients underwent early RVAD insertion (< 24 hours) while 7 underwent delayed insertion (> 24 hours). Bridging to transplant was successful in 11 (64.7%) RVAD patients versus 163 (72.1%) non-RVAD patients (p = 0.046). Of the 10 patients who underwent early RVAD insertion, 7 (70.0%) were successfully bridged. Of the 7 patients who underwent delayed RVAD insertion, 4 (57.1%) were successfully bridged (p < 0.001). There was no significant difference in post-transplant 1, 5, and 10-year survival between RVAD and non-RVAD patients (71.4%, 71.4%, and 71.4% for RVAD patients, vs 90.5%, 80.4%, and 78.5%, respectively, for non-RVAD patients; p = 0.366). Pretransplant RVAD support was not a risk factor for post-transplant mortality (p = 0.864).

CONCLUSIONS: Severe RVF adversely impacted bridging to transplant, although survival was improved with early RVAD insertion. The trend toward worse post-transplant survival in the RVAD cohort raises the possibility that if additional patients were evaluated, a difference in survival might be observed, suggesting the need for a multicenter analysis.

	Introduction

Top Abstract Introduction Patients and methods Results Comment Acknowledgments References

 
Left ventricular assist devices (LVAD) have been demonstrated to be effective in bridging patients with end-stage heart failure to transplantation [1, 2]. However, successful bridging can be limited by development of right ventricular failure (RVF) [3, 4]. Severe RVF, requiring insertion of a right ventricular assist device (RVAD), has been demonstrated to adversely affect successful bridging to transplant, increase device-related morbidity, prolong hospital stay, and increase overall hospital cost [5, 6].

Several series have reported preoperative risk factors for development of RVF in patients with implantable LVADs [7–9]. Ochiai and colleagues [7] concluded that preoperative circulatory support, female gender, and nonischemic etiology of heart failure were significant predictors of RVF. Other series have demonstrated low pulmonary artery pressure (PAP) and low RV stroke work index (SWI) to be significant risk factors for RVF [8]. The focus of this study was to ascertain whether development of severe RVF, requiring insertion of an RVAD, adversely affected bridging to transplant and post-transplant survival. Additionally, we sought to examine the issue of timing of RVAD insertion. Does early insertion of the RVAD improve survival?

	Patients and methods

Top Abstract Introduction Patients and methods Results Comment Acknowledgments References

 
Retrospectively, we reviewed our experience at Columbia Presbyterian Medical Center with bridge to transplant patients from February 1993 through February 2003. During this time period, 243 patients with end-stage heart failure underwent implantation of a Heartmate LVAD as a bridge to transplant (Thoratec, Pleasanton, CA, USA). Of these 243 patients, 17 (7.0%) developed severe RVF, requiring insertion of an Abiomed RVAD (Abiomed, Danvers, MA, USA). The definition of severe RVF and the indications for implantation of an RVAD are outlined in Table 1. Primary endpoints that were comparatively evaluated in RVAD and non-RVAD patients included successful bridging to transplant and post-transplant survival at 1, 5, and 10 years. We excluded patients who underwent a planned BIVAD insertion for biventricular failure (n = 41).

	Results

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Clinical demographics
Clinical demographics are outlined in Table 2. Age, gender, and race distribution were similar for RVAD and non-RVAD patients (p = NS). Additionally, etiology of heart failure was similar for both groups (p = NS), with coronary artery disease (CAD) the most frequent etiology (n = 138, 56.8%). A significantly increased number of patients in the RVAD group required preoperative ventilation (p = 0.042). Although more patients in the RVAD group required preoperative intraaortic balloon pumps (IABPs) and had previous cardiac surgery, the difference was not statistically significant (p = NS).

Pre-LVAD hemodynamic data
Pre-LVAD hemodynamic data for RVAD and non-RVAD patients is summarized in Table 3. Right ventricular assist device patients demonstrated significantly higher central venous pressure (CVP; 26.25 ± 20.19 mm Hg vs 20.75 ± 17.05 mm Hg; p = 0.044), lower systolic pulmonary artery pressure (PAP; 22.00 ± 16.45 mm Hg vs 40.36 ± 19.39 mm Hg; p = 0.046), lower diastolic PAP (18.75 ± 12.31 mm Hg vs 27.20 ± 10.54 mm Hg; p = 0.037), lower mean PAP (14.50 ± 10.28 mm Hg vs 29.75 ± 13.85 mm Hg; p = 0.032), lower right ventricular stroke work (RVSW; 10.34 ± 3.45 mm Hg mL vs 15.88 ± 22.93 mm Hg mL; p = 0.045), and lower right ventricular stroke work index (RVSWI; 5.02 ± 2.24 mm Hg mL/m² vs 8.29 ± 11.36; p = 0.034).

Impact of timing of RVAD insertion on post-LVAD survival
Ten patients underwent early RVAD insertion (within 24 hours) while 7 patients underwent delayed RVAD insertion (after 24 hours; 5 at 24 hours, 1 at 48 hours, and 1 at 96 hours after LVAD placement). Of the 10 patients who underwent early RVAD insertion, 7 (70.0%) were successfully bridged to transplant, with 6/7 (85.7%) successfully weaned off RVAD support before transplantation. Of the 7 patients who underwent delayed RVAD insertion, 4 (57.1%) were successfully bridged to transplant (p < 0.001), with 3/4 (75.0%) patients successfully weaned off RVAD support before transplantation.

Other factors affecting successful bridging to transplant
Recently, we reported our experience over the last 12 years using LVADs as a bridge to transplant [11]. Using univariate analysis, significant risk factors adversely affecting survival included female gender (p = 0.001), etiology of heart failure (coronary artery disease [CAD], p = 0.044; ischemic cardiomyopathy [ICM], p = 0.003; other, p = 0.048), duration of LVAD support (p < 0.001), and LVAD score (p < 0.001). Additionally, there was a trend toward significance for advanced age (p = 0.080) and pocket infections (p = 0.095). Using multivariate, stepwise logistic regression analysis, only the LVAD score was a significant predictor of survival to transplant (OR 1.214, 95% CI 1.119 to 1.316, p < 0.001, SE 0.041). Bridging to transplant was successful in 88.6% of low-scoring (scores of 1 to 4) patients, 64.5% of medium-scoring [5–7] patients, and 48.9% of high-scoring [8–10] patients (p < 0.001).

Post-transplant survival
Actuarial survival at 1, 5, and 10 years post-transplant was 71.4%, 71.4%, and 71.4% for the RVAD group, versus 90.5%, 80.4%, and 78.5% for the non-RVAD group (p = 0.366) (Fig 1). Although actuarial survival was higher for the non-RVAD group at each time point, the differences were not statistically significant (p = NS). There was no significant difference in post-transplant survival between those patients who underwent early insertion of the RVAD (< 24 hours) versus delayed insertion (> 24 hours) (p = NS).

View larger version (21K): [in this window] [in a new window]   Fig 1. Actuarial post-transplant survival for patients supported with RVAD versus those patients without severe right ventricular failure. (RVAD = right ventricular assist device.)

	Comment

Top Abstract Introduction Patients and methods Results Comment Acknowledgments References

 
Ventricular assist devices have contributed immensely to the management of patients with end-stage heart failure [12–14]. Patients bridged to transplant using LVADs have demonstrated improvements in blood pressure, hepatic function, renal function, physical function, and quality of life [12, 14]. This can be accomplished without adversely affecting post-transplant survival [15]. However, two major limiting factors to further success with LVADs have been right ventricular dysfunction and device-related complications, such as thromboembolism, infection, and bleeding. Depending on the preexisting condition of the right ventricle, an LVAD may have a beneficial effect by reducing afterload, or a detrimental effect by increasing preload to an already-compromised RV, due to cardiomyopathy, ischemia, arrhythmias, or pulmonary hypertension. Although the incidence of post-LVAD RV failure has decreased with improved patient selection (such as BIVAD use for biventricular failure), use of nitric oxide, phosphodiesterase inhibitors, and reduction of postoperative bleeding with the use of the serine protease inhibitor aprotonin, it is still a major contributor of post-LVAD morbidity and prolonged length of hospital stay [16, 17].

To maximize the likelihood of a patient with post-LVAD RV failure being successfully bridged to transplantation, we have devised an algorithm for the evaluation of RV dysfunction after implantation of an LVAD (Fig 2). We believe that severe RV dysfunction(failure) should be treated with early implantation of an RVAD. Patients are anticoagulated after RVAD insertion but only after there is evidence that bleeding has ceased. Early RVAD insertion can limit progression to significant, potentially irreversible multisystem organ failure (MSOF). This is not to suggest that trials with more conservative therapies, such as nitric oxide and milrinone, should not be attempted. However, careful observation of the overall clinical picture beginning in the operating room is essential, with strong consideration of early RVAD insertion.

View larger version (19K): [in this window] [in a new window]   Fig 2. Algorithm for assessment of RV failure after insertion of an LVAD. (ICU = intensive care unit; LVAD = left ventricular assist device; NO = nitric oxide; OR = operating room; RV = right ventricle; RVAD = right ventricular assist device.)

Our challenge is to be more selective in implanting LVADs to minimize RVF and the need for RVAD insertion. In patients who clearly require biventricular support, isolated LVAD implantation should be avoided. However, the decision between the need for univentricular versus biventricular support remains controversial and requires further analysis. This is particularly important in patients who are being considered for LVADs as destination therapy. In this patient population, it is prudent to consider predictors of RVF in establishing exclusion criteria for LVAD placement. Patients who would be excluded would include those patients who are high risk for development of right ventricular failure while on left ventricular support.

Limitations of this study include those related to a retrospectively performed analysis. Data were obtained by chart review, which has inherent limitations such as access and accuracy of the data. Additionally, the number of patients in the RVAD group (17 implanted, 11 successfully bridged to transplant) was relatively low, limiting statistical power. Although we demonstrated no statistically significant difference in post-transplant survival between RVAD and non-RVAD patients, a trend toward worse survival in the group of patients that required RVAD support raises the possibility that if a larger cohort of patients with severe RVF requiring insertion of an RVAD was studied by conducting a multi-institutional analysis, a statistically significant difference in survival might be observed. Additionally, patients with clinically significant RV failure (not requiring RVAD) were not evaluated in this study. It is important to note that these patients probably constitute the majority of patients with RV dysfunction after LVAD insertion. Furthermore, late RVAD insertion could not be evaluated in multivariate analysis as a potential independent predictor of adverse outcome due to limitations regarding sample size. Finally, it is possible that the worse survival in the delayed group was due to those patients being sicker, although, anecdotally, this did not seem to be the case.

In conclusion, we believe that RVAD insertion should be performed early after the development of severe RV failure after LVAD implantation, and that RVAD support should be continued for an adequate duration to allow for RV recovery or until transplantation. It is essential that while on RVAD support, opportunities to maximally improve the patient's hemodynamic status and fluid balance, such as the use of continuous venovenous hemofiltration and dialysis, be pursued. It is important to note that while optimal timing of RVAD insertion for severe RV failure after LVAD implantation has yet to be clearly defined, a low threshold for early RVAD insertion may be preferable to subsequent development of multisystem organ failure that could potentially develop with a more conservative approach. Fortunately, the incidence of severe RVF requiring an RVAD after insertion of an LVAD in the current era is relatively low. Therefore, even in a single center large experience, the number of such patients is too low to allow for the traditional complete statistical analysis with substantial power. Nevertheless, we believe that our experience highlights the importance of this major complication after LVAD implantation, especially with the increased use of LVADs as destination therapy. Additionally, with several new heart support devices available, an improved understanding of interventricular interactions, as well as the pathophysiology of RV dysfunction after left heart support, is essential to further success in the treatment of patients with end-stage heart failure.

	Acknowledgments

Top Abstract Introduction Patients and methods Results Comment Acknowledgments References

 
Dr Yoshifumi Naka is Herbert Irving Assistant Professor of Surgery at Columbia University, College of Physicians and Surgeons.

	References

Top Abstract Introduction Patients and methods Results Comment Acknowledgments References

 

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