Renal Function After Implantation of Continuous Versus Pulsatile Flow Left Ventricular Assist Devices

Long-term kidney outcomes in pediatric continuous-flow ventricular assist device patients

BACKGROUND

Continuous-flow ventricular assist devices (CF-VADs) are used increasingly in pediatric end-stage heart failure (ESHF) patients. Alongside common risk factors like oxidant injury from hemolysis, non-pulsatile flow constitutes a unique circulatory stress on kidneys. Post-implantation recovery after acute kidney injury (AKI) is commonly reported, but long-term kidney outcomes or factors implicated in the evolution of chronic kidney disease (CKD) with prolonged CF-VAD support are unknown.

METHODS

We studied ESHF patients supported > 90 days on CF-VAD from 2008 to 2018. The primary outcome was CKD (per Kidney Disease Improving Global Outcomes (KDIGO) criteria). Secondary outcomes included AKI incidence post-implantation and CKD evolution in the 6-12 months of CF-VAD support.

RESULTS

We enrolled 134 patients; 84/134 (63%) were male, median age was 13 [IQR 9.9, 15.9] years, 72/134 (54%) had preexisting CKD at implantation, and 85/134 (63%) had AKI. At 3 months, of the 91/134 (68%) still on a CF-VAD, 34/91 (37%) never had CKD, 13/91 (14%) developed de novo CKD, while CKD persisted or worsened in 49% (44/91). Etiology of heart failure, extracorporeal membrane oxygenation use, duration of CF-VAD, AKI history, and kidney replacement therapy were not associated with different CKD outcomes. Mortality was higher in those with AKI or preexisting CKD.

CONCLUSIONS

In the first multicenter study to focus on kidney outcomes for pediatric long-term CF-VAD patients, preimplantation CKD and peri-implantation AKI were common. Both de novo CKD and worsening CKD can happen on prolonged CF-VAD support. Proactive kidney function monitoring and targeted follow-up are important to optimize outcomes.

The impact of preoperative kidney replacement therapy on kidney outcome and survival in patients with left ventricular assist device

Left ventricular assist device (LVAD) has been highlighted as a new treatment option in the end-stage heart failure (HF). Kidney outcome after LVAD in severe cardiorenal syndrome (CRS) patients requiring kidney replacement therapy (KRT) is unclear. We investigated the impact of preoperative KRT on kidney function and survival in LVAD patients with severe CRS. A total of 50 patients followed up for at least 1 year after LVAD implantation was analyzed. The primary outcomes were estimated glomerular filtration rate and survival rate. Patients were divided into two groups depending on in-hospital KRT before LVAD implantation: the control group (n = 33) and the KRT group (n = 17). Postoperative KRT was performed for 76.5% of patients in the KRT group, and all of them discontinued KRT before discharge. There were no statistically significant differences in the degree of eGFR decline in survivors according to preoperative KRT. Although there were no statistically significant differences in the degree of eGFR decline in survivors regardless of preoperative KRT, old age (β -0.94, p < 0.01), preexisting chronic kidney disease (β -21.89, p < 0.01), and high serum creatinine (β -13.95, p < 0.01) were identified as independent predictors of post-LVAD eGFR decline. Mortality rate was higher, and more patients progressed to end-stage kidney disease in KRT group than control group. However, LVAD still can be considered as the treatment option in end-stage HF patients with severe CRS requiring KRT, especially in those with young age and previous normal kidney function.

Acute Kidney Injury Management Strategies Peri-Cardiovascular Interventions

In many countries, the aging population and the higher incidence of comorbid conditions have resulted in an ever-growing need for cardiac interventions. Acute kidney injury (AKI) is a common complication of these interventions, associated with higher mortalities, chronic or end-stage kidney disease, readmission rates, and hospital and post-discharge costs. The AKI pathophysiology includes contrast-associated AKI, hemodynamic changes, cardiorenal syndrome, and atheroembolism. Preventive measures include limiting contrast media dose, optimizing hemodynamic conditions, and limiting exposure to other nephrotoxins. This review article outlines the current state-of-art knowledge regarding AKI pathophysiology, risk factors, preventive measures, and management strategies in the peri-interventional period.

A Universal Device to Convert a Continuous Flow Assist Device to a Pulsatile Flow Device to Simulate Normal Blood Flow and Pressure Patterns

BACKGROUND

Continuous follow assist devices (CFAD) are the most commonly used mechanical circulatory support devices. Compared to Pulsatile flow assist devices (PFAD), CFADs deliver a non-physiologic type of flow, which might contribute to complications related to lack of pulsatility in these devices. Moreover, lack of pulsatility complicates the clinical management of these patients who often present with good perfusion but with no palpable pulse and none or a negligible pulse pressure on blood pressure measurement.

METHODS AND RESULTS

Presented here is a concept of a universal converter device that can be added inline other CFADs to convert the flow from continuous to pulsatile, simulating a normal flow and pressure pattern. After initial implantation and stabilization with a CFAD, adding this converter might potentially provide the benefits of pulsatile physiologic flow. The device is made of 2 components connected in parallel, working in tandem in user determined cycles. The continuous flow through a specifically positioned openings create a smooth conversion to a pulsatile flow. This device can convert a continuous flow to a physiologic pulsatile flow to achieve a native-like flow pattern and potentially prevent some CFAD complications.

CONCLUSION

This paper presents the concept of pulsatility generation and simulation for other assist devices. Such a device can be a universal add-on or a supplemental option for CFADs.

Long-Term Changes in Estimated Glomerular Filtration Rate in Left Ventricular Assist Device Recipients: A Longitudinal Joint Model Analysis

Background Advanced kidney disease is often a relative contraindication to left ventricular assist device (LVAD) implantation because of concerns for poor outcomes including worsening kidney disease. Data are lacking on long-term changes and sex-based differences in estimated glomerular filtration rate (eGFR), with published data limited by potential bias introduced by the competing risks of death and heart transplantation. Methods and Results We conducted a longitudinal analysis of 288 adults receiving durable continuous-flow LVADs from January 2010 to December 2017 at a single center. A joint model was constructed to evaluate change in eGFR over 2 years, the prespecified primary outcome, adjusted for the competing risks of death and heart transplantation. Median baseline eGFR was 60 mL/min per 1.73 m2 (interquartile range 42-78). At 2 years, 74 patients died and 104 received a heart transplant. In unadjusted analysis, LVAD recipients had a modest initial increase in eGFR of ≈2 mL/min per 1.73 m2 within the first 6 months after implantation, followed by a decrease in eGFR below baseline values at 1 and 2 years. Men experienced an eGFR decline of 5 to 10 mL/min per 1.73 m2 over the first year which then stabilized, while women had an ≈5 mL/min per 1.73 m2 increase in eGFR within the first 6 months followed by decline towards baseline eGFR levels (interaction P=0.005). Conclusions Estimated GFR remains relatively stable in most patients following LVAD implantation. Larger studies are needed to investigate sex-based differences in eGFR and to evaluate eGFR trajectory and mortality in LVAD recipients with lower eGFR.

The trajectory of renal function following mechanical circulatory support and subsequent heart transplantation

Aim

Patients with advanced heart failure (HF) frequently suffer from renal insufficiency. The impact of durable mechanical circulatory support (MCS) and subsequent heart transplantation (HTx) on kidney function is not well described.

Methods and results

We studied patients with advanced HF who received durable MCS as bridge to transplantation (BTT) and underwent subsequent HTx at our centre between 1996 and 2018. Glomerular filtration rate (GFR) was measured by ⁵¹Cr‐EDTA or iohexol clearance during heart failure work‐up; 3–6 months after MCS; and 1 year after HTx. Chronic kidney disease (CKD) was classified according to KDIGO criteria based on estimated GFR. A total of 88 patients (46 ± 15 years, 84% male) were included, 63% with non‐ischaemic heart disease. The median duration of MCS‐treatment was 172 (IQR 116–311) days, and 81 subjects were alive 1 year after HTx. Measured GFR increased from 54 ± 19 during HF work‐up to 60 ± 16 mL/min/1.73 m² after MCS (P < 0.001) and displayed a slight but nonsignificant decrease to 57 ± 22 mL/min/1.73 m² 1 year after HTx (P = 0.38). The trajectory of measured GFR did not differ between pulsatile and continuous flow (CF) pumps. Among patients 35–49 years and those who were treated in the most recent era (2012–2018), measured GFR increased following MCS implantation and subsequent HTx. Estimated GFR displayed a similar course as did measured GFR.

Conclusions

In patients with advanced heart failure, measured GFR improved after MCS with no difference between pulsatile and CF‐pumps. The total study group showed no further increase in GFR following HTx, but in certain subgroups, including patients aged 35–54 years and those treated during the latest era (2012–2018), renal function appeared to improve after transplant.

Heart, kidney and left ventricular assist device: a complex trio

BACKGROUND

Heart failure (HF) is a complex syndrome affecting the whole body, kidneys included. The left ventricular assist device (LVAD) is a valid option for patients with very severe HF. Focusing on renal function, LVAD implantation could theoretically reverse the detrimental effects of HF syndrome on kidneys. However, implanting an LVAD is a high-risk surgical procedure, and LVAD patients have higher risk of bleeding, device thrombosis, strokes, renal impairment, multi-organ failure and infections. Furthermore, an LVAD has its own particular effects on the renal system.

METHODS

In this review, we provide a comprehensive overview of the complex interaction between LVAD and the kidneys from the pathophysiological and clinical perspectives. An analysis of the different effects of pulsatile-flow and continuous-flow LVAD is provided.

RESULTS

Despite their limitations, creatinine-based estimated glomerular filtration rate (eGFR) formulas help to stratify patients by their post-LVAD placement prognosis. Poor basal renal function, the onset of acute kidney injury or the need for renal replacement therapy after LVAD implantation negatively influences a patient's prognosis. LVAD can also prompt an improvement in renal function, however, with some counterintuitive effects on a patient's prognosis.

CONCLUSION

It is still hard to say whether different trends in eGFR depend on different renal conditions before LVAD placement, on a patient's better overall status or on a particular patient management strategy before and/or after the device's implantation. Steps should be taken to solve this question because finding the best candidates for LVAD implantation is of paramount importance to ensure the best outcomes.

Change in Renal Function and Its Impact on Survival in Chronic Kidney Disease Patients Bridged to Heart Transplantation With a Left Ventricular Assist Device

The study investigates the incidence of change in renal function and its impact on survival in renal dysfunction patients who were bridged to heart transplantation with a left ventricular assist device (BTT-LVAD). BTT-LVAD patients with greater than or equal to moderately reduced renal function (estimated glomerular filtration rate [eGFR] ≤ 60 ml/min/1.73 m2) at the time of listing between 2008 and 2018 were identified from a prospectively maintained database of the United Network for Organ Sharing. Patients with a baseline eGFR less than or equal to 15 ml/min/1.73 m2 or on dialysis were excluded. Patients were divided into three groups based on percent change ([Pretransplant eGFR - listing eGFR/listing glomerular filtration rate (GFR)] × 100) in eGFR: Improvement greater than or equal to 10%, no change, decline greater than or equal to 10%, and their operative outcomes were compared. Posttransplant survival was estimated and compared among the three groups with the Kaplan-Meier survival curves and the log-rank test. Cox proportional hazards modeling was used to identify predictors of posttransplant survival. Out of 14,395 LVAD patients, 1,622 (11%) met the inclusion criteria. At the time of transplant, 900 (55%) had reported an improvement in eGFR greater than or equal to 10%, 436 (27%) had no change, and 286 (18%) experienced a decline greater than or equal to 10%. Postoperatively, the incidence of dialysis was higher in the decline than in the unchanged or improved groups (22% vs. 12% vs. 12%; p = 0.002). After a median follow-up of 5 years, there was no difference in posttransplant survival among the stratified groups (improved eGFR: 24.8%, unchanged eGFR: 23.2%, declined eGFR: 20.3%; p = 0.680). On Cox proportional hazard modeling, independent predictors of worse survival were: [hazard ratio: 95% CI; p] history of diabetes (1.43 [1.13-1.81]; p = 0.002) or tobacco use (1.40 [1.11-1.79]; p = 0.005) and ischemic time greater than 4 hours (1.36 [1.03-1.76]; p = 0.027). More than half of the patients with compromised renal function who undergo BTT-LVAD demonstrate an improvement in renal function at the time of transplant. A 10% change in GFR while listed was not associated with worse posttransplant survival.

Improvement in Kidney Function After Ventricular Assist Device Implantation and Its Influence on Thromboembolism, Hemorrhage, and Mortality

Although heart transplantation remains the gold standard for management of heart failure, ventricular assist devices (VAD) have emerged as viable alternatives. VAD implantation improves kidney function. However, whether the improvement is sustained or associated with improved outcomes is unclear. Herein we assess kidney function improvement, predictors of improvement, and associations with thromboembolism, hemorrhage, and mortality in VAD patients. Kidney function was defined using chronic kidney disease (CKD) stages: stage 1 (glomerular filtration rate [eGFR] ≥ 90 ml/min/1.73 m), stage 2 (eGFR 60-90 ml/min/1.73 m), stage 3a (eGFR 45-59 ml/min/1.73 m), stage 3b (eGFR 30-44 ml/min/1.73 m), stage 4 (eGFR 15-30 ml/min/1.73 m), and stage 5 (eGFR < 15 ml/min/1.73 m). Improvement in kidney function was defined as an improvement in eGFR that resulted in a CKD stage change to one of lesser severity. Kidney function improved post implant, and was maintained over 1 year for all patients, except those with baseline stage 5 CKD. Younger age at implantation (OR 0.93, 95% CI: 0.90-0.96, P < 0.0001) was associated with sustained improvement in kidney function. Poor kidney function was associated increased mortality but not with thromboembolism or hemorrhage. Compared to patients with baseline eGFR > 45 ml/min/1.73 m; patients with eGFR < 45 ml/min/1.73 m had a higher mortality risk (HR 3.32, 95% CI: 1.10-9.98, p = 0.03 for stage 3b; HR 4.07, 95% CI: 1.27-13.1, p = 0.02 for stage 4; and HR 4.01, 95% CI: 1.17-13.7, p = 0.03 for stage 5 CKD). Kidney function was not associated with thromboembolism or hemorrhage, and sustained improvement was not associated with lower risk of death. However, poor kidney function at implantation was associated with an increased risk of mortality.

Incidence and impact of acute kidney injury on patients with implantable left ventricular assist devices: a Meta-analysis

Background: We aimed to evaluate the acute kidney injury (AKI) incidence and its associated risk of mortality in patients with implantable left ventricular assist devices (LVAD).Methods: A systematic literature search in Ovid MEDLINE, EMBASE, and Cochrane Databases was conducted through January 2020 to identify studies that provided data on the AKI incidence and AKI-associated mortality risk in adult patients with implantable LVADs. Pooled effect estimates were examined using random-effects, generic inverse variance method of DerSimonian-Laird.Results: Fifty-six cohort studies with 63,663 LVAD patients were enrolled in this meta-analysis. The pooled incidence of reported AKI was 24.9% (95%CI: 20.1%-30.4%) but rose to 36.9% (95%CI: 31.1%-43.1%) when applying the standard definition of AKI per RIFLE, AKIN, and KDIGO criteria. The pooled incidence of severe AKI requiring renal replacement therapy (RRT) was 12.6% (95%CI: 10.5%-15.0%). AKI incidence did not differ significantly between types of LVAD (p = .35) or indication for LVAD use (p = .62). While meta-regression analysis did not demonstrate a significant association between study year and overall AKI incidence (p = .55), the study year was negatively correlated with the incidence of severe AKI requiring RRT (slope = -0.068, p < .001). The pooled odds ratios (ORs) of mortality at 30 days and one year in AKI patients were 3.66 (95% CI, 2.00-6.70) and 2.22 (95% CI, 1.62-3.04), respectively. The pooled ORs of mortality at 30 days and one year in severe AKI patients requiring RRT were 7.52 (95% CI, 4.58-12.33) and 5.41 (95% CI, 3.63-8.06), respectively.Conclusion: We found that more than one-third of LVAD patients develop AKI based on standard definitions, and 13% develop severe AKI requiring RRT. There has been a potential improvement in the incidence of severe AKI requiring RRT for LVAD patients. AKI in LVAD patients was associated with increased 30-day and 1 year mortality.

Maturation of arteriovenous fistulas in patients with ventricular assist devices

OBJECTIVE

Postoperative renal dysfunction necessitating hemodialysis after implantation of ventricular assist devices presents a challenge with respect to establishment of hemodialysis access. Lack of pulsatile flow has led to concerns that arteriovenous fistulas will not mature. This study aims to evaluate arteriovenous fistula as a method of hemodialysis.

METHODS

Consecutive patients who underwent implantation of a ventricular assist device between 1988 and 2016 with a subsequent need for hemodialysis were identified. Retrospective data were collected for patients requiring hemodialysis through an arteriovenous fistula or arteriovenous graft. Access flow rates and duration of patency are reported.

RESULTS

Sixty-four patients were identified (10 required long-term hemodialysis, 5 via arteriovenous fistula, 1 via arteriovenous graft). All six patients receiving long-term hemodialysis access were on continuous-flow ventricular assist devices. Brachiocephalic arteriovenous fistulas were performed in all arteriovenous fistula patients, and the average preoperative vein diameter was 4.1 ± 0.9 mm. On 30-day follow-up, the average flow rate was 1262 ± 643 mL/min (880-2220). In arteriovenous fistula patients, one died at 30 days, one arteriovenous fistula required ligation for steal syndrome at 5 months, and one was abandoned after 10.7 months for low flow. Of remaining fistulas, one was converted to an arteriovenous graft at 1.7 years for malfunction (with 5.3 month patency), and one remains open at 4.0 years.

CONCLUSION

Arteriovenous fistulas should be considered in selected patients with ventricular assist devices as a means of long-term hemodialysis access to avoid use of catheters. Maturation and usage of primary arteriovenous fistulas is possible despite lack of pulsatile flow.

Acute kidney injury following left ventricular assist device implantation: Contemporary insights and future perspectives

Currently, an increasing number of patients with end-stage heart failure are being treated with left ventricular assist device (LVAD) therapy as bridge-to-transplantation, bridge-to-candidacy, or destination therapy (DT). Potential life-threatening complications may occur, specifically in the early post-operative phase, which positions LVAD implantation as a high-risk surgical procedure. Acute kidney injury (AKI) is a frequently observed complication after LVAD implantation and is associated with high morbidity and mortality. The rapidly growing number of LVAD implantations necessitates better approaches of identifying high-risk patients, optimizing peri-operative management, and preventing severe complications such as AKI. This holds especially true for those patients receiving an LVAD as DT, who are typically older (with higher burden of comorbidities) with impaired renal function and at increased post-operative risk. Herein we outline the definition, diagnosis, frequency, pathophysiology, and risk factors for AKI in patients with an LVAD. We also review possible strategies to prevent and manage AKI in this patient population.

Prognostic relevance of hemodialysis for short-term survival in patients after LVAD implantation

End-stage heart failure (HF) is associated with renal failure (RF). This study aimed to determine the prognostic influence of RF and post-operative hemodialysis on short-term survival following left ventricular assist device (LVAD) implantation. This retrospective study includes 68 patients undergoing LVAD treatment. Kidney function was recorded prior to LVAD implantation, immediately afterwards and after 30 days, noting the need for hemodialysis. Median pre-operative Interagency Registry for Mechanically Assisted Circulatory Support (INTERMACS) classification was 3.47 ± 1.08. 30 days after implantation there was a significant improvement of estimated glomerular filtration rate (eGFR) and reduction of blood urea nitrogen (BUN). Of pre-operative RF parameters, BUN was associated with increased mortality and need for early post-operative hemodialysis. Post-operative hemodialysis was associated with significantly lower short-term survival, while pre-operative hemodialysis did not impact mortality. Post-operative acute kidney injury (AKI) requiring hemodialysis can be regarded as a strong negative prognostic marker for short-term survival. The absence of a clear correlation between most routine RF parameters and survival or the need for early post-operative hemodialysis calls into question the predictive value of pre-operative RF. The negative association of only post-operative hemodialysis on short-term survival emphasises the impact of the occurrence of AKI.

Left Ventricular Assist Devices and the Kidney

Left ventricular assist devices (LVADs) are common and implantation carries risk of AKI. LVADs are used as a bridge to heart transplantation or as destination therapy. Patients with refractory heart failure that develop chronic cardiorenal syndrome and CKD often improve after LVAD placement. Nevertheless, reversibility of CKD is hard to predict. After LVAD placement, significant GFR increases may be followed by a late return to near baseline GFR levels, and in some patients, a decline in GFR. In this review, we discuss changes in GFR after LVAD placement, the incidence of AKI and associated mortality after LVAD placement, the management of AKI requiring RRT, and lastly, we review salient features about cardiorenal syndrome learned from the LVAD experience. In light of the growing number of patients using LVADs as a destination therapy, it is important to understand the effect of these devices on the kidney. Additional research and long-term data are required to better understand the relationship between the LVAD and the kidney.

Initial Results of Clinical Trial with a New Left Ventricular Assist Device (LVAD) Providing Synchronous Pulsatile Flow

Objectives

A multicentric European Clinical Study is ongoing to evaluate safety and efficacy of a new pulsatile implantable LVAD (BestBeat), smaller and lighter than similar devices, capable of providing synchronous and counterpulsating flow with respect to the LV of end-stage heart failure patients. Preliminary clinical results are reported.

Methods

The new BestBeat LVAD was used, consisting of an implantable pulsatile blood pump, electromechanically driven by a ball screw mechanism, and a wearable electronic controller and power sources. The clinical trial was conducted at 5 European centers. Adult patients affected by CHF in NYHA Class IV despite optimized medical treatment were enrolled. The primary study endpoint was survival at 90 days. Further study endpoints were maintenance of adequate LVAD pump flow and a minimum rate of adverse events during support.

Results

As of June 2008, 6 patients received the implant. Cumulative support time was 3.7 years, median support time 176 days. All patients who completed the study survived except for one, who died after 48 days, due to combined infection and cerebrovascular accident. Another two patients died: one from intracranial bleeding 113 days after implant, and one from septic shock after 123 days. Hemodynamic improvement with Cl>2.0 l/min/m2 and recovery of end-organ function expressed by consistent improvement of BUN, creatinine and bilirubin were reached in all patients. No device failure was observed. There was no bleeding requiring re-exploration, no hemolysis and only two device-related infections (both in one patient). Neurologic events were reported, the most serious ones occurring in patients with pre-implant respiratory and kidney failure. Three patients were discharged home. Two patients were successfully transplanted, one after 6 months and one after 13 months on device.

Conclusions

Good performance and efficacy of the device were observed; the endpoints of the study were achieved, and its safety was consistent with expectations. The ongoing study will allow further conclusions to be drawn.

Improved identification of the electrocardio-signal for pulsatile ventricular assist devices

We introduce and investigate a method to identify the feature point of an electrocardiogram (ECG) to provide real-time and accurate trigger signals for pulsatile ventricular assist devices (PVADs). An important part of this method is an improved data processing algorithm, in which a differential calculator and another a low-pass filtering were added to avoid drift in the original signal and systematically delay caused by physical devices. The method was systematically illustrated in this article and a test-setup was built based on the LabVIEW program development environment. Both simulations and experiments were carried out to demonstrate the merits of the method. Simulated results based on four typical pathological ECG signals confirm the robustness and adaptability of this method. Experimental results verified the benefits of this method with regard to increased accuracy that can pick up the interested signal accurately in a degree of larger than 99%. This improved technology proposed in this research will be greatly beneficial to simultaneous triggering in VADs and eventually to the heart failure recovery.

Effects of Left Ventricular Assist Device Support on End-Organ Function in Patients With Heart Failure: Comparison of Pulsatile- and Continuous-Flow Support in a Single-Center Experience

BACKGROUND

Limited data exist about the effects of continuous-flow versus pulsatile-flow left ventricular assist devices (LVADs) on end-organ function. We hypothesized that a pulsatile Polvad MEV (PM) would result in outcomes similar to those of similarly ill patients implanted with a continuous-flow LVAD (Heartware [HW] or Heartmate II [HMII]). We aimed to compare renal, hepatic, and hematologic functions in the 1st 30 days of support.

METHODS

We retrospectively reviewed patients with 24 PM (21 M, 3 F; group P) and 15 HW and 5 HMII (20 M, 0 F); group C LVAD implantations from April 2007 to February 2014. Creatinine, bilirubin, aspartate (AST) and alanine (ALT) transaminases, hematocrit, platelet count, international normalized ratio (INR), and activated partial thromboplastin time (APTT) parameters were analyzed before implantation and during 30 days of support. Demographic parameters were similar.

RESULTS

No significant differences were found between the groups regarding baseline renal, hepatic, or hematologic function. Baseline INR and APTT were significantly higher in group P. Levels of creatinine were similar between groups. They increased from baseline to postoperative day (POD) 1 and then decreased. Bilirubin levels were insignificantly higher in group P. Transaminases were significantly higher in group P (AST in PODs 3-6, ALT in PODs 3-7). INR values were significantly higher at baseline and in POD 0. APTT values were insignificantly higher in group P.

CONCLUSIONS

The use of LVAD improved renal and hepatic function in our series. Patients in group P had more decreased hepatic function and presented slower regeneration.

Debate: creating adequate pulse with a continuous flow ventricular assist device: can it be done and should it be done? Probably not, it may cause more problems than benefits!

PURPOSE OF REVIEW

The feasibility and benefits of creating adequate pulsatility with continuous flow left ventricular assist devices (LVADs) have long been debated. This review discusses recent technical and clinical findings to answer whether such intervention should be implemented in the standard patient management.

RECENT FINDINGS

Only a limited amount of pulsatility can be generated by periodic speed steps, both considerably smaller in flow increase and in pace rate than the natural circulation. Organ systems are not impeded in their normal function and even not in recovery by a continuous flow. Known problems such as gastrointestinal bleeding are not necessarily due to pulsatility per se, or not important for therapeutic progress, such as minor modifications of the arterial walls.

SUMMARY

The speculative benefits of augmented pulsatility with continuous flow LVADs could be overrated and are still incompletely evaluated. Potential risks that might arise from this strategy should be carefully weighed before implementing extensive pulsatility as standard patient management.

Renal dysfunction and chronic mechanical circulatory support: from patient selection to long-term management and prognosis

PURPOSE OF REVIEW

The purpose of this review is to describe the effects of mechanical circulatory support (MCS) on changes in kidney function and their relationship with mortality, with an additional focus on the evaluation and management of both preimplant and post-MCS renal dysfunction.

RECENT FINDINGS

Renal dysfunction is highly prevalent in patients referred for MCS and is associated with significantly increased mortality and postoperative acute kidney injury. Most patients, including those with renal dysfunction, experience marked early improvement in renal function with MCS, likely secondary to correction of the cardiogenic shock, volume overload, and neurohormonal activation characteristic of advanced heart failure. Currently, there are no diagnostic tests to definitively distinguish reversible forms of renal dysfunction likely to improve with MCS from irreversible renal dysfunction. Furthermore, the characteristic improvements in renal function observed in the early months of MCS are often transient, with subsequent recurrence of renal dysfunction with longer durations of support. Venous congestion, right ventricular dysfunction, and reduced pulsatility are potential mechanisms involved in resurgence of renal dysfunction following MCS.

SUMMARY

With the exponential growth of MCS, research endeavors to both improve understanding of the mechanisms behind observed changes in renal function and elucidate the device-related effects on the kidney are imperative.

Arterial pulsatility under phasic left ventricular assist device support

The aim of this study is to understand whether the phasic Continuous Flow Left Ventricular Assist Device (CF-LVAD) support would increase the arterial pulsatility. A Micromed DeBakey CF-LVAD was used to apply phasic support in an ex-vivo experimental platform. CF-LVAD was operated over a cardiac cycle by phase-shifting the pulsatile pump control with respect to the heart cycle, in 0.05 s increments in each experiment. The pump flow rate was selected as the control variable and a reference model was used to operate the CF-LVAD at a pulsatile speed. Arterial pulse pressure was the highest (9 mmHg) when the peak pump flow is applied at the peak systole under varying speed CF-LVAD support over a cardiac cycle while it was the lowest (2 mmHg) when the peak pump flow was applied in the diastolic phase. The mean arterial pressure and mean CF-LVAD output were the same in each experiment while arterial pulse pressure and pulsatility index varied depending on the phase of reference pump flow rate signal. CF-LVAD speed should be synchronized considering the timing of peak systole over a cardiac cycle to increase the arterial pulsatility. Moreover, it is possible to decrease the arterial pulsatility under counter-pulsating CF-LVAD support.

Renal Function Recovery with Total Artificial Heart Support

Heart failure patients requiring total artificial heart (TAH) support often have concomitant renal insufficiency (RI). We sought to quantify renal function recovery in patients supported with TAH at our institution. Renal function data at 30, 90, and 180 days after TAH implantation were analyzed for patients with RI, defined as hemodialysis supported or an estimated glomerular filtration rate (eGFR) less than 60 ml/min/1.73 m. Between January 2008 and December 2013, 20 of the 46 (43.5%) TAH recipients (age 51 ± 9 years, 85% men) had RI, mean preoperative eGFR of 48 ± 7 ml/min/1.73 m. Renal function recovery was noted at each follow-up interval: increment in eGFR (ml/min/1.73 m) at 30, 90, and 180 days was 21 ± 35 (p = 0.1), 16.5 ± 18 (p = 0.05), and 10 ± 9 (p = 0.1), respectively. Six patients (30%) required preoperative dialysis. Of these, four recovered renal function, one remained on dialysis, and one died. Six patients (30%) required new-onset dialysis. Of these, three recovered renal function and three died. Overall, 75% (15 of 20) of patients' renal function improved with TAH support. Total artificial heart support improved renal function in 75% of patients with pre-existing significant RI, including those who required preoperative dialysis.

Enhancement of Arterial Pressure Pulsatility by Controlling Continuous-Flow Left Ventricular Assist Device Flow Rate in Mock Circulatory System

Continuous-flow left ventricular assist devices (CF-LVADs) generally operate at a constant speed, which reduces pulsatility in the arteries and may lead to complications such as functional changes in the vascular system, gastrointestinal bleeding, or both. The purpose of this study is to increase the arterial pulse pressure and pulsatility by controlling the CF-LVAD flow rate. A MicroMed DeBakey pump was used as the CF-LVAD. A model simulating the flow rate through the aortic valve was used as a reference model to drive the pump. A mock circulation containing two synchronized servomotor-operated piston pumps acting as left and right ventricles was used as a circulatory system. Proportional-integral control was used as the control method. First, the CF-LVAD was operated at a constant speed. With pulsatile-speed CF-LVAD assistance, the pump was driven such that the same mean pump output was generated. Continuous and pulsatile-speed CF-LVAD assistance provided the same mean arterial pressure and flow rate, while the index of pulsatility increased significantly for both arterial pressure and pump flow rate signals under pulsatile speed pump support. This study shows the possibility of improving the pulsatility of CF-LVAD support by regulating pump speed over a cardiac cycle without reducing the overall level of support.

Physiologic effects of continuous-flow left ventricular assist devices

BACKGROUND

Within the past 10 years, continuous-flow left ventricular assist devices (LVADs) have replaced pulsatile-flow LVADs as the standard of care for both destination therapy and bridging patients to heart transplantation. Despite the rapid clinical adoption of continuous-flow LVADs, an understanding of the effects of continuous-flow physiology, as opposed to more natural pulsatile-flow physiology, is still evolving.

MATERIALS AND METHODS

A thorough review of the relevant scientific literature regarding the physiological and clinical effects of continuous-flow physiology was performed. These effects were analyzed on an organ system basis and include an evaluation of the cardiovascular, respiratory, hematologic, gastrointestinal, renal, hepatic, neurologic, immunologic, and endocrine systems.

RESULTS

Continuous-flow physiology is, generally speaking, well tolerated over the long term. However, several changes are manifest at the organ system level. Although many of these changes are without appreciable clinical significance, other changes, such as an increased rate of gastrointestinal bleeding, appear to be associated with continuous-flow physiology.

CONCLUSIONS

Continuous-flow LVADs confer a significant advantage over their pulsatile-flow counterparts with regard to size and durability. From a physiological standpoint, continuous-flow physiology has limited clinical effects at the organ system level. Although improved over previous generations, challenges with this technology remain. Approaching these problems with a combination of clinical and engineering solutions may be needed to achieve continued progression in the field of durable mechanical circulatory support.

Impact of ventricular assist device placement on longitudinal renal function in children with end-stage heart failure

BACKGROUND

Although ventricular assist devices (VADs) restore hemodynamics in those with heart failure, reversibility of end-organ dysfunction with VAD support is not well characterized. Renal function often improves in adults after VAD placement, but this has not been comprehensively explored in children.

METHODS

Sixty-three children on VAD support were studied. Acute kidney injury (AKI) was defined by Kidney Disease: Improving Global Outcomes criteria. Estimated glomerular filtration rate (eGFR) was determined by the Schwartz method. Generalized linear mixed-effects models compared the pre-VAD and post-VAD eGFR for the cohort and sub-groups with and without pre-VAD renal dysfunction (pre-VAD eGFR < 90 ml/min/1.73 m(2)).

RESULTS

The pre-VAD eGFR across the cohort was 84.0 ml/min/1.73 m(2) (interquartile range [IQR] 62.3-122.7), and 55.6% (34 of 63) had pre-VAD renal dysfunction. AKI affected 60.3% (38 of 63), with similar rates in those with and without pre-existing renal dysfunction. Within the cohort, the nadir eGFR occurred 1 day post-operatively (62.9 ml/min/1.73 m(2); IQR, 51.2-88.9 ml/min/1.73 m(2); p < 0.001). By Day 5, however, the eGFR exceeded the baseline (99.0 ml/min/1.73 m(2); IQR, 59.3-146.7 ml/min/1.73 m(2); p = 0.03) and remained significantly higher through the first post-operative week. After adjusting for age, gender, and AKI, the eGFR continued to increase throughout the entire 180-day study period (β = 0.0025; 95% confidence interval, 0.0015-0.0036; p < 0.001). Patients with pre-VAD renal dysfunction experienced the greatest improvement in the eGFR (β = 0.0051 vs β = 0.0013, p < 0.001).

CONCLUSIONS

Renal dysfunction is prevalent in children with heart failure undergoing VAD placement. Although peri-operative AKI is common, renal function improves substantially in the first post-operative week and for months thereafter. This is particularly pronounced in those with pre-VAD renal impairment, suggesting that VADs may facilitate recovery and maintenance of kidney function in children with advanced heart failure.

Left ventricular assist devices: a kidney's perspective

The left ventricular assist device (LVAD) has become an established treatment option for patients with refractory heart failure. Many of these patients experience chronic kidney disease (CKD) due to chronic cardiorenal syndrome type II, which is often alleviated quickly following LVAD implantation. Nevertheless, reversibility of CKD remains difficult to predict. Interestingly, initial recovery of GFR appears to be transient, being followed by gradual but significant late decline. Nevertheless, GFR often remains elevated compared to preimplant status. Larger GFR increases are followed by a proportionally larger late decline. Several explanations for this gradual decline in renal function after LVAD therapy have been proposed, yet a definitive answer remains elusive. Mortality predictors of LVAD implantation are the occurrence of either postimplantation acute kidney injury (AKI) or preimplant CKD. However, patient outcomes continue to improve as LVAD therapy becomes more widespread, and adverse events including AKI appear to decline. In light of a growing destination therapy population, it is important to understand the cumulative effects of long-term LVAD support on kidney function. Additional research and passage of time are required to further unravel the intricate relationships between the LVAD and the kidney.

Cardiac Assist Devices and Hemodialysis Catheter Procedures - What Do the Nephrologists Need to Know?

The use of ventricular assist devices (VAD) and total artificial heart (TAH) is increasing rapidly, and a large proportion of these device recipients already have or will develop severe renal dysfunction at the time of device implantation. As a consequence, nephrologists are becoming more and more involved in the care of this challenging population. As nephrologists take upon themselves many aspects of dialysis vascular access care, they need to be familiar with the special circumstances of performing hemodialysis catheter procedures in these patients. This review describes the important characteristics of these devices that have serious implications for the technique of placing or replacing dialysis catheters. These implications apply for both tunneled and nontunneled dialysis catheters and so concern all nephrologists, not only the interventionalists. We describe the important anatomical factors, anticoagulation management, device management, vascular access management and technical considerations of placing or replacing tunneled and nontunneled hemodialysis catheters from the perspective of a nephrologist establishing and maintaining lifesaving dialysis vascular access. Without a good understanding of these devices, serious consequences such as VAD rotor damage or blockage, or artificial heart valve blockage or damage can occur. These artificial devices are lifesaving, and any such complication is unacceptable. This review describes steps to minimize the risks.

Kidney dysfunction and left ventricular assist device support: a comprehensive perioperative review

Left ventricular assist devices (LVADs) are used increasingly as a bridge to transplantation or as destination therapy in end-stage heart failure patients who do not respond to optimal medical therapy. Many of these patients have end-organ dysfunction, including advanced kidney dysfunction, before and after LVAD implantation. Kidney dysfunction is a marker of adverse outcomes, such as increased morbidity and mortality. This review discusses kidney dysfunction and associated management strategies during the dynamic perioperative time period of LVAD implantation. Furthermore, we suggest potential future research directions to better understand the complex relationship between renal pathophysiology and mechanical circulatory support.

Aortic Valve Function Under Support of a Left Ventricular Assist Device: Continuous vs. Dynamic Speed Support

Continuous flow left ventricular devices (CF-LVADs) support the failing heart at a constant speed and alters the loads on the aortic valve. This may cause insufficiency in the aortic valve under long-term CF-LVAD support. The aim of this study is to assess the aortic valve function under varying speed CF-LVAD support. A Medtronic freestyle valve and a Micromed DeBakey CF-LVAD were tested in a mock circulatory system. First, the CF-LVAD was operated at constant speeds between 7500 and 11,500 rpm with 1000 rpm intervals. The mean pump outputs obtained from these tests were applied in varying speed CF-LVAD support mode using a reference model for the pump flow. The peak of the instantaneous pump flow was applied at peak systole and mid-diastole, respectively. Ejection durations and in the aortic valve were the longest when the peak pump flow was applied at mid-diastole among the CF-LVAD operating modes. Furthermore, mean aortic valve area over a cardiac cycle was highest when the peak pump flow was applied at mid-diastole. The results show that changing phase of the reference flow rate signal may reduce the effects of the CF-LVADs on altered aortic valve closing behavior, without compromising the overall pump support level.

Implantable left ventricular assist devices and the kidney

The use of left ventricular assist devices (LVADs) in treating patients with advanced heart failure restores cardiac output resulting in improved perfusion to multiple organ systems with important clinical benefits. Renal pathophysiology during LVAD support remains an evolving, poorly understood, and potentially dynamic problem. Changes in renal function after LVAD placement have been investigated in multiple studies with contradictory results. Renal dysfunction is common prior to LVAD placement, which complicates postoperative clinical outcomes. The purpose of this review is to assess the latest information regarding the effects of LVADs on renal function with regard to hemodynamics, physiology, pathology and clinical issues prior to and after placement of the devices. The review should then aid in identifying patients best suited to benefit from this technology and to refine the therapy to reduce associated risks.

Improving Arterial Pulsatility by Feedback Control of a Continuous Flow Left Ventricular Assist Device via in Silico Modeling

Purpose

Continuous flow left ventricular assist devices (CF-LVADs) generally operate at a constant speed, which causes a decrease in pulse pressure and pulsatility in the arteries and allegedly may lead to late complications such as aortic insufficiency and gastrointestinal bleeding. The purpose of this study is to increase the arterial pulse pressure and pulsatility while obtaining more physiological hemodynamic signals, by controlling the CF-LVAD flow rate.

Methods

A lumped parameter model was used to simulate the cardiovascular system including the heart chambers, heart valves, systemic and pulmonary arteries and veins. A baroreflex model was used to regulate the heart rate and a model of the Micromed DeBakey CF-LVAD (Micromed Technology, Houston, TX, USA) to simulate the pump dynamics at different operating speeds. A model simulating the flow rate through the aortic valve served as reference model. CF-LVAD operating speed was regulated by applying proportional-integral (PI) control to the pump flow rate. For comparison, the CF-LVAD was also operated at a constant speed, equaling the mean CF-LVAD speed as applied in pulsatile mode.

Results

In different operating modes, at the same mean operating speeds, mean pump output, mean arterial pressure, end-systolic and end-diastolic volume and heart rate were the same over the cardiac cycle. However, the arterial pulse pressure and index of pulsatility increased by 50% in the pulsatile CF-LVAD support mode with respect to constant speed pump support.

Conclusions

This study shows the possibility of obtaining more physiological pulsatile hemodynamics in the arteries by applying output-driven varying speed control to a CF-LVAD.

Evolution of renal function after partial and full mechanical support for chronic heart failure

PURPOSE

Recently a minimal invasive, partial support continuous flow left ventricular assist device (LVAD) became available for treatment of chronic heart failure. The aim of this study was to analyze whether partial support is capable of improving kidney function in end-stage heart failure.

METHODS

We performed a single-center retrospective analysis of patients how received a full (n = 43) or partial support LVAD (n = 18) between 2007 and 2013. Patients on dialysis or in INTERMACS class I were excluded. Renal function was assessed until 3 months after the implantation. A calculated GFR less than 60 m/min was considered to be renal failure.

RESULTS

Creatinine level after LVAD implant decreased 23% in patients on full support (1.3 ± 0.4 mg/dl vs. 1.0 ± 0.3 mg/dl; p<0.001) and 24% in patients on partial support (1.6 ± 0.6 mg/dl vs. 1.2 ± 0.4 mg/dl; p = 0.17) within 3 months. In each group patients with a preoperative GFR less than 60 ml/min were selected. In this subgroup there was a 35% decrease in creatinine levels for patients on full support (1.7 ± 0.4 mg/dl vs. 1.1 ± 0.5 mg/dl; p<0.01) and a 32% decrease in patients on partial support (2 ± 0.4 mg/dl vs. 1.4 ± 0.3 mg/dl; p<0.05) at 3 months.

CONCLUSIONS

We observed a significant improvement in renal function in patients supported by full or partial support devices, even if the preoperative renal function was severly impaired. The use of diuretics decreased in both groups. In chronic heart failure patients with impaired renal function, partial support is sufficient to improve renal function significantly.

Hepatic and renal function with successful long-term support on a continuous flow left ventricular assist device

INTRODUCTION

Data regarding the long-term clinical effects of a continuous flow left ventricular assist device (CF-LVAD) on hepato-renal function is limited. Hence our aim was to assess changes in hepato-renal function over a one-year period in patients supported on a CF-LVAD.

METHODS

During the study period 126 patients underwent CF-LVAD implant. Changes in hepato-renal laboratory parameters were studied in 61/126 patients successfully supported on a CF-LVAD for period of one year. A separate cohort of a high-risk group (HCrB) of patients (56/126) with a serum creat>1.9 mg/dL (168 μmol/L) (75th percentile) or a serum bil>1.5 mg/dL (25.65 μmol/L) (75th percentile) was created. Changes in serum creatinine and bilirubin were analysed at regular intervals for this group along with the need for renal replacement therapy.

RESULTS

Baseline creatinine and blood urea nitrogen (BUN) for the entire cohort was 1.4[1.2,1.9 mg/dL] [123.7(106,168) μmol/L) and 27[20,39.5 mg/dL] [9.6(7.1,14.1) mmol/L] respectively. After an initial reduction at the end of one month [1(0.8,1.2) mg/dL; 88(70,105) μmol/L] (p<0.0001), a gradual increase was noted over the study period to reach (1.25[1.1,1.5] mg/dL; 106(97.2,132.6) μmol/L] (p=0.0003). The serum bilirubin normalised from a [1(0.7,1.55) mg/dL] [17(18.8,25.7) μmol/L) to 0.9(0.6,1.2)mg/dL [15.4(10.2,20.5) μmol/L] (p=0.0005) and continued to decline over one year. Improvement in the synthetic function of the liver was demonstrated by a rise in the serum albumin levels to reach 4.3[4.1,4.5] [43(41,45) gm/L] at the end of one year (p<0.0001). The baseline serum creatinine and bilirubin for the high-risk cohort (HCrB) was 1.9(1.3,2.4) mg/dL [168(115,212) μmol/L] and 1.7(1.00,2.4) mg/dL [29(17.1,68.4) μmol/L] respectively. The high-risk cohort (HCrB) demonstrated a trend towards higher 30-day mortality (p=0.06). While the need for temporary renal replacement therapy was higher in this cohort (16% vs. 4%; p=0.03), only 3% need it permanently. A significant reduction in creatinine was apparent at the end of one month [1.1(0.8,1.4) mg/dL; 97(70.7,123.7) μmol/L] (p<0.0001) and then remained stable at [1.3(1.1,1.5) mg/dL; 115(97,132.6) μmol/L]. Bilirubin demonstrated a 30% decline over one month and then remained low at [0.7(0.5,0.8) mg/dL; 62(44,70) μmol/L] p=0.0005 compared to the pre-operative baseline.

CONCLUSION

Hepato-renal function demonstrates early improvement and then remains stable in the majority of patients on continuous flow left ventricular assist device support for one year. High-risk patients demonstrate a higher 30-day mortality and temporary need for renal replacement therapy. Yet even in this cohort, improvement is present over a period of one year on the device, with a minimal need for permanent haemodialysis.

Acute kidney injury and mortality following ventricular assist device implantation

BACKGROUND

Ventricular assist devices (VADs) are increasingly common, and their surgical implantation predisposes patients to an increased risk of acute kidney injury (AKI). We sought to evaluate the incidence, risk factors and short- and long-term all-cause mortality of patients with AKI following VAD implantation.

METHODS

We identified all patients who underwent VAD implantation at the University of Chicago between January 1, 2008, and January 31, 2012. We evaluated the incidence of AKI, defined as a ≥50% increase in serum creatinine over the first 7 postoperative days (RIFLE Risk-Creatinine). A logistic regression model was used to identify risk factors for the development of AKI, and a Cox proportional hazards model was used to examine factors associated with 30-day and 365-day all-cause mortality.

RESULTS

A total of 157 eligible patients had VAD implantations with 44 (28%) developing postimplantation AKI. In a multivariate analysis, only diabetes mellitus [odds ratio = 2.25 (1.03-4.94), p = 0.04] was identified as a significant predictor of postoperative AKI. Using a multivariable model censored for heart transplantation, only AKI [hazard ratio, HR = 3.01 (1.15-7.92), p = 0.03] and cardiopulmonary bypass time [HR = 1.01 (1.001-1.02), p = 0.02] were independent predictors of 30-day mortality. Preoperative body mass index [HR = 0.95 (0.90-0.99), p = 0.03], preoperative diabetes mellitus [HR = 1.89 (1.07-3.35), p = 0.03] and postimplantation AKI [HR = 1.85 (1.06-3.21), p = 0.03] independently predicted 365-day mortality.

CONCLUSION

AKI is common following VAD implantation and is an independent predictor of 30-day and 1-year all-cause mortality.

Ventricular Assist Devices - Evolution of Surgical Heart Failure Treatment

End-stage heart failure represents a substantial worldwide problem for the healthcare system. Despite significant improvements (medical heart failure treatment, implantable cardioverters, cardiac resyschronisation devices), long-term survival and quality of life of these patients remains poor. Heart transplantation has been an effective therapy for terminal heart failure, but it remains limited by an increasing shortage of available donor organs along with strict criteria defining acceptable recipients. For the last 50 years, mechanical alternatives to support the circulation have been investigated; however, during the early years device development has been marked in general by slow progress. However, in the past two decades, the technology has evolved dramatically. The purpose of this review is to give a short summary on the evolution of ventricular assist device (VAD) therapy and to give perspectives for future treatment of heart failure.

Prevalence and prognostic importance of changes in renal function after mechanical circulatory support

BACKGROUND

The long-term durability and prognostic significance of improvement in renal function after mechanical circulatory support (MCS) has yet to be characterized in a large multicenter population. The primary goals of this analysis were to describe serial post-MCS changes in estimated glomerular filtration rate (eGFR) and determine their association with all-cause mortality.

METHODS AND RESULTS

Adult patients enrolled in the Interagency Registry for Mechanically Assisted Circulatory Support (INTERMACS) with serial creatinine levels available (n=3363) were studied. Early post-MCS, eGFR improved substantially (median improvement, 48.9%; P<0.001) with 22.3% of the population improving their eGFR by ≥100% within the first few weeks. However, in the majority of patients, this improvement was transient, and by 1 year, eGFR was only 6.7% above the pre-MCS value (P<0.001). This pattern of early improvement followed by deterioration in eGFR was observed with both pulsatile and continuous-flow devices. Interestingly, poor survival was associated with both marked improvement (adjusted hazard ratio [HR], 1.64; 95% confidence interval [CI], 1.19-2.26; P=0.002) and worsening in eGFR (adjusted HR, 1.63; 95% CI, 1.15-2.13; P=0.004).

CONCLUSIONS

Post-MCS, early improvement in renal function is common but seems to be largely transient and not necessarily indicative of an improved prognosis. This pattern was observed with both pulsatile and continuous-flow devices. Additional research is necessary to better understand the mechanistic basis for these complex post-MCS changes in renal function and their associated survival disadvantage.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT00119834.

Cardiorenal syndrome: pathophysiology and potential targets for clinical management

Combined dysfunction of the heart and the kidneys, which can be associated with haemodynamic impairment, is classically referred to as cardiorenal syndrome (CRS). Cardiac pump failure with resulting volume retention by the kidneys, once thought to be the major pathophysiologic mechanism of CRS, is now considered to be only a part of a much more complicated phenomenon. Multiple body systems may contribute to the development of this pathologic constellation in an interconnected network of events. These events include heart failure (systolic or diastolic), atherosclerosis and endothelial cell dysfunction, uraemia and kidney failure, neurohormonal dysregulation, anaemia and iron disorders, mineral metabolic derangements including fibroblast growth factor 23, phosphorus and vitamin D disorders, and inflammatory pathways that may lead to malnutrition-inflammation-cachexia complex and protein-energy wasting. Hence, a pathophysiologically and clinically relevant classification of CRS based on the above components would be prudent. With the existing medical knowledge, it is almost impossible to identify where the process has started in any given patient. Rather, the events involved are closely interrelated, so that once the process starts at a particular point, other pathways of the network are potentially activated. Current therapies for CRS as well as ongoing studies are mostly focused on haemodynamic adjustments. The timely targeting of different components of this complex network, which may eventually lead to haemodynamic and vascular compromise and cause refractoriness to conventional treatments, seems necessary. Future studies should focus on interventions targeting these components.

Significance of postoperative acute renal failure after continuous-flow left ventricular assist device implantation

BACKGROUND

Deteriorating renal function is common in patients with advanced heart failure and is associated with poor outcomes. The relationship between renal function and left ventricular assist device (LVAD) implantation is complex and has been explored in multiple studies with contradictory results. The aim of our study is to examine the significance of postoperative renal failure after implantation of a continuous-flow LVAD and its relationship to outcomes.

METHODS

From March 2006 to July 2011, 100 patients underwent implantation of a HeartMate II (Thoratec Corp, Pleasanton, CA) or HeartWare (Heart International, Inc, Framingham, MA) LVAD at our institution. Patients were stratified based on postoperative development of acute renal failure (ARF). Variables were compared using 2-sided t tests, χ(2) tests, Cox proportional hazards models, and log-rank tests to determine whether there was a difference between the 2 groups and whether postoperative renal failure was a significant independent predictor of outcome.

RESULTS

We identified 28 patients (28%) with postoperative ARF and 72 patients (72%) without postoperative ARF. The 2 groups were similar with regard to demographics and comorbidities. The patients with ARF were more likely to be intubated preoperatively (14.3% versus 1.4%; p = 0.021) and had higher preoperative central venous pressure (CVP) (14.3 mm Hg versus 10.7 mm Hg; p = 0.015). Postoperatively patients with ARF had a longer hospital stay (32.4 versus 18.7; p = 0.05), were more likely to experience right ventricular (RV) failure (25% versus 5.6%; p = 0.01) and ventilator-dependent respiratory failure (VDRF) (28.6% versus 6.9%; p = 0.007). There was a significant difference when comparing the ARF and non-ARF groups for 30-day (17.9% versus 0%; p < 0.001), 180-day (28.6% versus 2.8%; p < 0.001), and 360-day mortality (28.6% versus 6.9%; p = 0.012).

CONCLUSIONS

Patients in whom ARF developed after LVAD implantation had a higher rate of VDRF and RV failure and a longer length of stay (LOS). Postoperative ARF was associated with higher mortality at the 30-day, 180-day, and 360-day intervals. ARF after LVAD may be an early marker of poor outcome, particularly RV failure, and may be an opportunity for early intervention and rescue.

Changes in renal function after implantation of continuous-flow left ventricular assist devices

OBJECTIVES

The aim of this study was to determine renal outcomes after left ventricular assist device (LVAD) implantation.

BACKGROUND

Renal dysfunction before LVAD placement is frequent, and it is unclear whether it is due to primary renal disease or to poor perfusion.

METHODS

A retrospective single-center analysis was conducted in 83 consecutive patients implanted with HeartMate II continuous-flow LVADs (Thoratec Corp., Pleasanton, California). Calculated glomerular filtration rate (GFR) was assessed on admission and 1, 3, and 6 months after implantation. To define predictors for improvement in GFR, clinical variables were examined in patients with decreased renal function (GFR <60 ml/min/1.73 m(2)) before LVAD, surviving and dialysis-free at 1 month (n = 44).

RESULTS

GFR significantly increased from admission (53.2 ± 21.4 ml/min/1.73 m(2)) to 1 month after LVAD implantation (87.4 ± 27.9 ml/min/1.73 m(2)) (p < 0.0001). Subsequently, at 3 and 6 months, GFR remained significantly (p < 0.0001) above pre-LVAD values. Of the 51 patients with GFRs <60 ml/min/1.73 m(2) before LVAD surviving at 1 month, 34 (67%) improved to GFRs >60 ml/min/1.73 m(2). Univariate pre-operative predictors for improvement in renal function at 1 month included younger age (p = 0.049), GFR improvement with optimal medical therapy (p < 0.001), intra-aortic balloon pump use (p = 0.004), kidney length above 10 cm (p = 0.023), no treatment with angiotensin-converting enzyme inhibitors or angiotensin receptor blockers (p = 0.029), higher bilirubin (p = 0.002), higher Lietz-Miller score (p = 0.019), and atrial fibrillation (p = 0.007). Multivariate analysis indicated pre-operative improved GFR (slope = 0.5 U per unit improved; 95% confidence interval: 0.2 to 0.8; p = 0.003), atrial fibrillation (slope = 27; 95% confidence interval: 8 to 46; p = 0.006), and intra-aortic balloon pump use (slope = 14; 95% confidence interval: 2 to 26; p = 0.02) as independent predictors.

CONCLUSIONS

In most patients with end-stage heart failure considered for LVAD implantation, renal dysfunction is reversible and likely related to poor renal perfusion.