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

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.

Physiology of Continuous-Flow Left Ventricular Assist Device Therapy

The expanding use of continuous-flow left ventricular assist devices (CF-LVADs) for end-stage heart failure warrants familiarity with the physiologic interaction of the device with the native circulation. Contemporary devices utilize predominantly centrifugal flow and, to a lesser extent, axial flow rotors that vary with respect to their intrinsic flow characteristics. Flow can be manipulated with adjustments to preload and afterload as in the native heart, and ascertainment of the predicted effects is provided by differential pressure-flow (H-Q) curves or loops. Valvular heart disease, especially aortic regurgitation, may significantly affect adequacy of mechanical support. In contrast, atrioventricular and ventriculoventricular timing is of less certain significance. Although beneficial effects of device therapy are typically seen due to enhanced distal perfusion, unloading of the left ventricle and atrium, and amelioration of secondary pulmonary hypertension, negative effects of CF-LVAD therapy on right ventricular filling and function, through right-sided loading and septal interaction, can make optimization challenging. Additionally, a lack of pulsatile energy provided by CF-LVAD therapy has physiologic consequences for end-organ function and may be responsible for a series of adverse effects. Rheological effects of intravascular pumps, especially shear stress exposure, result in platelet activation and hemolysis, which may result in both thrombotic and hemorrhagic consequences. Development of novel solutions for untoward device-circulatory interactions will facilitate hemodynamic support while mitigating adverse events. © 2021 American Physiological Society. Compr Physiol 12:1-37, 2021.

Hemodynamic Predictors of Renal Function After Pediatric Left Ventricular Assist Device Implantation

Although renal function often improves after pediatric left ventricular assist device (LVAD) implantation, recovery is inconsistent. We aimed to identify hemodynamic parameters associated with improved renal function after pediatric LVAD placement. A single-center retrospective cohort study was conducted in patients less than 21 years who underwent LVAD placement between June 2004 and December 2015. The relationship between hemodynamic parameters and estimated glomerular filtration rate (eGFR) was assessed using univariate and multivariate modeling. Among 54 patients, higher preoperative central venous pressure (CVP) was associated with eGFR improvement after implantation (p = 0.012). However, 48 hours postimplantation, an increase in CVP from baseline was associated with eGFR decline over time (p = 0.01). In subgroup analysis, these associations were significant only for those with normal pre-ventricular assist device renal function (p = 0.026). In patients with preexisting renal dysfunction, higher absolute CVP values 48 and 72 hours after implantation predicted better renal outcome (p = 0.005). Our results illustrate a complex relationship between ventricular function, volume status, and renal function. Additionally, they highlight the challenge of using CVP to guide management of renal dysfunction in pediatric heart failure. Better methods for evaluating right heart function and volume status are needed to improve our understanding of how hemodynamics impact renal function in this population.

Exercise physiology in left ventricular assist device patients: insights from hemodynamic simulations

Left ventricular assist devices (LVADs) assure longer survival to patients, but exercise capacity is limited compared to normal values. Overall, LVAD patients show high wedge pressure and low cardiac output during maximal exercise, a phenomenon hinting at the need for increased LVAD support. Clinical studies investigating the hemodynamic benefits of an LVAD speed increase during exercise, ended in inhomogeneous and sometimes contradictory results. The native ventricle-LVAD interaction changes between rest and exercise, and this evolution is complex, multifactorial and patient-specific. The aim of this paper is to provide a comprehensive overview on the patient-LVAD interaction during exercise and to delineate possible therapeutic strategies for the future. A computational cardiorespiratory model was used to simulate the hemodynamics of peak bicycle exercise in LVAD patients. The simulator included the main cardiovascular and respiratory impairments commonly observed in LVAD patients, so as to represent an average hemodynamic response to exercise. In addition, other exercise responses were simulated, by tuning the chronotropic, inotropic and vascular functions, and implementing aortic regurgitation and stenosis in the simulator. These profiles were tested under different LVAD speeds and LVAD pressure-flow characteristics. Simulations output showed consistency with clinical data from the literature. The simulator allowed the working condition of the assisted ventricle at exercise to be investigated, clarifying the reasons behind the high wedge pressure and poor cardiac output observed in the clinics. Patients with poorer inotropic, chronotropic and vascular functions, are likely to benefit more from an LVAD speed increase during exercise. Similarly, for these patients, a flatter LVAD pressure-flow characteristic can assure better hemodynamic support under physical exertion. Overall, the study evidenced the need for a patient-specific approach on supporting exercise hemodynamics. In this frame, a complex simulator can constitute a valuable tool to define and test personalized speed control algorithms and strategies.

Ambulatory advanced heart failure patients: timing of mechanical circulatory support - delaying the inevitable?

PURPOSE OF REVIEW

Current indications for continuous-flow left ventricular assist device (cfLVAD) implantation is for patients in cardiogenic shock or inotrope-dependent advanced heart failure. Risk stratification of noninotrope dependent ambulatory advanced heart failure patients is a subject of registries designed to help shared-decision making by clinicians and patients regarding the optimal timing of mechanical circulatory support (MCS).

RECENT FINDINGS

The Registry Evaluation of Vital Information for VADs in Ambulatory Life enrolled ambulatory noninotrope dependent advanced systolic heart failure patients who had 25% annualized risk of death, MCS, or heart transplantation (HT). Freedom from composite clinical outcome at 1-year follow-up was 23.5% for the entire cohort. Seattle Heart Failure Model Score and Natriuretic pepides were predictors with modest discriminatory power. Interagency Registry for Mechanically Assisted Circulatory Support (INTERMACS) profile 4 patients had the highest risk (3.7-fold) of death, MCS or HT compared to INTERMACS profile 7.

SUMMARY

We propose individualized risk stratification for noninotrope dependent ambulatory advanced heart failure patients and include serial changes in end-organ function, nutritional parameters, frailty assessment, echocardiographic and hemodynamic data. The clinical journey of a patient with advanced heart failure should be tracked and discussed at each clinic visit for shared decision-making regarding timing of cfLVAD.

Prognostic role of albumin level in heart failure: A systematic review and meta-analysis

BACKGROUND

Hypoalbuminemia (HA) is common in HF, however, its pathophysiology and clinical implications are poorly understood. While multiple studies have been published in the past decade investigating the role of serum albumin in HF, there is still no consensus on the prognostic value of this widely available measure. The objective of this study is to assess the prognostic role of albumin in heart failure (HF) patient.

METHODS

Unrestricted searches of MEDLINE, EMBASE, Cochrane databases were performed. The results were screened for relevance and eligibility criteria. Relevant data were extracted and analyzed using Comprehensive Meta-Analysis software. The Begg and Mazumdar rank correlation test was utilized to evaluate for publication bias.

RESULTS

A total of 48 studies examining 44,048 patients with HF were analyzed. HA was found in 32% (95% confidence interval [CI] 28.4%-37.4%) HF patients with marked heterogeneity (I2 = 98%). In 10 studies evaluating acute HF, in-hospital mortality was almost 4 times more likely in HA with an odds ratios (OR) of 3.77 (95% CI 1.96-7.23). HA was also associated with a significant increase in long-term mortality (OR: 1.5; 95% CI: 1.36-1.64) especially at 1-year post-discharge (OR: 2.44; 95% CI: 2.05-2.91; I2 = 11%). Pooled area under the curve (AUC 0.73; 95% CI 0.67-0.78) was comparable to serum brain natriuretic peptide (BNP) in predicting mortality in HF patients.

CONCLUSION

Our results suggest that HA is associated with significantly higher in-hospital mortality as well as long-term mortality with a predictive accuracy comparable to that reported for serum BNP. These findings suggest that serum albumin may be useful in determining high-risk patients.

Ventricular Assist Devices and Chronic Kidney Replacement Therapy: Technology and Outcomes

Heart failure and kidney failure are very common conditions, precipitating and exacerbating each other. Left ventricular assist devices (LVADs) represent a relatively new technology for treatment of advanced heart failure. Kidney dysfunction, if present, makes candidate selection for LVADs challenging and contributes to multiple complications while the patients are on an LVAD support. Although kidney function generally improves after LVAD implantation, some patients develop acute and then chronic kidney disease sometimes requiring kidney replacement therapies (KRTs). Overall, chronic KRT in LVAD recipients is feasible and well tolerated, but routine technique of blood pressure monitoring should be adjusted to the continuous blood flow. Both hemodialysis and peritoneal dialysis can be used. Unique challenges for chronic KRT posed by the presence of LVAD are discussed in this review.

Risk of Liver Dysfunction After Left Ventricular Assist Device Implantation

BACKGROUND

Incident liver dysfunction after left ventricular assist device implantation has been previously associated with adverse outcomes, yet data on perioperative risk markers are sparse.

METHODS

We retrospectively reviewed consecutive patients undergoing continuous-flow left ventricular assist device implant between 2007 and 2017 at a single institution. Perioperative variables were evaluated by univariate modeling and adjusted for false discovery rate. Variables most significantly associated with incident Interagency Registry for Mechanically Assisted Circulatory Support-defined liver dysfunction (INT-LD) were evaluated using logistic regression and optimal cutpoints were defined. One-year survival was evaluated using Kaplan-Meier analysis.

RESULTS

We included 359 patients (79% male; mean age 59 ± 13 years; 46% ischemic; 64% destination therapy). Lower right ventricular stroke work index at the time of right heart catheterization, higher right atrial pressure 6 hours after right heart catheterization, higher preoperative total bilirubin, longer cardiopulmonary bypass time, and greater volume of intraoperative ultrafiltration were most strongly associated with incident INT-LD (adjusted P < .01 for each). Initial right ventricular stroke work index less than 460 mm Hg∗mL/m2 (odds ratio [OR] 4.6; 95% confidence interval [CI], 2.3 to 9.4), 6-hour right heart catheterization 14 mm Hg or greater (OR 4.3; 95% CI, 2.1 to 8.8), cardiopulmonary bypass time longer than 137 minutes (OR 3.3; 95% CI, 1.8 to 6.2; P < .01 for all), ultrafiltration more than 2.95 L (OR 3.7; 95% CI, 2 to 6.8), and total bilirubin greater than 1.4 mg/dL (OR 2.7; 95% CI, 1.4 to 5) were each strongly associated with risk of INT-LD, which was associated with decreased unadjusted 1-year survival (P < .001).

CONCLUSIONS

Right ventricular stroke work index, right heart catheterization, cardiopulmonary bypass time, and ultrafiltration were each more strongly associated with elevated risk of INT-LD after left ventricular assist device implant than total bilirubin. Therefore, optimization of right ventricular hemodynamics and minimizing cardiopulmonary bypass time and ultrafiltration could potentially reduce the risk of liver dysfunction, but these observations require prospective validation.

Comparison of Renal Outcomes in Patients With Left Ventricular Assist Device and Heart Transplantation

BACKGROUND

Renal function is a major consideration for orthotopic heart transplantation (OHT) and left ventricular assist device (LVAD) therapy. We compared serial changes in renal function and outcomes between patients who underwent OHT and LVAD therapy over 12 months.

METHODS

Forty-five and 58 consecutive patients who underwent LVAD implantation (all bridge to transplant or candidacy) and OHT from April 2014 to November 2016 were included. Six of these patients were in both LVAD and OHT cohorts. Survival analysis was calculated using Kaplan Meier and log rank methods. Univariate analysis of data was performed using χ², Mann-Whitney, Kruskal-Wallis, and Wilcoxon signed rank tests where appropriate. Comparisons of the renal function to baseline were conducted using generalized estimating equations.

RESULTS

Renal function had a biphasic course among the LVAD cohort, increasing at 30 days but reducing at 6 and 12 months. Meanwhile, estimated glomerular filtration rate (eGFR) was seen to progressively decline among OHT recipients. Altogether, eGFR was significantly higher at 6 and 12 months among the LVAD cohort compared to OHT (68.3 vs 59.4, P = .046; 68.3 vs 50.4, P = .015). Compared to the baseline average, eGFR had risen among the LVAD patients (P = .031) but had decreased among the OHT group (P < .001) at 12 months. No significant difference in survival was seen at 1 year (84.4% vs 81.0%; P = .540) and 2 years (78.3% vs 78.8%, P = .687) between the cohorts.

CONCLUSION

Despite poorer baseline renal function, LVAD therapy was associated with comparable survival and better renal outcomes compared to OHT at 12 months. Renal impairment may favor the use of LVAD therapy over OHT in the short term.

Preoperative renal dysfunction does not affect outcomes of left ventricular assist device implantation

OBJECTIVE

Selection criteria for durable left ventricular assist device (LVAD) implantation remain unclear. One such criterion is renal function. In this study we evaluated outcomes of LVAD implantation in patients with preoperative renal dysfunction.

METHODS

Patients with implanted LVADs as destination therapy (DT) or bridge to transplantation (BTT) at a single institution between 2006 and 2015 were included. Primary stratification was according to pre-implantation glomerular filtration rate (GFR): >60 mL/min versus <60 mL/min or dialysis dependence. The primary outcome was post-LVAD implantation overall survival.

RESULTS

Two hundred thirty-eight patients underwent LVAD implantation during the study period as DT (60%; n = 142) or BTT (40%; n = 96). Reduced GFR was present in 56% (n = 132), with 8% (n = 18) being dialysis-dependent. Normal versus reduced GFR cohorts were well matched except for a higher incidence of coronary artery disease in the patients with reduced GFR (61% vs 48%; P = .04). Mean follow-up was 13.5 ± 17.0 months. Unadjusted and risk-adjusted survival at 1, 3, 6, and 12 months after LVAD implantation were similar between the cohorts for DT and BTT. Rates of transplantation were comparable in BTT patients (61% normal vs 53% reduced GFR; P = .43). Recovery of renal function to a GFR >60 mL/min occurred in 43% (n = 17) and 57% (n = 42) of patients with reduced GFR in the BTT and DT cohorts, respectively, by 1 year post implantation.

CONCLUSIONS

Well selected patients with preexisting renal dysfunction can undergo LVAD implantation with acceptable outcomes. Approximately half of LVAD recipients with preimplantation renal dysfunction will recover normal renal function within the first postoperative year. Renal dysfunction alone should not serve as an absolute contraindication to LVAD therapy.

Evolution of Biventricular Loading Condition in Pediatric LVAD Patient: A Prospective and Observational Study

The aim of this study was to describe the echocardiographic trend of left ventricular (LV) and right ventricular (RV) function after implantation of a pulsatile flow left ventricular assist device (LVAD) in children. From 2013 to 2016, we prospectively evaluated 13 consecutive pediatric Berlin Heart EXCOR LVAD patients. Clinical and echocardiographic data were collected at baseline, within 24 h after implantation and monthly until LVAD explant. Median age and weight at the implantation was 8 (4-23) months and 5 (4.6-8.3) kg at the time of implantation, respectively. All were affected by dilated cardiomyopathy. Average LVAD support time was 226.2 ± 121.2 days. Nine (70%) were transplanted, 4 (30%) died. LV end-systolic and end-diastolic volumes were reduced until the follow up of two months (P = 0.019 and P = 0.001). A progressive increase in RV dimensions was observed. After 4 months of follow up, RV fractional area change worsening was statistically related with the deterioration of LV unloading (P = 0.0036). Four patients needed prolonged inotropic support for RV failure. Pulsatile LVAD in pediatrics is followed by an early and mid-term LV unloading, as expressed by a decrease in LV volumes and diameters at echocardiogram. The effects of unloading do not remain stable at long term follow up. RV function improved in the acute phase, but a progressive dilatation of RV was noted over time. In some patients, RV failure might lead to the need of an increase of inotropic support at long term follow up.

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.

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.

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.