The official publication of the American Society for Artificial Internal Organs

What if Disney Ran Your LVAD Program? In defining success, Disney did something different. Fred Lee worked at Disney after a distinguished career in hospital senior leadership, consulting, and training. Shortly after his arrival at Disney, he recalls noting Disney’s satisfaction scores were often in the 75% range, much lower than the 90+% satisfaction scores to which he was accustomed at healthcare organizations. He quickly discovered there was more to the story. In contrast to the common practice of lumping, the top couple of choices on a 5-point Likert scale as “satisfied” and hailing teams with 90+% satisfaction scores, anything less than the top score at Disney was counted as a failure.1 This aspirational message on striving for excellence and combating the Lake Woebegon effect, in which “all the children are above average,”2 has appeal in thinking differently about how to define success in medical care. But when it comes to left ventricular assist devices (LVADs), would we rather have the renowned cardiac surgeon Dr. Walt Dembitsky at the helm or Walt Disney? Advanced heart failure is a mortal disease; 1-year survival lags many feared metastatic malignancies. Mechanical circulatory support has transformed care for this population. With 74.7% of LVAD patients alive and free from disabling stroke or reoperation to replace or remove a malfunctioning device at 2 years in a recent cohort,3 LVADs are firmly established as mainstream care for advanced heart failure. Despite the dramatic improvements in mortality, morbid adverse events remain a prominent reminder of the work remaining to understand the pathophysiology and mitigate adverse events. Gastrointestinal bleeding, stroke, driveline infection, and thromboembolic complications remain distressingly common. The rate of hospitalization following LVAD is also high, and impacts patient quality of life and cost of care beyond the high upfront device expense. These adverse events certainly blunt patient enthusiasm for such a major surgery, and may lead many physicians to shy away from recommending evaluation for implant. With these tradeoffs in patient outcomes, defining LVAD success will be difficult. From a provider perspective, we have observed disagreements within our center’s professionals over whether implanting an LVAD in a particular patient have been a “success” or a “mistake.” We have also witnessed instances where the medical team would adjudicate a “success,” but the patient or caregiver’s expectations are not met and the patient wishes they had chosen another path of care. Conversely, patients with recurrent complications can rave about how glad they are to be alive and able to ambulate without oppressive dyspnea. Nuances in patient perspectives will challenge efforts to craft a unifying definition of success. Anwer et al.4 propose a quantitative measure of LVAD implant success, defined as alive or transplanted at 2 years, two or less readmissions in the first year, no major adverse events in the first year, and a New York Heart Association class of ≤II at 6 months. Applying this definition to a single-center cohort of 278 patients, they found that 81 (29%) met this definition of success. This is an important contribution to the discussion of LVAD success and echoes Disney’s thinking—anything less than perfect is failure. One might ask why two readmissions are still perfect and if we are to follow the Disney model, why accept any readmissions? This component of the proposed measure is arbitrary. Regardless of whether we accept this measure, complications will occur even with perfectly delivered care. For some patients, failure to achieve some aspects of a measure of perfect LVAD care may be preferable to the death and disability associated with advanced heart failure. This is particularly troublesome if aggressive application of this definition by regulatory bodies or payors limited access to LVAD care among patients deemed at high risk of an imperfect outcome. As an alternative, the proposed “success” measure might be more helpful in setting the stage for patients and families to understand the likelihood of a “perfect” result. We might frame the risks with a 10% chance of a perfect outcome, 50% chance of avoiding the feared complications such as stroke or GI bleeding, but a 90% chance of experiencing one or more adverse events, if hospital admissions are included. Extensive data on rates of infection, stroke, bleeding, and hospitalization are available and should be presented to candidates, but information on aggregate risk of any event may not be part of usual disclosure. Such a shift in presenting risks might improve communication and expectations. On a more granular level, outstanding questions remain, and could be considered for future iterations of such efforts. First and foremost is greater insight into the tradeoffs faced by patients as it relates to life with and without an LVAD. For patients who have experienced life with advanced heart failure and then complications of LVAD, which was more significant? Heart failure symptoms and hospitalization or post-LVAD GI bleeding and a driveline infection? This understanding could identify LVAD complications that from a patient’s perspective negate the longevity and symptom benefit provided by LVAD. In a similar way, by weighting different adverse events, we can acknowledge that for many patients, frequent hospitalization is not equivalent to death or disabling stroke. The patient’s voice needs more weight to inform discussion. Second, although we strive for perpetually lower rates of adverse events, should experiencing a known complication be considered a failure, or should we reserve this label for something else? Clinical trials typically make this distinction by designating unexpected adverse events in a separate category. Finally, we should consider degrees of success—perhaps “highly successful” and “moderately successful” to help guide preimplant discussions about anticipated outcomes. Most people would probably consider receiving an LVAD the antithesis of the customer service of visiting a Disney theme park, but creating a summary measure that accurately reflects success for individuals will be difficult and future efforts will need to more completely incorporate the patient perspective. Nevertheless, collective efforts by the community to reduce the inevitable exposure to the “Adventureland” that follows an LVAD are worthy and ongoing work to define success is essential.

The Importance of Left Ventricular Assist Device Inflow Cannula Angle and the Relationship to Cardiac and Anatomical Geometry No abstract available

New Approaches to Respiratory Assist: Bioengineering an Ambulatory, Miniaturized Bioartificial Lung Although state-of-the-art treatments of respiratory failure clearly have made some progress in terms of survival in patients suffering from severe respiratory system disorders, such as acute respiratory distress syndrome (ARDS), they failed to significantly improve the quality of life in patients with acute or chronic lung failure, including severe acute exacerbations of chronic obstructive pulmonary disease or ARDS as well. Limitations of standard treatment modalities, which largely rely on conventional mechanical ventilation, emphasize the urgent, unmet clinical need for developing novel (bio)artificial respiratory assist devices that provide extracorporeal gas exchange with a focus on direct extracorporeal CO2 removal from the blood. In this review, we discuss some of the novel concepts and critical prerequisites for such respiratory lung assist devices that can be used with an adequate safety profile, in the intensive care setting, as well as for long-term domiciliary therapy in patients with chronic ventilatory failure. Specifically, we describe some of the pivotal steps, such as device miniaturization, passivation of the blood-contacting surfaces by chemical surface modifications, or endothelial cell seeding, all of which are required for converting current lung assist devices into ambulatory lung assist device for long-term use in critically ill patients. Finally, we also discuss some of the risks and challenges for the long-term use of ambulatory miniaturized bioartificial lungs.

Left Ventricular Assist Devices: How Do We Define Success? Despite the growing acceptance of left ventricular assist device (LVAD) therapy to improve survival and quality of life in heart failure (HF) patients, uncertainties persist regarding the definition of a successful implant. We sought to define an innovative approach to assess success and subsequently compare preoperative variables affecting outcomes. From January 2007 to 2015, 278 patients underwent LVAD implantation. Median age at implant was 62 years and 81% patients were males. Indication for support was bridge-to-transplantation in 36% patients and the etiology of HF was ischemic in 49% patients. Based on clinically relevant and accepted standards, we defined successful LVAD implant as someone who was alive or transplanted at 2 years, had two or less readmissions in the first year, had no major adverse events in the first year, and had a New York Heart Association class of ≤ II at 6 months. Follow-up was obtained for a median of 1.7 years for a total of 605 patient-years-of-support. Based on our criteria, 81/278 (29%) patients were defined as having a successful implant. Univariate predictors of LVAD failure included destination therapy indication (hazard ratio [HR] = 2.11 [1.24, 3.58]), ischemic cardiomyopathy (HR = 1.73 [1.02, 2.94]), and a higher left ventricular ejection fraction (HR = 1.54 [1.07, 2.22]). After multivariable analysis, only destination therapy indication (HR = 2.2 [1.28, 3.78]) was found to be independently predictive of success failure. Despite an overall trend toward improved outcomes on device therapy, our criteria classified only one-third of patients as successful. Continued improvements in adverse event profiles, appropriate patient selection, and optimal time of implantation, together hold the key to improve outcomes after LVAD therapy.

Risk Assessment in Patients with a Left Ventricular Assist Device Across INTERMACS Profiles Using Bayesian Analysis Current risk stratification models to predict outcomes after a left ventricular assist device (LVAD) are limited in scope. We assessed the performance of Bayesian models to stratify post-LVAD mortality across various International Registry for Mechanically Assisted Circulatory Support (INTERMACS or IM) Profiles, device types, and implant strategies. We performed a retrospective analysis of 10,206 LVAD patients recorded in the IM registry from 2012 to 2016. Using derived Bayesian algorithms from 8,222 patients (derivation cohort), we applied the risk-prediction algorithms to the remaining 2,055 patients (validation cohort). Risk of mortality was assessed at 1, 3, and 12 months post implant according to disease severity (IM profiles), device type (axial versus centrifugal) and strategy (bridge to transplantation or destination therapy). Fifteen percentage (n = 308) were categorized as IM profile 1, 36% (n = 752) as profile 2, 33% (n = 672) as profile 3, and 15% (n = 311) as profile 4–7 in the validation cohort. The Bayesian algorithms showed good discrimination for both short-term (1 and 3 months) and long-term (1 year) mortality for patients with severe HF (Profiles 1–3), with the receiver operating characteristic area under the curve (AUC) between 0.63 and 0.74. The algorithms performed reasonably well in both axial and centrifugal devices (AUC, 0.68–0.74), as well as bridge to transplantation or destination therapy indication (AUC, 0.66–0.73). The performance of the Bayesian models at 1 year was superior to the existing risk models. Bayesian algorithms allow for risk stratification after LVAD implantation across different IM profiles, device types, and implant strategies.

Meet the Authors No abstract available

Baseline Thromboelastogram as a Predictor of Left Ventricular Assist Device Thrombosis Left ventricular assist device (LVAD) pump thrombosis occurs in up to 8.4% of patients within 3-months postimplantation. Thromboelastography (TEG) could be used to signal hypercoagulability at LVAD implantation to predict patients at high risk for thrombosis. We sought to evaluate whether TEG maximum amplitude (MA) hypercoagulability (MA ≥69 mm) at the time of LVAD implantation predicts pump thrombosis. A single center, retrospective, nested case–control study was conducted using patients from January 1, 2005, to March 31, 2015. Each pump thrombosis case was matched to two control subjects based on age ± 5 years, sex, and duration of follow-up. A multivariable logistic regression analysis was performed on the matched sets; the odds ratio with 95% confidence interval (CI) was calculated to estimate the relative risk. Thirty-seven age- and sex-matched case–control sets were included for a total of 111 study participants. TEG-MA hypercoagulability occurred in 10.8% of the case group versus 6.8% of controls. There was no association between TEG-MA hypercoagulability and device thrombosis (odds ratio 1.71, 95% confidence interval 0.42–7.05, p = 0.46). Utilization of baseline TEG-MA hypercoagulability to detect individuals at risk for LVAD thrombosis is a novel concept. This study found no significant association between TEG-MA and LVAD thrombosis.

Performance of Noninvasive Assessment in the Diagnosis of Right Heart Failure After Left Ventricular Assist Device Right heart failure (RHF) after left ventricular assist device (LVAD) is associated with poor outcomes. Interagency Registry for Mechanically Assisted Circulatory Support (Intermacs) defines RHF as elevated right atrial pressure (RAP) plus venous congestion. The purpose of this study was to examine the diagnostic performance of the noninvasive Intermacs criteria using RAP as the gold standard. We analyzed 108 patients with LVAD who underwent 341 right heart catheterizations (RHC) between January 1, 2006, and December 31, 2013. Physical exam, echocardiography, and laboratory data at the time of RHC were collected. Conventional two-by-two tables were used and missing data were excluded. The noninvasive Intermacs definition of RHF is 32% sensitive (95% cardiac index (CI), 0.21–0.44) and 97% specific (95% CI, 0.95–0.99) for identifying elevated RAP. Clinical assessment failed to identify two-thirds of LVAD patients with RAP > 16 mm Hg. More than half of patients with elevated RAP did not have venous congestion, which may represent a physiologic opportunity to mitigate the progression of disease before end-organ damage occurs. One-quarter of patients who met the noninvasive definition of RHF did not actually have elevated RAP, potentially exposing patients to unnecessary therapies. In practice, if any component of the Intermacs definition is present or equivocal, our data suggest RHC is warranted to establish the diagnosis.

Atrial Fibrillation Is Not Associated With Thromboembolism in Left Ventricular Assist Device Patients: A Systematic Review and Meta-Analysis Atrial fibrillation (AF) is a well-established risk factor of thromboembolism (TE). Thromboembolism is one of the most common complications in patients supported by continuous-flow left ventricular assisted devices (CF-LVADs). However, the association between AF and TE complications in this population is controversial. We conducted a systematic review and meta-analysis to assess the association between AF and overall TE, stroke, and device thrombosis events in CF-LVAD patients. We performed a comprehensive literature search through September 2017 in the databases of MEDLINE and EMBASE. Included studies were prospective or retrospective cohort studies that compared the risk of developing overall TE, stroke, and device thrombosis events in CF-LVAD patients with AF and those without AF. We calculated pooled risk ratio (RR) with 95% confidence intervals (CI) and I2 statistic using the random-effects model. Eleven studies were included involving 6,351 patients who underwent CF-LVAD implantation. Overall, TE outcome was available in four studies involving 1,106 AF and 3,556 non-AF patients. Stroke outcome was available in seven studies (1,455 AF and 4,037 non-AF patients). Device thrombosis outcome was available in three studies (1,010 AF and 3,327 non-AF patients). There was no association between AF and TE events (RR = 0.95; 95% CI: 0.57–1.59, I2 = 79%, p = 0.85), stroke (RR = 1.10; 95% CI: 0.74–1.64, I2 = 73%, p = 0.65), and device thrombosis (RR = 0.97; 95% CI: 0.56–1.67, I2 = 42%, p = 0.91). AF in CF-LVAD patients was not associated with overall TE, stroke, or device thrombosis events. These findings might be explained by the highly thrombogenic property of CF-LVADs that exceeds the thromboembolic risk driven by AF.

Wave Intensity Analysis of Right Ventricular Function during Pulsed Operation of Rotary Left Ventricular Assist Devices Changing the speed of left ventricular assist devices (LVADs) cyclically may be useful to restore aortic pulsatility; however, the effects of this pulsation on right ventricular (RV) function are unknown. This study investigates the effects of direct ventricular interaction by quantifying the amount of wave energy created by RV contraction when axial and centrifugal LVADs are used to assist the left ventricle. In 4 anesthetized pigs, pressure and flow were measured in the main pulmonary artery and wave intensity analysis was used to identify and quantify the energy of waves created by the RV. The axial pump depressed the intensity of waves created by RV contraction compared with the centrifugal pump. In both pump designs, there were only minor and variable differences between the continuous and pulsed operation on RV function. The axial pump causes the RV to contract with less energy compared with a centrifugal design. Diminishing the ability of the RV to produce less energy translates to less pressure and flow produced, which may lead to LVAD-induced RV failure. The effects of pulsed LVAD operation on the RV appear to be minimal during acute observation of healthy hearts. Further study is necessary to uncover the effects of other modes of speed modulation with healthy and unhealthy hearts to determine if pulsed operation will benefit patients by reducing LVAD complications.