Destination Therapies Research Articles

CARD3: Wall Shear Stress Signature of the Axial B-impeller Design with Superior Hemodynamics

Purpose: Ventricular assist devices (VADs) present great promise as both bridge-to-transplant and destination therapies for patients with end-stage heart failure. However, complications—such as hemolysis, gastrointestinal bleeding, and degradation of the von Willebrand factor—stand in the way of their widespread application. High levels of wall shear stress resulting from poor hemodynamics within the bladed flow domain are primarily responsible. Computational fluid dynamics (CFD) software was used to map the hemodynamic performance of the B-impeller—a biologically-inspired, helicoid VAD impeller design—and provide detailed insight into the internal flow structures, leading to the shear stress levels within. Methods: The B-impeller with casing was parametrically modeled using a computer aided design software. The geometry was exported to a CFD software and simulations were subsequently run to assess the impeller hemodynamics with respect to the wall shear stress parameter. Results: The B-impeller was found to have a very low shear stress signature versus typical VAD designs, which exhibit much higher signatures than the defined hemolytic threshold of 400 Pascals. The peak and area-averaged values of shear stress were found to be 304.512 Pa (at a flow rate of 9 L/min) and 39.949 Pa (averaged over multiple input flow rate simulations), respectively. Conclusion: The B-impeller concept shows great potential to reduce the adverse hemolytic events associated with most other turbo VADs, in addition to its ability to generate high rates of flow in a minimally intrusive diameter of 8 mm. This biologically inspired, rim-driven impeller design was found to reduce shear stress levels over competitive designs by virtue of its radical, open architecture. This low shear stress signature translates to lowering rates of hemolysis, bleeding, and von Willebrand factor degradation, thereby improving post-implantation outcomes of patients.

Abstract 9963: Early Guided Palliative Communication Intervention to Optimize Family Support and Manage Expectations for Patients Receiving Extracorporeal Membrane Oxygenation (ECMO)

Introduction: Extracorporeal membrane oxygenation (ECMO) is increasingly instituted for patients with severe circulatory or respiratory failure and as bridge to recovery or destination therapies (device implantation or organ transplantation). Morbidity and mortality for those patients is high. Hypothesis: ECMO combined with COVID isolation presents an additional set of challenges for patients, families. Objective: To test feasibility of an early, concurrent, and semi-structured palliative care intervention in improving communication, clarifying goals of care, and highlighting the experience of patients’ families. Methods: IRB Approved Qualitative study using content analysis of guided, in-depth discussions with families of COVID-19 patients within 48-72 hours of being cannulated for ECMO between March- October 2020. Scripted template was developed to guide and facilitate goals of care conversations and to ensure consistent communication with family members throughout patients’ disease trajectory. Patient demographics, comorbidities, clinical course, length of stay, and discharge disposition was obtained from the institution’s COVID-19 Data Warehouse and analyzed using descriptive statistics Setting: Large urban academic medical center. Results: Patients were 44 ± 10 years, Hispanic or Latino 27/43 (63%), white 3 (7%), Black 8 (19%). Palliative care documentation for ECMO acknowledgement meeting was 36/43 (84%). Timely and guided communication demonstrated themes expressed by families including 1) social isolation and related grief of not being at patient’s bedside; 2) helping children of patients adjust to a new normal; 3) coping with multiple family members suffering from COVID-19; 4) importance of faith and spirituality; 5) need for hope and gratitude 6) futility of prolonged ECMO stay. Survival to discharge 24/43 (56%). There was no statistical difference in hospital survival or length of stay between patients with and without documented palliative care. Conclusions: Early and ongoing palliative care intervention is feasible to support families’ acknowledgment of complexity, benefits and limitations of ECMO, and it is useful in highlighting families’ experiences, managing expectations and alleviating suffering.

Contemporary Nationwide Heart Transplantation and Left Ventricular Assist Device Outcomes in Patients with Histories of Bariatric Surgery

Bariatric surgery may play a role in the management of morbidly obese patients with end-stage heart failure through increasing eligibility and improving the outcomes of destination therapies. We conducted a nationally representative, retrospective cohort study of patients with previous bariatric surgery undergoing either heart transplantation or left ventricular assist device implantation. Of 200 patients, < 6% experienced in-hospital mortality after destination therapy, comparable to that reported in the general population of heart recipients. Risk-adjusted outcomes differed minimally from those of obese patients undergoing destination therapy without previous bariatric surgery. This study provides important safety benchmarking data and demonstrates the feasibility of bariatric surgery as a potential bridge to left ventricular assist device implantation or heart transplantation in obese patients with end-stage heart failure.

Survival Outcomes with Regards to Implant Strategies in Heart Transplantation

Purpose Strategies underlying the use of Left ventricular assist devices (LVAD) for patients with end-stage heart failure include its use as bridge to transplant (BTT) or as destination therapies (DT). Survival outcomes of patients undergoing these LVAD implant strategies were evaluated and compared. Methods A retrospective analysis of single center database heart transplant patients that received LVADs from Nov. 2009 to Sep. 2020 (n=137). Patients were placed into the following cohorts based on the implant strategy: 1) BTT (n=31), 2) DT (n=106). Demographics were compared between groups for significance. Kaplan Meier curves were calculated and compared via log rank tests, and Cox Regression Analysis was performed. P-values Results Demographics between the groups were: diagnosis (p=0.257), CPB time (p=0.957), XC time (p=0.763), ischemic time (p=0.478), warm ischemic time (p=0.332), age (p=0.323), race (p=0.067), length of stay (p=0.355) and PRA (p=0.701). Of 137 patients that received LVADs used for BTT or DT prior to heart transplant, the BTT group had better survival outcomes than DT (p=0.0467). Median survival time for DT group was 2554 days, and median survival time for BTT group was 3030 days. The type of LVADs used between the two groups were significantly different (p=0.0009), therefore cox regression was run to control for statistically significant variables, with device showing no significant effect on survival. In cox regression BTT had a protective effect over DT with a hazard ratio of 1.439, p=0.0364. Conclusion Implant strategies for LVAD as BTT or DT show a difference in survival outcomes for end-stage heart failure patients, however both had reasonable outcomes. This paper supports the current literature in that LVADs are viable for use in patients of all types, with slightly better effects in BTT patients.

Update Cardiac Support and Assist Therapies

The management of acute and chronic heart failure utilizes various different techniques and medical devices. Different mechanical chest compression devices (mCPR), intraaortic balloon pump, catheter-based heart pumps like Impella®, and different kinds of ECLS/ECMO are mainly used as bridge to recovery. Venovenous ECMO gained wide acceptance after the CESAR trial. Venoarterial ECMO plays an increasing role as extracorporeal CPR (eCPR). Newer concepts include venovenoarterial ECMO and the combination of ECMO and Impella. Principles and limitations of these concepts are discussed. Surgically implanted devices that include left and right ventricular assist devices (LVAD, RVAD), biventricular VADs and the total artificial heart (TAH) are commonly used as bridge to transplant or destination therapies. Quality of life must be considered in the use of the devices, as the life-saving devices come with restrictions in the patients' lives.

Management strategy during neonatal/paediatric VV ECMO run

Introduction: Strategy during extracorporeal membrane oxygenation (ECMO) support is guided by available outcome data. Boundaries limiting selection of cases are shifting with advances in ECMO technology, conventional support, and destination therapies. Evolution: Neonatal respiratory ECMO numbers continue to decline due to improved conventional therapies, whereas infants historically excluded from ECMO (for example, ex-premature infants with O2-dependent chronic lung disease and severe RSV) are now successfully supported. ECMO for bridging of children to lung transplant is now established.1 Advances are also being made in mobile ECMO,2 long duration of ECMO support, and ECMO while wide awake. Initiation: Flow requirements and patient or vessel size govern cannula choice. Percutaneous cannulation of vessels with ultrasound guidance is described in all sizes of children, including small infants.3 Serial imaging and ECHO control are needed for optimisation of cannula position and orientation. Transoesophageal ECHO is preferable to transthoracic where available. Reconfiguration of the circuit may prove necessary in some cases and is better done early in the run.4Troubleshooting: Protocol and bundle adherence are the keys to preventing complications. Detection requires vigilance and rigorous checks along with comprehensive handover and tight teamwork. Management is about appropriate escalation and pathway utilisation. Simulation is an essential component of staff training and a powerful tool for reinforcing these points.5Lung recovery: ECMO can be considered the ultimate in “lung rest” techniques. Enhancing lung recovery during the rest provided by ECMO is mainly achieved by attention to fluid balance, pulmonary toilet, and adoption of ventilator rest settings. Bronchoscopy is also particularly useful in this context.6 Other therapies such as prone position, steroid use, surfactant, perfluorocarbon,7 and even individual lung ventilation2 have a role in selected cases. De-cannulation: Patience can be needed when timing the end to VV ECMO support. Removing the sweep gas from the oxygenator can be done simply without having to wean ECMO flow. In more difficult situations, 12–24 h trial off can be used. Radiological lung clearance, improving lung compliance, reduction of sweep gas requirements, and oxygen challenges are all informative in the run up to a decision to trial off. Lung biopsy8 or genetic test results are useful when recovery is absent to help establish futility. Earlier de-cannulation can be indicated in the setting of an intractable or severe complication. Summary: Strategy for management of VV ECMO support is evolving with improvements in ECMO techniques and advances in supporting therapies. A proactive, rigorous but flexible approach to individual cases can deliver excellence.

Mechanical Circulatory Support for Advanced Heart Failure

Patients with end-stage heart failure or cardiogenic shock experience unacceptably high mortality despite advances in treatment made over the past 50 years. The effects of vasoactive drugs used to manage cardiogenic shock may be limited, being highly dependent on “remaining” heart function. Mechanical circulatory support improves cardiac output independent of heart function. Intra-aortic balloon pumps (IABPs) and extracorporeal membrane oxygenation (ECMO) are the devices most commonly used in Korea. Despite frequent use, the utility of IABPs in acute myocardial patients remains controversial, whereas ECMO affords sufficient systemic perfusion pressure to reverse end-organ dysfunction. Both can only be used as acute treatments, thus as a bridge-to-recovery or a bridge-to-transplantation. Percutaneous left ventricular assist devices (LVADs) such as TandemHeart® and Impella are not in use in Korea. Implanted LVADs improve long-term outcomes and may also serve as destination therapies. In the present manuscript, we briefly review percutaneous and implantable devices currently used in Korea for the management of advanced heart failure. (Korean J Med 2015;88:142-149)

Heart Failure Options Broaden: Tipping the balance between artificial and transplanted hearts

Advances in mechanical circulatory devices have challenged heart transplantation as the gold standard therapy for patients with heart failure. This month, we explore just how close we are to tipping the balance between using the devices as bridges to transplantation and as destination therapies. Also this month, we look at possible changes to the OPTN/UNOS heart allocation policy.

Left Ventricular Reverse Remodeling With a Continuous Flow Left Ventricular Assist Device Measured by Left Ventricular End-Diastolic Dimensions and Severity of Mitral Regurgitation

Pulsatile flow left ventricular assist devices (LVADs) maximally unload the left ventricle (LV), leading to reverse remodeling of the myopathic LV that manifests as decreased LV end-diastolic dimension (LVEDD) and decreased severity of mitral regurgitation (MR). There is a paucity of data, however, regarding the ability of continuous flow (CF) pumps to adequately decompress the LV to induce similar reverse remodeling. We sought to evaluate the effects of CF-LVADs on LV reverse remodeling. From March 2006 through July 2011, one hundred patients with chronic heart failure underwent implantation of CF-LVAD (93 HeartMate II LVADs and seven HeartWare LVADs) as bridge-to-transplant (n = 68) and destination therapies (n = 32). Echocardiograms and right heart catheterizations were reviewed preoperatively and at 1 and 6 months post-LVAD implantation. Mean age was 52.1 ± 12.1 years; etiology of heart failure was ischemic cardiomyopathy in 34 patients and nonischemic dilated cardiomyopathy in 66 patients. Median LVAD support time was 378.3 days; 371.5 days for patients who received bridge-to-transplant therapy and 422.2 days for patients who underwent destination therapy. Left ventricular end-diastolic dimension significantly decreased at 1 month post-LVAD implantation from 71.6 ± 12.4 to 58.3 ± 13.8 mm (p < 0.001). Severity of MR also significantly decreased from 76.0% of patients having moderate or severe MR preoperatively to 8.0% with moderate or severe MR at 1 month post-LVAD (p < 0.001). These reductions were maintained at 6 months. These data demonstrate the ability of a CF-LVAD to significantly decompress the LV, leading to significant reductions in LVEDD and severity of MR. This reverse remodeling was apparent in the early postoperative period and was sustained at 6 months. Further studies are warranted to investigate whether this correlates with clinical LV recovery.

478: Ethical Considerations for Cardiac Ventricular Assist Device Support: A 12 Point Protocol

While cardiac ventricle assist devices (VAD) as bridges to transplant (BTT) and destination therapies (DT) are advancing technical, medical and surgical supports for end stage heart disease collateral ethical advances have not occurred. The increasing use of elective or emergent VADs are creating unique ethical issues. This is a 12 point patient protocol to reduce potential ethical dilemmas.

Quantification of Pulsatility as a Function of Vascular Input Impedance: An In Vitro Study

The physiological benefits of pulsatility generated by ventricular assist device (VAD) support continue to be heavily debated as application of VAD support has been expanded to include destination and recovery therapies. In this study, the relationship between input impedance (Zart) and vascular pulsatility during continuous flow (CF) or pulsatile flow (PF) VAD support was investigated. Hemodynamic waveforms were recorded at baseline failure and with 50%, 75%, and 100% CF or PF VAD support for nine different Zart test conditions (combination of three different resistance and compliance settings) in a mock circulatory system simulating left ventricular failure. High-fidelity hemodynamic pressure and flow waveforms were recorded to calculate mean arterial pressure (MAP), Zart, energy equivalent pressure (EEP), and surplus hemodynamic energy (SHE) as metrics for quantifying vascular pulsatility. MAP and EEP were elevated with increasing resistance whereas SHE was reduced with increasing compliance. Vascular pulsatility was restored with increasing PF VAD support, but diminished by up to 90% with increasing CF VAD support. The nonpulsatile energy component (MAP) of the pressure waveform is dependent on resistance whereas the pulsatile energy component (SHE) is dependent on compliance. The impact of Zart and vascular pulsatility on patient recovery with VAD support warrants further investigation.

Cardiac Resynchronization Therapy: A Review and Future Directions

In millennia past, descriptions of congestive heart failure (CHF) often included ancient remedies. The earliest Egyptian papyri translated in the last century reveal a remarkably sophisticated understanding of heart ailments being the prime culprit in conditions of generalized edema (also called dropsy) and CHF.1 Starting in medieval times and continuing until the late 19th century, treatment for CHF included bloodletting to restore balance among the four humors.2 Writings as early as 1250 A.D. described using adjunctive pharmacologic therapy such as cardiac glycoside-containing herbal extracts to treat CHF.3 Several centuries ago, William Withering, a physician and botanist, wrote about the clinical effects of a foxglove plant extract in treating CHF. As a result, digitalis and its derivatives became one of the earliest medicines used in heart failure therapy. Rather than bloodletting, medical management of CHF has progressed in the last century to include diuretics to reduce pulmonary congestion; vasodilators of differing stripes; and, in the last 15 years, the initially counterintuitive use of beta-blockers as therapeutic mainstays. Other therapies are directed at treating the underlying cause of CHF, such as revascularization or valve replacement. Ultimate destination therapies include cardiac transplantation or the implantation of mechanical assist devices (e.g., left ventricular assist devices), while new strategies such as immunomodulation or stem cell therapy remain in various stages of investigation. In the late 1990s, the important role of electrical conduction disease was recognized in a significant number of patients with moderate to severe CHF; these patients demonstrated electrocardiac evidence of ventricular dyssynchrony (VD), Small clinical studies subsequently demonstrated that restoration of ventricular-ventricular synchrony could acutely improve parameters of cardiac performance.4-6 This concept of electromechanical therapy led to the initial trials of cardiac resynchronization therapy (CRT) as an important adjunctive treatment for patients with moderate to severe CHF. CRT is now a well-established adjunctive therapy for drug-refractory CHF in patients with moderate to severe diminishment in functional capacity.7-12