Utilization of the percutaneous left ventricular support as bridge to heart transplantation across the United States: In-depth UNOS database analysis

Percutaneous Microaxial Ventricular Assist Device Versus Intra-Aortic Balloon Pump for Nonacute Myocardial Infarction Cardiogenic Shock

BACKGROUND

Evidence on the comparative outcomes following percutaneous microaxial ventricular assist devices (pVAD) versus intra-aortic balloon pump for nonacute myocardial infarction cardiogenic shock is limited.

METHODS AND RESULTS

We included 704 and 2140 Medicare fee-for-service beneficiaries aged 65 to 99 years treated with pVAD and intra-aortic balloon pump, respectively, for nonacute myocardial infarction cardiogenic shock from 2016 to 2020. Patients treated using pVAD compared with those treated using intra-aortic balloon pump were more likely to be concurrently treated with mechanical ventilation, renal replacement therapy, and blood transfusions. We computed propensity scores for undergoing pVAD using patient- and hospital-level factors and performed a matching weight analysis. The use of pVAD was associated with higher 30-day mortality (adjusted odds ratio, 1.92 [95% CI, 1.59-2.33]) but not associated with in-hospital bleeding (adjusted odds ratio, 1.00 [95% CI, 0.81-1.24]), stroke (adjusted odds ratio, 0.91 [95% CI, 0.56-1.47]), sepsis (OR, 0.91 [95% CI, 0.64-1.28]), and length of hospital stay (adjusted mean difference, +0.4 days [95% CI, -1.4 to +2.3]). A quasi-experimental instrumental variable analysis using the cross-sectional institutional practice preferences showed similar patterns, though not statistically significant (adjusted odds ratio, 1.38; 95% CI, 0.28-6.89).

CONCLUSIONS

Our investigation using the national sample of Medicare beneficiaries showed that the use of pVAD compared with intra-aortic balloon pump was associated with higher mortality in patients with nonacute myocardial infarction cardiogenic shock. Providers should be cautious about the use of pVAD for nonacute myocardial infarction cardiogenic shock, while adequately powered high-quality randomized controlled trials are warranted to determine the clinical effects of pVAD.

An explainable machine learning approach using contemporary UNOS data to identify patients who fail to bridge to heart transplantation

Background

The use of Intra-aortic Balloon Pump (IABP) and Impella devices as a bridge to heart transplantation (HTx) has increased significantly in recent times. This study aimed to create and validate an explainable machine learning (ML) model that can predict the failure of status two listings and identify the clinical features that significantly impact this outcome.

Methods

We used the UNOS registry database to identify HTx candidates listed as UNOS Status 2 between 2018 and 2022 and supported with either Impella (5.0 or 5.5) or IABP. We used the eXtreme Gradient Boosting (XGBoost) algorithm to build and validate ML models. We developed two models: (1) a comprehensive model that included all patients in our cohort and (2) separate models designed for each of the 11 UNOS regions.

Results

We analyzed data from 4,178 patients listed as Status 2. Out of them, 12% had primary outcomes indicating Status 2 failure. Our ML models were based on 19 variables from the UNOS data. The comprehensive model had an area under the curve (AUC) of 0.71 (±0.03), with a range between 0.44 (±0.08) and 0.74 (±0.01) across different regions. The models' specificity ranged from 0.75 to 0.96. The top five most important predictors were the number of inotropes, creatinine, sodium, BMI, and blood group.

Conclusion

Using ML is clinically valuable for highlighting patients at risk, enabling healthcare providers to offer intensified monitoring, optimization, and care escalation selectively.

Heart Transplantation

Heart transplantation (HTx) remains the last therapeutic resort for patients with advanced heart failure. The present work is a clinically focused review discussing current issues in heart transplantation. Several factors have been associated with the outcome of HTx, such as ABO and HLA compatibility, graft size, ischemic time, age, infections, and the cause of death, as well as imaging and laboratory tests. In 2018, UNOS changed the organ allocation policy for HTx. The aim of this change was to prioritize patients with a more severe clinical condition resulting in a reduction in mortality of people on the waiting list. Advanced heart failure and resistant angina are among the main indications of HTx, whereas active infection, peripheral vascular disease, malignancies, and increased body mass index (BMI) are important contraindications. The main complications of HTx include graft rejection, graft angiopathy, primary graft failure, infection, neoplasms, and retransplantation. Recent advances in the field of HTx include the first two porcine-to-human xenotransplantations, the inclusion of hepatitis C donors, donation after circulatory death, novel monitoring for acute cellular rejection and antibody-mediated rejection, and advances in donor heart preservation and transportation. Lastly, novel immunosuppression therapies such as daratumumab, belatacept, IL 6 directed therapy, and IgG endopeptidase have shown promising results.