The future of cardiac transplantation

Matrix Metalloproteinases and Heart Transplantation-A Pathophysiological and Clinical View

Heart transplantation is undergoing a continuous development, with rates of success increasing substantially due to advances in immunosuppressive therapy and surgical techniques. The most worrying complication occurring after cardiac transplantation is graft rejection, a phenomenon that is much affected by matrix metalloproteinases (MMPs), with the role of these proteases in the cardiac remodeling process being well established in the literature. A detailed investigation of the association between MMPs and cardiac rejection is necessary for the future development of more targeted therapies in transplanted patients, and to discover prognostic serum and immunohistochemical markers that will lead to more organized therapeutic management in these patients. The aim of this review is therefore to highlight the main MMPs relevant to cardiovascular pathology, with particular emphasis on those involved in complications related to heart transplantation, including cardiac graft rejection.

Cardiac Rehabilitation in Severe Heart Failure Patients with Impella 5.0 Support via the Subclavian Artery Approach Prior to Left Ventricular Assist Device Implantation

Impella 5.0 circulatory support via subclavian artery (SA) access may be a safe approach for patients undergoing cardiac rehabilitation (CR). In this case series, we retrospectively analyzed the demographic characteristics, physical function, and CR data of six patients who underwent Impella 5.0 implantation via the SA prior to left ventricular assist device (LVAD) implantation between October 2013 and June 2021. The median age was 48 years, and one patient was female. Grip strength was maintained or increased in all patients before LVAD implantation (pre-LVAD) compared to after Impella 5.0 implantation. The pre-LVAD knee extension isometric strength (KEIS) was less than 0.46 kgf/kg in two patients and more than 0.46 kgf/kg in three patients (unavailable KEIS data, n = 1). With Impella 5.0 implantation, two patients could ambulate, one could stand, two could sit on the edge of the bed, and one remained in bed. One patient lost consciousness during CR due to decreased Impella flow. There were no other serious adverse events. Impella 5.0 implantation via the SA allows mobilization, including ambulation, prior to LVAD implantation, and CR can be performed relatively safely.

The Molecular Microscope Diagnostic System: Assessment of Rejection and Injury in Heart Transplant Biopsies

This review describes the development of the Molecular Microscope Diagnostic System (MMDx) for heart transplant endomyocardial biopsies (EMBs). MMDx-Heart uses microarrays to measure biopsy-based gene expression and ensembles of machine learning algorithms to interpret the results and compare each new biopsy to a large reference set of earlier biopsies. MMDx assesses T cell-mediated rejection (TCMR), antibody-mediated rejection (AMR), recent parenchymal injury, and atrophy-fibrosis, continually "learning" from new biopsies. Rejection-associated transcripts mapped in kidney transplants and experimental systems were used to identify TCMR, AMR, and recent injury-induced inflammation. Rejection and injury emerged as gradients of intensity, rather than binary classes. AMR was one-third donor-specific antibody (DSA)-negative, and many EMBs first considered to have no rejection displayed minor AMR-like changes, with increased probability of DSA positivity and subtle inflammation. Rejection-associated transcript-based algorithms now classify EMBs as "Normal," "Minor AMR changes," "AMR," "possible AMR," "TCMR," "possible TCMR," and "recent injury." Additionally, MMDx uses injury-associated transcript sets to assess the degree of parenchymal injury and atrophy-fibrosis in every biopsy and study the effect of rejection on the parenchyma. TCMR directly injures the parenchyma whereas AMR usually induces microcirculation stress but relatively little initial parenchymal damage, although slowly inducing parenchymal atrophy-fibrosis. Function (left ventricular ejection fraction) and short-term risk of failure are strongly determined by parenchymal injury. These discoveries can guide molecular diagnostic applications, either as a central MMDx system or adapted to other platforms. MMDx can also help calibrate noninvasive blood-based biomarkers to avoid unnecessary biopsies and monitor response to therapy.

An Analysis of Waitlist Inactivity Among Patients With Ventricular Assist Devices

BACKGROUND

Ventricular assist devices (VADs) are commonly used mechanical circulatory support for bridge to transplant therapy in end-stage heart failure; however, it is not understood how VADs influence incidence of waitlist inactive status. We sought to characterize and compare waitlist inactivity among patients with and without VADs.

METHODS

Using the Organ Procurement and Transplantation Network database, we investigated the VAD's impact on incidence and length of inactive periods for heart transplant candidates from 2005 through 2018. We compared median length of inactivity between patients with and without VADs and investigated inactivity risk with time-to-event regression models.

RESULTS

Among 46,441 heart transplant candidates, 32% (n = 14,636) had a VAD. Thirty-eight percent (n = 17,873) of all patients experienced inactivity, of which 42% (7538/17,873) had a VAD. Median inactivity length was 31 d for patients without VADs and 62 d for VAD patients (P < 0.0005). Multivariable analysis showed no significant difference in risk of inactivity for deteriorating conditions between patients with and without VADs after controlling for demographic and baseline clinical variables. A larger proportion of patients without VADs were inactive for deteriorating conditions than VAD patients (54%, n = 8242/15,221 versus 32%, n = 3583/11,086, P < 0.001). Ten percent (1155/11,086) of VAD patients' inactive periods were for VAD-related complications.

CONCLUSIONS

Although VAD patients were inactive longer and had an overall increased risk of any-cause inactivity, their risk of inactivity for deteriorating condition was not significantly different from patients without VADs. Furthermore, VAD patients had a smaller proportion of inactivity periods due to deteriorating conditions. Thus, VADs are protective from morbidity for waitlist patients.

Thrombolysis as first-line therapy for Medtronic/HeartWare HVAD left ventricular assist device thrombosis

OBJECTIVES

METHODS

From March 2006 to November 2018, 30 Medtronic/HeartWare HVAD left ventricular assist device patients had 48 PT events. We analysed outcomes with intravenous Alteplase as a first-line therapy for PT. Pump exchange or urgent heart transplantation was only considered after the failure of TL or existing contraindications to TL.

RESULTS

TL was used as the first-line therapy in 44 PT events in 28 patients without a contraindication to TL. TL was successful in 61.4% of PT events. More than 1 cycle of TL was necessary in 55.6% of events. The combined success of TL and heart transplantation or device exchange was 81.8%. In 15.9% of events, PT was fatal. Causes of death were severe complications (9.1%) related to TL or discontinuation of therapy for multi-organ failure (6.8%). Intracranial bleeding and arterial thromboembolism were observed in 4.5% and 11.5% of the PT events after TL.

CONCLUSIONS

Intravenous TL as a first-line therapy for PT in Medtronic/HeartWare HVAD patients can be a reasonable treatment option and does not preclude subsequent heart transplantation or device exchange. However, thromboembolic and bleeding complications are common. The decision to perform TL or device exchange should, therefore, be made on an individual basis after balancing the risks and benefits of different treatment approaches.

A nonrandomized open-label phase 2 trial of nonischemic heart preservation for human heart transplantation

Pre-clinical heart transplantation studies have shown that ex vivo non-ischemic heart preservation (NIHP) can be safely used for 24 h. Here we perform a prospective, open-label, non-randomized phase II study comparing NIHP to static cold preservation (SCS), the current standard for adult heart transplantation. All adult recipients on waiting lists for heart transplantation were included in the study, unless they met any exclusion criteria. The same standard acceptance criteria for donor hearts were used in both study arms. NIHP was scheduled in advance based on availability of device and trained team members. The primary endpoint was a composite of survival free of severe primary graft dysfunction, free of ECMO use within 7 days, and free of acute cellular rejection ≥2R within 180 days. Secondary endpoints were I/R-tissue injury, immediate graft function, and adverse events. Of the 31 eligible patients, six were assigned to NIHP and 25 to SCS. The median preservation time was 223 min (IQR, 202–263) for NIHP and 194 min (IQR, 164–223) for SCS. Over the first six months, all of the patients assigned to NIHP achieved event-free survival, compared with 18 of those assigned to SCS (Kaplan-Meier estimate of event free survival 72.0% [95% CI 50.0–86.0%]). CK-MB assessed 6 ± 2 h after ending perfusion was 76 (IQR, 50–101) ng/mL for NIHP compared with 138 (IQR, 72–198) ng/mL for SCS. Four deaths within six months after transplantation and three cardiac-related adverse events were reported in the SCS group compared with no deaths or cardiac-related adverse events in the NIHP group. This first-in-human study shows the feasibility and safety of NIHP for clinical use in heart transplantation. ClinicalTrial.gov, number NCT03150147

Ischemia and reperfusion damage contribute to early graft dysfunction and recipient’s death. Here the authors show the feasibility and safety of a non-ischemic heart preservation method for heart transplantation in a non-randomized trial.

Use of Ventricular Assist Devices and Heart Transplantation for Advanced Heart Failure

There are only 2 treatments for the thousands of patients who progress to the most advanced form of heart failure despite the application of guideline-based medical therapy, use of ventricular assist devices and heart transplantation. There has been a great deal of progress in both of these therapies that have led to improved outcomes including significant improvement in survival and functional capacity. Heart transplantation offers the best short- and long-term survival for patients with end-stage heart failure, and the majority of these recipients achieve relatively limitless functional capacity for their age. However, the chronic shortage of available donors limits the number of recipients in the United States to an only 2500 patients/y or only a fraction of potential candidates. The significant improvement in outcomes now possible with durable ventricular assist devices has led to a significant increase in their use, which now exceeds the volume of heart transplants in the United States, with the greatest growth in use for those not considered to be candidates for heart transplantation, previously referred to as destination therapy. This article will review the substantial progress that has taken place for both of these life-saving treatment options, as well as the future directions.

Deployment of acute mechanical circulatory support devices via the axillary artery

Introduction: Use of acute mechanical circulatory support (MCS) devices for high-risk cardiac intervention, cardiogenic shock, and advanced heart failure is growing. Alternate vascular access options for these devices remains a clinical challenge. Building on experience from trans-aortic valve replacement procedures, the axillary artery is becoming a common access route for acute MCS and represents an important advance in the development of acute MCS technologies. Areas covered: Authors review the clinical data and technical aspect of acute MCS deployment via the axillary artery. Axillary access is particularly useful for patients: 1) with severe peripheral vascular disease, 2) with hostile femoral access due to infection, indwelling endovascular devices, or obesity, and 3) to provide early mobility and ambulation. In this review, we discuss the deployment, technical issues and hemostasis regarding the use of intraaortic balloon pump, specifically, axillary intraaortic balloon pumps, trans-valvular left ventricular Impella pumps and arterial outflow of VA-ECMO. Expert opinion: Vascular comorbidities or device design may limit the traditional iliofemoral access route for acute mechanical circulatory support devices. Large bore access for the deployment of these devices through the axillary artery is feasible and safe when appropriate vascular access and closure techniques are used.