Deactivation of Left Ventricular Assist Devices at the End of Life: Narrative Review and Ethical Framework.

Left ventricular assist devices (LVADs) have become an increasingly common advanced therapy in patients with severe symptomatic heart failure. Their unique nature in prolonging life through incorporation into the circulatory system raises ethical questions regarding patient identity and values, device ontology, and treatment categorization; approaching requests for LVAD deactivation requires consideration of these factors, among others. To that end, clinicians would benefit from a deeper understanding of: 1) the history and nature of LVADs; 2) the wider context of device deactivation and associated ethical considerations; and 3) an introductory framework incorporating best practices in requests for LVAD deactivation (specifically in controversial situations without obvious medical or device-related complications). In such decisions, heart failure teams can safeguard patient preferences without compromising ethical practice through more explicit advance care planning before LVAD implantation, early integration of hospice and palliative medicine specialists (maintained throughout the disease process), and further research interrogating behaviors and attitudes related to LVAD deactivation.

Telerehabilitation: Future of Phase II Cardiac Rehabilitation: Review of Preliminary Outcomes.

In this brief communication, we reported Telehealth Home-Based Cardiac Rehabilitation (CR) program structure and preliminary outcomes from patients that completed a 12-week program after coronary artery bypass graft surgery (CABG). We aim to advocate the use of Telerehabilitation as a Phase II CR in patients immediately after the CABG. This approach was innovative and encouraging because the patients were still in subacute phase. The program can serve as a continuation of care for the patients after being discharged from a hospital while regaining their functional ability at home. Our preliminary outcomes demonstrated improvements in resting heart rate, activity level, nutrition status, self-efficacy for managing cardiac diseases, muscle strength, endurance and depression. There were no adverse events during the virtual sessions. Patient satisfaction score was high.

2022 AHA/ACC/HFSA Guideline for the Management of Heart Failure: A Report of the American College of Cardiology/American Heart Association Joint Committee on Clinical Practice Guidelines.

AIM: The "2022 AHA/ACC/HFSA Guideline for the Management of Heart Failure" replaces the "2013 ACCF/AHA Guideline for the Management of Heart Failure" and the "2017 ACC/AHA/HFSA Focused Update of the 2013 ACCF/AHA Guideline for the Management of Heart Failure." The 2022 guideline is intended to provide patient-centric recommendations for clinicians to prevent, diagnose, and manage patients with heart failure. METHODS: A comprehensive literature search was conducted from May 2020 to December 2020, encompassing studies, reviews, and other evidence conducted on human subjects that were published in English from MEDLINE (PubMed), EMBASE, the Cochrane Collaboration, the Agency for Healthcare Research and Quality, and other relevant databases. Additional relevant clinical trials and research studies, published through September 2021, were also considered. This guideline was harmonized with other American Heart Association/American College of Cardiology guidelines published through December 2021. Structure: Heart failure remains a leading cause of morbidity and mortality globally. The 2022 heart failure guideline provides recommendations based on contemporary evidence for the treatment of these patients. The recommendations present an evidence-based approach to managing patients with heart failure, with the intent to improve quality of care and align with patients' interests. Many recommendations from the earlier heart failure guidelines have been updated with new evidence, and new recommendations have been created when supported by published data. Value statements are provided for certain treatments with high-quality published economic analyses.

2022 AHA/ACC/HFSA Guideline for the Management of Heart Failure: Executive Summary: A Report of the American College of Cardiology/American Heart Association Joint Committee on Clinical Practice Guidelines.

AIM: The "2022 AHA/ACC/HFSA Guideline for the Management of Heart Failure" replaces the "2013 ACCF/AHA Guideline for the Management of Heart Failure" and the "2017 ACC/AHA/HFSA Focused Update of the 2013 ACCF/AHA Guideline for the Management of Heart Failure." The 2022 guideline is intended to provide patient-centric recommendations for clinicians to prevent, diagnose, and manage patients with heart failure. METHODS: A comprehensive literature search was conducted from May 2020 to December 2020, encompassing studies, reviews, and other evidence conducted on human subjects that were published in English from MEDLINE (PubMed), EMBASE, the Cochrane Collaboration, the Agency for Healthcare Research and Quality, and other relevant databases. Additional relevant clinical trials and research studies, published through September 2021, were also considered. This guideline was harmonized with other American Heart Association/American College of Cardiology guidelines published through December 2021. Structure: Heart failure remains a leading cause of morbidity and mortality globally. The 2022 heart failure guideline provides recommendations based on contemporary evidence for the treatment of these patients. The recommendations present an evidence-based approach to managing patients with heart failure, with the intent to improve quality of care and align with patients' interests. Many recommendations from the earlier heart failure guidelines have been updated with new evidence, and new recommendations have been created when supported by published data. Value statements are provided for certain treatments with high-quality published economic analyses.

2022 AHA/ACC/HFSA Guideline for the Management of Heart Failure: A Report of the American College of Cardiology/American Heart Association Joint Committee on Clinical Practice Guidelines.

AIM: The "2022 AHA/ACC/HFSA Guideline for the Management of Heart Failure" replaces the "2013 ACCF/AHA Guideline for the Management of Heart Failure" and the "2017 ACC/AHA/HFSA Focused Update of the 2013 ACCF/AHA Guideline for the Management of Heart Failure." The 2022 guideline is intended to provide patient-centric recommendations for clinicians to prevent, diagnose, and manage patients with heart failure. METHODS: A comprehensive literature search was conducted from May 2020 to December 2020, encompassing studies, reviews, and other evidence conducted on human subjects that were published in English from MEDLINE (PubMed), EMBASE, the Cochrane Collaboration, the Agency for Healthcare Research and Quality, and other relevant databases. Additional relevant clinical trials and research studies, published through September 2021, were also considered. This guideline was harmonized with other American Heart Association/American College of Cardiology guidelines published through December 2021. STRUCTURE: Heart failure remains a leading cause of morbidity and mortality globally. The 2022 heart failure guideline provides recommendations based on contemporary evidence for the treatment of these patients. The recommendations present an evidence-based approach to managing patients with heart failure, with the intent to improve quality of care and align with patients' interests. Many recommendations from the earlier heart failure guidelines have been updated with new evidence, and new recommendations have been created when supported by published data. Value statements are provided for certain treatments with high-quality published economic analyses.

2022 AHA/ACC/HFSA Guideline for the Management of Heart Failure: Executive Summary: A Report of the American College of Cardiology/American Heart Association Joint Committee on Clinical Practice Guidelines.

AIM: The "2022 AHA/ACC/HFSA Guideline for the Management of Heart Failure" replaces the "2013 ACCF/AHA Guideline for the Management of Heart Failure" and the "2017 ACC/AHA/HFSA Focused Update of the 2013 ACCF/AHA Guideline for the Management of Heart Failure." The 2022 guideline is intended to provide patient-centric recommendations for clinicians to prevent, diagnose, and manage patients with heart failure. METHODS: A comprehensive literature search was conducted from May 2020 to December 2020, encompassing studies, reviews, and other evidence conducted on human subjects that were published in English from MEDLINE (PubMed), EMBASE, the Cochrane Collaboration, the Agency for Healthcare Research and Quality, and other relevant databases. Additional relevant clinical trials and research studies, published through September 2021, were also considered. This guideline was harmonized with other American Heart Association/American College of Cardiology guidelines published through December 2021. STRUCTURE: Heart failure remains a leading cause of morbidity and mortality globally. The 2022 heart failure guideline provides recommendations based on contemporary evidence for the treatment of these patients. The recommendations present an evidence-based approach to managing patients with heart failure, with the intent to improve quality of care and align with patients' interests. Many recommendations from the earlier heart failure guidelines have been updated with new evidence, and new recommendations have been created when supported by published data. Value statements are provided for certain treatments with high-quality published economic analyses.

2022 American College of Cardiology/American Heart Association/Heart Failure Society of America Guideline for the Management of Heart Failure: Executive Summary.

BACKGROUND: The 2022 American College of Cardiology/American Heart Association/Heart Failure Society of America (AHA/ACC/HFSA) Guideline for the Management of Heart Failure replaces the 2013 ACCF/AHA Guideline for the Management of Heart Failure and the 2017 ACC/AHA/HFSA Focused Update of the 2013 ACCF/AHA Guideline for the Management of Heart Failure. The 2022 guideline is intended to provide patient-centric recommendations for clinicians to prevent, diagnose and manage patients with heart failure. METHODS: A comprehensive literature search was conducted from May 2020 to December 2020, encompassing studies, reviews and other evidence conducted in human subjects that were published in English from MEDLINE (PubMed), EMBASE, the Cochrane Collaboration, the Agency for Healthcare Research and Quality, and other relevant databases. Additional relevant clinical trials and research studies published through September 2021 were also considered. This guideline was harmonized with other American Heart Association/American College of Cardiology guidelines published through December 2021. RESULTS AND CONCLUSIONS: Heart failure remains a leading cause of morbidity and mortality globally. The 2022 heart failure guideline provides recommendations based on contemporary evidence for the treatment of these patients. The recommendations present an evidence-based approach to managing patients with heart failure, with the intent to improve quality of care and align with patients' interests. Many recommendations from the earlier heart failure guidelines have been updated with new evidence, and new recommendations have been created when supported by published data. Value statements are provided for certain treatments that have high-quality published economic analyses.

Acute Kidney Injury With Ventricular Assist Device Placement: National Estimates of Trends and Outcomes.

RATIONALE & OBJECTIVE: Ventricular assist devices (VADs) are used for end-stage heart failure not amenable to medical therapy. Acute kidney injury (AKI) in this setting is common due to heart failure decompensation, surgical stress, and other factors. Little is known about national trends in AKI diagnosis and AKI requiring dialysis (AKI-D) and associated outcomes with VAD implantation. We investigated national estimates and trends for diagnosed AKI, AKI-D, and associated patient and resource utilization outcomes in hospitalizations in which implantable VADs were placed. STUDY DESIGN: Cohort study of 20% stratified sample of US hospitalizations. SETTING & PARTICIPANTS: Patients who underwent implantable VAD placement in 2006 to 2015. EXPOSURE: No AKI diagnosis, AKI without dialysis, AKI-D. OUTCOMES: In-hospital mortality, length of stay, estimated hospitalization costs. ANALYTICAL APPROACH: Multivariate logistic and linear regression using survey design methods to account for stratification, clustering, and weighting. RESULTS: An estimated 24,140 implantable VADs were placed, increasing from 853 in 2006 to 3,945 in 2015. AKI was diagnosed in 56.1% of hospitalizations and AKI-D occurred in 6.5%. AKI diagnosis increased from 44.0% in 2006 to 2007 to 61.7% in 2014 to 2015; AKI-D declined from 9.3% in 2006 to 2007 to 5.2% in 2014 to 2015. Mortality declined in all AKI categories but this varied by category: those with AKI-D had the smallest decline. Adjusted hospitalization costs were 19.1% higher in those with diagnosed AKI and 39.6% higher in those with AKI-D, compared to no AKI. LIMITATIONS: Administrative data; timing of AKI with respect to VAD implantation cannot be determined; limited pre-existing chronic kidney disease ascertainment; discharge weights not derived for subpopulation of interest. CONCLUSIONS: A decreasing proportion of patients undergoing VAD implantation experience AKI-D, but mortality among these patients remains high. AKI diagnosis with VAD implantation is increasing, possibly reflecting changes in AKI surveillance, awareness, and coding.

Implantable Ventricular Assist Device Use and Outcomes in People With End-Stage Renal Disease.

BACKGROUND: People with end-stage renal disease (ESRD) are at risk for advanced heart failure, but little is known about use and outcomes of durable mechanical circulatory support in this setting. We examined use and outcomes of implantable ventricular assist devices (VADs) in a national ESRD cohort. METHODS AND RESULTS: We performed a retrospective cohort study of Medicare beneficiaries with ESRD who underwent implantable VAD placement from 2006 to 2014. We examined in-hospital and 1-year mortality, all-cause and cause-specific hospitalizations, and heart/kidney transplantation outcomes. We investigated as predictors demographic factors, time-period of VAD implantation, primary or post-cardiotomy implantation, and duration of ESRD before VAD implantation. We identified 96 people with ESRD who underwent implantable VAD placement. At time of VAD implantation, 74 (77.1%) were receiving hemodialysis, 10 (10.4%) were receiving peritoneal dialysis and 12 (12.5%) had renal transplant. Time from incident ESRD to VAD implantation was median 4.0 (interquartile range 1.1, 8.2) years. Mortality during the implantation hospitalization was 40.6%. Within 1 year of implantation 61.5% of people had died. On multivariable analysis, males had half the mortality risk of females. Lower mortality risk was also seen with VAD implantation in a primary setting, and with more recent year of implantation, but these results did not reach statistical significance. CONCLUSIONS: Medicare beneficiaries with ESRD are undergoing durable VAD implantation, often several years after incident ESRD, although in low numbers. Mortality is high among these patients, highlighting the need for investigations to improve treatment selection and management.

Myocardial perfusion reserve and global longitudinal strain as potential markers of coronary allograft vasculopathy in late-stage orthotopic heart transplantation.

Coronary allograft vasculopathy (CAV) is a major cause of mortality in late-stage orthotopic heart transplantation (OHT) patients. Recent evidence has shown that myocardial perfusion reserve (MPR) derived from vasodilator cardiovascular magnetic resonance imaging (vCMR) and global longitudinal strain (GLS) from transthoracic echocardiography (TTE) are useful to detect CAV. However, previous studies have not comprehensively addressed whether these parameters are confounded by allograft rejection, myocardial scar/fibrosis, or allograft dysfunction. Our aim was to determine whether changes in late post-OHT MPR and GLS are due to CAV or other confounding factors. Twenty OHT patients (time from transplant to vCMR was 8.1 ± 4.1 years) and 30 controls (10 healthy volunteers and 20 with prior myocardial infarction to provide perspective with regards to the severity of any abnormalities seen in post-OHT patients) underwent vasodilator vCMR from which MPR index (MPRi), left ventricular ejection fraction (LVEF), and burden of late gadolinium enhancement (LGE) were quantified. TTE was used to measure GLS. The presence of CAV was determined from invasive coronary angiograms using thrombolysis in myocardial infarction (TIMI) frame counts and grading severity per guidelines. Previous endomyocardial biopsies were reviewed to assess association with episodes of rejection. We examined the correlations between MPRi and GLS with markers of CAV, allograft function, scar/fibrosis, and rejection. MPRi was abnormal in post-OHT patients compared to both healthy volunteers and MI controls. While there was no relationship between MPRi or GLS and LVEF, episodes of rejection, or LGE burden, both MPRi and GLS were associated with TIMI frame counts and presence and severity of CAV. Additionally, MPRi correlated with GLS (R = 0.68, P = 0.0002). In conclusion, MPRi and GLS are abnormal in late-stage OHT and associated with CAV, but not related to allograft rejection, myocardial scar/fibrosis, or allograft dysfunction. Non-invasive monitoring of MPRi and GLS may be a useful strategy to detect CAV.

Mapping the Informed Consent Process for Left Ventricular Assist Devices.

Ethical, practical, and medical challenges affect decisions about left ventricular assist device (LVAD) implantation. The informed consent document (IC-Doc) is integral to the decision-making process and structures informed consent conversations. The objective of this study was to analyze IC-Docs to identify the information patients and their families receive about LVAD implantation to create a model IC-Doc. We requested IC-Doc for LVAD implantation from LVAD programs in the United States. We analyzed them in three areas: medical and technical content, patient knowledge gaps, and syntax. Nineteen IC-Docs representing all United Network of Organ Sharing regions were included. Seventeen (89.5%) mentioned the indications for LVAD implantation (bridge to transplant or destination therapy), and six indicated which category applied to the patient. Palliative care was mentioned as an alternative in nine (47.4%); no IC-Doc discussed nonsurgical palliative care. Eight forms (42.1%) specifically mentioned turning off the LVAD. Eighteen forms mention general bleeding, and four referred to long-term gastrointestinal bleeding. Two IC-Docs addressed driveline infections. One form was written at an 8th grade reading level. There is wide variation in LVAD IC-Docs and omission of some benefits and risks. We have written an IC-Doc that meets criteria for disclosure, fills many knowledge gaps, and has an acceptable readability score.

Routine C4d immunohistochemistry in cardiac allografts: Long-term outcomes.

BACKGROUND: In the past decade, C4d has emerged as a potential marker for antibody-mediated rejection (AMR); however, evidence on its use as a prognostic tool has been controversial. Although the International Society for Heart and Lung Transplantation guideline recommends early routine surveillance of C4d in heart transplantation, there is no consensus on its value in the pathologic assessment of AMR. Herein we present a correlation analysis of C4d immunoreactivity in endomyocardial biopsies with clinical cardiac dysfunction, cellular rejection, human leukocyte antigen (HLA) status, cardiac allograft vasculopathy (CAV) and death. METHODS: A total of 5,840 endomyocardial biopsies from 296 heart transplant recipients (January 2004 to December 2014) were stained prospectively for C4d. Strong, diffuse endothelial staining was considered positive. All patients had at least 1 year of follow-up. Positive C4d staining was present in 53 biopsies from 28 patients. Sixteen of 28 patients had clinically significant cardiac dysfunction at the time of positive biopsy. In C4d-positive patients, the mean panel-reactive antibody (PRA) level was 33%. Ten patients demonstrated a first C4d positivity within the first year post-transplant, whereas 18 patients had C4d positivity after 1 year post-transplant. At autopsy, all 11 C4d-positive patients examined demonstrated cardiac allograft vasculopathy (CAV) as the underlying cause of death. In contrast, only 2 of 8 (25%) C4d-negative patients had CAV at autopsy. In the surviving cohort, there was an angiographic diagnosis of higher-than-moderate CAV in 10 patients (3.8%). RESULTS: C4d-positive patients contributed to 67% of the overall institutional mortality in heart transplant recipients. Late C4d positivity (>1 year post-transplant) demonstrated an even higher risk for developing CAV and poor prognosis than early C4d positivity (within 1 year). In the C4d-negative group with postmortem examination, 75% (6 of 8) deaths were due to non-cardiac causes. CONCLUSIONS: Our findings show a positive association of C4d with CAV and death. We identified a prognostic role for C4d in heart transplantation warranting routine long-term detection of this marker in the pathologic evaluation of cardiac AMR.

Elevated Angiopoietin-2 Level in Patients With Continuous-Flow Left Ventricular Assist Devices Leads to Altered Angiogenesis and Is Associated With Higher Nonsurgical Bleeding.

BACKGROUND: Nonsurgical bleeding is the most common adverse event in patients with continuous-flow left ventricular assist devices (LVADs) and is caused by arteriovenous malformations. We hypothesized that deregulation of an angiogenic factor, angiopoietin-2 (Ang-2), in patients with LVADs leads to increased angiogenesis and higher nonsurgical bleeding. METHODS: Ang-2 and thrombin levels were measured by ELISA and Western blotting, respectively, in blood samples from 101 patients with heart failure, LVAD, or orthotopic heart transplantation. Ang-2 expression in endothelial biopsy was quantified by immunofluorescence. Angiogenesis was determined by in vitro tube formation from serum from each patient with or without Ang-2-blocking antibody. Ang-2 gene expression was measured by reverse transcription-polymerase chain reaction in endothelial cells incubated with plasma from each patient with or without the thrombin receptor blocker vorapaxar. RESULTS: Compared with patients with heart failure or those with orthotopic heart transplantation, serum levels and endothelial expression of Ang-2 were higher in LVAD patients (P=0.001 and P<0.001, respectively). This corresponded to an increased angiogenic potential of serum from patients with LVADs (P<0.001), which was normalized with Ang-2 blockade. Furthermore, plasma from LVAD patients contained higher amounts of thrombin (P=0.003), which was associated with activation of the contact coagulation system. Plasma from LVAD patients induced more Ang-2 gene expression in endothelial cells (P<0.001), which was reduced with thrombin receptor blockade (P=0.013). LVAD patients with Ang-2 levels above the mean (12.32 ng/mL) had more nonsurgical bleeding events compared with patients with Ang-2 levels below the mean (P=0.003). CONCLUSIONS: Our findings indicate that thrombin-induced Ang-2 expression in LVAD patients leads to increased angiogenesis in vitro and may be associated with higher nonsurgical bleeding events. Ang-2 therefore may contribute to arteriovenous malformation formation and subsequent bleeding in LVAD patients.

Predictors of survival following trans-catheter aortic valve closure for left ventricular assist device associated aortic insufficiency.

OBJECTIVE: This study sought to assess the long-term clinical benefits and predictors of survival of trans-catheter aortic valve closure in left ventricular assist device (LVAD) patients. BACKGROUND: LVADs have been shown to increase survival and quality of life in patients with end-stage heart failure. However, severe aortic insufficiency (AI) can develop in up to 50% of patients at 12 months resulting in significant morbidity and mortality. Trans-catheter treatment of LVAD associated AI has emerged as a potential alternative to surgical treatment. METHODS: We conducted a retrospective analysis of all patients undergoing trans-catheter aortic valve closure using an Amplatzer Multi-Fenestrated Septal Occluder "Cribriform" device to assess potential clinical and procedural factors associated with survival. Student's t-tests were used to compare baseline patient demographics and procedural characteristics, as well as patient outcomes immediately post procedure and at 6 months. A P-value of less than 0.05 was considered statistically significant. RESULTS: A total of 10 patients (70% male, median age 59 years) were included. Technical success was accomplished in 100% of patients with a 6 month survival rate of 30% (3/10). Compared with survivors, non-survivors had a higher rate of pre-procedural clinical co-morbidities, an increased likelihood of right ventricular failure, and received larger occluder devices. CONCLUSIONS: Trans-catheter aortic valve closure successfully treats late severe AI in LVAD patients, however, the presence or development of right heart failure portends a worse prognosis. Further studies are needed to investigate the factors involved in the development of right ventricular failure, and potential treatment, in patients undergoing trans-catheter aortic valve closure.

Successful percutaneous trans-catheter treatment of left ventricular assist device outflow graft stenosis with a covered stent.

Left ventricular assist devices improve survival in patients with advanced heart failure but can be associated with significant complication including infection, pump thrombosis, and de novo severe aortic insufficiency. Outflow graft stenosis is a much more rare complication, but one with significant hemodynamic consequences. Surgical repair is often necessary, but many patients are too high risk for further surgical intervention. We describe the first case of left ventricular assist device outflow graft stenosis treated with percutaneous trans-catheter placement of a covered stent.

Reversal of impaired myocardial beta-adrenergic receptor signaling by continuous-flow left ventricular assist device support.

BACKGROUND: Myocardial beta-adrenergic receptor (beta-AR) signaling is severely impaired in chronic heart failure (HF). This study was conducted to determine if left ventricular (LV) beta-AR signaling could be restored after continuous-flow LV assist device (LVAD) support. METHODS: Twelve patients received LVADs as a bridge to transplant. Paired LV biopsy specimens were obtained at the time of LVAD implant (HF group) and transplant (LVAD group). The mean duration of LVAD support was 152 +/- 34 days. Myocardial beta-AR signaling was assessed by measuring adenylyl cyclase (AC) activity, total beta-AR density (B(max)), and G protein-coupled receptor kinase-2 (GRK2) expression and activity. LV specimens from 8 non-failing hearts (NF) were used as controls. RESULTS: Basal and isoproterenol-stimulated AC activity was significantly lower in HF vs NF, indicative of beta-AR uncoupling. Continuous-flow LVAD support restored basal and isoproterenol-stimulated AC activity to levels similar to NF. B(max) was decreased in HF vs NF and increased to nearly normal in the LVAD group. GRK2 expression was increased 2.6-fold in HF vs NF and was similar to NF after LVAD support. GRK2 activity was 3.2-fold greater in HF vs NF and decreased to NF levels in the LVAD group. CONCLUSIONS: Myocardial beta-AR signaling can be restored to nearly normal after continuous-flow LVAD support. This is similar to previous data for volume-displacement pulsatile LVADs. Decreased GRK2 activity is an important mechanism and indicates that normalization of the neurohormonal milieu associated with HF is similar between continuous-flow and pulsatile LVADs. This may have important implications for myocardial recovery.

Immunohistochemistry staining of C4d to diagnose antibody-mediated rejection in cardiac transplantation.

BACKGROUND: Antibody-mediated rejection (AMR) is associated with poorer outcomes in cardiac transplantation. The clinical diagnosis of AMR has been confirmed by immunofluorescence for C4d on fresh-frozen cardiac tissue. Immunohistochemistry (IHC) has been suggested as a more practical diagnostic tool because it can be performed on routine paraffin-embedded tissue. There are few published data about hemodynamics and C4d staining. We prospectively performed C4d staining on endomyocardial biopsies (EMBs) and present the pattern of tissue staining and its correlation with intracardiac hemodynamics. METHODS: EMBs were evaluated by IHC for C4d staining and graded for cellular rejection using ISHLT criteria on hematoxylin-and-eosin-stained sections. Hemodynamic measurements were taken concurrently. Staining for C4d was described as absent, present with serum staining, or present with only tissue staining. The pattern of tissue staining was categorized by location of staining and correlated with intracardiac hemodynamics. Patient demographics, cytomegalovirus status, panel-reactive antibody levels and hemodynamics were analyzed by analysis of variance and chi-square statistics. RESULTS: Of the 400 EMBs, 50 had no C4d staining, 330 had tissue and serum staining, whereas 20 had only tissue staining. Forty EMBs had endothelial staining, including 35 with serum and 5 with isolated tissue staining. Endothelial staining correlated with higher intracardiac pressures. CONCLUSIONS: IHC staining for C4d has been suggested for the diagnosis of AMR. Our data suggest there is a high rate of background C4d staining, but endothelial staining correlates with poorer hemodynamics. Methods for IHC staining and interpretation need to be standardized for widespread use and clinical studies.