Human induced pluripotent stem cells (hiPSC) harbor the potential to differentiate into diverse cardiac cell types. Previous experimental efforts were primarily directed at the generation of hiPSC-derived cells with ventricular cardiomyocyte characteristics. Aiming at a straightforward approach for pacemaker cell modeling and replacement, we sought to selectively differentiate cells with nodal-type properties. hiPSC were differentiated into spontaneously beating clusters by co-culturing with visceral endoderm-like cells in a serum-free medium. Subsequent culturing in a specified fetal bovine serum (FBS)-enriched cell medium produced a pacemaker-type phenotype that was studied in detail using quantitative real-time polymerase chain reaction (qRT-PCR), immunocytochemistry, and patch-clamp electrophysiology. Further investigations comprised pharmacological stimulations and co-culturing with neonatal cardiomyocytes. hiPSC co-cultured in a serum-free medium with the visceral endoderm-like cell line END-2 produced spontaneously beating clusters after 10–12 days of culture. The pacemaker-specific genes HCN4, TBX3, and TBX18 were abundantly expressed at this early developmental stage, while levels of sarcomeric gene products remained low. We observed that working-type cardiomyogenic differentiation can be suppressed by transfer of early clusters into a FBS-enriched cell medium immediately after beating onset. After 6 weeks under these conditions, sinoatrial node (SAN) hallmark genes remained at high levels, while working-type myocardial transcripts (NKX2.5, TBX5) were low. Clusters were characterized by regular activity and robust beating rates (70–90 beats/min) and were triggered by spontaneous Ca2+ transients recapitulating calcium clock properties of genuine pacemaker cells. They were responsive to adrenergic/cholinergic stimulation and able to pace neonatal rat ventricular myocytes in co-culture experiments. Action potential (AP) measurements of cells individualized from clusters exhibited nodal-type (63.4%) and atrial-type (36.6%) AP morphologies, while ventricular AP configurations were not observed. We provide a novel culture media-based, transgene-free approach for targeted generation of hiPSC-derived pacemaker-type cells that grow in clusters and offer the potential for disease modeling, drug testing, and individualized cell-based replacement therapy of the SAN.

Background: Permanent pacemaker (PPM) implantation after heart transplantation (HTX) may be required due to severe bradycardia. The aim of this study was to investigate the risk factors, indications, perioperative outcomes and complications of PPM implantation after HTX as well as the underlying effect on post-transplant mortality including causes of death. Methods: This registry study included 621 patients receiving HTX at Heidelberg Heart Center between 1989 and 2018. Patients were stratified by PPM implantation after HTX. Data analysis of risk factors for PPM implantation included donor and recipient demographics, post-transplant medication, mortality, and causes of death. Results: Thirty-six patients (5.8%) received PPM implantation after HTX, 12 (33.3%) with early PPM and 24 (66.7%) with late PPM. Indications for PPM implantation after HTX included sinus node dysfunction (SND) (n=15; 41.7%) and atrioventricular block (AVB) (n=21; 58.3%). Multivariate analysis revealed recipient body mass index (BMI) [hazard ratio (HR): 1.10; confidence interval (CI): 1.01–1.21; P=0.03], donor age (HR: 1.07; CI: 1.03–1.10; P<0.01), and biatrial HTX (HR: 2.63; CI: 1.22–5.68; P=0.01) as significant risk factors for PPM implantation after HTX. Kaplan–Meier estimator displayed a statistically significant inferior 5-year post-transplant survival among patients with early PPM after HTX in comparison to patients with late PPM or no PPM after HTX (P<0.01) along with a higher percentage of death due to infection (P<0.01). Conclusions: Multivariate risk factors for PPM implantation after HTX include recipient BMI, donor age, and biatrial HTX. Early PPM implantation after HTX is associated with increased 5-year post-transplant mortality due to infection.

Aims Severely elevated pre‐transplant pulmonary vascular resistance (PVR) has been linked to adverse effects after heart transplantation (HTX). The impact of a moderately increased PVR before HTX on post‐transplant outcomes remains uncertain. The aim of this study was to investigate the effects of an elevated pre‐transplant PVR ≥ 300 dyn·s·cm⁻⁵ (≥3.75 Wood units) on outcomes after HTX. Methods and results This observational retrospective single‐centre study included 561 patients receiving HTX at Heidelberg Heart Center between 1989 and 2015. Patients were stratified by degree of pre‐transplant PVR. Analyses covered demographics, post‐transplant medication, mortality and causes of death after HTX, early post‐transplant atrial fibrillation (AF), and length of the initial hospital stay after HTX. Ninety‐four patients (16.8%) had a PVR ≥ 300 dyn·s·cm⁻⁵ (≥3.75 Wood units). These patients had a higher rate of early post‐transplant AF [20.2 vs. 10.7%, difference: 9.5%, 95% confidence interval (CI): 0.9–18.1%, P = 0.01] and an increased 30 day post‐transplant mortality (25.5 vs. 6.4%, hazard ratio: 4.4, 95% CI: 2.6–7.6, P < 0.01), along with a higher percentage of death due to transplant failure (21.2 vs. 4.1%, difference: 17.1%, 95% CI: 8.7–25.5%, P < 0.01). Multivariate analysis revealed a PVR ≥ 300 dyn·s·cm⁻⁵ (≥3.75 Wood units) as a significant risk factor for increased 30 day mortality after HTX (hazard ratio: 4.4, 95% CI: 2.5–7.6, P < 0.01). Kaplan–Meier estimator showed a lower 2 year survival after HTX (P < 0.01) in patients with a PVR ≥ 300 dyn·s·cm⁻⁵ (≥3.75 Wood units). Conclusions Elevated pre‐transplant PVR ≥ 300 dyn·s·cm⁻⁵ (≥3.75 Wood units) is associated with early post‐transplant AF and increased mortality after HTX.

Aims: Cardiac transplant recipients often suffer from type 2 diabetes mellitus (T2DM) but its influence on graft failure and post-transplant mortality remains unknown. The aim of this study was to investigate the long-term effects of pre-transplant T2DM in patients after heart transplantation (HTX).Methods: This study included a total of 376 adult patients who received HTX at Heidelberg Heart Center between 01/01/2000 and 01/10/2016. HTX recipients were stratified by diagnosis of T2DM at the time of HTX. Patients with T2DM were further subdivided by hemoglobin A1c (HbA1c ≥ 7.0%). Analysis included donor and recipient data, immunosuppressive drugs, concomitant medications, post-transplant mortality, and causes of death. Five-year post-transplant mortality was further assessed by multivariate analysis (Cox regression) and Kaplan–Meier estimator.Results: About one-third of all HTX recipients had T2DM (121 of 376 [32.2%]). Patients with T2DM showed an increased 5-year post-transplant mortality (41.3% versus 29.8%; P = 0.027) and had a higher percentage of death due to graft failure (14.9% versus 7.8%; P = 0.035). Multivariate analysis showed T2DM (HR: 1.563; 95% CI: 1.053–2.319; P = 0.027) as an independent risk factor for 5-year mortality after HTX. Kaplan–Meier analysis showed a significantly better 5-year post-transplant survival of patients with T2DM and a HbA1c < 7.0% than patients with T2DM and a HbA1c ≥ 7.0% (68.7% versus 46.3%; P = 0.008) emphasizing the clinical relevance of a well-controlled T2DM in HTX recipients.Conclusion: Pre-transplant T2DM is associated with higher graft failure and increased 5-year mortality after HTX.

Objectives: COPD is associated with reduced physical activity, an increased risk for pulmonary infections, and impaired survival in nontransplant patients. The aim of this study was to investigate the influence of COPD in patients after heart transplantation (HTX). Methods: We performed an observational retrospective single-center study of 259 patients receiving HTX at Heidelberg University Hospital between 2003 and 2012. Patients were stratified by the Tiffeneau index (forced expiratory volume in 1 second/forced vital capacity [FEV1/FVC]) <0.70 before HTX. The analysis included demographics, posttransplant medication, length of the initial hospital stay after HTX, early posttransplant atrial fibrillation (AF), mortality, and causes of death. Results: In total, 63 (24.3%) patients had an FEV1/FVC <0.70. These patients showed a prolonged hospital stay after HTX (52.0 days vs 43.4 days, mean difference (MD) = 8.6 days, 95% CI: 0.2, 17.0 days), a higher rate of early posttransplant AF (19.0% vs 8.2%, MD = 10.8%, 95% CI: 0.4%, 21.2%), and an increased 30-day mortality (9.5% vs 2.6%, HR = 3.79, 95% CI: 1.16, 12.40). Kaplan–Meier analysis showed a significant inferior 5-year survival in patients with an FEV1/FVC <0.70, along with a higher percentage of death due to transplant failure and infection/sepsis. In addition, a multivariate analysis for mortality within 5 years after HTX indicated an FEV1/FVC <0.70 as a significant risk factor for impaired 5-year posttransplant survival (HR =4.77, 95% CI: 2.76, 8.22). Conclusion: COPD in patients after HTX is associated with a prolonged hospital stay, early posttransplant AF, and impaired posttransplant survival.

Aims Atrial fibrillation (AF) after heart transplantation (HTX) is associated with worse clinical outcomes. The current study aimed to analyse the association between AF before HTX and AF within 30 days after HTX. Methods and results This study included 639 adults who received HTX at Heidelberg Heart Center. Patients were subdivided into four groups depending on the status of AF before and after HTX. Analyses comprised recipient and donor data, medication, echocardiographic features, permanent pacemaker implantation, stroke, and mortality after HTX. Three hundred thirty-two patients (52.0%) had neither AF before nor after HTX, 15 patients (2.3%) had no AF before HTX but showed AF after HTX, 219 patients (34.3%) showed AF before HTX but had no AF after HTX, and 73 patients (11.4%) had AF before and after HTX. Patients with AF before and after HTX had a higher 1 year post-transplant mortality (39.7%) than patients without AF before or after HTX (18.1%, P < 0.01). Secondary outcomes showed a higher percentage of enlarged atria, ventricular dysfunction, mitral regurgitation, 1-year stroke, and 1-year permanent pacemaker implantation in patients with AF before and after HTX. Multivariate analysis revealed a six-fold elevated risk for post-transplant AF in patients with AF before HTX (hazard ratio: 6.59, confidence interval: 3.72–11.65; P < 0.01). Further risk factors for post-transplant AF were higher donor age and prolonged ischaemic time, whereas total orthotopic HTX was associated with a two-fold lower risk for post-transplant AF. Conclusions Atrial fibrillation before HTX is a risk factor for post-transplant AF, permanent pacemaker implantation, and mortality after HTX.