How to counteract the lack of donor tissue in cardiac surgery? Initial experiences with a newly established homograft procurement program.

Homograft heart valves may have significant advantages and are preferred for the repair of congenital valve malformations, especially in young women of childbearing age, athletes and in patients with active endocarditis. A growing problem, however, is the mismatch between tissue donation and the increasing demand. The aim of this paper is to describe the initiation process of a homograft procurement program to attenuate the shortage of organs. A comprehensive description of the infrastructure and procedural steps required to initiate a cardiac and vascular tissue donation program combined with a prospective follow-up of all homografts explanted at our institution. Between January 2020 and May 2022, 28 hearts and 12 pulmonary bifurcations were harvested at our institution and delivered to the European homograft bank. Twenty-seven valves (19 pulmonary valves, 8 aortic valves) were processed and allocated for implantation. The reasons for discarding a graft were either contamination (n = 14), or morphology (n = 13) or leaflet damage (n = 2). Five homografts (3 PV, 2 AV) have been cryopreserved and stored while awaiting allocation. One pulmonary homograft with a leaflet cut was retrieved by bicuspidization technique and awaits allocation, as a highly requested small diameter graft. The implementation of a tissue donation program in cooperation with a homograft bank can be achieved with reasonable additional efforts at a transplant center with an in-house cardiac surgery department. Challenging situations with a potential risk of tissue injury during procurement include re-operation, harvesting by a non-specialist surgeon and prior central cannulation for mechanical circulatory support.

ECMO therapy in COVID-19: An experience from Zurich.

BACKGROUND: The current coronavirus disease 2019 (COVID-19) pandemic has a huge impact on society and the economy and represents one of the biggest challenges for healthcare systems all over the world. Reports from healthcare institutions in different countries show a variety of crisis exit strategies. METHODS: The following is a review and update of the situation and crisis management in Zürich and Switzerland with a special focus on the impact on the cardiac surgery program and extracorporeal membrane oxygenation (ECMO)-therapy in COVID-19. RESULTS: Regional and national measures had avoided the collapse of the health system in Switzerland. There was a reduction of over 50% of the surgical and transcatheter caseload during the first wave of the pandemic. Twenty-three ECMO devices, 150 oxygenators, and more than 300 different cannulas were at our disposal. Between March and May 2020, nine COVID-19 patients were treated by us with ECMO-therapy. Three patients were transported by us from distant institutions. Median age at ECMO implantation was 59 years. Two patients died on support. CONCLUSIONS: Measures to prevent a collapse of the healthcare system were effective. Our local ECMO-Program on the ongoing COVID-19 pandemic has proven to be a useful tool to control mortality and organ failure in critically ill patients.

Transcatheter mitral valve repair using the Cardioband® system: Histopathological insights in device ingrowth and biocompatibility.

Surgical implantation of a complete or incomplete ring to reduce the valve annulus and improve leaflet coaptation is the mainstay of mitral valve surgery. The Cardioband® system (Edwards Lifesciences) was designed to address the pathophysiological mechanism of annular dilatation through a catheter-based approach. We present the histopathological workup of a Cardioband® device, which had been implanted 21 months earlier in a 34-year-old male with ischemic cardiomyopathy. Device examination demonstrate a well-positioned and securely anchored device. The described tissue reactions may have an impact on choice of device and timing in case of re-do surgery.

Indications and outcomes of second aortic procedures after acute type A dissection repair.

OBJECTIVES: Aortic arch or aortic root replacement is not performed in all cases of acute type A aortic dissection (ATAD), and a second aortic procedure will become necessary over time for some patients. Indications and outcomes, of second aortic procedures have not been studied extensively. METHODS: Characteristics and in-hospital outcomes of all patients undergoing surgical repair for type A acute aortic dissection were analysed and patients needing second aortic procedure during follow-up were identified. The latter group was divided in 2 subgroups: on-pump includes patients operated on using cardiopulmonary bypass and off-pump without cardiopulmonary bypass. RESULTS: A total of 638 patients underwent surgery for ATAD; 8% required a second aortic procedure. The most frequent indication for the second aortic procedure was dehiscence of suture lines (44%), followed by arch dilatation (24%). In-hospital mortality was 12%. Isolated ascending aorta replacement at the first surgery was associated with higher incidence of second aortic procedure (P = 0.006). Most patients in the on-pump group underwent a proximal reoperation (75%), with a mortality rate of 14.2%. In-hospital mortality of patients in the off-pump group was 7.7%. Long-term survival analysis showed no difference between groups (P = 0,526), Off-pump patients have greater likelihood of a second intervention during follow-up (P = 0.004). CONCLUSIONS: Extended aortic root surgery and customized aortic arch repair in ATAD could be reasonable to reduce the incidence and mortality of high-risk second aortic procedures.

The oxidative burst reaction in mammalian cells depends on gravity.

Gravity has been a constant force throughout the Earth's evolutionary history. Thus, one of the fundamental biological questions is if and how complex cellular and molecular functions of life on Earth require gravity. In this study, we investigated the influence of gravity on the oxidative burst reaction in macrophages, one of the key elements in innate immune response and cellular signaling. An important step is the production of superoxide by the NADPH oxidase, which is rapidly converted to H2O2 by spontaneous and enzymatic dismutation. The phagozytosis-mediated oxidative burst under altered gravity conditions was studied in NR8383 rat alveolar macrophages by means of a luminol assay. Ground-based experiments in "functional weightlessness" were performed using a 2 D clinostat combined with a photomultiplier (PMT clinostat). The same technical set-up was used during the 13th DLR and 51st ESA parabolic flight campaign. Furthermore, hypergravity conditions were provided by using the Multi-Sample Incubation Centrifuge (MuSIC) and the Short Arm Human Centrifuge (SAHC). The results demonstrate that release of reactive oxygen species (ROS) during the oxidative burst reaction depends greatly on gravity conditions. ROS release is 1.) reduced in microgravity, 2.) enhanced in hypergravity and 3.) responds rapidly and reversible to altered gravity within seconds. We substantiated the effect of altered gravity on oxidative burst reaction in two independent experimental systems, parabolic flights and 2D clinostat / centrifuge experiments. Furthermore, the results obtained in simulated microgravity (2D clinorotation experiments) were proven by experiments in real microgravity as in both cases a pronounced reduction in ROS was observed. Our experiments indicate that gravity-sensitive steps are located both in the initial activation pathways and in the final oxidative burst reaction itself, which could be explained by the role of cytoskeletal dynamics in the assembly and function of the NADPH oxidase complex.

Percutaneous large-bore aspiration embolectomy with veno-arterial extracorporal membrane oxygenation support or standby in patients with high-risk pulmonary embolism and contraindications to thrombolysis: a preliminary single centre experience.

AIMS: Large-bore catheter aspiration embolectomy reduces thrombus burden and right ventricle strain and improves haemodynamics after pulmonary embolism (PE). Sparse data are available for patients with high-risk PE and contraindications to thrombolysis or thrombolysis failure, particularly if veno-arterial extracorporal membrane oxygenation (VA-ECMO) is required. METHODS AND RESULTS: All patients with acute high-risk PE and contraindications to thrombolysis undergoing FlowTriever® percutaneous embolectomy and VA-ECMO circulatory support (or standby) at the University Hospital Zurich between April 2021 and August 2022 were retrospectively analysed. The primary outcome was the combination of recurrent PE, heart failure hospitalization, and all-cause death at 30 days. The analysis included 15 patients: mean age was 63.1 years and 14 (93%) were men. Overall, four (27%) patients presented with cardiac arrest, eight (53%) with ongoing obstructive shock, and three (20%) with persistent arterial hypotension. Veno-arterial extracorporal membrane oxygenation was implanted prior to aspiration embolectomy in eight (53%) patients. Three of seven patients without initial VA-ECMO support experienced periprocedural cardiac arrest, of whom two received ECMO support before completion of embolectomy. Veno-arterial extracorporal membrane oxygenation weaning was successful in all patients after a mean of 5.4 days. There was one periprocedural death in a patient who did not receive VA-ECMO support following a periprocedural cardiac arrest. The primary outcome at 30 days occurred in five (33.3%; 95% confidence interval 13.0-61.3%) patients. CONCLUSION: This study provides preliminary evidence for the feasibility of percutaneous large-bore aspiration embolectomy in combination with VA-ECMO support (or standby) in patients with high-risk PE and contraindications to thrombolysis.

Twenty-five year experience with aortic valve-sparing root replacement in a single teaching center.

Objectives: Aortic valve-sparing root replacement (AVSRR) is a technically demanding procedure. In experienced centers it offers excellent short- and long-term results, making the procedure an attractive alternative for aortic root replacement especially in young patients. The aim of this study was to analyze long-term results of AVSRR using the David operation in our institution over the last 25 years. Methods: This is a single-center retrospective analysis of outcomes of David operations performed in a teaching institution not running a large AVSRR-program. Pre-, intra- and postoperative data were collected from the institutional electronic medical record system. Follow-up data were collected through direct contact of the patients and their cardiologists/primary care physicians. Results: Between 02/1996 and 11/2019, 131 patients underwent David operation in our institution by a total of 17 different surgeons. Median age was 48 (33-59), 18% were female. Elective surgery was performed in 89% of the cases, 11% were operated as emergency in the setting of an acute aortic dissection. Connective tissue disease was present in 24% and 26% had a bicuspid aortic valve. At hospital admission 61% had aortic regurgitation grade ≥3, 12% were in functional NYHA-class ≥III. 30-day mortality was 2%, 97% of the patients were discharged with aortic regurgitation ≤2. In 10-year follow-up, 15 (12%) patients had to be re-operated because of root-related complications. Seven patients (47%) received a transcatheter aortic valve implantation, 8 (53%) required surgical replacement of the aortic valve or a Bentall-De Bono operation. Estimated reoperation-free survival at 5 and 10 years was 93.5% ± 2.4% and 87.0% ± 3.5%, respectively. Subgroup analysis showed no differences in reoperation-free survival for patients presenting with a bicuspid valve or preoperative aortic regurgitation ≥3. However a preoperative left ventricular end diastolic diameter of ≥5.5 cm was associated with worse outcome. Conclusion: David operations can be performed with excellent perioperative and 10-year follow-up outcomes in centers not running large AVSRR-programs.

Dismal prognosis of patients with operative indication without surgical intervention in active left-sided infective endocarditis.

Introduction: Around 25% of patients with left-sided infective endocarditis and operative indication do not undergo surgery. Baseline characteristics and outcomes are underreported. This study describes characteristics and outcomes of surgical candidates with surgical intervention or medical treatment only. Methods: Retrospective analysis of ongoing collected data from a single-center from an observational cohort of patients with infective endocarditis (ENVALVE). Kaplan-Meier estimates for survival was calculated. Factors associated with survival were assessed using a bivariable Cox model. To adjust for confounding by indication, uni- and multivariable logistic regression for the propensity to receive surgery were adjusted. Results: From January 2018 and December 2021, 154 patients were analyzed: 116 underwent surgery and 38 received medical treatment only. Surgical candidates without surgery were older (70 vs. 62 years, p = 0.001). They had higher preoperative risk profile (EuroSCORE II 14% (7.2-28.6) vs. 5.8% (2.5-20.3), p = 0.002) and more comorbidities. One patient was lost-to-follow-up. Survival analysis revealed a significant higher one-year survival rate among patients following surgery (83.7% vs. 15.3% in the non-surgical group; log-rank test <0.0001). In the final multivariable adjusted model, surgery was less likely among patients with liver cirrhosis [OR = 0.03 (95% CI 0.00-0.30)] and with hemodialysis [OR = 0.014 (95% CI 0.00-0.47)]. Conclusion: Patients with left-sided infective endocarditis who do not undergo surgery despite an operative indication are older, have more comorbidities and therefore higher preoperative risk profile and a low 1-year survival. The role of the Endocarditis Team may be particularly important for the decision-making process in this specific group.

Prospective long-term evaluation of incomplete distal renal tubular acidosis in idiopathic calcium nephrolithiasis diagnosed by low-dose NH4CL loading - gender prevalences and impact of alkali treatment.

PURPOSE: Prospective evaluation of the prevalence of incomplete distal renal tubular acidosis (idRTA) in idiopathic calcium stone formers (ICSF) diagnosed by half-dose ammonium chloride loading (NH4Cl, 0.05 g/kg body weight/day) and impact of alkali treatment of idRTA. METHODS: Evaluation of 386 consecutive idiopathic calcium stone formers (ICSF) (280 males, 106 females) for idRTA. If screening fasting urine pH was > 5.80, 1-day NH4Cl loading was performed without severe adverse effects. Normally, urine pH falls below 5.45. RESULTS: Sixty-four idiopathic calcium stone formers exhibited idRTA, one complete dRTA. Prevalence was higher in women (25.4%) than in men (13.6%). Thus, for more equilibrated comparisons, we formed pairs of 62 idiopathic calcium stone formers (ICSF) with and 62 without idRTA, matched for gender, age, BMI and serum creatinine. Idiopathic calcium stone formers with idRTA more often had hypercalciuria (p < 0.025) and urine citrate < 2 mmol/d (p < 0.05), formed calcium phosphate stones more frequently, exhibited higher numbers of stones/year (1.4 ± 1.5 vs. 0.9 ± 0.8, p = 0.034) and 2.5 times more intrarenal calcifications (4.6 ± 5.9 vs. 1.8 ± 3.6, p = 0.002). All idiopathic calcium stone formers with idRTA were recommended chronic alkali therapy. After 4-15 years of follow-up, stone events /years follow-up (stone passage or urologic intervention) were higher in patients non-adherent to alkali therapy (0.61 ± 0.92) than in patients adherent to treatment (0.11 ± 0.21, p = 0.006). CONCLUSION: Incomplete distal renal tubular acidosis is 1.8-fold more prevalent among female idiopathic calcium stone formers, predicts more stone recurrences, predisposes to calcium phosphate stones and is associated with 2.5 times more intrarenal calcifications vs. non-idRTA patients. Chronic alkali treatment reduces clinical stone recurrences by 5.5 times.

[Diagnostic and management of acute aortic syndrome]. / Diagnóstico y manejo del síndrome aórtico agudo.

Acute aortic syndrome includes a group of serious aortic pathologies, with a mortality rate of up to 90% in the first 40 days after the onset of symptoms. Depending on the location of the lesion, the treatment will be medical or surgical which has been shown to improve the prognosis of these patients both in the short- and long-term. Timey diagnosis is essential to increase survival and decrease the rate of related complications; however, due to the low incidence and sometimes non-specific clinical picture, the diagnosis can be delayed or missed, leading to catastrophic consequences for the patients. This article will focus on the diagnostic approach of type A acute aortic syndrome, in addition to offering a brief review regarding the medical and surgical treatment of these pathologies.

El síndrome aórtico agudo incluye un grupo de patologías graves de la aorta, con una mortalidad hasta del 90% en los primeros 40 días tras el inicio de los síntomas. Según la localización de la lesión el tratamiento puede ser médico o quirúrgico, el cual ha demostrado mejorar el pronóstico de estos pacientes tanto a corto como a largo plazo. El diagnóstico oportuno es esencial para incrementar la supervivencia y disminuir la tasa de complicaciones relacionadas; no obstante, debido a la baja incidencia y presentación clínica en ocasiones inespecífica, el diagnóstico puede retrasarse u obviarse, ocasionando consecuencias catastróficas para los pacientes. Este artículo se centrará en el abordaje diagnóstico del síndrome aórtico agudo tipo A, además de ofrecer una breve revisión respecto al tratamiento médico y quirúrgico de estas patologías.

What does an explanted PASCAL device look like?

We report the case of a 78-year-old female patient who had a PASCAL device implanted for severe degenerative mitral regurgitation. Intraprocedural echocardiography revealed persistent severe mitral regurgitation due to device dislocation. Implanting another device was not possible. After 8 days, the device was explanted, and the valve was replaced with a biological prosthesis. The PASCAL device and resected mitral valve leaflets were sent for histopathological workup.

A case series of rare pathologies of the aorta and the aortic arch in adolescents and younger adults: Transfer of experience for an individualized approach.

Objective: While aneurysm of the aortic root, interrupted aortic arch, and aortic coarctation are the most frequent aortic diseases in adolescents and younger adults, there are a number of rare pathologies of the thoracic aorta that need individualized treatment. Patients: We present a small case series of unusual aortic pathologies in patients presenting with a broad spectrum of symptoms: tiredness, dysphagia, dyspnea, arterial hypertension, renal failure, and claudication. (1). Segmental agenesia of the descending aorta. (2). Balanced double aortic arch with complete vascular ring. (3). Right descending aortic arch, left lusorian artery with Kommerell diverticulum. (4). Large patent ductus (2.5 cm) and ventricular septal defect. (5). Aneurysm of the aortic arch in the presence of tuberous sclerosis. (6). Pseudo-aneurysm of the proximal descending aorta following coarctation patch plasty. (7). Supravalvular aortic stenosis combined with severe aortic valve stenosis. (8). Pseudo-aneurysm following ascendens-to-descendens bypass because of recurrent coarctation. (9). Takayasu arteriitis with severe stenosis in the thoraco-abdominal aorta. Results: The following procedures were performed, using individualized cardiopulmonary bypass, canulation and cerebral protection strategies. (1). Ascending to supraceliac extra-anatomic bypass. (2). Division of the ductus ligament and of the anterior aortic arch distally to the left subclavian artery. (3). Excision of the Kommerell diverticulum and translocation of the left subclavian artery. (4). Patch closure of the aorto-pulmonary window (patent ductus) and closure of the ventricular septal defect. (5). Complete aortic arch replacement combined with debranching of the supra-aortic vessels. (6). Graft interposition of the proximal descending aorta. (7). Enlargement of the ascending aorta and aortic valve replacement. (8). Exclusion of the pseudo-aneurysm, end-to-side graft interposition. (9). Ascending aorta to infrarenal aorta or ascending to bi-iliac artery bypass (planned). All patients were operated on without operative mortality. One patient died in-hospital from pulmonary complications one week after surgery. One patient is still awaiting surgery. All other patients recovered very well from the operation and did not show any residual symptoms. Conclusion: Rare pathologies of the thoracic aorta in younger patients may cause a broad spectrum of unusual symptoms; in some of them, diagnosis is delayed. Cross-sectional imaging is mandatory for optimal operative planning Surgical treatment can be performed with very satisfying results. The prognosis of these patients is usually favorable following surgery.

Aortic wrapping is life-saving in high-risk acute aortic dissection and intramural haematoma.

Aortic wrapping is a controversial repair in patients presenting with acute type A aortic dissection or intramural haematoma, but this method may be a potential alternative to medical treatment or conventional repair in patients aged >80 years and in those presenting with prohibitive co-morbidities such as stroke, circulatory collapse, full oral anticoagulation with the last generation drugs. We report on 5 high-risk and/or patients over 80 years who received external aortic wrapping with or without cardiopulmonary bypass during the last 18 months. All survived the procedure and could be extubated early postoperatively. No patient remained on the intensive care longer than 2 days and all were discharged without additional complications. Postoperative radiological control was acceptable and no patient had any new aortic event up to 18 months postoperatively.

Concomitant Coronary Artery Bypass in Patients with Acute Type A Aortic Dissection.

Coronary Artery Bypass Grafting (CABG) is sometimes necessary in acute Type A Aortic Dissection (AAAD) repair. The aim of this study is to analyze the incidence, indications and influence in-hospital outcomes of AAAD repair requiring concomitant CABG in a high-volume single-center experience. Retrospective study of all consecutive AAAD patients. Those who underwent concomitant CABG were identified. Preoperative, intraoperative, postoperative and follow-up data were collected and analyzed. Between January 1, 2010 and December 31, 2016, 382 patients underwent emergency surgery for AAAD. Forty-one (10.7%) underwent concomitant CABG. In this group, mean age was 64 ± 14 years, 32 were male (78%). Indication for CABG was coronary dissection in 28 patients (68.3%), post-cardiopulmonary bypass (CPB) right heart failure in 7 (17.1%), post CPB left heart failure in (7.3%) and native coronary pathology in 3 (7.3%). In 33 (80.5%) one graft was needed, in 7 (17%) two were performed and in 1 patient (2.4%) 3 were necessary. The right coronary artery (RCA) was the only revascularized vessel in 26 cases (63.4%), the left coronary artery (LCA) alone in 11 (26.8%), and both coronary systems in 4 (9.8%). In-hospital mortality was 51.2% (N = 21); eight (19.5%) patients had postoperative myocardial infarction (MI) and 11 (26.8%) had a major neurological event. Multivariable logistic regression identified concomitant CABG as a predictor of in-hospital mortality (Odds Ratio (OR) = 3.8115, 95% CI= 0.514-2.138, p = 0.001). In our study, concomitant CABG was performed in 10.7% of AAAD repair surgery and it was associated with high in-hospital mortality.

The impact of age and sex on in-hospital outcomes in acute type A aortic dissection surgery.

Background: Older age and female sex are thought to be risk factors for adverse outcomes after repair of acute type A aortic dissection (AAAD). The aim of this study is to analyze age- and sex-related outcomes in patients undergoing AAAD repair. Methods: Retrospective analysis of patients undergoing emergency AAAD repair. Patients were divided in Group A, patients aged ≥75 years and Group B <75. Intraoperative and postoperative data were compared between groups before and after propensity score matching. Sex differences were analyzed by age group. Results: Between January 2006 and December 2018, 638 patients underwent emergency AAAD repair. Group A included 143 patients (22.4%), Group B 495 (77.6%). More patients in Group A presented with circulatory collapse (Penn C 26.6% vs. 9.7%, P=0.001) while Group B presented with circulatory collapse-branch malperfusion (Penn BC 29.3% vs. 15.4% P=0.001). After propensity score matching, Group B patients received more complex aortic root (33.6% vs. 23.2%, P=0.019) and concomitant bypass surgery (12.3% vs. 6.3%, P=0.042). There was no significant difference in in-hospital mortality between age groups (18% vs. 12% P=0.12). In Group B, in-hospital mortality was significantly higher in females (22.2% vs. 8.2%, P=0.028). Differences in mortality disappeared after the age of 75 (18.3% vs. 19.4% P=0.87). Conclusions: Morbidity and mortality are comparable between patients under and over 75 years after AAAD repair. Female patients <75 had higher in-hospital mortality than their male counterparts.

Prior intake of new oral anticoagulants adversely affects outcome following surgery for acute type A aortic dissection.

OBJECTIVES: Oral anticoagulation prior to emergency surgery is associated with an increased risk of perioperative bleeding, especially when this therapy cannot be discontinued or reversed in time. The goal of this study was to analyse the impact of different oral anticoagulants on the outcome of patients who underwent emergency surgery for acute type A aortic dissection (ATAAD). METHODS: This was a single-centre retrospective study of patients treated with oral anticoagulation at the time of surgery for ATAAD. Outcomes of patients on new oral anticoagulant (NOAC) therapy were compared to respective outcomes of patients on Coumadin. Additionally, a survival analysis was performed comparing these 2 groups with patients who were operated on with no prior anticoagulation. RESULTS: Between January 2013 and April 2020, a total of 437 patients (63.8 ± 11.8 years, 68.4% male) received emergency surgery for ATAAD; 35 (8%) were taking oral anticoagulation at the time of hospital admission: 20 received phenprocoumon; 14, rivaroxaban; and 1, dabigatran. Compared to Coumadin, NOAC was associated with a greater need for blood-product transfusions and haemodynamic compromise. Operative mortality was 53% in the NOAC group and 30% in the Coumadin group. A 5-year survival analysis showed no significant difference between the NOAC and the Coumadin group (P = 0.059). Compared to 402 patients treated during the study period without anticoagulation, patients taking NOAC had significantly worse survival (P = 0.001), whereas that effect was not observed in patients undergoing surgery who were taking Coumadin (P = 0.99). CONCLUSIONS: Emergency surgery for ATAAD in patients taking NOAC is associated with high morbidity and mortality. NOAC are a major risk factor for uncontrollable bleeding and haemodynamic compromise. New treatment strategies must be defined to improve surgical outcomes in these high-risk patients.

A retrospective analysis of blood culture-negative endocarditis at a tertiary care centre in Switzerland.

AIMS OF THE STUDY: Numerous studies from different countries have contributed to an improved understanding of blood culture-negative infective endocarditis. However, little is known about its epidemiology and microbiology in Switzerland. We aimed to assess the epidemiology and microbiology of blood culture-negative endocarditis at the University Hospital Zurich, Switzerland. METHODS: We screened all patients hospitalised between 1997 and 2020 with possible or definite endocarditis at our institution. Thereof, we identified all cases with blood culture-negative endocarditis and retrospectively retrieved patient characteristics, microbiological, histopathological, radiographic and surgical data from medical records. RESULTS: Among 861 patients screened, 66 (7.7%) cases of blood culture-negative endocarditis were identified. Thereof, 31 cases could be microbiologically documented or not documented (n = 30), and in five cases a non-infectious aetiology was confirmed. Endocarditis predominantly affected men (77%) and the left heart (79%); predisposing factors were prosthetic valves (42%), congenital heart disease (35%) and prior endocarditis (14%). The most common reasons for negative blood cultures were antibiotic treatment prior to blood culture sampling (35%), fastidious and slow growing microorganisms (30%) and definite non-infective endocarditis (8%). Coxiella burnetii and Bartonella spp. were the most common fastidious bacteria identified. In addition to serology, identification of causative microorganisms was possible by microbiological and/or histopathological analysis of tissue samples, of which polymerase chain reaction testing (PCR) of the 16S ribosomal RNA proved to be most successful. CONCLUSIONS: The present study provides a detailed analysis of blood culture-negative endocarditis over a time span of more than 20 years in Zurich, Switzerland. Antibiotic treatment prior to blood collection, and fastidious and slow growing organisms were identified as main reasons for sterile blood cultures. Typical culture-negative bacteria were mainly found by PCR and/or culture of tissue samples.