Oxidative Stress in Structural Valve Deterioration: A Longitudinal Clinical Study.

The cause of structural valve deterioration (SVD) is unclear. Therefore, we investigated oxidative stress markers in sera from patients with bioprosthetic heart valves (BHVs) and their association with SVD. Blood samples were taken from SVD (Phase A) and BHV patients during the first 24 (Phase B1) and >48 months (Phase B2) after BHV implantation to assess total antioxidant capacity (TAC), malondialdehyde (MDA), and nitrotyrosine (NT). The results show that MDA levels increased significantly 1 month after surgery in all groups but were higher at 6 months only in incipient SVD patients. NT levels increased gradually for the first 24 months after implantation in the BHV group. Patients with transcatheter aortic valve implantation (TAVI) showed even higher levels of stress markers. After >48 months, MDA and NT continued to increase in BHV patients with a further elevation after 60-72 months; however, these levels were significantly lower in the incipient and established SVD groups. In conclusion, oxidative stress may play a significant role in SVD, increasing early after BHV implantation, especially in TAVI cases, and also after 48 months' follow-up, but decreasing when SVD develops. Oxidative stress potentially represents a target of therapeutic intervention and a biomarker of BHV dysfunction.

The role of antibody responses against glycans in bioprosthetic heart valve calcification and deterioration.

Bioprosthetic heart valves (BHVs) are commonly used to replace severely diseased heart valves but their susceptibility to structural valve degeneration (SVD) limits their use in young patients. We hypothesized that antibodies against immunogenic glycans present on BHVs, particularly antibodies against the xenoantigens galactose-α1,3-galactose (αGal) and N-glycolylneuraminic acid (Neu5Gc), could mediate their deterioration through calcification. We established a large longitudinal prospective international cohort of patients (n = 1668, 34 ± 43 months of follow-up (0.1-182); 4,998 blood samples) to investigate the hemodynamics and immune responses associated with BHVs up to 15 years after aortic valve replacement. Early signs of SVD appeared in <5% of BHV recipients within 2 years. The levels of both anti-αGal and anti-Neu5Gc IgGs significantly increased one month after BHV implantation. The levels of these IgGs declined thereafter but anti-αGal IgG levels declined significantly faster in control patients compared to BHV recipients. Neu5Gc, anti-Neu5Gc IgG and complement deposition were found in calcified BHVs at much higher levels than in calcified native aortic valves. Moreover, in mice, anti-Neu5Gc antibodies were unable to promote calcium deposition on subcutaneously implanted BHV tissue engineered to lack αGal and Neu5Gc antigens. These results indicate that BHVs manufactured using donor tissues deficient in αGal and Neu5Gc could be less prone to immune-mediated deterioration and have improved durability.

Invasive Pulmonary Aspergillosis with Disseminated Infection in Immunocompetent Patient.

Invasive pulmonary aspergillosis (IPA) is a rare pathology with increasing incidence mainly in critical care settings and recently in immunocompetent patients. The mortality of the disease is very high, regardless of an early diagnosis and aggressive treatment. Here, we report a case of a 56 yr old previously healthy woman who was found unconscious at home and admitted to the emergency room with mild respiratory insufficiency. In the first 24 hours she developed an acute respiratory failure with new radiographic infiltrates requiring Intensive Care Unit admission. A severe obstructive pattern with impossibility of ventilation because of bilateral atelectasis was observed, requiring emergent venovenous extracorporeal membrane oxygenator device insertion. Bronchoscopy revealed occlusion of main bronchi, demonstrating by biopsy an invasive infection by Aspergillus fumigatus and A. flavus. Despite an aggressive treatment and vital support the patient had a fatal outcome. The forensic study confirms the diagnosis of IPA but also revealed the presence of disseminated aspergillosis.

Outcomes of abdominal surgery in patients with liver cirrhosis.

Patients suffering from liver cirrhosis (LC) frequently require non-hepatic abdominal surgery, even before liver transplantation. LC is an important risk factor itself for surgery, due to the higher than average associated morbidity and mortality. This high surgical risk occurs because of the pathophysiology of liver disease itself and to the presence of contributing factors, such as coagulopathy, poor nutritional status, adaptive immune dysfunction, cirrhotic cardiomyopathy, and renal and pulmonary dysfunction, which all lead to poor outcomes. Careful evaluation of these factors and the degree of liver disease can help to reduce the development of complications both during and after abdominal surgery. In the emergency setting, with the presence of decompensated LC, alcoholic hepatitis, severe/advanced LC, and significant extrahepatic organ dysfunction conservative management is preferred. A multidisciplinary, individualized, and specialized approach can improve outcomes; preoperative optimization after risk stratification and careful management are mandatory before surgery. Laparoscopic techniques can also improve outcomes. We review the impact of LC on surgical outcome in non-hepatic abdominal surgeries required in this cirrhotic population before, during, and after surgery.

Evaluation of Serial Arterial Lactate Levels as a Predictor of Hospital and Long-Term Mortality in Patients After Cardiac Surgery.

OBJECTIVES: Although hyperlactatemia is common after cardiac surgery, its value as a prognostic marker is unclear. The aim of the present study was to determine whether postoperative serial arterial lactate (AL) measurements after cardiac surgery could predict outcome. DESIGN: Prospective, observational study. SETTING: Surgical intensive care unit in a tertiary-level university hospital. PARTICIPANTS: Participants included 2,935 consecutive patients. INTERVENTIONS: AL was measured on admission to the intensive care unit and 6, 12, and 24 hours after surgery, and evaluated together with clinical data and outcomes including in-hospital and long-term mortality. MEASUREMENTS AND MAIN RESULTS: In-hospital and long-term mortality (mean follow-up 6.3±1.7 years) were 5.9% and 8.7%, respectively. Compared with survivors, nonsurvivors showed higher mean AL values in all measurements (p<0.001). Hyperlactatemia (AL>3.0 mmol/L) was a predictor for in-hospital mortality (odds ratio = 1.468; 95% confidence interval = 1.239-1.739; p<0.001) and long-term mortality (hazard ratio = 1.511; 95% confidence interval = 1.251-1.825; p<0.001). Recent myocardial infarction and longer cardiopulmonary bypass time were predictors of hyperlactatemia. The pattern of AL dynamics was similar in both groups, but nonsurvivors showed higher AL values, as confirmed by repeated measures analysis of variance (p<0.001). The area under the curve also showed higher levels of AL in nonsurvivors (80.9±68.2 v 49.71±25.8 mmol/L/h; p = 0.038). Patients with hyperlactatemia were divided according to their timing of peak AL, with higher mortality and worse survival in patients in whom AL peaked at 24 hours compared with other groups (79.1% v 86.7%-89.2%; p = 0.03). CONCLUSIONS: The dynamics of the postoperative AL curve in patients undergoing cardiac surgery suggests a similar mechanism of hyperlactatemia in survivors and nonsurvivors, albeit with a higher production or lower clearance of AL in nonsurvivors. The presence of a peak of hyperlactatemia at 24 hours is associated with higher in-hospital and long-term mortality.

Influence of cirrhosis in cardiac surgery outcomes.

Liver cirrhosis has evolved an important risk factor for cardiac surgery due to the higher morbidity and mortality that these patients may suffer compared with general cardiac surgery population. The presence of contributing factors for a poor outcome, such as coagulopathy, a poor nutritional status, an adaptive immune dysfunction, a degree of cirrhotic cardiomyopathy, and a degree of renal and pulmonary dysfunction, have to be taken into account for surgical evaluation when cardiac surgery is needed, together with the degree of liver disease and its primary complications. The associated pathophysiological characteristics that liver cirrhosis represents have a great influence in the development of complications during cardiac surgery and the postoperative course. Despite the population of cirrhotic patients who are referred for cardiac surgery is small and recommendations come from small series, since liver cirrhotic patients have increased their chance of survival in the last 20 years due to the advances in their medical care, which includes liver transplantation, they have been increasingly considered for cardiac surgery. Indeed, there is an expected rise of cirrhotic patients within the cardiac surgical population due to the increasing rates of non-alcoholic fatty liver disease and non-alcoholic steatohepatitis, especially in western countries. In consequence, a more specific approach is needed in the assessment of care of these patients if we want to improve their management. In this article, we review the pathophysiology and outcome prediction of cirrhotic patients who underwent cardiac surgery.

The influence of body mass index on outcomes in patients undergoing cardiac surgery: does the obesity paradox really exist?

PURPOSE: Obesity influences risk stratification in cardiac surgery in everyday practice. However, some studies have reported better outcomes in patients with a high body mass index (BMI): this is known as the obesity paradox. The aim of this study was to quantify the effect of diverse degrees of high BMI on clinical outcomes after cardiac surgery, and to assess the existence of an obesity paradox in our patients. METHODS: A total of 2,499 consecutive patients requiring all types of cardiac surgery with cardiopulmonary bypass between January 2004 and February 2009 were prospectively studied at our institution. Patients were divided into four groups based on BMI: normal weight (18.5-24.9 kg∙m-2; n = 523; 21.4%), overweight (25-29.9 kg∙m-2; n = 1150; 47%), obese (≥ 30-≤ 34.9 kg∙m-2; n = 624; 25.5%) and morbidly obese (≥ 35kg∙m-2; n = 152; 6.2%). Follow-up was performed in 2,379 patients during the first year. RESULTS: After adjusting for confounding factors, patients with higher BMI presented worse oxygenation and better nutritional status, reflected by lower PaO2/FiO2 at 24h and higher albumin levels 48 h after admission respectively. Obese patients showed a higher risk for Perioperative Myocardial Infarction (OR: 1.768; 95% CI: 1.035-3.022; p = 0.037) and septicaemia (OR: 1.489; 95% CI: 1.282-1.997; p = 0.005). In-hospital mortality was 4.8% (n = 118) and 1-year mortality was 10.1% (n = 252). No differences were found regarding in-hospital mortality between BMI groups. The overweight group showed better 1-year survival than normal weight patients (91.2% vs. 87.6%; Log Rank: p = 0.029. HR: 1.496; 95% CI: 1.062-2.108; p = 0.021). CONCLUSIONS: In our population, obesity increases Perioperative Myocardial Infarction and septicaemia after cardiac surgery, but does not influence in-hospital mortality. Although we found better 1-year survival in overweight patients, our results do not support any protective effect of obesity in patients undergoing cardiac surgery.

Evaluation of the PaO2/FiO2 ratio after cardiac surgery as a predictor of outcome during hospital stay.

BACKGROUND: The arterial partial pressure of O2 and the fraction of inspired oxygen (PaO2/FiO2) ratio is widely used in ICUs as an indicator of oxygenation status. Although cardiac surgery and ICU scores can predict mortality, during the first hours after cardiac surgery few instruments are available to assess outcome. The aim of this study was to evaluate the usefulness of PaO2/FIO2 ratio to predict mortality in patients immediately after cardiac surgery. METHODS: We prospectively studied 2725 consecutive cardiac surgery patients between 2004 and 2009. PaO2/FiO2 ratio was measured on admission and at 3 h, 6 h, 12 h and 24 h after ICU admission, together with clinical data and outcomes. RESULTS: All PaO2/FIO2 ratio measurements differed between survivors and non-survivors (p < 0.001). The PaO2/FIO2 at 3 h after ICU admission was the best predictor of mortality based on area under the curve (p < 0.001) and the optimum threshold estimation gave an optimal cut-off of 222 (95% Confidence interval (CI): 202-242), yielding three groups of patients: Group 1, with PaO2/FIO2 > 242; Group 2, with PaO2/FIO2 from 202 to 242; and Group 3, with PaO2/FIO2 < 202. Group 3 showed higher in-ICU mortality and ICU length of stay and Groups 2 and 3 also showed higher respiratory complication rates. The presence of a PaO2/FIO2 ratio < 202 at 3 h after admission was shown to be a predictor of in-ICU mortality (OR:1.364; 95% CI:1.212-1.625, p < 0.001) and of worse long-term survival (88.8% vs. 95.8%; Log rank p = 0.002. Adjusted Hazard ratio: 1.48; 95% CI:1.293-1.786; p = 0.004). CONCLUSIONS: A simple determination of PaO2/FIO2 at 3 h after ICU admission may be useful to identify patients at risk immediately after cardiac surgery.

Influence of acute kidney injury on short- and long-term outcomes in patients undergoing cardiac surgery: risk factors and prognostic value of a modified RIFLE classification.

INTRODUCTION: The development of acute kidney injury (AKI) is associated with poor outcome. The modified RIFLE (risk, injury, failure, loss of kidney function, and end-stage renal failure) classification for AKI, which classifies patients with renal replacement therapy needs according to RIFLE failure class, improves the predictive value of AKI in patients undergoing cardiac surgery. Our aim was to assess risk factors for post-operative AKI and the impact of renal function on short- and long-term survival among all AKI subgroups using the modified RIFLE classification. METHODS: We prospectively studied 2,940 consecutive cardiosurgical patients between January 2004 and July 2009. AKI was defined according to the modified RIFLE system. Pre-operative, operative and post-operative variables usually measured on and during admission, which included main outcomes, were recorded together with cardiac surgery scores and ICU scores. These data were evaluated for association with AKI and staging in the different RIFLE groups by means of multivariable analyses. Survival was analyzed via Kaplan-Meier and a risk-adjusted Cox proportional hazards regression model. A complete follow-up (mean 6.9 ± 4.3 years) was performed in 2,840 patients up to April 2013. RESULTS: Of those patients studied, 14% (n = 409) were diagnosed with AKI. We identified one intra-operative (higher cardiopulmonary bypass time) and two post-operative (a longer need for vasoactive drugs and higher arterial lactate 24 hours after admission) predictors of AKI. The worst outcomes, including in-hospital mortality, were associated with the worst RIFLE class. Kaplan-Meier analysis showed survival of 74.9% in the RIFLE risk group, 42.9% in the RIFLE injury group and 22.3% in the RIFLE failure group (P <0.001). Classification at RIFLE injury (Hazard ratio (HR) = 2.347, 95% confidence interval (CI) 1.122 to 4.907, P = 0.023) and RIFLE failure (HR = 3.093, 95% CI 1.460 to 6.550, P = 0.003) were independent predictors for long-term patient mortality. CONCLUSIONS: AKI development after cardiac surgery is associated mainly with post-operative variables, which ultimately could lead to a worst RIFLE class. Staging at the RIFLE injury and RIFLE failure class is associated with higher short- and long-term mortality in our population.

Age and sex differences in perioperative myocardial infarction after cardiac surgery.

We investigate age and sex differences in acute myocardial infarction (AMI) after cardiac surgery in a prospective study of 2038 consecutive patients undergoing cardiac surgery with cardiopulmonary bypass. An age of ≥ 70 years implied changes in the type of AMI from the ST-segment elevation myocardial infarction (STEMI) to non-ST-segment elevation myocardial infarction (non-STEMI). Men were more likely than women to suffer from AMI after cardiac surgery (11.8% vs. 5.6%), as a result of the higher frequency of STEMI (6% of men vs. 1.8% of women; P < 0.001) in both age groups. A troponin-I (Tn-I) peak was significantly higher in patients ≥ 70 years old. In-hospital mortality was higher in patients ≥ 70 (7.3%) than in those < 70 years old (3.3%), because of the increased mortality observed in men with non-AMI (2.1% vs. 6.3%) and women with STEMI (0% vs. 28.6%) and non-STEMI (0% vs. 36.8%, P < 0.05). Old age was associated with a higher frequency of non-STEMI, Tn-I peak, mortality and length of stay in the intensive care unit (ICU). Regardless of age, men more often suffer from AMI (particularly STEMI). AMI in women had a notable impact on excess mortality and ICU stay observed in patients ≥ 70 years of age. Clinical and Tn-I peak differences are expected in relation to age and gender after AMI post-cardiac surgery.

TNF, pig CD86, and VCAM-1 identified as potential targets for intervention in xenotransplantation of pig chondrocytes.

Xenotransplantation of genetically engineered porcine chondrocytes may benefit many patients who suffer cartilage defects. In this work, we sought to elucidate the molecular bases of the cellular response to xenogeneic cartilage. To this end, we isolated pig costal chondrocytes (PCC) and conducted a series of functional studies. First, we determined by flow cytometry the cell surface expression of multiple immunoregulatory proteins in resting conditions or after treatment with human TNF-alpha, IL-1alpha, or IL-1beta, which did not induce apoptosis. TNF-alpha and to a lesser extent IL-1alpha led to a marked upregulation of SLA I, VCAM-1, and ICAM-1 on PCC. SLA II and E-selectin remained undetectable in all the conditions assayed. Notably, CD86 was constitutively expressed at moderate levels, whereas CD80 and CD40 were barely detected. To assess their function, we next studied the interaction of PCC with human monoblastic U937 and Jurkat T cells. U937 cells adhered to resting and in a greater proportion to cytokine-stimulated PCC. Consistent with its expression pattern, pig VCAM-1 was key, mediating the increased adhesion after cytokine stimulation. We also conducted coculture experiments with U937 and PCC and measured the release of pig and human cytokines. Stimulated PCC secreted IL-6 and IL-8, whereas U937 secreted IL-8 in response to PCC. Finally, coculture of PCC with Jurkat in the presence of PHA led to a marked Jurkat activation as determined by the increase in IL-2 secretion. This process was dramatically reduced by blocking pig CD86. In summary, CD86 and VCAM-1 on pig chondrocytes may be important triggers of the xenogeneic cellular immune response. These molecules together with TNF could be considered potential targets for intervention in order to develop xenogeneic therapies for cartilage repair.

Serum levels of anti-alphaGalactosyl antibodies predict survival and peritoneal dialysis-related enteric peritonitis rates in patients undergoing renal replacement therapy.

BACKGROUND: Anti-Galalpha1-3Gal antibodies (anti-alphaGal) represent a significant fraction of natural antibodies and were implicated in several disease states, yet their origin and physiological significance remain largely undisclosed. METHODS: Under a prospective observational design, we estimated anti-alphaGal immunoglobulin G (IgG)/IgM and antipig hemolytic antibody (APA) levels in 133 patients starting dialysis therapy and again after a 1-year follow-up. We used baseline data to show correlations with demographic, nutritional, inflammatory, and anemia markers and analyzed their correlation with outcomes by using univariate and multivariate strategies of survival analysis. RESULTS: Serum anti-alphaGal and APA levels showed wide baseline variability, but remained relatively stable in time. Both were measurable in dialysate of peritoneal dialysis (PD) patients, showing close correlation to serum levels. We observed no association between levels of anti-alphaGal/APA and nutritional markers, but showed direct correlations of anti-alphaGal IgM (P = 0.005) and APA levels (P = 0.001) with tumor necrosis factor alpha (TNF-alpha) levels. High APA levels also were associated with severe anemia (P = 0.006). High baseline anti-alphaGal IgM (P = 0.03) and APA levels (P = 0.045) predicted later risk for enteric peritonitis in PD patients. Finally, univariate and multivariate analyses showed a consistent association between high baseline anti-alphaGal IgM (P = 0.014) and APA (P = 0.021) levels and global risk for mortality during follow-up. CONCLUSION: Anti-alphaGal IgM and APA levels at the start of dialysis therapy are significant predictors of later risk for mortality and, in PD patients, enteric peritonitis. Both correlate directly with TNF-alpha levels and, in the case of APA, severity of anemia in these patients.

A randomized double-blind trial of iseganan in prevention of ventilator-associated pneumonia.

RATIONALE: Iseganan, an antimicrobial peptide, is active against aerobic and anaerobic gram-positive and gram-negative bacteria as well as fungi and yeasts. The drug has shown little resistance in vitro and to be safe and well tolerated in 800 patients with cancer treated for up to 6 wk. OBJECTIVES: To determine the efficacy of iseganan for the prevention of ventilator-associated pneumonia (VAP). METHODS: Mechanically ventilated patients in the United States and Europe were randomized to oral topical iseganan or placebo (1:1) and treated six times per day while intubated for up to 14 d. Patients were eligible if randomized within 24 h of intubation and estimated to survive and remain mechanically ventilated for 48 h or more. The primary efficacy endpoint of the study was VAP measured among survivors at Day 14. MEASUREMENTS AND MAIN RESULTS: A total of 709 patients were randomized and received at least one dose of study drug. The two groups were comparable at baseline except iseganan-treated patients were, on average, 3 yr older. The rate of VAP among survivors at Day 14 was 16% (45/282) in patients treated with iseganan and 20% (57/284) in those treated with placebo (p = 0.145). Mortality at Day 14 was 22.1% (80/362) in the iseganan group compared with 18.2% (63/347) in the placebo group (p = 0.206). No pattern of excess adverse events in the iseganan group compared with placebo was observed. CONCLUSIONS: Iseganan is not effective in improving outcome in patients on prolonged mechanical ventilation.

Lack of cross-species transmission of porcine endogenous retrovirus in pig-to-baboon xenotransplantation with sustained depletion of anti-alphagal antibodies.

BACKGROUND: Nonhuman primates are potential permissive animals for studying the risk of in vivo infection with porcine endogenous retrovirus (PERV). Anti-alphaGal natural antibodies are considered one of the barriers for preventing PERV infection, and it has been postulated that reduction of these antibodies could increase the risk of this infection. The aim of this study was to investigate the role of GAS 914, which depletes anti-alphaGal antibodies, in the potential in vivo transfer of PERV after pig-to-baboon organ xenotransplantation. METHODS: Twenty-seven baboons underwent xenotransplantation with hDAF or hMCP/hDAF transgenic pig organs, including heterotopic heart (n = 14) and kidney (n = 13) transplants. All of them received GAS 914 along with different immunosuppression protocols. PERV sequences were investigated by reverse-transcriptase polymerase chain reaction and by polymerase chain reaction assays in samples obtained at autopsy. The presence of PERV-specific antibodies and/or pig xenomicrochimerism was also evaluated. RESULTS: PERV RNA was not detected in any baboon plasma sample. In addition, all plasma samples were negative for PERV antibodies. However, PERV DNA sequences were detected in peripheral blood mononuclear cells from 6 of 14 (43%) animals investigated. Porcine mitochondrial DNA was also found in all of these positive samples and in six of the eight (75%) samples with negative PERV DNA, indicating that the detection of PERV sequences was attributable to xenochimerism. PERV-positive cells as a result of xenochimerism were also found in eight of nine (89%) spleen and lymph node tissue samples tested. CONCLUSIONS: Sustained depletion of anti-alphaGal antibodies does not augment the risk of PERV infection in pig-to-baboon organ transplantation.

Cellular participation in delayed xenograft rejection of hCD55 transgenic pig hearts by baboons.

Delayed xenograft rejection (DXR) of pig organs by baboons currently represents the major obstacle to successful xenotransplantation. Although antibodies (Abs) are believed to play a fundamental role in this form of rejection, so far little is known concerning the potential cellular component. Biopsies taken during DXR of human CD55 transgenic pig hearts by non-treated (n = 2), alpha-Gal immunoadsorbed (n = 2), or immunosuppressed (n = 9) baboons were studied. The cellular element was explored by determining not only its phenotype by classical immunohistochemical techniques but also its activity in terms of cytokines, cytolytic enzymes and other mediators using quantitative reverse transcription polymerase chain reaction. All porcine xenografts underwent DXR; within 5 days in non-treated and immunoadsorbed animals but significantly delayed (6 to 29 days) in immunosuppressed animals. Cellular infiltration in non-immunosuppressed grafts consisted predominantly of monocytes/macrophages, CD8 cells and a few CD4 T-cells. The predominant baboon transcripts detectable were the proinflammatory cytokines interleukin1-alpha and tumor necrosis factor-alpha, the lymphokine interferon-gamma and the cytotoxic enzyme granzyme B. However, these cellular components were lacking in the immunosuppressed animals. Despite these differences, strong immunoglobulin M (IgM) and C5b-9 complement deposition was observed in all animals at rejection. Together our findings suggest that although the humoral response plays a predominant role in DXR through IgM Abs and complement activation, there is a clear cellular infiltrate in DXR in this model that is likely to contribute to rejection through a strong pro-inflammatory and cytotoxic environment, necessitating substantial immunosuppression for a prolonged graft survival.

Current trends in transplantation and immunosuppressive treatment.

The American Society of Transplant Surgeons and the American Society of Transplantation jointly sponsored their third American Transplant Congress on May 30-June 4, 2003. The meeting, which took place in Washington, D.C., U.S.A., thoroughly reviewed the different immunosuppressive protocols for every kind of transplantation. Also presented were the immunological and nonimmunological factors influencing the success or failure of transplants from the point of view of genetics, the place of new investigative agents and the current status of various therapeutic protocols intended to induce tolerance or normal function of grafts in the absence of immunosuppressive treatment. Presentations on renal, liver, heart, lung, multivisceral and islet transplantation are covered in this report, as well as aspects of new immunosuppressive agents, genomics in transplantation and tolerance induction in allotransplantation.

Selective use of diagnostic tests inpatients with syncope of unknown cause.

OBJECTIVE: We sought to prospectively assess the diagnostic yielding of a protocol in which electrophysiologic studies (EPS), tilt-table tests (TTTs), and loop recorder implantation are selectively used. BACKGROUND: The optimal strategy in the diagnosis of patients with syncope of unknown cause has not been defined. METHODS: A total of 184 consecutive patients with syncope of unknown cause were classified into two groups. Group A consisted of 72 patients fulfilling any of the following criteria: 1) presence of structural heart disease or family history of sudden death; 2) abnormal electrocardiogram; 3) significant non-symptomatic arrhythmia on Holter monitoring; and 4) paroxysmal palpitations immediately before or after syncope. These patients initially underwent an EPS and, if this study was negative, TTT. In the remaining 112 patients (group B), TTT was performed. RESULTS: The EPS was positive in 32 patients (44%) in group A. The TTT was positive in 80 patients (71%) in group B. An additional patient had carotid sinus hypersensitivity. In patients of group A with a negative EPS, the TTT was positive in 23 (57%). A loop recorder was implanted in 15 patients from group A with negative conventional testing, and diagnostic activation was obtained in seven patients. Overall, a positive diagnosis was achieved in 143 patients (78%). CONCLUSIONS: In patients with syncope of unknown cause, selective use of EPS or TTT leads to a positive diagnosis in >70% of the cases. An implantable loop recorder can be useful in non-diagnosed cases.