Neurocardiac Axis Physiology and Clinical Applications.

The neurocardiac axis constitutes the neuronal circuits between the arteries, heart, brain, and immune organs (including thymus, spleen, lymph nodes, and mucosal associated lymphoid tissue) that together form the cardiovascular brain circuit. This network allows the individual to maintain homeostasis in a variety of environmental situations. However, in dysfunctional states, such as exposure to environments with chronic stressors and sympathetic activation, this axis can also contribute to the development of atherosclerotic vascular disease as well as other cardiovascular pathologies and it is increasingly being recognized as an integral part of the pathogenesis of cardiovascular disease. This review article focuses on 1) the normal functioning of the neurocardiac axis; 2) pathophysiology of the neurocardiac axis; 3) clinical implications of this axis in hypertension, atherosclerotic disease, and heart failure with an update on treatments under investigation; and 4) quantification methods in research and clinical practice to measure components of the axis and future research areas.

Peroxisome Proliferator-Activated Receptor Gamma Regulates Interleukin-6-Induced Lipoprotein (a) Gene Expression in Human HepG2 Cells.

Lipoprotein(a) [Lp(a)] is a risk factor for coronary disease. Although levels are primarily genetically determined, data from patients with inflammatory diseases indicate that the inflammatory milieu is associated with increased Lp(a) levels. Lp(a) is synthesized in the liver and the LPA gene promoter contains an interleukin-6 (IL-6) responsive binding site, but the regulatory steps linking inflammation with hepatic Lp(a) synthesis are not well clarified. We explored the interplay between IL-6, peroxisome proliferator-activated receptor gamma (PPARγ), and Lp(a) synthesis in HepG2 cells. Through genetic mapping, a regulatory variant within the LPA promoter overlapping with a PPARγ binding site was identified. In in vitro experiments, IL-6-mediated LPA gene transcription was heightened with PPARγ knock-down and suppressed with pioglitazone, a PPARγ agonist. These results demonstrate an important role of PPARγ as a negative regulator of IL-6 induced hepatic Lp(a) production and may represent a new therapeutic target for patients with inflammatory conditions characterized by elevated Lp(a).

Intra-individual variability in lipoprotein(a): the value of a repeat measure for reclassifying individuals at intermediate risk.

Aims: Lipoprotein(a) [Lp(a)] levels are predominantly genetically determined and repeat measurements are generally considered unlikely to be clinically useful. However, the temporal variation of Lp(a) is not well characterized. Our aim was to determine the intra-individual variability of Lp(a) and whether a repeated measure reclassified Lp(a)-specific cardiovascular risk using the European Atherosclerosis Society (EAS) consensus statement risk categories. Methods and results: This retrospective cohort study analysed initial and repeated serum Lp(a) levels measured using the same methodology from 609 individuals in the Nashville Biosciences database, a de-identified electronic medical records database. Baseline and follow-up paired values were significantly different (P < 0.05), with an absolute change of ≥10 mg/dL in 38.1% [95% CI 34.2-42%] and a >25% change in 40.5% [95% CI 36.6-44.3%] of individuals. Although the categories of those whose values were in the EAS low-risk and high-risk categories did not change, 53% of those in the intermediate 'grey-zone' category transitioned to either the low-risk (20%) or high-risk (33%) category. Black individuals exhibited greater variability than White individuals and women exhibited greater variability than men. There was a positive correlation between the baseline Lp(a) levels and the absolute changes in Lp(a), (r = 0.59, P < 0.01). Conclusion: Temporal-related changes in Lp(a) variability were present in many individuals. A repeat Lp(a) measure may allow more precise Lp(a)-specific cardiovascular risk prediction for individuals whose initial value is in the EAS-defined intermediate 'grey-zone' category. Lp(a) variability should be included in calculating the expected effect sizes in future clinical research studies targeting Lp(a).

VERICIGUAT RESCUES CYCLIC GUANOSINE MONOPHOSPHATE PRODUCTION IN HUMAN AORTIC VASCULAR SMOOTH MUSCLE CELLS AND AUGMENTS VASORELAXATION IN AORTIC RINGS EXPOSED TO HIGH GLUCOSE.

Background: Normal endothelial cell dependent vascular smooth muscle cell function is mediated by nitric oxide (NO), which stimulates soluble guanylyl cyclase (sGC) production of the second messenger, cyclic guanosine monophosphate (cGMP) leading to increased protein kinase G (PKG) activity and vascular smooth muscle relaxation. NO bioavailability is impaired in inflammatory settings, such as high glucose (HG). We examined whether the direct sGC sensitizer/stimulator vericiguat, augments cGMP production in human vascular smooth muscle cells (HVSMC) exposed to high glucose and explored its effect on vasorelaxation. Methods: Aortic HVSMCs were exposed to HG for 24h. In the treatment group, cells also received 1uM vericiguat for 24h. After incubation, cGMP and PKG activity were measured. Additionally, thoracic murine aortas were exposed to HG or to normal glucose (NG) control. The rings were then placed in an organ chamber bath and dose response curves to increasing doses of acetylcholine (Ach) and sodium nitroprusside were constructed for three groups: control (normal glucose), HG alone, and HG + vericiguat. Results: HVSMCs exposed to HG produced significantly less cGMP than those exposed to NG. cGMP production in the presence of HG was rescued when treated with 1uM vericiguat. Additionally, PKG activity was impaired in the presence of HG and enzyme activity was restored with vericiguat. In isolated mouse aortic rings, ACh mediated relaxation was impaired following treatment with HG, but was improved when a HG group was treated with vericiguat. Conclusions: The sGC sensitizer/stimulator vericiguat restored cGMP production and PKG activity in the setting of HG. Vericiguat enhanced ACh-mediated vasorelaxation in the setting of HG. The findings suggest clinical studies are warranted to investigate the potential of sGC sensitization/stimulation as a therapeutic intervention to improve vascular endothelial-dependent function that is impaired in pro-inflammatory settings that are associated with the development of atherosclerotic disease.

Emerging clinical role of proprotein convertase subtilisin/kexin type 9 inhibition-Part one: Pleiotropic pro-atherosclerotic effects of PCSK9.

BACKGROUND: Proprotein convertase subtilisin/kexin type 9 (PCSK9) is primarily recognized for its role in lipid metabolism, but recent evidence suggests that it may have broader implications due to its diverse tissue expression. OBJECTIVE: This review aims to explore the multifaceted functions of PCSK9, highlighting its pro-atherosclerotic effects, including its impact on circulating lipoprotein variables, non-low-density lipoprotein receptors, and various cell types involved in atherosclerotic plaque development. CONCLUSIONS: PCSK9 exhibits diverse roles beyond lipid metabolism, potentially contributing to atherosclerosis through multiple pathways. Understanding these mechanisms could offer new insights into therapeutic strategies targeting PCSK9 for cardiovascular disease management.

Emerging clinical role of proprotein convertase subtilisin/kexin type 9 inhibition-Part two: Current and emerging concepts in the clinical use of PCSK9 inhibition.

BACKGROUND: Proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors have emerged as a novel class of drugs with cardioprotective effects through their lipid-lowering effects. OBJECTIVE: This review aims to discuss existing and novel strategies of PCSK9 inhibition, providing an overview of established randomized controlled trials and ongoing outcome trials that assess the efficacy and long-term safety of PCSK9 inhibitors. It also explores the evolving role of PCSK9 beyond lipid metabolism and outlines the pleiotropic actions of PCSK9 inhibition in various disorders and future directions including novel strategies to target PCSK9. CONCLUSION: PCSK9 inhibition shows promise not only in lipid metabolism but also in other disease processes, including atherosclerotic plaque remodeling, acute coronary syndrome, stroke, inflammation, and immune response.

Homocysteine modifies the association of coronary stenosis and HIV infection in an inner city African American population.

BACKGROUND AND AIMS: People with HIV (PWH) whose disease is controlled on anti-retroviral regimens remain at an increased risk for coronary artery disease (CAD). Traditional cardiovascular risk factors do not fully explain the residual risk in PWH suggesting contributions from nontraditional factors. Homocysteine (Hcy) may be one of these as prior work in adults without HIV demonstrate that Hcy may impair endothelial function by decreasing the availability of nitric oxide, promoting the development of atherosclerosis. In addition, plasma Hcy levels are higher in PWH than in individuals living without HIV. The aim of this study was to investigate whether Hcy levels influence the association between HIV and coronary stenosis in an inner city African American population. METHODS: African Americans from the Heart Study in Baltimore, with and without HIV, recruited from inner-city Baltimore between June 2004 and February 2015, were included in this analysis. Participants underwent coronary CT angiography to evaluate the presence of coronary stenosis, defined as luminal stenosis >10%. Hcy was measured from stored serum samples. RESULTS: In this analysis, the median [IQR] age of the 664 participants was 56 [50-66] years; 68.1% were living with HIV and 43.1% were women. Elevated Hcy (>15 µmol/L) was more prevalent in those with coronary stenosis (23.3%, 95% CI: 18.4%-28.2%) than in those without coronary stenosis (13.1%, 95% CI: 9.7%-16.5%) (p = 0.0007), and HIV was associated with coronary stenosis in those participants with an elevated Hcy (Prevalence Ratio: 1.94, 95% CI: 1.04-3.64, p = 0.0038) and not in those with a Hcy ≤15 µmol/L (Prevalence Ratio: 1.02, 95% CI: 0.83-1.25, p = 0.87). CONCLUSIONS: Our data suggest an association between elevated Hcy levels (>15 µmol/L) and the prevalence of coronary stenosis in PWH from this inner city African American population.

Coronary artery endothelial function and aging in people with HIV and HIV-negative individuals.

Coronary artery disease (CAD) is a common comorbidity in people with human immunodeficiency virus (HIV) (PWH) and impaired coronary endothelial function (CEF) plays a central role in the pathogenesis of CAD. Age-related impaired CEF among PWH, however, is not well characterized. We investigated the association between CEF and age in males and females with and without HIV using 3-T magnetic resonance imaging (MRI). We measured the changes in coronary cross-sectional area (CSA) and coronary blood flow during isometric handgrip exercise (IHE), an established endothelial-dependent stressor with smaller increases in CSA and coronary blood flow indicative of impaired CEF. We included 106 PWH and 82 individuals without HIV. Differences in demographic and clinical characteristics between PWH and individuals without HIV were explored using Pearson's χ2 test for categorical variables and Welch's t test for continuous variables. Linear regression models were used to examine the association between CEF and age. CEF was significantly lower in PWH as compared with individuals without HIV. Coronary endothelial dysfunction was also present at younger ages in PWH than in the individuals without HIV and there were significant differences in CEF between the PWH and individuals without HIV across age groups. Among the individuals without HIV, the percent changes in CSA were inversely related to age in unadjusted and adjusted models. There was no significant association between CEF and age in PWH. To the best of our knowledge, this is the first study to examine the relationship between age and CEF in PWH, and our results suggest that factors other than age significantly impair CEF in PWH across the life span.NEW & NOTEWORTHY This is the first study to examine the relationship between age and coronary endothelial function (CEF) in people with human immunodeficiency virus (HIV) (PWH). CEF was assessed using magnetic resonance imaging (MRI) in people with and without HIV. Although age and CEF were significantly inversely related in individuals without HIV, there was no association between age and CEF in PWH.

Defining Misinformation and Related Terms in Health-Related Literature: Scoping Review.

BACKGROUND: Misinformation poses a serious challenge to clinical and policy decision-making in the health field. The COVID-19 pandemic amplified interest in misinformation and related terms and witnessed a proliferation of definitions. OBJECTIVE: We aim to assess the definitions of misinformation and related terms used in health-related literature. METHODS: We conducted a scoping review of systematic reviews by searching Ovid MEDLINE, Embase, Cochrane, and Epistemonikos databases for articles published within the last 5 years up till March 2023. Eligible studies were systematic reviews that stated misinformation or related terms as part of their objectives, conducted a systematic search of at least one database, and reported at least 1 definition for misinformation or related terms. We extracted definitions for the terms misinformation, disinformation, fake news, infodemic, and malinformation. Within each definition, we identified concepts and mapped them across misinformation-related terms. RESULTS: We included 41 eligible systematic reviews, out of which 32 (78%) reviews addressed the topic of public health emergencies (including the COVID-19 pandemic) and contained 75 definitions for misinformation and related terms. The definitions consisted of 20 for misinformation, 19 for disinformation, 10 for fake news, 24 for infodemic, and 2 for malinformation. "False/inaccurate/incorrect" was mentioned in 15 of 20 definitions of misinformation, 13 of 19 definitions of disinformation, 5 of 10 definitions of fake news, 6 of 24 definitions of infodemic, and 0 of 2 definitions of malinformation. Infodemic had 19 of 24 definitions addressing "information overload" and malinformation had 2 of 2 definitions with "accurate" and 1 definition "used in the wrong context." Out of all the definitions, 56 (75%) were referenced from other sources. CONCLUSIONS: While the definitions of misinformation and related terms in the health field had inconstancies and variability, they were largely consistent. Inconstancies related to the intentionality in misinformation definitions (7 definitions mention "unintentional," while 5 definitions have "intentional"). They also related to the content of infodemic (9 definitions mention "valid and invalid info," while 6 definitions have "false/inaccurate/incorrect"). The inclusion of concepts such as "intentional" may be difficult to operationalize as it is difficult to ascertain one's intentions. This scoping review has the strength of using a systematic method for retrieving articles but does not cover all definitions in the extant literature outside the field of health. This scoping review of the health literature identified several definitions for misinformation and related terms, which showed variability and included concepts that are difficult to operationalize. Health practitioners need to exert caution before labeling a piece of information as misinformation or any other related term and only do so after ascertaining accurateness and sometimes intentionality. Additional efforts are needed to allow future consensus around clear and operational definitions.

Efficacy of lung cancer screening at the American University of Beirut Medical Center.

Introduction: In Lebanon, a dedicated screening program for lung cancer is absent. Screening is largely based on the recommendation of an informed physician or the initiative of a patient. To better understand the situation, it is important to look at the available data on patients currently being screened for lung cancer in this country. Our aim in this study is to review the data and compare it with that in the literature as well as to assess the efficacy of the screening process followed. Methods: Our study accessed the electronic medical records of patients at the American University of Beirut Medical Center (AUBMC), a tertiary care center in Lebanon. We collected information on patients who underwent screening low-dose computed tomography (LDCT) scan between June 2019 and June 2021 inclusive. Records of all patients who underwent a non-contrast computed tomography (CT) scan at AUBMC during this period were collected and analyzed. Results: On average, our population had a 52.6 pack-year smoking history. Moreover, 47% of our population had an accurate pack-year reported, while 12% did not have enough information to even estimate their pack-year history. When looking at the accurate and estimated data, 5% of our population did not even meet the ≥20 pack-year smoking history. Eight patients had positive findings on the screening LDCT, which we defined as suspicious findings that require further workup (e.g., PET/CT or biopsy) or other significant incidental findings. Conclusion: A well-organized program for lung cancer screening in Lebanon is absent. Screening largely depends on the initiative of the physician or the patient. We were able to uncover multiple flaws in the screening method used, including poor documentation and follow-up. Although the screening method adopted retained some benefits in terms of detecting early malignancy, it lacked proper organization and was not ideal. A better, systematized screening program is needed to have optimal outcomes.

Platelet activation and endothelial dysfunction biomarkers in acute coronary syndrome: the impact of PCSK9 inhibition.

AIMS: Platelet activation and endothelial dysfunction contribute to adverse outcomes in patients with acute coronary syndromes (ACS). The goals of this study were to assess the impact of proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibition on markers of platelet activation and endothelial dysfunction in ACS patients and the interaction among PCSK9, platelets, and endothelial cells (ECs) on left internal mammary artery (LIMA) vascular endothelium using specimens obtained during coronary artery bypass surgery (CABG). METHODS AND RESULTS: Acute coronary syndromes patients enrolled in the Evolocumab in ACS trials were randomized to placebo or a single dose of 420 mg evolocumab within 24 h of hospitalization. Serum samples for analysis of platelet factor 4 (PF4) and P-selectin, markers of platelet activation, and von Willebrand factor (vWF), a marker of endothelial dysfunction, were obtained at baseline and 30 days. Additionally, LIMA segments obtained during CABG from patients who were and were not receiving evolocumab were immunostained with PCSK9; CD61, a platelet-specific marker; and CD31, an endothelial cell-specific marker. Forty-six participants were randomized to placebo or to evolocumab. Controlling for baseline levels, PF4 and vWF were significantly lower in the evolocumab, than in the placebo, group at 30 days. Immunostaining of LIMA specimens from twelve participants undergoing CABG revealed colocalization of PCSK9, CD61, and CD31 at the vascular endothelium. Administration of evolocumab was associated with decreased overlap of PCSK9, CD61, and CD31. CONCLUSIONS: Proprotein Convertase Subtilisin/Kexin 9 inhibition decreases markers of platelet activation and endothelial dysfunction in ACS patients. PCSK9 is associated with platelets and vascular ECs in LIMA segments and PCSK9 inhibition decreases that interaction.

Novel Diagnostic Imaging Approach for Patients With Spontaneous Coronary Artery Dissection: The Utility of 18 F-FDG PET Imaging.

ABSTRACT: Spontaneous coronary artery dissection (SCAD) is an underdiagnosed etiology of acute coronary syndrome in women. Accurate diagnosis remains challenging but is imperative for treatment and prevention. We show here the utility of 18 F-FDG PET imaging in SCAD diagnosis. We present 1 representative case of 4 women with suspected SCAD on coronary angiography from the EVACS (Evolocumab in Acute Coronary Syndromes) clinical trial. 18 F-FDG PET imaging showed acute inflammation in the distribution of the suspected dissected coronary artery identified on angiography. Localized myocardial inflammation identified on 18 F-FDG PET imaging can aid in diagnosing SCAD suspected on coronary angiography.

Lipoprotein(a) concentrations in acute myocardial infarction patients are not indicative of levels at six month follow-up.

Aims: Lipoprotein(a) [Lp(a)] levels are generally constant throughout an individual's lifetime, and current guidelines recommend that a single measurement is sufficient to assess the risk of coronary artery disease (CAD). However, it is unclear whether a single measurement of Lp(a) in individuals with acute myocardial infarction (MI) is indicative of the Lp(a) level six months following the event. Methods and results: Lp(a) levels were obtained from individuals with non-ST-elevation myocardial infarction (NSTEMI) or ST-elevation myocardial infarction (STEMI) (n = 99) within 24 h of hospital admission and after six months, who were enrolled in two randomized trials of evolocumab and placebo, and in individuals with NSTEMI or STEMI (n = 9) who enrolled in a small observation arm of the two protocols and did not receive study drug, but whose levels were obtained at the same time points. Median Lp(a) levels increased from 53.5 nmol/L (19, 165) during hospital admission to 58.0 nmol/L (14.8, 176.8) six months after the acute infarction (P = 0.02). Subgroup analysis demonstrated no difference in the baseline, six-month, or change between the baseline and six-month Lp(a) values between the STEMI and NSTEMI groups and between the group which received evolocumab and the group that did not. Conclusion: This study demonstrated that Lp(a) levels in individuals with acute MI are significantly higher six months after the initial event. Therefore, a single measurement of Lp(a) in the peri-infarction setting is not sufficient to predict the Lp(a)-associated CAD risk in the post-infarction period. Registration: Evolocumab in Acute Coronary Syndrome Trial [EVACS I] NCT03515304, Evolocumab in Patients with Acute Myocardial Infarction [EVACS II], NCT04082442.

A Framework for the Development of Living Practice Guidelines in Health Care.

BACKGROUND: Living practice guidelines are increasingly being used to ensure that recommendations are responsive to rapidly emerging evidence. OBJECTIVE: To develop a framework that characterizes the processes of development of living practice guidelines in health care. DESIGN: First, 3 background reviews were conducted: a scoping review of methods papers, a review of handbooks of guideline-producing organizations, and an analytic review of selected living practice guidelines. Second, the core team drafted the first version of the framework. Finally, the core team refined the framework through an online survey and online discussions with a multidisciplinary international group of stakeholders. SETTING: International. PARTICIPANTS: Multidisciplinary group of 51 persons who have experience with guidelines. MEASUREMENTS: Not applicable. RESULTS: A major principle of the framework is that the unit of update in a living guideline is the individual recommendation. In addition to providing definitions, the framework addresses several processes. The planning process should address the organization's adoption of the living methodology as well as each specific guideline project. The production process consists of initiation, maintenance, and retirement phases. The reporting should cover the evidence surveillance time stamp, the outcome of reassessment of the body of evidence (when applicable), and the outcome of revisiting a recommendation (when applicable). The dissemination process may necessitate the use of different venues, including one for formal publication. LIMITATION: This study does not provide detailed or practical guidance for how the described concepts would be best implemented. CONCLUSION: The framework will help guideline developers in planning, producing, reporting, and disseminating living guideline projects. It will also help research methodologists study the processes of living guidelines. PRIMARY FUNDING SOURCE: None.

Predicting uterine weight before hysterectomy: ultrasound measurements versus clinical assessment.

OBJECTIVE: The purpose of this study was to determine the most accurate method in estimating the preoperative uterine weight of enlarged nongravid uteri. STUDY DESIGN: We performed a retrospective review of 1238 patients who were premenopausal and underwent hysterectomy for benign indications between January 1993 and July 1999. Eight hundred and sixty-four patients were selected to include only those that had both a reported bimanual assessment of preoperative uterine size and an ultrasonography report with all 3 estimated uterine dimensions. Reported uterine sizes on bimanual examination were converted to clinical weight (CWT). Two different calculations were used to estimate uterine weight from ultrasound measurements (UWT 1 and 2). Actual uterine weights (AWT) in pathology reports were then compared with the findings of bimanual assessment and the calculated weights to determine which method is the best predictor of AWT. Simple linear regression analysis was used to measure and compare how closely the estimated weights predicted the actual weight. Predictive residuals sum of squares (PRESS) was then used to determine the best predictor of actual weight. RESULTS: After exploring the data using linear modeling, all 3 estimated weights were significantly correlated to the actual weight when compared, but PRESS scores showed that the clinical weight estimate was superior by far compared with the other 2. CONCLUSION: In this study, bimanual assessment was shown to be the most accurate method of preoperative uterine weight estimation. Ultrasound examination may not be routinely needed when deciding the route of hysterectomy based on estimated weight.

The small-for-gestational-age twin: blessing or curse?

OBJECTIVE: To compare small-for-gestational-age (SGA) twins to appropriate-for-gestational-age (AGA) twins regarding preterm delivery (PTD). STUDY DESIGN: Retrospective review of maternal and neonatal records of live, nonanomalous twins > or = 25 weeks' gestation delivered in 1984-2000 in a tertiary care center. Pregnancies (N = 679) were divided into AGA/ AGA (n = 347), SGA-AGA (n = 191) and SGA/SGA (n = 141) groups using singleton growth curves. The PTD rate was compared and logistic regression analysis was done to study factors that influenced PTD at < or = 34 weeks. p < 0.05 was considered significant. RESULTS: The PTD rate at < or = 34 weeks was AGA/AGA (38.6%), SGA-AGA (14.7%) and SGA/SGA (1.4%) (p < 0.001). On multiple logistic regression analysis, discordance significantly increased PTD (OR = 5.05, 2.47-10.31, p = 0.001), while smallness for gestational age significantly decreased PTD (OR = 0.095, 0.05-0.17, p < 0.001). The PTD rate increased directly with the increase in the relative overall weight of the twins. CONCLUSION: The PTD rate is higher in AGA twins as compared to SGA twins. The PTD rate is directly related to the overall weight of the twins.

Pregnancy outcome in spontaneous twins versus twins who were conceived through in vitro fertilization.

OBJECTIVE: The purpose of this study was to compare maternal and neonatal complications in spontaneous versus in vitro fertilization twins. STUDY DESIGN: Twin gestations that were delivered from 1995 to 2000 were reviewed. Cases consisted of 56 in vitro fertilization twins, each of which was matched to two control mothers by age and parity. They were compared regarding various maternal and neonatal complications. RESULTS: In vitro fertilization twins were more likely to have preterm labor compared with control twins, with no difference in the incidences of pregnancy-induced hypertension, gestational diabetes mellitus, placenta previa, or preterm premature rupture of membranes between the two groups. The cesarean delivery rate was significantly higher in cases of twins who were conceived by in vitro fertilization (76.8% vs 58.0%, P=.026), despite a similar rate of elective cesarean delivery and the incidence of nonvertex twin A in both groups. The preterm delivery rate was significantly higher (67.9% vs 41.1%, P=.002) and the gestational age was significantly lower (35+/-3 weeks vs 36+/-3 weeks, P=.043) in cases compared with control subjects. Both twins were, on the average, 230 g lighter in the in vitro fertilization group compared with the control group. However, intrauterine growth restriction was more frequent in the control group (36.6% vs 25%, P=.044). There was a significantly higher incidence of admission to the neonatal intensive care unit, respiratory distress syndrome, a need for mechanical ventilation, and pneumothorax in cases compared with control subjects. CONCLUSION: When compared with spontaneous twins, in vitro fertilization twins are more likely to be delivered by cesarean delivery and to have a higher incidence of preterm birth and prematurity-related respiratory complications with a longer nursery stay.