Evaluating the Rates of Mortality and Cardiac Catheterization Using High-Sensitivity Troponin and Conventional Troponin Assays.

Non-ST segment elevation myocardial infarction (NSTEMI) is an acute coronary syndrome event where myocardial ischemia is present, with an increase of cardiac troponins without an elevation of the ST segment. One of the fundamental measures used to diagnose or rule out acute coronary syndrome (ACS) is troponin levels in the blood. Troponin is a broad term used for the category of muscle contraction regulatory proteins and is commonly measured during ACS evaluation. Troponin I is only released by cardiac tissue, while some assay measurements will also pick up troponin released by skeletal muscle injury. This retrospective observational study was performed investigating troponin assays and how they relate to patient's outcomes. The troponin assays used in this Miami hospital where the database of patients was collected between 2018 and 2023 were troponin I (cTnI), the conventional troponin assay, and the newer high-sensitivity troponin I assay (hs-cTn). In this observational study patients who received an admitting diagnosis of NSTEMI corroborated by an independent cardiologist had their respective troponin assay levels included. Patients found to have ECG changes significant for non-ischemic pathologies, or echocardiogram findings suggestive of myocardial dysfunction not clinically correlated to an ACS were excluded from the study. A total of 75 patients were included in this study and the mean age was 75.97 ±14.72 years, with a presentation of chest pain, dyspnea and general weakness recorded in 59% (n = 45) of patients. The median time between troponin samples was 6.63 hours across both assays and hs-cTn showed a 4.99% increase in variation between samples while cTnI had a decrease of 2.53%. The study objective is to support whether there is a difference in rates of cardiac catheterization or mortality based on the type of troponin testing. There was no significant association found between, the type of troponin assay used during hospital admission, and the outcomes of catheterization and death (p > 0.009).

Development of a new definition of maternal near miss based on organ dysfunction in Latin America and the Caribbean: A prospective multicenter cohort study.

BACKGROUND: There has been debate over whether the existing World Health Organization (WHO) criteria accurately represent the severity of maternal near misses. OBJECTIVE: This study assessed the diagnostic accuracy of two WHO clinical and laboratory organ dysfunction markers for determining the best cutoff values in a Latin American setting. METHODS: A prospective multicenter cohort study was conducted in five Latin American countries. Patients with severe maternal complications were followed up from admission to discharge. Organ dysfunction was determined using clinical and laboratory data, and participants were classified according to severe maternal outcomes. This study compares the diagnostic criteria of Latin American Centre for Perinatology, Network for Adverse Maternal Outcomes (CLAP/NAMO) to WHO standards. RESULTS: Of the 698 women studied, 15.2% had severe maternal outcomes. Most measured variables showed significant differences between individuals with and without severe outcomes (all P-values <0.05). Alternative cutoff values suggested by CLAP/NAMOs include pH ≤7.40, lactate ≥2.3 mmol/L, respiratory rate ≥ 24 bpm, oxygen saturation ≤ 96%, PaO2/FiO2 ≤ 342 mmHg, platelet count ≤189 × 109 × mm3, serum creatinine ≥0.8 mg/dL, and total bilirubin ≥0.67 mg/dL. No significant differences were found when comparing the diagnostic performance of the CLAP/NAMO criteria to that of the WHO standards. CONCLUSION: The CLAP/NAMO values were comparable to the WHO maternal near-miss criteria, indicating that the WHO standards might not be superior in this population. These findings suggest that maternal near-miss thresholds can be adapted regionally, improving the identification and management of severe maternal complications in Latin America.

Evaluating the strength and quality of evidence in american heart association/American stroke association's guidelines for aneurysmal subarachnoid hemorrhage and spontaneous intracerebral hemorrhage.

BACKGROUND: Clinical practice recommendations guide healthcare decisions. This study aims to evaluate the strength and quality of evidence supporting the American Heart Association (AHA)/American Stroke Association (ASA) guidelines for aneurysmal subarachnoid hemorrhage (aSAH) and spontaneous intracerebral hemorrhage (ICH). METHODS: We reviewed the current AHA/ASA guidelines for aSAH and spontaneous ICH and compared with previous guidelines. Guidelines were classified based on the Class of recommendation (COR) and Level of evidence (LOE). COR signifies recommendation strength (COR 1: Strong; COR 2a: Moderate; COR 2b: Weak; COR 3: No Benefit/Harm), while LOE denotes evidence quality (LOE A: High-Quality; LOE B-NR: Moderate-Quality, Not Randomized; LOE B-R: Moderate-Quality, Randomized; LOE C-EO: Expert Opinion; LOE C-LD: Limited Data). RESULTS: For aSAH, we identified 84 recommendations across 15 guideline categories. Of these, 31% were classified as COR I, 30% as COR 2a, 17% as COR 2b, and 18% as COR 3. In terms of LOE, 7% were based on LOE A, 10% on LOE B-R, 65% on LOE B-NR, 14% on LOE C-LD, and 5% on LOE C-EO. Compared to previous guidelines, there was a 46% decrease in LOE A, a 45% increase in LOE B, and an 11% decrease in LOE C. For spontaneous ICH, 124 guidelines were identified across 31 guideline categories. Of these, 28% were COR I, 32% COR 2b, and 9% COR 3. For LOE, 4% were based on LOE A, 35% on LOE B-NR, and 42% on LOE C-LD. Compared to previous guidelines, there was a 78% decrease in LOE A, an 82% increase in LOE B, and a 14% increase in LOE C. This analysis highlights that less than a third of AHA/ASA guidelines are classified as the highest class of recommendation, with less than 10% based on the highest LOE. CONCLUSION: Less than a third of AHA/ASA guidelines on aSAH and spontaneous ICH are classified as the highest class of recommendation with less than 10% based on highest LOE. There appears to be a decrease in proportion of guidelines based on highest LOE in most recent guidelines.

Addressing the Evidence Gap in Aneurysmal Subarachnoid Hemorrhage: The Need for a Pragmatic Randomized Trial Platform.

Aneurysmal subarachnoid hemorrhage (aSAH) occurs less often than other stroke types but affects younger patients, imposing a disproportionately high burden of long-term disability. Although management advances have improved outcomes over time, relatively few aSAH treatments have been tested in randomized clinical trials (RCTs). One lesson learned from COVID-19 is that trial platforms can facilitate the efficient execution of multicenter RCTs even in complex diseases during challenging conditions. An aSAH trial platform with standardized eligibility criteria, randomization procedures, and end point definitions would enable the study of multiple targeted interventions in a perpetual manner, with treatments entering and leaving the platform based on predefined decision algorithms. An umbrella institutional review board protocol and clinical trial agreement would allow individual arms to be efficiently added as amendments rather than stand-alone protocols. Standardized case report forms using the National Institutes of Health/National Institute of Neurological Disorders and Stroke common data elements and general protocol standardization across arms would create synergies for data management and monitoring. A Bayesian analysis framework would emphasize frequent interim looks to enable early termination of trial arms for futility, common controls, borrowing of information across arms, and adaptive designs. A protocol development committee would assist investigators and encourage pragmatic designs to maximize generalizability, reduce site burden, and execute trials efficiently and cost-effectively. Despite decades of steady clinical progress in the management of aSAH, poor patient outcomes remain common, and despite the increasing availability of RCT data in other fields, it remains difficult to perform RCTs to guide more effective care for aSAH. The development of a platform for pragmatic RCTs in aSAH would help close the evidence gap between aSAH and other stroke types and improve outcomes for this important disease with its disproportionate public health burden.

Prevalence and Neurological Outcomes of Comatose Patients With Extracorporeal Membrane Oxygenation.

OBJECTIVES: To investigate prevalence, risk factors, and in-hospital outcomes of comatose extracorporeal membrane oxygenation (ECMO) patients. DESIGN: Retrospective observational. SETTING: Tertiary academic hospital. PARTICIPANTS: Adults received venoarterial (VA) or venovenous (VV) ECMO support between November 2017 and April 022. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: We defined 24-hour off sedation as no sedative infusion (except dexmedetomidine) or paralytics administration over a continuous 24-hour period while on ECMO. Off-sedation coma (comaoff) was defined as a Glasgow Coma Scale score of ≤8 after achieving 24-hour off sedation. On-sedation coma (comaon) was defined as a Glasgow Coma Scale score of ≤8 during the entire ECMO course without off sedation for 24 hours. Neurological outcomes were assessed at discharge using the modified Rankin scale (good, 0-3; poor, 4-6). We included 230 patients (VA-ECMO 143, 65% male); 24-hour off sedation was achieved in 32.2% VA-ECMO and 26.4% VV-ECMO patients. Among all patients off sedation for 24 hours (n = 69), 56.5% VA-ECMO and 52.2% VV-ECMO patients experienced comaoff. Among those unable to be sedation free for 24 hours (n = 161), 50.5% VA-ECMO and 17.2% VV-ECMO had comaon. Comaoff was associated with poor outcomes (p < 0.05) in VA-ECMO and VV-ECMO groups, whereas comaon only impacted the VA-ECMO group outcomes. In a multivariable analysis, requirement of renal replacement therapy was an independent risk factor for comaoff after adjusting for ECMO configuration, after adjusting for ECMO configuration, acute brain injury, pre-ECMO partial pressure of oxygen in arterial blood, partial pressure of carbon dioxide in arterial blood, pH, and bicarbonate level (worst value within 24 hours before cannulation). CONCLUSIONS: Comaoff was common and associated with poor outcomes at discharge. Requirement of renal replacement therapy was an independent risk factor.

Development of a Smartwatch with Gas and Environmental Sensors for Air Quality Monitoring.

In recent years, there has been a growing interest in developing portable and personal devices for measuring air quality and surrounding pollutants, partly due to the need for ventilation in the aftermath of COVID-19 situation. Moreover, the monitoring of hazardous chemical agents is a focus for ensuring compliance with safety standards and is an indispensable component in safeguarding human welfare. Air quality measurement is conducted by public institutions with high precision but costly equipment, which requires constant calibration and maintenance by highly qualified personnel for its proper operation. Such devices, used as reference stations, have a low spatial resolution since, due to their high cost, they are usually located in a few fixed places in the city or region to be studied. However, they also have a low temporal resolution, providing few samples per hour. To overcome these drawbacks and to provide people with personalized and up-to-date air quality information, a personal device (smartwatch) based on MEMS gas sensors has been developed. The methodology followed to validate the performance of the prototype was as follows: firstly, the detection capability was tested by measuring carbon dioxide and methane at different concentrations, resulting in low detection limits; secondly, several experiments were performed to test the discrimination capability against gases such as toluene, xylene, and ethylbenzene. principal component analysis of the data showed good separation and discrimination between the gases measured.

Neurological Complications of Cannabinoids.

Cannabinoid use, particularly for recreational purposes, is increasing exponentially across all age groups, especially in younger populations, due to its perceived low risk and legalization. While cannabinoids may be largely considered as safe, there is mounting evidence of increased risk of systemic and neurological complications through their interaction with the poorly understood endocannabinoid receptor network within the central nervous system and other organ systems. Acute cannabinoid exposure can cause neuropsychiatric symptoms in addition to altering cerebral blood flow, leading to cerebrovascular complications such as ischemic stroke, subarachnoid hemorrhage, and reversible cerebral vasoconstriction syndrome (RCVS). Chronic use, particularly among adolescents, may be associated with increased risk of long-term cognitive deficits, schizophrenia, and other neuropsychiatric effects. Synthetic cannabinoids have increased potency, with reports of causing profound neurological complications including coma, seizures, posterior reversible encephalopathy syndrome, and RCVS. Despite increasing evidence, the quality of literature describing neurologic complications with cannabinoids remains limited to case series and retrospective cohort studies, with significant confounding factors such as concomitant use of other illicit drugs, limiting interpretation. In this review, we summarize the effect of cannabinoids on the neurologic system and associated neurological complications.

Wuchereria bancrofti Lymphatic Filariasis, Barrancabermeja, Colombia, 2023.

We describe a recent case of lymphatic filariasis in Colombia caused by Wuchereria bancrofti nematodes. Our study combines clinical-epidemiologic findings with phylogenetic data. Resurgence of lymphatic filariasis may be linked to increasing urbanization trends and migration from previously endemic regions. Fieldwork can be a beneficial tool for screening and containing transmission.

The Accelerated Onset of Calciphylaxis in a 72-Year-Old Female Hemodialysis Patient.

Calciphylaxis is a unique medical condition characterized by calcification of the medial layer of arterioles and soft tissues in a patient's skin at the level of the dermis and subcutaneous adipose tissue. The rate of progression of calciphylaxis is rapid, starting with a reduction of blood flow that leads to ischemic changes in the skin that can manifest as painful cutaneous erythematous nodules or plaques and later as skin ulceration. The majority of patients affected by calciphylaxis have predisposing comorbidities such as end-stage renal disease with a long history of hemodialysis and electrolyte abnormalities in calcium, phosphate, and parathyroid hormone levels. This report presents the case of a 72-year-old female patient on hemodialysis who developed calciphylaxis. The methods for early prognosis (the methods of early diagnosis), including clinical presentation, risk factors, imaging techniques, and laboratory investigations, are discussed. The presented case is particularly noteworthy given the onset of calciphylaxis within a mere three months of initiating hemodialysis, a timeline significantly shorter than the typically observed period in most patients. (The case detailed in this report outlines the rapid onset of calciphylaxis in a patient who was receiving hemodialysis for only three months.) This patient with early-onset calciphylaxis highlights the unpredictable nature of calciphylaxis and the need for increased clinical vigilance even in the initial stages of hemodialysis.

Machine Learning Identifies Variation in Timing of Palliative Care Consultations Among Traumatic Brain Injury Patients.

Background and Objective Timely palliative care involvement offers demonstrable benefits for traumatic brain injury (TBI) patients; however, palliative care consultations (PCCs) are used inconsistently during TBI management. This study aimed to employ advanced machine learning techniques to elucidate the primary drivers of PCC timing variability for TBI patients. Methods Data on admission, hospital course, and outcomes were collected for a cohort of 232 TBI patients who received both PCCs and neurosurgical consultations during the same hospitalization. Principal Component Analysis (PCA) and K-means clustering were used to identify patient phenotypes, which were then compared using Kaplan-Meier analysis. An extreme gradient boosting model (XGBoost) was employed to determine drivers of PCC timing, with model interpretation performed using SHapley Additive exPlanations (SHAP). Results Cluster A (n = 86) consisted mainly of older (median [IQR] = 87 [78, 94] years), White females with mild TBIs and demonstrated the shortest time-to-PCC (2.5 [1.0, 7.0] days). Cluster B (n = 108) also sustained mild TBIs but comprised moderately younger (81 [75, 86] years) married White males with later PCC (5.0 [3.0, 10.8] days). Cluster C (n = 38) represented much younger (46.5 [29.5, 59.8] years), more severely injured, non-White patients with the latest PCC initiation (9.0 [4.2, 17.0] days). The clusters did not differ by discharge disposition (p = 0.4) or frequency inpatient mortality (p > 0.9); however, Kaplan-Meier analysis revealed a significant difference in the time from admission to PCC (p < 0.001), despite no differences in time from admission to mortality (p = 0.18). SHAP analysis of the XGBoost model identified age, sex, and race as the most influential drivers of PCC timing. Conclusions This study highlights crucial disparities in PCC timing for TBI patients and underscores the need for targeted strategies to ensure timely and equitable palliative care integration for this vulnerable population.

Evaluation of the Glasgow Coma Scale-Pupils score for predicting inpatient mortality among patients with traumatic subdural hematoma at United States trauma centers.

OBJECTIVE: The Glasgow Coma Scale-Pupils (GCS-P) score has been suggested to better predict patient outcomes compared with GCS alone, while avoiding the need for more complex clinical models. This study aimed to compare the prognostic ability of GCS-P versus GCS in a national cohort of traumatic subdural hematoma (SDH) patients. METHODS: Patient data were obtained from the National Trauma Data Bank (2017-2019). Inclusion criteria were traumatic SDH diagnosis with available data on presenting GCS score, pupillary reactivity, and discharge disposition. Patients with severe polytrauma or nonsurvivable head injury at presentation were excluded. Sensitivity, specificity, and area under the receiver operating characteristic curve (AUC) of GCS-P versus GCS scores for inpatient mortality prediction were evaluated across the entire cohort, as well as in subgroups based on age and traumatic brain injury (TBI) type (blunt vs penetrating). Calibration curves were plotted based on predicted probabilities and actual outcomes. RESULTS: A total of 196,747 traumatic SDH patients met the study inclusion criteria. Sensitivity (0.707 vs 0.702), specificity (0.821 vs 0.823), and AUC (0.825 vs 0.814, p < 0.001) of GCS-P versus GCS scores for prediction of inpatient mortality were similar. Calibration curve analysis revealed that GCS scores slightly underestimated inpatient mortality risk, whereas GCS-P scores did not. In patients > 65 years of age with blunt TBI (51.9%, n = 102,148), both GCS-P and GCS scores underestimated inpatient mortality risk. In patients with penetrating TBI (2.4%, n = 4,710), the AUC of the GCS-P score was significantly higher (0.902 vs 0.851, p < 0.001). In this subgroup, both GCS-P and GCS scores underestimated inpatient mortality risk among patients with lower rates of observed mortality and overestimated risk among patients with higher rates of observed mortality. This effect was more pronounced in the GCS-P calibration curve. CONCLUSIONS: The GCS-P score provides better short-term prognostication compared with the GCS score alone among traumatic SDH patients with penetrating TBI. The GCS-P score overestimates inpatient mortality risk among penetrating TBI patients with higher rates of observed mortality. For penetrating TBI patients, which comprised 2.4% of our SDH cohort, a low GCS-P score should not justify clinical nihilism or forgoing aggressive treatment.

Coma Prevalence in Critical Care Units in Chile: Results of a Cross-Sectional Survey on World Coma Day.

BACKGROUND: The purpose of this study was to assess the prevalence of coma among patients in critical care units in Chile. We also aimed to provide insight into the demographic characteristics, etiologies, and complications associated with coma. METHODS: A single day cross-sectional study was conducted through a national survey of public and private hospitals with critical and intensive cardiac care units across Chile. Data were collected using an online questionnaire that contained questions regarding critically ill patients' information, demographic characteristics, etiology and duration of coma, medical complications, and support requirements. RESULTS: A total of 84% of all health facilities answered, accounting for a total of 2,708 patients. The overall coma prevalence was 2.9%. The median age of the comatose patients was 61 years (interquartile range 50-72) and 66.2% were male. The median coma duration was five days (interquartile range 2-9). Cerebral hemorrhage was the most common etiology, followed by severe hypoxic-ischemic encephalopathy, acute ischemic stroke, and traumatic brain injury. A total of 48.1% of coma patients experienced acute and ongoing treatment complications, with pneumonia being the most common complication, and 97.4% required support during comatose management. CONCLUSIONS: This study provides an overview of the prevalence of coma in Chilean critical and cardiac care units. Coma is a common condition. Comatose patients frequently experience medical complications during their hospitalization.

An Update on Curing Coma Campaign.

The Curing Coma Campaign (CCC) and its contributing collaborators identified multiple key areas of knowledge and research gaps in coma and disorders of consciousness (DoC). This step was a crucial effort and essential to prioritize future educational and research efforts. These key areas include defining categories of DoC, assessing DoC using multimodal approach (e.g., behavioral assessment tools, advanced neuroimaging studies), discussing optimal clinical trials' design and exploring computational models to conduct clinical trials in patients with DoC, and establishing common data elements to standardize data collection. Other key areas focused on creating coma care registry and educating clinicians and patients and promoting awareness of DoC to improve care in patients with DoC. The ongoing efforts in these key areas are discussed.

Orthotopic Robot-assisted Kidney Transplantation: Surgical Technique and Preliminary Results.

BACKGROUND AND OBJECTIVE: Orthotopic kidney transplantation (KT) has been proposed as an option for patients ineligible for heterotopic KT. In this scenario, orthotopic robot-assisted KT (oRAKT) represents a novel, minimally invasive alternative to the open approach. Here we describe the largest oRAKT series of patients, with a focus on the surgical technique, perioperative surgical outcomes, and functional results. METHODS: We queried prospectively maintained databases from three referral centers to identify patients who underwent oRAKT and evaluated surgical and functional outcomes. KEY FINDINGS AND LIMITATIONS: Overall, 16 oRAKT procedures were performed between January 2020 and August 2023. These involved four donors after cardiovascular death, five donors after brain death, and seven living donors. All oRAKT procedures were carried out in the left renal fossa. The indication for oRAKT was extensive calcification of the external iliac vessels (100%), frequently associated with prior KT (31%). The median operative time was 295 min (interquartile range [IQR] 268-360) and the median rewarming time 48 min (IQR 40-54). Conversion to open surgery occurred in two cases (12%), and delayed graft function was observed in two cases (12%). Postoperative complications occurred in 11 patients (69%) and three (18%) experienced Clavien-Dindo grade >II complications. At median follow-up of 9 mo (IQR 7-17), 14 patients had a functioning graft and median creatinine of 1.49 mg/dl (IQR 1.36-1.72). CONCLUSIONS AND CLINICAL IMPLICATIONS: Although oRAKT is a challenging procedure, it represents a feasible option for individuals ineligible for heterotopic KT and yields favorable perioperative and mid-term functional outcomes. PATIENT SUMMARY: We evaluated outcomes of orthotopic robot-assisted kidney transplantation (KT), in which the native kidney is removed and the donor kidney is transplanted into its place, in patients who are not eligible for heterotopic KT, in which the native kidney is left in place and the donor kidney is transplanted into a new location. We found that robot-assisted surgery is a safe and feasible alternative to traditional open surgery for orthotopic KT.

Snakebite-Associated Infections: A Systematic Review and Meta-Analysis.

Snakebites still constitute a significant public health problem in developing countries and are considered a neglected tropical condition by the WHO. Snake accidents are associated with substantial morbidity and mortality and may produce secondary complications, such as severe infections. The objective of this systematic review was to determine the prevalence of snakebite infections and characterize the bacteria isolated from these infections. A systematic literature review in five databases was carried out to assess the prevalence of snakebite infection. A meta-analysis was performed using a random-effects model to calculate the pooled prevalence and 95% CIs. Cochran's Q test and the I2 statistic were used to assess between-study heterogeneity. The pooled prevalence of infection due to snakebite was 27.0% (95% CI: 22.0-32.0%), with high heterogeneity among studies (I2 = 99.7%). The prevalence was higher in Asia (32%) than in the Americas (21%). Snakebite infections required surgical interventions in 68% (95% CI: 37.0-98.0%). The leading group of pathogens identified corresponded to Gram-negative bacteria (63%), particularly Morganella morganii (32%), but also, Gram-positive cocci (40%), especially Enterococcus spp. (23%) and Staphylococcus aureus (15%). However, multiple other pathogens, including anaerobes, were found. A high prevalence of snakebite-associated infection has been described, primarily due to M. morganii, with the corresponding implications for empirical therapy. Rational use of antimicrobials is recommended, and this should guide initial empirical treatment. Moreover, isolation and identification of the possible bacteria present in snakebite wounds is recommended in all cases to confirm or rule out associated infection.

Maternal high-care and intensive care units in low- and middle-income countries.

Despite notable advancements in minimizing maternal mortality during recent decades, a pronounced disparity persists between high-income nations and low-to middle-income countries (LMICs), particularly in intensive and high-care for pregnant and postpartum individuals. This divergence is multifactorial and influenced by factors such as the availability and accessibility of community-based maternity healthcare services, the quality of preventive care, timeliness in accessing hospital or critical care, resource availability, and facilities equipped for advanced interventions. Complications from various conditions, including human immunodeficiency virus (HIV), unsafe abortions, puerperal sepsis, and, notably, the COVID-19 pandemic, intensify the complexity of these challenges. In confronting these challenges and deliberating on potential solutions, we hope to contribute to the ongoing discourse around maternal healthcare in LMICs, ultimately striving toward an equitable health landscape where every mother, regardless of geographic location or socioeconomic status, has access to the care they require and deserve. The use of traditional and innovative methods to achieve adequate knowledge, appropriate skills, location of applicable resources, and strong leadership is essential. By implementing and enhancing these strategies, limited-resource settings can optimize the available resources to promptly recognize the severity of illness in obstetric individuals, ensuring timely and appropriate interventions for mothers and children. Additionally, strategies that could significantly improve the situation include increased investment in healthcare infrastructure, effective resource management, enhanced supply chain efficiency, and the development and use of low-cost, high-quality equipment. Through targeted investments, innovations, efficient resource management, and international cooperation, it is possible to ensure that every maternal high-care and ICU unit, regardless of geographical location or socioeconomic status, has access to high-quality critical care to provide life-saving care.

Effect of Abutment Height on Marginal Bone Loss Around Dental Implants: A Systematic Review.

PURPOSE: To analyze the influence of abutment height (AH) on marginal bone loss (MBL). MATERIALS AND METHODS: A literature search was performed for human studies (RCTs, prospective and retrospective cohorts) reporting on AH and MBL. The data obtained-including clinical outcomes, treatment covariates, and patient characteristics-were analyzed. Meta-regression was performed on the effect size of the differences between the shorter and larger AHs on the MBL of each study. The estimation was done using the restricted maximum likelihood method. RESULTS: The initial screening and full-text analysis resulted in 7,936 and 46 articles, respectively. Finally, 14 articles were included in the systematic review, reporting a total of 1,606 implants. An overall high-to-moderate risk of bias was determined among the included investigations. Meta-regression analysis revealed that AH had a significant effect on MBL (b = -1.630, P < .003), demonstrating that longer abutments were correlated with less MBL. No effects were observed for the study type (P = .607), the number of stages (P = .510), or the elapsed time (P = .491). CONCLUSIONS: The height of the abutment has a significant impact on MBL. As such, increased AH is related to less MBL. Nevertheless, the role of confounding variables remains to be studied and determined.