Multivariable analysis in cerebrovascular research: practical notes for the clinician

Anticoagulation in acute ischemic stroke patients with mechanical heart valves: To bridge or not with heparin. The ESTREM study

INTRODUCTION

The best therapeutic strategy for patients with mechanical heart valves (MHVs) having acute ischemic stroke during treatment with vitamin K antagonists (VKAs) remain unclear. Being so, we compared the outcomes for: (i) full dose heparin along with VKA (bridging therapy group) and (ii) restarting VKA without heparin (nonbridging group).

PATIENTS AND METHODS

For this multicenter observational cohort study, data on consecutive acute ischemic stroke patients with MHV was retrospectively collected from prospective registries. Propensity score matching (PSM) was adopted to adjust for any treatment allocation confounders. The primary outcome was the composite of stroke, systemic embolism, symptomatic cerebral bleeding, and major extracerebral bleeding at 90 days.

RESULTS

Overall, 255 out of 603 patients (41.3%) received bridging therapy: 36 (14.1%) had combined outcome, compared with 28 (8.0%) in the nonbridging group (adjusted OR 1.83; 95% CI 1.05-3.18; p = 0.03). Within the bridging group, 13 patients (5.1%) compared to 12 (3.4%) in the nonbridging group had an ischemic outcome (adjusted OR 1.71; 95% CI 0.84-3.47; p = 0.2); major bleedings were recorded in 23 (9.0%) in the bridging group and 16 (4.6%) in the nonbridging group (adjusted OR 1.88; 95% CI 0.95-3.73; p = 0.07). After PSM, 36 (14.2%) of the 254 bridging patients had combined outcome, compared with 23 (9.1%) of 254 patients in the nonbridging group (OR 1.66; 95% CI 0.95-2.85; p = 0.07).

CONCLUSION

Acute ischemic stroke patients with MHV undergoing bridging therapy had a marginally higher risk of ischemic or hemorrhagic events, compared to nonbridging patients.

Protective Effect of Subcutaneous Drains on Wound Infections in Kidney Transplantation

BACKGROUND

Wound infections following kidney transplantation are common, with a reported incidence of 5%-19%. In the first few days after surgery, these patients receive extremely high doses of immunosuppression and high volumes of intravenous fluids, and they represent a specific subgroup of surgical patients that may benefit from using prophylactic subcutaneous drains.

METHODS

We analyzed a nonrandomized series of 112 consecutive kidney transplants between January 2017 and December 2019: those who received a subcutaneous drain in addition to the standard retroperitoneal drain (SQ drain group) vs those with a retroperitoneal drain alone (standard group).

RESULTS

The SQ drain group had a significantly higher median BMI (31.2 vs 25.8, P < .0001) and a trend towards more patients having diabetes and receiving thymoglobulin on induction. Nonetheless, 1/36 (3%) of patients in the SQ drain group had a documented wound infection requiring packing compared to the standard group 13/73 (17%) (P = .032). When multivariate regression analysis accounted for the potential confounders BMI, thymoglobulin use, and diabetes, the protective effect of the SQ drain was more significant (P = .001).

CONCLUSIONS

An SQ drain may be a simple and inexpensive method to reduce the rate of wound complications in kidney transplant recipients; prospective studies are warranted.

The Terms "Multivariate" and "Multivariable" Are Used Incorrectly and Interchangeably in Orthopaedic Publications: Should We Care About the Distinction?

ABSTRACT

Orthopaedic surgery research increasingly utilizes statistical models to adjust for confounding, provide additional precision, and describe complex relationships. Traditionally, a statistical model is termed "multivariable" if it examines the relationship between multiple independent variables (e.g., covariables). The term "multivariate" is used to describe statistical models with multiple dependent variables (e.g., outcomes). The precise use of statistical terminology is important for study appraisal and reproducibility. The term "multivariate" is frequently used incorrectly in the orthopaedic literature to describe statistical models with a single dependent variable. In our analysis, we found that the term "multivariate" was used frequently, and in >90% of cases, the term was used to describe models that contain only a single dependent variable. Consistent with our perception, the terms "multivariable" and "multivariate" are not used with optimal precision. Below, we discuss the impact of the misuse of statistical terminology and present suggestions for improving statistical reporting.

Variable or variate? A conundrum in pharmacometrics exposure-response models

Key elements of scientific writing-consistency and clarity-can be compromised in case of inaccurate use of methodological terms, especially in complex and multidisciplinary scientific fields. Such is the case in reports of pharmacometrics exposure-response analyses with the use of the terms univariate/multivariate and univariable/multivariable. This perspective outlines the issues in the use of these terms, clarifies their definitions, provides examples, and makes recommendations for authors, reviewers, and journals in the fields of clinical pharmacology and pharmacometrics.

Moderation of marital status and living arrangements in the relationship between social participation and life satisfaction among older Indian adults

Social participation is considered one of the central components of successful and healthy aging. This study aimed to examine the moderating role of marital status and living arrangement with social participation and its association with life satisfaction of older Indian adults. Samples of 31,464 individuals aged ≥ 60 years were extracted from the Longitudinal Ageing Study in India, wave-1. Descriptive statistics, bivariate analysis, and multivariable linear regression were performed for the analysis. The moderation effect of marital status and living arrangements on the relationship between social participation and level of life satisfaction among Indian older adults were also analyzed. Overall, life satisfaction among older men was relatively higher than older women in this study. Older adults' involvement in social participation [β = 0.39, p < 0.05], being in marital union [β = 0.68, p < 0.001] and co-residing either with spouse [β = 1.73, p < 0.001] or with other family members [β = 2.18, p < 0.001] were positively related to their greater life satisfaction. Interaction of social participation with marital status showed that participating in social activities can boost life satisfaction only among married older people. Further, moderation effect of social participation with living arrangements showed that older adults who were not involved in social participation but living with a spouse or any other household members had higher life satisfaction, and again participation in social activities increased their life satisfaction to a greater level. The establishment of social clubs and advocating social policies oriented toward meaningful social connections are highly needed, especially for older Indians living alone or currently not in a marital union, which will help to enhance their overall life satisfaction.

Recurrent Ischemic Stroke and Bleeding in Patients With Atrial Fibrillation Who Suffered an Acute Stroke While on Treatment With Nonvitamin K Antagonist Oral Anticoagulants: The RENO-EXTEND Study

BACKGROUND

In patients with atrial fibrillation who suffered an ischemic stroke while on treatment with nonvitamin K antagonist oral anticoagulants, rates and determinants of recurrent ischemic events and major bleedings remain uncertain.

METHODS

This prospective multicenter observational study aimed to estimate the rates of ischemic and bleeding events and their determinants in the follow-up of consecutive patients with atrial fibrillation who suffered an acute cerebrovascular ischemic event while on nonvitamin K antagonist oral anticoagulant treatment. Afterwards, we compared the estimated risks of ischemic and bleeding events between the patients in whom anticoagulant therapy was changed to those who continued the original treatment.

RESULTS

After a mean follow-up time of 15.0±10.9 months, 192 out of 1240 patients (15.5%) had 207 ischemic or bleeding events corresponding to an annual rate of 13.4%. Among the events, 111 were ischemic strokes, 15 systemic embolisms, 24 intracranial bleedings, and 57 major extracranial bleedings. Predictive factors of recurrent ischemic events (strokes and systemic embolisms) included CHA₂DS₂-VASc score after the index event (odds ratio [OR], 1.2 [95% CI, 1.0-1.3] for each point increase; P=0.05) and hypertension (OR, 2.3 [95% CI, 1.0-5.1]; P=0.04). Predictive factors of bleeding events (intracranial and major extracranial bleedings) included age (OR, 1.1 [95% CI, 1.0-1.2] for each year increase; P=0.002), history of major bleeding (OR, 6.9 [95% CI, 3.4-14.2]; P=0.0001) and the concomitant administration of an antiplatelet agent (OR, 2.8 [95% CI, 1.4-5.5]; P=0.003). Rates of ischemic and bleeding events were no different in patients who changed or not changed the original nonvitamin K antagonist oral anticoagulants treatment (OR, 1.2 [95% CI, 0.8-1.7]).

CONCLUSIONS

Patients suffering a stroke despite being on nonvitamin K antagonist oral anticoagulant therapy are at high risk of recurrent ischemic stroke and bleeding. In these patients, further research is needed to improve secondary prevention by investigating the mechanisms of recurrent ischemic stroke and bleeding.

Development and Validation of a Predictive Model for Spontaneous Hemorrhagic Transformation After Ischemic Stroke

Background: Hemorrhagic transformation (HT) after reperfusion therapy for acute ischemic stroke (AIS) has been well studied; however, there is scarce research focusing on spontaneous HT (sHT). Spontaneous HT is no less important with a relatively high incidence and could be associated with neurological worsening. We aimed to develop and validate a simple and practical model to predict sHT after AIS (SHAIS) and compared the predictive value of the SHAIS score against the models of post-Reperfusion HT for sHT.

Methods: Patients with AIS admitted within 24 h of onset were prospectively screened to develop and validate the SHAIS score. The primary outcome was sHT during hospitalization (within 30 days after onset), and the secondary outcomes were symptomatic sHT and parenchymal hematoma (PH). Clinical information, laboratory, and neuroimaging data were screened to construct the SHAIS score. We selected six commonly used scales for predicting HT after reperfusion therapy and compared their predictive ability for sHT with the SHAIS score using Delong's test.

Results: The derivation cohort included 539 patients (mean age, 68.1 years; men, 61.4%), of whom 91 (16.9%) patients developed sHT with 25.3% (23/91) being symptomatic sHT and 62.6% (57/91) being PH. Five variables (atrial fibrillation, NIHSS score ≥ 10, hypodensity > 1/3 of middle cerebral artery territory, hyperdense artery sign, and anterior circulation infarction) composed the SHAIS score, which ranged from 0 to 11 points. The area under the receiver-operating characteristic curve (AUC) was 0.86 (95% CI 0.82–0.91, p < 0.001) for the overall sHT, 0.85 (95% CI 0.76–0.92, p < 0.001) for symptomatic sHT, and 0.89 (95% CI 0.85–0.94, p < 0.001) for PH. No evidence of miscalibration of the SHAIS score was found to predict the overall sHT (p = 0.19), symptomatic sHT (p = 0.44), and PH (p = 0.22). The internal (n = 245) and external validation cohorts (n = 200) depicted similar predictive performance compared to the derivation cohort. The SHAIS score had a higher AUC to predict sHT than any of the six pre-Existing models (p < 0.05).

Conclusions: The SHAIS score provides an easy-to-use model to predict sHT, which could help providers with decision-making about treatments with high bleeding risk, and to counsel patients and families on the baseline risk of HT, aligning expectations with probable outcomes.

Hemorrhagic Transformation in Patients With Acute Ischemic Stroke and Atrial Fibrillation: Time to Initiation of Oral Anticoagulant Therapy and Outcomes

Background

In patients with acute ischemic stroke and atrial fibrillation, early anticoagulation prevents ischemic recurrence but with the risk of hemorrhagic transformation (HT). The aims of this study were to evaluate in consecutive patients with acute stroke and atrial fibrillation (1) the incidence of early HT, (2) the time to initiation of anticoagulation in patients with HT, (3) the association of HT with ischemic recurrences, and (4) the association of HT with clinical outcome at 90 days.

Methods and Results

HT was diagnosed by a second brain computed tomographic scan performed 24 to 72 hours after stroke onset. The incidence of ischemic recurrences as well as mortality or disability (modified Rankin Scale scores >2) were evaluated at 90 days. Ischemic recurrences were the composite of ischemic stroke, transient ischemic attack, or systemic embolism. Among the 2183 patients included in the study, 241 (11.0%) had HT. Patients with and without HT initiated anticoagulant therapy after a mean 23.3 and 11.6 days, respectively, from index stroke. At 90 days, 4.6% (95% confidence interval, 2.3–8.0) of the patients with HT had ischemic recurrences compared with 4.9% (95% confidence interval, 4.0–6.0) of those without HT; 53.1% of patients with HT were deceased or disabled compared with 35.8% of those without HT. On multivariable analysis, HT was associated with mortality or disability (odds ratio, 1.71; 95% confidence interval, 1.24–2.35).

Conclusions

In patients with HT, anticoagulation was initiated about 12 days later than patients without HT. This delay was not associated with increased detection of ischemic recurrence. HT was associated with increased mortality or disability.

A longitudinal magnetic resonance imaging study of neurodegenerative and small vessel disease, and clinical cognitive trajectories in non demented patients with transient ischemic attack: the PREVENT study

BACKGROUND

Late-life cognitive decline, caused by progressive neuronal loss leading to brain atrophy years before symptoms are detected, is expected to double in Canada over the next two decades. Cognitive impairment in late life is attributed to vascular and lifestyle related risk factors in mid-life in a substantial proportion of cases (50%), thereby providing an opportunity for effective prevention of cognitive decline if incipient disease is detected earlier. Patients presenting with transient ischemic attack (TIA) commonly display some degree of cognitive impairment and are at a 4-fold increased risk of dementia. In the Predementia Neuroimaging of Transient Ischemic Attack (PREVENT) study, we will address what disease processes (i.e., Alzheimer's vs. vascular disease) lead to neurodegeneration, brain atrophy, and cognitive decline, and whether imaging measurements of brain iron accumulation using quantitative susceptibility mapping predicts subsequent brain atrophy and cognitive decline.

METHODS

A total of 440 subjects will be recruited for this study with 220 healthy subjects and 220 TIA patients. Early Alzheimer's pathology will be determined by cerebrospinal fluid samples (including tau, a marker of neuronal injury, and amyloid β1-42) and by MR measurements of iron accumulation, a marker for Alzheimer's-related neurodegeneration. Small vessel disease will be identified by changes in white matter lesion volume. Predictors of advanced rates of cerebral and hippocampal atrophy at 1 and 3 years will include in vivo Alzheimer's disease pathology markers, and MRI measurements of brain iron accumulation and small vessel disease. Clinical and cognitive function will be assessed annually post-baseline for a period of 5-years using a clinical questionnaire and a battery of neuropsychological tests, respectively.

DISCUSSION

The PREVENT study expects to demonstrate that TIA patients have increased early progressive rates of cerebral brain atrophy after TIA, before cognitive decline can be clinically detected. By developing and optimizing high-level machine learning models based on clinical data, image-based (quantitative susceptibility mapping, regional brain, and white matter lesion volumes) features, and cerebrospinal fluid biomarkers, PREVENT will provide a timely opportunity to identify individuals at greatest risk of late-life cognitive decline early in the course of disease, supporting future therapeutic strategies for the promotion of healthy aging.

Early Recurrence and Major Bleeding in Patients With Acute Ischemic Stroke and Atrial Fibrillation Treated With Non-Vitamin-K Oral Anticoagulants (RAF-NOACs) Study

BACKGROUND

The optimal timing to administer non-vitamin K oral anticoagulants (NOACs) in patients with acute ischemic stroke and atrial fibrillation is unclear. This prospective observational multicenter study evaluated the rates of early recurrence and major bleeding (within 90 days) and their timing in patients with acute ischemic stroke and atrial fibrillation who received NOACs for secondary prevention.

METHODS AND RESULTS

Recurrence was defined as the composite of ischemic stroke, transient ischemic attack, and symptomatic systemic embolism, and major bleeding was defined as symptomatic cerebral and major extracranial bleeding. For the analysis, 1127 patients were eligible: 381 (33.8%) were treated with dabigatran, 366 (32.5%) with rivaroxaban, and 380 (33.7%) with apixaban. Patients who received dabigatran were younger and had lower admission National Institutes of Health Stroke Scale score and less commonly had a CHA₂DS₂-VASc score >4 and less reduced renal function. Thirty-two patients (2.8%) had early recurrence, and 27 (2.4%) had major bleeding. The rates of early recurrence and major bleeding were, respectively, 1.8% and 0.5% in patients receiving dabigatran, 1.6% and 2.5% in those receiving rivaroxaban, and 4.0% and 2.9% in those receiving apixaban. Patients who initiated NOACs within 2 days after acute stroke had a composite rate of recurrence and major bleeding of 12.4%; composite rates were 2.1% for those who initiated NOACs between 3 and 14 days and 9.1% for those who initiated >14 days after acute stroke.

CONCLUSIONS

In patients with acute ischemic stroke and atrial fibrillation, treatment with NOACs was associated with a combined 5% rate of ischemic embolic recurrence and severe bleeding within 90 days.

Associations of Mitral and Aortic Valve Calcifications with Complex Aortic Atheroma in Patients with Embolic Stroke of Undetermined Source

BACKGROUND

This study investigated the associations of mitral and aortic valve calcification with complex aortic atheroma among patients with embolic stroke of undetermined source.

METHODS

We included 52 consecutive patients (mean age 58.1 years; 75.0% male) with embolic stroke of undetermined source. Mitral annular calcification, aortic annular calcification, and aortic valve sclerosis were assessed by transthoracic echocardiography. Complex aortic atheroma was assessed by transesophageal echocardiography and was defined as plaque protruding greater than or equal to 4 mm into the lumen or with ulcerated or mobile components.

RESULTS

Ten patients (19.2%) had complex aortic atheroma. Patients with and without complex aortic atheroma showed significant differences in terms of hypertension (80.0% versus 38.1%, P = .017), dyslipidemia (90.0% versus 31.0%, P <.01), chronic kidney disease (60.0% versus 14.3%, P <.01), previous coronary artery disease (30.0% versus 4.8%, P = .013), prior stroke (40.0% versus 7.1%, P <.01), left atrial dimension (4.0 cm versus 3.6 cm, P = .023), aortic valve sclerosis (80.0% versus 26.2%, P <.01), aortic valve calcification (aortic annular calcification or aortic valve sclerosis) (80.0% versus 26.0%, P <.01), and left-sided valve calcification (mitral annular calcification or aortic annular calcification or aortic valve sclerosis) (80.0% versus 28.6%, P <.01). In multivariate analysis, left-sided valve calcification was independently associated with complex aortic atheroma (odds ratio 4.1, 95% confidence interval 1.3-26.1, P = .049).

CONCLUSIONS

Mitral or aortic valve calcification detected by transthoracic echocardiography can be a useful marker for predicting complex aortic atheroma in patients with embolic stroke of undetermined source.

Sex-related differences in risk factors, type of treatment received and outcomes in patients with atrial fibrillation and acute stroke: Results from the RAF-study (Early Recurrence and Cerebral Bleeding in Patients with Acute Ischemic Stroke and Atrial Fibrillation)

Introduction

Atrial fibrillation is an independent risk factor of thromboembolism. Women with atrial fibrillation are at a higher overall risk for stroke compared to men with atrial fibrillation. The aim of this study was to evaluate for sex differences in patients with acute stroke and atrial fibrillation, regarding risk factors, treatments received and outcomes.

Methods

Data were analyzed from the “Recurrence and Cerebral Bleeding in Patients with Acute Ischemic Stroke and Atrial Fibrillation” (RAF-study), a prospective, multicenter, international study including only patients with acute stroke and atrial fibrillation. Patients were followed up for 90 days. Disability was measured by the modified Rankin Scale (0–2 favorable outcome, 3–6 unfavorable outcome).

Results

Of the 1029 patients enrolled, 561 were women (54.5%) (p < 0.001) and younger (p < 0.001) compared to men. In patients with known atrial fibrillation, women were less likely to receive oral anticoagulants before index stroke (p = 0.026) and were less likely to receive anticoagulants after stroke (71.3% versus 78.4%, p = 0.01). There was no observed sex difference regarding the time of starting anticoagulant therapy between the two groups (6.4 ± 11.7 days for men versus 6.5 ± 12.4 days for women, p = 0.902). Men presented with more severe strokes at onset (mean NIHSS 9.2 ± 6.9 versus 8.1 ± 7.5, p < 0.001). Within 90 days, 46 (8.2%) recurrent ischemic events (stroke/TIA/systemic embolism) and 19 (3.4%) symptomatic cerebral bleedings were found in women compared to 30 (6.4%) and 18 (3.8%) in men (p = 0.28 and p = 0.74). At 90 days, 57.7% of women were disabled or deceased, compared to 41.1% of the men (p < 0.001). Multivariate analysis did not confirm this significance.

Conclusions

Women with atrial fibrillation were less likely to receive oral anticoagulants prior to and after stroke compared to men with atrial fibrillation, and when stroke occurred, regardless of the fact that in our study women were younger and with less severe stroke, outcomes did not differ between the sexes.

Cystatin C and risk of mortality among patients undergoing percutaneous coronary intervention

AIMS

We tested the prognostic value of cystatin C in patients with documented coronary artery disease (CAD) who underwent percutaneous coronary artery intervention (PCI). We also tested the hypothesis that the incremental predictive value of cystatin C on all-cause mortality was superior to that of glomerular filtration rate (GFR) by the Modification of Diet in Renal Disease (MDRD) formula.

METHODS AND RESULTS

Included in the study were 2,757 patients (mean age 63 years, 77% men). Blood samples for cystatin C levels were collected immediately before PCI. During a median follow-up of two years, 114 patients died. In multivariable Cox analyses, after adjustment for several confounders, GFR (p=0.004) and cystatin C concentration (p<0.0001) were independent predictors of all-cause death. Cystatin C predicted all-cause death (c-statistic: 0.794) better than GFR estimate based on creatinine (c-statistic: 0.776, p=0.008 for comparison), and significantly reclassified 15% of patients into categories that reflected their actual likelihood of death more accurately (p=0.005). Adding cystatin C and GFR in the same multivariable survival model, only cystatin C level was a significant predictor of death.

CONCLUSIONS

This study presents for the first time the incremental predictive value of cystatin C over the creatinine-based MDRD formula on all-cause mortality for CAD patients undergoing PCI.

A risk score for predicting 1-year mortality in patients ≥75 years of age presenting with non-ST-elevation acute coronary syndrome

Approximately 1/3 of patients with non-ST-segment elevation (NSTE) acute coronary syndromes (ACS) are ≥75 years of age. Risk stratification in these patients is generally difficult because supporting evidence is scarce. The investigators developed and validated a simple risk prediction score for 1-year mortality in patients ≥75 years of age presenting with NSTE ACS. The derivation cohort was the Italian Elderly ACS trial, which included 313 patients with NSTE ACS aged ≥75 years. A logistic regression model was developed to predict 1-year mortality. The validation cohort was a registry cohort of 332 patients with NSTE ACS meeting the same inclusion criteria as for the Italian Elderly ACS trial but excluded from the trial for any reason. The risk score included 5 statistically significant covariates: previous vascular event, hemoglobin level, estimated glomerular filtration rate, ischemic electrocardiographic changes, and elevated troponin level. The model allowed a maximum score of 6. The score demonstrated a good discriminating power (C statistic = 0.739) and calibration, even among subgroups defined by gender and age. When validated in the registry cohort, the scoring system confirmed a strong association with the risk for all-cause death. Moreover, a score ≥3 (the highest baseline risk group) identified a subset of patients with NSTE ACS most likely to benefit from an invasive approach. In conclusion, the risk for 1-year mortality in patients ≥75 years of age with NSTE ACS is substantial and can be predicted through a score that can be easily derived at the bedside at hospital presentation. The score may help in guiding treatment strategy.

Acute stroke symptoms: do differences exist between sexes?

BACKGROUND

Previous studies have reported that women with stroke often present different stroke symptoms than men. The aim of our study was to assess for the relevance of these differences from a large case series.

METHODS

Consecutive patients admitted to the Stroke Unit at the University of Perugia, with acute stroke or transient ischemic attack between 1 June, 2005, and May 2012, and recorded in Perugia Stroke Registry were prospectively included. Associations between the recorded symptoms and sex were assessed by preliminary cross-tabulations with the Chi-square test or Fisher exact test with Yate correction when appropriate. Multivariable regression analysis was used to identify independent predictors of a single symptom including sex as an independent variable.

RESULTS

Overall, 1072 men and 811 women were included in this study. Women had a higher average age at onset (75.40 ± 12.90 years in women and 70.14 ± 12.61 years in men) and presented more severe strokes with higher National Institute of Health Stroke Scale scores than men, whereas men were more likely to have a posterior stroke.Regarding symptoms, multivariate analysis revealed correlations between postural instability and male sex and between dysphagia and female sex.

CONCLUSIONS

We found no differences in the clinical presentation of stroke between the sexes, except that men were more likely to have postural instability and females were more likely to have dysphagia. These findings suggest that stroke locations and stroke severity were associated with sex.