Statistical Methods to Examine Racial and Ethnic Disparities in the Surgical Literature: A Review and Recommendations for Improvement.

OBJECTIVE: We characterized the quality of statistical methods for studies of racial and ethnic disparities in the surgical-relevant literature during 2021-2022. BACKGROUND: Hundreds of scientific papers are published each year describing racial and ethnic disparities in surgical access, quality, and outcomes. The content and design quality of this literature has never been systematically reviewed. METHODS: We searched for 2021-2022 studies focused on describing racial and/or ethnic disparities in surgical or perioperative access, process quality, or outcomes. Identified studies were characterized in terms of three methodological criteria: 1) adjustment for variables related to both race/ethnicity and outcomes, including social determinants of health (SDOH); 2) accounting for clustering of patients within hospitals or other subunits ("providers") and; 3) distinguishing within- and between-provider effects. RESULTS: We identified 224 papers describing racial and/or ethnic differences. Of the 38 single institution studies, 24 (63.2%) adjusted for at least one SDOH variable. Of the 186 multisite studies, 113 (60.8%) adjusted for at least one SDOH variable, and 43 (23.1%) accounted for clustering of patients within providers using appropriate statistical methods. Only 10 (5.4%) of multi-institution studies made efforts to examine how much of overall disparities were driven by within versus between provider effects. CONCLUSIONS: Most recently published papers on racial and ethnic disparities in the surgical literature do not meet these important statistical design criteria and therefore may risk inaccuracy in the estimation of group differences in surgical access, quality, and outcomes. The most potent leverage points for these improvements are changes to journal publication guidelines and policies.

Type II odontoid fractures in the elderly presenting to the emergency department: an assessment of factors affecting in-hospital mortality and discharge to skilled nursing facilities.

BACKGROUND CONTEXT: Type II odontoid fractures (OF) are among the most common cervical spine injuries in the geriatric population. However, there is a paucity of literature regarding their epidemiology. Additionally, the optimal management of these injuries remains controversial, and no study has evaluated the short-term outcomes of geriatric patients presenting to emergency departments (ED). PURPOSE: This study aims to document the epidemiology of geriatric patients presenting to EDs with type II OFs and determine whether surgical management was associated with early adverse outcomes such as in-hospital mortality and discharge to skilled nursing facilities (SNF). STUDY DESIGN: This is a retrospective cohort study. PATIENT SAMPLE: Data was used from the 2016-2020 Nationwide Emergency Department Sample. Patient encounters corresponding to type II OFs were identified. Patients younger than 65 at the time of presentation to the ED and those with concomitant spinal pathology were excluded. OUTCOME MEASURES: The association between the surgical management of geriatric type II OFs and outcomes such as in-hospital mortality and discharge to SNFs. METHODS: Patient, fracture, and surgical management characteristics were recorded. A propensity score matched cohort was constructed to reduce differences in age, comorbidities, and injury severity between patients undergoing operative and nonoperative management. Additionally, to develop a positive control for the analysis of geriatric patients with type II OFs and no other concomitant spinal pathology, a cohort of patients that had been excluded due to the presence of a concomitant spinal cord injury (SCI) was also constructed. Multivariate regressions were then performed on both the matched and unmatched cohorts to ascertain the associations between surgical treatment and in-hospital mortality, inpatient length of stay, encounter charges, and discharge to SNFs. RESULTS: A total of 11,325 encounters were included. The mean total charge per encounter was $60,221. 634 (5.6%) patients passed away during their encounters. In total, 1,005 (8.9%) patients were managed surgically. Surgical management of type II OFs was associated with a 316% increase in visit charge (95% CI: 291%-341%, p<.001), increased inpatient length of stay (IRR: 2.87, 95% CI: 2.62-3.12, p<.001), and increased likelihood of discharge to SNFs (OR=2.62, 95% CI: 2.26-3.05, p<.001), but decreased in-hospital mortality (OR=0.32, CI: 0.21-0.45, p<.001). The propensity score matched cohort consisted of 2,010 patients, matching each of the 1,005 that underwent surgery to 1,005 that did not. These cohorts were well balanced across age (78.24 vs 77.91 years), Elixhauser Comorbidity Index (3.68 vs 3.71), and Injury Severity Score (30.15 vs 28.93). This matching did not meaningfully alter the associations determined between surgical management and in-hospital mortality (OR=0.34, CI=0.21-0.55, p<.001) or SNF discharge (OR=2.59, CI=2.13-3.16, p<.001). Lastly, the positive control cohort of patients with concurrent SCI had higher rates of SNF discharge (50.0% vs 42.6%, p<.001), surgical management (32.3% vs 9.7%, p<.001), and in-hospital mortality (28.9% vs 5.6%, p<.001). CONCLUSIONS: This study lends insight into the epidemiology of geriatric type II OFs and quantifies risk factors influencing adverse outcomes. Patient informed consent should include a discussion of the protective association between definitive surgical management and in-hospital mortality against potential operative morbidity, increased lengths of hospital stay, and increased likelihood of discharge to SNFs. This information may impact patient treatment selection and decision making.

Experience with the utilization of new-generation shared-control robotic system for spinal instrumentation.

BACKGROUND: Robotic assistance in spine surgery is emerging as an accurate, effective and enabling technology utilized in the treatment of patients with surgical spinal pathology. The safety and reproducibility of robotic assistance in the placement of pedicle screw instrumentation is still being investigated. The objective of this study was to present our experience of instrumented spinal fusion utilizing an intraoperative robotic guidance system. METHODS: We retrospectively reviewed all cases of spinal instrumentation of the thoracic and lumbo-sacral spine using the Mazor X robotic system (Medtronic Inc, Minneapolis, MN, USA), performed at our institution by one surgeon between July 2017 and June 2020. Wilcoxon Rank test was used to compare time taken to place each screw during the first 20 cases and the cases thereafter. RESULTS: A total of 28 patients were included. A total of 159 screws were placed using the Mazor X robotic system. The overall mean time for screw placement was 7.8±2.3 minutes and there was a significant reduction in the mean time for screw placement after the 20th case or 120 screws (8.70 vs. 5.42 min, P=0.008). No postoperative neurologic deficit or new radiculopathy was noted to occur secondary to hardware placement. No revision surgery was required for replacement or removal of a mispositioned screw. CONCLUSIONS: From this single-center, single-surgeon series we conclude that robot-assisted spine surgery can be safely and efficiently integrated into the operating room workflow, which improves after a learning curve of approximately 20 operative interventions. We found robot-assisted spinal instrumentation to be reliable, safe, effective and highly precise.

Misplaced intraspinal venous stent causing cauda equina syndrome: illustrative case.

BACKGROUND: Endovenous stents for deep venous thrombosis treatment can be unintentionally placed in the spinal canal, resulting in neurological deficit. OBSERVATIONS: The authors report the case of a patient presenting to our institution with intraspinal misplacement of an endovenous stent, resulting in cauda equina syndrome. The authors also performed a systematic literature review, evaluating the few previously reported cases. This review was performed according to the updated Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. In four of five cases describing stent misplacement into the spinal canal, the authors report that only anteroposterior monoplanar imaging modalities were utilized for venous localization and stent deployment. The anteroposterior plane cannot assess the relative depth of structures, nor can it distinguish between superimposed structures well. Therefore, the use of biplanar imaging should at least be considered before stent deployment, as intraspinal stent placement can lead to disastrous consequences. LESSONS: This report should serve as an impetus for the use of biplanar or three-dimensional imaging modalities for iliac venous stent placement. Additionally, this work should increase spine surgeons' awareness about management and operative techniques when faced with this complication.

Applying natural language processing to patient messages to identify depression concerns in cancer patients.

OBJECTIVE: This study aims to explore and develop tools for early identification of depression concerns among cancer patients by leveraging the novel data source of messages sent through a secure patient portal. MATERIALS AND METHODS: We developed classifiers based on logistic regression (LR), support vector machines (SVMs), and 2 Bidirectional Encoder Representations from Transformers (BERT) models (original and Reddit-pretrained) on 6600 patient messages from a cancer center (2009-2022), annotated by a panel of healthcare professionals. Performance was compared using AUROC scores, and model fairness and explainability were examined. We also examined correlations between model predictions and depression diagnosis and treatment. RESULTS: BERT and RedditBERT attained AUROC scores of 0.88 and 0.86, respectively, compared to 0.79 for LR and 0.83 for SVM. BERT showed bigger differences in performance across sex, race, and ethnicity than RedditBERT. Patients who sent messages classified as concerning had a higher chance of receiving a depression diagnosis, a prescription for antidepressants, or a referral to the psycho-oncologist. Explanations from BERT and RedditBERT differed, with no clear preference from annotators. DISCUSSION: We show the potential of BERT and RedditBERT in identifying depression concerns in messages from cancer patients. Performance disparities across demographic groups highlight the need for careful consideration of potential biases. Further research is needed to address biases, evaluate real-world impacts, and ensure responsible integration into clinical settings. CONCLUSION: This work represents a significant methodological advancement in the early identification of depression concerns among cancer patients. Our work contributes to a route to reduce clinical burden while enhancing overall patient care, leveraging BERT-based models.

Machine Learning in Neurosurgery: Toward Complex Inputs, Actionable Predictions, and Generalizable Translations.

Machine learning can predict neurosurgical diagnosis and outcomes, power imaging analysis, and perform robotic navigation and tumor labeling. State-of-the-art models can reconstruct and generate images, predict surgical events from video, and assist in intraoperative decision-making. In this review, we will detail the neurosurgical applications of machine learning, ranging from simple to advanced models, and their potential to transform patient care. As machine learning techniques, outputs, and methods become increasingly complex, their performance is often more impactful yet increasingly difficult to evaluate. We aim to introduce these advancements to the neurosurgical audience while suggesting major potential roadblocks to their safe and effective translation. Unlike the previous generation of machine learning in neurosurgery, the safe translation of recent advancements will be contingent on neurosurgeons' involvement in model development and validation.

Emerging Outlook on Personalized Neuromodulation for Depression: Insights From Tractography-Based Targeting.

BACKGROUND: Deep brain stimulation has shown promise in treating individual patients with treatment-resistant depression, but larger-scale trials have been less successful. Here, we created what is, to our knowledge, the largest meta-analysis with individual patient data to date to explore whether the use of tractography enhances the efficacy of deep brain stimulation for treatment-resistant depression. METHODS: We systematically reviewed 1823 articles, selecting 32 that contributed data from 366 patients. We stratified the individual patient data based on stimulation target and use of tractography. Using 2-way type III analysis of variance, Welch's 2-sample t tests, and mixed-effects linear regression models, we evaluated changes in depression severity 1 year (9-15 months) postoperatively and at last follow-up (4 weeks to 8 years) as assessed by depression scales. RESULTS: Tractography was used for medial forebrain bundle (MFB) (n = 17 tractography/32 total), subcallosal cingulate (SCC) (n = 39 tractography/241 total), and ventral capsule/ventral striatum (n = 3 tractography/41 total) targets; it was not used for bed nucleus of stria terminalis (n = 11), lateral habenula (n = 10), and inferior thalamic peduncle (n = 1). Across all patients, tractography significantly improved mean depression scores at 1 year (p < .001) and last follow-up (p = .009). Within the target cohorts, tractography improved depression scores at 1 year for both MFB and SCC, though significance was met only at the α = 0.1 level (SCC: ß = 15.8%, p = .09; MFB: ß = 52.4%, p = .10). Within the tractography cohort, patients with MFB tractography showed greater improvement than patients with SCC tractography (72.42 ± 7.17% vs. 54.78 ± 4.08%) at 1 year (p = .044). CONCLUSIONS: Our findings underscore the promise of tractography in deep brain stimulation for treatment-resistant depression as a method for personalization of therapy, supporting its inclusion in future trials.

Accuracy of predicted postoperative segmental lumbar lordosis in spinal fusion using an intraoperative robotic planning and guidance system.

BACKGROUND: Restoring lumbar lordosis is one of the main goals in lumbar spinal fusion surgery. The Mazor X-AlignTM software allows for the prediction of postoperative segmental lumbar lordosis based on preoperative imaging. There is limited data on the accuracy of this preoperative prediction, especially in patients undergoing short segment lumbar fusion. The objective of our study was to determine the accuracy of predicted postoperative segmental lumbar lordosis using the Mazor X-AlignTM software in patients requiring short segmental fusion. METHODS: Retrospective analysis of adult patients undergoing pedicle screw spinal instrumentation of not more than four levels using the Mazor XTM Robot (Medtronic Inc., Minneapolis, MN, USA) between July 2017 to June 2020. The robotic guidance software, Mazor X-AlignTM (Medtronic Inc., Minneapolis, MN, USA) was used to calculate the predicted segmental lumbar lordosis based on preoperative CT-imaging and the plan was executed under intraoperative robotic guidance. Predicted segmental lumbar lordosis was compared to achieved segmental lumbar lordosis on 1-month postoperative x-rays using the Cobb angle methodology. RESULTS: A total of 15 patients (46.6% female) with a mean age of 61.5±10.9 years were included. All patients underwent posterior lumbo-sacral spinal fusion with the Mazor XTM robotic system with 11 patients (73.3%) undergoing anterior column reconstruction prior to posterior fixation. Instrumentation was performed across a mean of 2.6 levels per case. Preoperative, the mean segmental lumbar lordosis was 30.2±13.6 degrees. The mean planned segmental lumbar lordosis was 35.5±17.0 degrees while the mean achieved segmental lumbar lordosis was 35.8±16.7 degrees. There was no significant mean difference between the planned and achieved segmental lumbar lordosis (P=0.334). CONCLUSIONS: The Mazor XTM intraoperative robotic planning and guidance is accurate in predicting postoperative segmental lumbar lordosis after short segmental fusion. Our findings may assure surgical decision making and planning.

Clinical Outcomes and Cost Differences Between Patients Undergoing Primary Anterior Cervical Discectomy and Fusion Procedures with Private or Medicare Insurance: A Propensity Score-Matched Study.

OBJECTIVE: We assessed whether the insurance type reflects a patient's quality of care after an anterior discectomy and fusion (ACDF) procedure by comparing differences in the postoperative complications, readmission rates, reoperation rates, lengths of hospital stay, and cost of treatment between patients with Medicare versus private insurance. METHODS: Propensity score matching was used to match patient cohorts insured by Medicare and private insurance in the MarketScan Commercial Claims and Encounters Database (2007-2016). Age, sex, year of operation, geographic region, comorbidities, and operative factors were used to match cohorts of patients who had undergone an ACDF procedure. RESULTS: A total of 110,911 patients met the inclusion criteria. Of these patients, 97,543 patients (87.9%) were privately insured and 13,368 patients (12.1%) were insured by Medicare. The propensity score matching algorithm matched 7026 privately insured patients to 7026 Medicare patients. After matching, no significant differences were found in the 90-day postoperative complication rates, lengths of stay, or reoperation rates between the Medicare and privately insured cohorts. The Medicare group had had lower postoperative readmission rates for all time points: 30 days (1.8% vs. 4.6%; P < 0.001), 60 days (2.5% vs. 6.3%; P < 0.001), and 90 days (4.2% vs. 7.7%; P < 0.001). The median payment to physicians was significantly lower for the Medicare group ($3885 vs. $5601; P < 0.001). CONCLUSIONS: In the present study, propensity score matched patients covered by Medicare and private insurance who had undergone an ACDF procedure had had similar treatment outcomes.

Algorithmic Prediction of Delayed Radiology Turn-Around-Time during Non-Business Hours.

RATIONALE AND OBJECTIVES: Radiology turnaround time is an important quality measure that can impact hospital workflow and patient outcomes. We aimed to develop a machine learning model to predict delayed turnaround time during non-business hours and identify factors that contribute to this delay. MATERIALS AND METHODS: This retrospective study consisted of 15,117 CT cases from May 2018 to May 2019 during non-business hours at two hospital campuses after applying exclusion criteria. Of these 15,177 cases, 7,532 were inpatient cases and 7,585 were emergency cases. Order time, scan time, first communication by radiologist, free-text indications, and other clinical metadata were extracted. A combined XGBoost classifier and Random Forest natural language processing model was trained with 85% of the data and tested with 15% of the data. The model predicted two measures of delay: when the exam was ordered to first communication (total time) and when the scan was completed to first communication (interpretation time). The model was analyzed with the area under the curve (AUC) of receiver operating characteristic (ROC) and feature importance. Source code: https://bit.ly/2UrLiVJ RESULTS: The algorithm reached an AUC of 0.85, with a 95% confidence interval [0.83, 0.87], when predicting delays greater than 245 minutes for "total time" and 0.71, with a 95% confidence interval [0.68, 0.73], when predicting delays greater than 57 minutes for "interpretation time". At our institution, CT scan description (e.g. "CTA chest pulmonary embolism protocol"), time of day, and year in training were more predictive features compared to body part, inpatient status, and hospital campus for both interpretation and total time delay. CONCLUSION: This algorithm can be applied clinically when a physician is ordering the scan to reasonably predict delayed turnaround time. Such a model can be leveraged to identify factors associated with delays and emphasize areas for improvement to patient outcomes.

Polyvinylpyrrolidone-Coated Catheters Decrease Astrocyte Adhesion and Improve Flow/Pressure Performance in an Invitro Model of Hydrocephalus.

The leading cause of ventricular shunt failure in pediatric patients is proximal catheter occlusion. Here, we evaluate various types of shunt catheters to assess in vitro cellular adhesion and obstruction. The following four types of catheters were tested: (1) antibiotic- and barium-impregnated, (2) polyvinylpyrrolidone, (3) barium stripe, and (4) barium impregnated. Catheters were either seeded superficially with astrocyte cells to test cellular adhesion or inoculated with cultured astrocytes into the catheters to test catheter performance under obstruction conditions. Ventricular catheters were placed into a three-dimensional printed phantom ventricular replicating system through which artificial CSF was pumped. Differential pressure sensors were used to measure catheter performance. Polyvinylpyrrolidone catheters had the lowest median cell attachment compared to antibiotic-impregnated (18 cells), barium stripe (17 cells), and barium-impregnated (21.5 cells) catheters after culture (p < 0.01). In addition, polyvinylpyrrolidone catheters had significantly higher flow in the phantom ventricular system (0.12 mL/min) compared to the antibiotic coated (0.10 mL/min), barium stripe (0.02 mL/min) and barium-impregnated (0.08 mL/min; p < 0.01) catheters. Polyvinylpyrrolidone catheters showed less cellular adhesion and were least likely to be occluded by astrocyte cells. Our findings can help suggest patient-appropriate proximal ventricular catheters for clinical use.

Intrathecal Access Through Suboccipital Port in Patients With Spinal Muscular Atrophy and Complex Spines: Case Series and Technical Note.

Introduction Many patients with the spinal muscular atrophy (SMA) have complex spinal anatomy, secondary to thoraco-lumbar spinal fusions. Their fragile musculoskeletal anatomy potentiates limb and joint injury if conventional spinal fluid access modalities are utilized. This creates a challenge when attempting to deliver intrathecal medications such as nusinersen (Spinraza®). Catheter placement in the cervical subarachnoid space with a caudally directed tip is potentially beneficial. This article describes our experience with Spinraza injections into the thecal space through a suboccipital port. This allowed for simple, chronic, and reliable cerebrospinal fluid (CSF) aspiration and intrathecal injections. Methods A total of 15 patients with SMA and complex spinal anatomy were implanted with a cervical subarachnoid catheter, connected to a suboccipital access port. We retrospectively reviewed the charts of these patients for clinical outcomes and complications. All patients then underwent serial port cannulation, aspiration of CSF, and injection of Spinraza following standard manufacturer dosage guidelines. Results The age range was 3 to 49. Two had type-1 SMA, 10 had type-2 SMA, and three had type-3 SMA. We were able to successfully cannulate the port, aspirate CSF, and inject Spinraza during all access attempts. Two incidents of subcutaneous CSF leaks were resolved through reoperation and one incident of transient CSF leak was resolved without surgical repair. Conclusion Patients with SMA requiring intrathecal injections of Spinraza can be treated safely and efficiently with this novel implantation technique. The complication rates are low and the injection time is dramatically lower than with conventional injection techniques.

Calmodulin kinase II inhibition shortens action potential duration by upregulation of K+ currents.

The multifunctional Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) is activated by elevated intracellular Ca(2+) (Ca(2+)(i)), and mice with chronic myocardial CaMKII inhibition (Inh) resulting from transgenic expression of a CaMKII inhibitory peptide (AC3-I) unexpectedly showed action potential duration (APD) shortening. Inh mice exhibit increased L-type Ca(2+) current (I(Ca)), because of upregulation of protein kinase A (PKA) activity, and decreased CaMKII-dependent phosphorylation of phospholamban (PLN). We hypothesized that CaMKII is a molecular signal linking Ca(2+)(i) to repolarization. Whole cell voltage-clamp recordings revealed that the fast transient outward current (I(to,f)) and the inward rectifier current (I(K1)) were selectively upregulated in Inh, compared with wild-type (WT) and transgenic control, mice. Breeding Inh mice with mice lacking PLN returned I(to,f) and I(K1) to control levels and equalized the APD and QT intervals in Inh mice to control and WT levels. Dialysis of AC3-I into WT cells did not result in increased I(to,f) or I(K1), suggesting that enhanced cardiac repolarization in Inh mice is an adaptive response to chronic CaMKII inhibition rather than an acute effect of reduced CaMKII activity. Increasing PKA activity, by cell dialysis with cAMP, or inhibition of PKA did not affect I(K1) in WT cells. Dialysis of WT cells with cAMP also reduced I(to,f), suggesting that PKA upregulation does not increase repolarizing K(+) currents in Inh mice. These findings provide novel in vivo and cellular evidence that CaMKII links Ca(2+)(i) to cardiac repolarization and suggest that PLN may be a critical CaMKII target for feedback regulation of APD in ventricular myocytes.

Comparison of effect of concurrent phone texting on gait speed in young and middle aged healthy subjects

Background: Around the world today, adoption of mobile media phones and its advancement have been growing at dizzying pace in all age groups. People use phone while walking on/crossing roads, climbing stairs, driving cars, etc. Using a smartphone while walking has shown decrease in walking speed and affect dynamic balance by reducing cognitive ability. The objective of study is to see and compare effect of concurrent phone texting while obstacle walking on walking time in young and middle-aged healthy subjects.Methods: An observational study with 100 healthy individuals (50 young and 50 middle-aged) were taken and had to walk on a 15 m walkway with obstacle (approximately 10% of subject’s height) at 8m distance from start without and with texting. The text messages used were all short objective questions and were sent to them approximately 2 steps prior to reaching the obstacle. Their walking time was analyzed.Results: Wilcoxon test used to analyze difference within group. In young people without phone texting it was11.41±1.24 seconds and with texting was14.79±2.67seconds, (z=-6.101, p<0.001) and in middle aged was14.93±1.20 seconds and 20.52±1.87 seconds respectively (z=-6.154, p<0.001). Mann Whitney test used to analyze difference between groups. For without texting in young and middle aged walking time (U=48.0, p<0.001), with texting young and middle aged walking time (U=122.00, p<0.001) and comparing the difference in walking time between young and middle aged with and without phone texting (U=372.5, p<0.001).Conclusions: Phone texting increases walking time in young and middle aged with difference in walking time more in middle aged adults.

Investigation of age-related cognitive decline using mice as a model system: neurophysiological correlates.

OBJECTIVE: Learning and memory impairments without overt pathology often accompany advancing age. To gain a better understanding of the underlying neuronal substrates associated with this age-related cognitive decline, the authors have begun to use mice as an animal model system. As described in the companion paper, mice exhibit age-related impairments in cognition. Here, the authors explore the possibility that age-related changes in neuronal function may be the result of deregulation of cytosolic free calcium homeostasis. METHODS: Calcium homeostasis in young and aged mice was examined by measuring the slow afterhyperpolarization (sAHP) in hippocampal neurons as well as assessing voltage-dependent calcium channel mediated long-term potentiation (vdccLTP). In addition, putative changes in phosphorylation of the L-type channel Ca(V)1.2 by cAMP-dependent protein kinase were examined. RESULTS: Both neurophysiological measures of calcium homeostasis indicated an increase in activity-dependent calcium influx. This increase was not the result of an age-related increase in phosphorylation of the L-type channel Ca(V)1.2 by cAMP-dependent protein kinase. CONCLUSIONS: Like in other areas of biomedical research, mice have become an invaluable research tool in the investigation of learning and memory. It is expected that similar benefits can be realized by developing mouse models for age-related cognitive decline.

Unique modulation of L-type Ca2+ channels by short auxiliary beta1d subunit present in cardiac muscle.

Recent studies have identified a growing diversity of splice variants of auxiliary Ca2+ channel Ca(v)beta subunits. The Ca(v)beta(1d) isoform encodes a putative protein composed of the amino-terminal half of the full-length Ca(v)beta(1) isoform and thus lacks the known high-affinity binding site that recognizes the Ca2+ channel alpha1-subunit, the alpha-binding pocket. The present study investigated whether the Ca(v)beta(1d) subunit is expressed at the protein level in heart, and whether it exhibits any of the functional properties typical of full-length Ca(v)beta subunits. On Western blots, an antibody directed against the unique carboxyl terminus of Ca(v)beta(1d) identified a protein of the predicted molecular mass of 23 kDa from canine and human hearts. Immunocytochemistry and surface-membrane biotinylation experiments in transfected HEK-293 cells revealed that the full-length Ca(v)beta(1b) subunit promoted membrane trafficking of the pore-forming alpha1C (Ca(v)1.2)-subunit to the surface membrane, whereas the Ca(v)beta(1d) subunit did not. Whole cell patch-clamp analysis of transfected HEK-293 cells demonstrated no effect of coexpression of the Ca(v)beta(1d) with the alpha1C-subunit compared with the 15-fold larger currents and leftward shift in voltage-dependent activation induced by full-length Ca(v)beta(1b) coexpression. In contrast, cell-attached patch single-channel studies demonstrated that coexpression of either Ca(v)beta(1b) or Ca(v)beta(1d) significantly increased mean open probability four- to fivefold relative to the alpha1C-channels alone, but only Ca(v)beta(1b) coexpression increased the number of channels observed per patch. In conclusion, the Ca(v)beta(1d) isoform is expressed in heart and can modulate the gating of L-type Ca2+ channels, but it does not promote membrane trafficking of the channel complex.