Rationale and clinical context

For primary reperfusion in ST-elevation myocardial infarction, the transradial route is widely adopted for emergent angiography and intervention, driven by lower bleeding risk and high patient comfort. Within this framework, operators are increasingly evaluating distal radial entry in the anatomical snuffbox or distal forearm versus conventional puncture at the proximal radial segment. The DR-STEMI protocol emerges to examine whether shifting the puncture site can preserve or enhance safety while maintaining procedural efficiency that is essential for STEMI care. It focuses on operationally relevant outcomes where access choice is most likely to matter.

Distal radial access offers theoretical advantages, such as preserving proximal radial patency for future procedures and possibly reducing local compression pressure requirements. Potential tradeoffs include smaller vessel caliber, more variable anatomy, and an operator learning curve that might influence cannulation success or speed. The protocol is designed to balance these considerations without compromising clinical urgency. By standardizing technique and escalation pathways, it seeks to quantify whether a distal strategy can be implemented reliably when time is muscle.

In emergent workflows, teams must integrate door, puncture, and device-delivery steps while coordinating pharmacology and imaging. Any access-site approach used in STEMI must therefore demonstrate not only safety but also predictable efficiency. The trial makes a point to operationalize definitions around puncture attempts, cannulation, sheath insertion, fluoroscopy use, and escalation decisions. These procedural definitions enable consistent measurement of performance and offer a foundation for later quality improvement, irrespective of which approach proves preferable.

Another driver for this design is the persistent clinical burden of radial artery occlusion, which can limit future vascular access, affect hand perfusion, and constrain options for repeat procedures or bypass grafting. Whether distal entry reduces the risk of occlusive injury by leaving the proximal segment untouched remains an important question. The protocol elevates patency and access-site complication endpoints to primary or key secondary status to ensure that the trial addresses outcomes clinicians and patients will notice. These choices align with access-site best practices and the current literature.

Why STEMI access choice matters

In STEMI, every minute between first medical contact and reperfusion affects myocardial salvage, left ventricular function, and survival. As a result, any innovation must fit seamlessly into the rapid sequence of care. Distal radial entry may offer ergonomic and hemostatic benefits, but the technique must be fast to learn, repeatable across operators and centers, and robust to real-world variation in wrist anatomy and patient habitus. The DR-STEMI design confronts these questions with multicenter randomization to separate technique effects from site or operator idiosyncrasies.

Implementing a new access site involves more than needle placement. Cath lab staffing, hand positioning, sheath selection, and hemostasis protocols must be adapted, and these adaptations cannot jeopardize timely reperfusion. The protocol encourages training standardization and prespecifies procedural definitions, such as the maximum number of puncture attempts before escalation. These details are critical for reproducibility and for interpreting any differences observed between arms. Clarity on when and how to switch approaches is equally important to avoid undue delays.

Downstream, the implications extend beyond a single procedure. A preserved proximal radial artery is valuable for future diagnostic work, repeat PCI, or surgical conduit. Conversely, a failed distal approach that delays reperfusion could negate any long-term benefits. The protocol aims to provide the comparative evidence needed to inform access selection in patients likely to require lifelong vascular access. It also addresses a key knowledge gap for operators who already use distal techniques electively but remain cautious in STEMI.

Finally, patient-reported factors, including comfort and hand function, also shape the perceived value of an access strategy. Although STEMI prioritizes speed and survival, recovery experience matters to patients returning to work and daily activity. The protocol acknowledges this by including functional and comfort assessments where feasible within the emergent care context. Together, these elements create a comprehensive framework to evaluate distal versus conventional radial access under conditions that stress every aspect of the workflow.

Trial design and operational plan

The trial is structured as a prospective, multicenter, randomized controlled trial comparing distal with conventional radial access in the setting of emergent coronary catheterization for suspected STEMI. Investigational sites follow a harmonized set of procedural definitions and post-procedural assessments to ensure consistency across diverse practice environments. Randomization is stratified at the patient level, with operators instructed to adhere to the assigned access strategy unless prespecified failure or safety criteria trigger crossover. The design reflects routine care pathways and is intended to maximize pragmatic generalizability.

Operators receive standardized training materials to reduce technique variability, including guidance on needle approach angles, ultrasound use, sheath and catheter selection, and compression protocols. The protocol documents how unsuccessful puncture attempts are counted and defines thresholds at which escalation to alternate routes is recommended. These operational guardrails allow fair comparison between strategies while preserving clinician judgment in urgent scenarios. All time stamps and key procedural milestones are recorded for subsequent analysis.

Because access-site selection influences the trajectory of the entire case, the protocol specifies how to capture prehospital and in-hospital timing markers. Metrics include arrival time, activation of the catheterization team, initial arterial puncture, sheath insertion, diagnostic contrast injection, and first device deployment when applicable. In combination, these measurements form a granular picture of procedural efficiency. They also create the context needed to interpret outcomes in terms of workflow realities that vary across regions and institutions.

Safety oversight is integral to an emergent trial. Procedures for event surveillance, independent adjudication of access-site complications, and timely reporting are prespecified. An independent board may review safety signals at intervals, and stopping guidelines are defined a priori to protect participants. This infrastructure is particularly important when a trial involves both an evolving technique and a high-acuity population where even small delays may be consequential.

Patient population and eligibility

Eligible participants are adults presenting with suspected STEMI who are candidates for emergent coronary angiography with possible intervention. The protocol aims to reflect real-world inclusivity while applying exclusions that preserve safety and interpretability. Typical exclusions for access-site trials include conditions that preclude radial cannulation or safe compression, profound hemodynamic instability requiring immediate femoral access, or anatomic constraints known to cause failure. The final criteria are tailored to emergent care and the study objectives without overselecting a narrowly defined population.

Because anatomy and comorbidities influence radial success, baseline factors such as wrist circumference, palpable pulse quality, and ulnar collateral adequacy are documented when feasible. Prior access-site use, surgical conduit needs, and known vascular disease are captured to support subgroup analyses. Capturing these covariates provides context for interpreting any differences observed between distal and conventional strategies. It also aids in extrapolating results to patients typically encountered in routine practice who may differ from highly selected elective cohorts.

Informed consent procedures are adapted to emergent care, leveraging deferred or abbreviated consent where permitted by local regulations and ethics boards. Investigators ensure that patient rights are respected while maintaining the urgent timeline required for reperfusion. The protocol delineates the process for confirmation or withdrawal of consent once patients are stabilized. This approach balances ethical rigor with the practical realities of STEMI management.

Documentation processes are streamlined to minimize interruptions to care. Data capture emphasizes critical fields necessary for the primary and key secondary endpoints, while avoiding redundant or nonessential items that could slow the team. This prioritization reflects lessons from prior acute care trials where excessive data burden can impair compliance. The focus remains on collecting high-quality, actionable information aligned with the trial objectives.

Randomization and procedures

Participants are randomly allocated to distal or conventional radial access before arterial puncture. The allocation process uses secure methods to prevent selection bias, and assignment is recorded electronically with time stamps. Operators are expected to attempt the randomized approach first, with prespecified criteria guiding when crossover to the alternative radial site or femoral access is appropriate. This approach ensures patient safety and preserves analytic integrity via intention-to-treat while enabling per-protocol sensitivity analyses.

Procedural technique is standardized to the extent possible. The protocol outlines recommended patient positioning, wrist support, and needle entry angles for each access site. Guidance is provided for optional ultrasound guidance, sheath size selection, and spasm prophylaxis, with flexibility to adjust for clinical circumstances. Hemostasis methods, including compression devices and timing, are prespecified to harmonize post-procedure care. Such standardization reduces noise in comparisons that would otherwise be attributed to operator preference.

Escalation pathways are defined to avoid prolonged attempts that could jeopardize reperfusion targets. The protocol specifies how many puncture attempts constitute a failed strategy and the time intervals prompting consideration of crossover. These definitions strike a balance between allowing a fair trial of the assigned technique and preventing delays that could worsen patient outcomes. All crossovers are recorded with detailed reasons to support nuanced interpretation of efficacy and safety signals.

Post-procedural assessments include evaluation of local access-site complications, neurologic symptoms in the hand, and radial patency. Patency assessment methods may include physical examination, plethysmography, Doppler interrogation, or other noninvasive tests, applied consistently across sites per protocol. A standardized time window for follow-up facilitates uniform capture of early and short-term events. These assessments support the primary and secondary endpoints centered on safety and vascular integrity.

Safety oversight and monitoring

Given the acuity of STEMI, safety procedures are explicit. Investigators promptly report serious events, including major bleeding, vascular injury, or ischemic complications related to access. An independent committee adjudicates events using standardized definitions. If emergent concerns arise, predefined stopping rules allow for temporary or permanent modifications to the trial. This governance structure aligns with international standards for patient safety in acute cardiovascular trials.

Site monitoring focuses on protocol adherence, data integrity, and timely follow-up assessments. Monitoring visits or remote reviews verify that randomization occurred appropriately and that crossover criteria were applied as intended. Training refreshers are offered if deviations cluster around specific procedural steps. Transparent feedback loops help maintain consistency and protect the validity of comparative analyses across centers.

Data management systems capture time points and outcomes with robust audit trails. The platform supports rapid entry of emergent care data and delayed entry of follow-up information to accommodate clinical workflow. Security and privacy protections conform to applicable regulations, and data are deidentified for central analyses. This infrastructure ensures that conclusions rest on high-quality data reflective of real-world practice.

Collectively, these oversight measures promote a disciplined trial environment that still respects the imperative of rapid reperfusion. They also generate practical insights into implementation strategies that centers can adopt regardless of the final comparative results. As such, the trial doubles as a vehicle for procedural quality improvement. The monitoring plan is designed to evolve as sites gain experience and as interim operational feedback accumulates.

Endpoints, analysis, and anticipated limitations

The endpoint framework prioritizes access-site outcomes, vascular patency, and time efficiency. The principal endpoint focuses on access-site safety and radial patency, measured with standardized methods at prespecified time points. Key secondary endpoints capture procedural success, puncture-to-sheath time, diagnostic and interventional success, crossover rates, and access-site complications relevant to patient outcomes. Additional measures include patient-reported comfort and hand function assessments, as feasible in an emergent setting.

To reflect the realities of acute care, efficiency endpoints are emphasized. These include lesion crossing and device delivery timing where applicable, as well as the relationship between access strategy and the overall door-to-balloon time. The trial records the number of puncture attempts and time to successful sheath placement as direct markers of access feasibility. By linking process metrics to clinical and safety outcomes, the analysis can illuminate whether differences in technique translate into meaningful tradeoffs or advantages. The focus is on practical, decision-informing insights for cath lab teams.

Bleeding outcomes are captured using standardized classification systems to ensure comparability with other trials and registries. Access-site hematomas, need for transfusion, and major bleeding events are adjudicated using recognized criteria such as the BARC bleeding scale. The protocol also tracks nerve-related symptoms and occlusive complications that may influence hand function. These safety endpoints help characterize the full spectrum of consequences associated with the choice of puncture site.

Procedural success is defined with clarity, typically as the ability to complete diagnostic angiography and, when indicated, intervention via the assigned or escalated route without conversion delays beyond prespecified thresholds. The analysis accounts for crossover by using intention-to-treat as the primary analytic principle, supplemented by per-protocol and as-treated sensitivity evaluations. This layered approach tests the robustness of findings to real-world deviations while maintaining the integrity of randomization. It also allows operators to understand how much of any observed difference is attributable to technique versus execution.

Primary and secondary endpoints

The primary endpoint centers on access-site outcomes and radial vessel patency within a defined follow-up interval, using standardized assessment techniques. This emphasis reflects the hypothesized advantage of preserving proximal radial integrity with distal entry and the clinical relevance of avoiding occlusive injury. Secondary endpoints extend to procedural timings, success metrics, and patient experience. Collectively, these measures are meant to capture both the immediate and short-term consequences of the access decision.

Additional secondary endpoints consider the frequency and reasons for crossover, the need for adjunctive imaging or guidance, and sheath size compatibility with complex interventions. The trial tracks device success and any limitations encountered due to sheath or catheter selection related to the access strategy. Understanding these constraints is vital in STEMI, where lesion complexity cannot be predicted with certainty. The goal is to delineate the operational envelope within which each radial approach performs optimally.

Safety-related secondary endpoints include nerve symptoms, compartment-like syndromes, and rare but important vascular injuries. Pain scores and patient-reported experience are collected when clinically appropriate to complement objective safety metrics. The protocol specifies how missing data for patient-reported outcomes will be handled to avoid bias. These considerations round out a comprehensive endpoint suite aligned with the questions clinicians most frequently ask about radial access strategies.

Exploratory analyses may evaluate center-level or operator-level learning effects, particularly as teams accrue experience with distal techniques. Time trends in puncture-to-sheath intervals or crossover rates can inform training needs and the scalability of the approach. Similarly, the protocol anticipates subgroup analyses based on anatomical or clinical features that could influence success. These exploratory findings, while hypothesis-generating, can guide future targeted research and practical implementation.

Statistical framework

The statistical plan specifies intention-to-treat as the primary analysis, ensuring that randomization balances measured and unmeasured confounders. Per-protocol and as-treated analyses serve as sensitivity checks to test robustness against crossover and protocol deviations. Power calculations are informed by expected event rates for patency and access-site complications in the target population. The sample size is selected to detect clinically meaningful differences without excessive exposure of patients to investigational procedures.

Baseline characteristics are summarized descriptively, and key variables are compared across groups to confirm balance. Primary endpoint analysis employs appropriate models for binary or time-to-event outcomes, with confidence intervals reported alongside point estimates. Secondary endpoints are analyzed with multiplicity considerations detailed in the plan, prioritizing clinical interpretability. Missing data strategies, including imputation rules and hierarchy of data sources, are prespecified to limit bias.

Prespecified subgroup analyses assess whether effects differ by age, sex, body habitus, anatomical features, or clinical presentation characteristics. Interaction testing is applied cautiously to avoid overinterpretation of spurious findings. Center and operator clustering are considered in secondary models to account for intragroup correlation. These measures together enhance the credibility and generalizability of conclusions, should meaningful differences emerge.

Interim analyses, if planned, use conservative boundaries to avoid premature claims of benefit or harm. An independent committee oversees any interim looks with clear charters and decision rules. The reporting strategy specifies transparent dissemination of protocol updates, analysis changes, and final outcomes. This promotes trust, facilitates replication, and smooths the path for guideline integration if warranted by eventual results.

Anticipated operational challenges

Operator experience with distal radial cannulation varies globally, and a learning curve can influence puncture times and crossover. The protocol addresses this by recommending training prerequisites and by documenting operator experience levels. Even so, heterogeneity remains a potential source of variability that must be acknowledged in interpretation. Monitoring and supportive retraining can mitigate these risks and promote consistent execution across sites.

Anatomical variability in distal radial vessel size and course can complicate cannulation, especially in patients with vasospasm or shock physiology. Equipment choices and pharmacologic adjuncts are standardized to reduce variability, but some cases will test the limits of the assigned approach. The protocol manages this with clear escalation criteria and caps on attempts. These provisions protect patients while offering a fair test of feasibility under realistic conditions.

Time pressures in STEMI heighten the importance of streamlined workflows. Even small delays from access difficulty can accumulate across steps from activation to wire crossing. Capturing detailed time metrics allows the analysis to quantify any efficiency penalty or benefit associated with each access site. If differences are small but consistent, these findings can still guide policy and training priorities for high-volume centers.

Finally, blinding is not feasible for operators or patients in an access-site trial, introducing potential observation bias for subjective endpoints. The design mitigates this through objective definitions, independent adjudication, and standardized assessment protocols. While these measures cannot eliminate all bias, they substantially reduce its magnitude and preserve the integrity of comparative analyses. The net effect is a pragmatic yet rigorous evaluation suited to the realities of emergent cardiovascular care.

Implications and next steps

If distal radial access demonstrates noninferior or superior safety and efficiency, adoption in STEMI could expand, with training programs emphasizing rapid, reliable execution. Alternatively, if tradeoffs appear, such as higher crossover or longer access times without safety gains, operators may favor a selective use strategy. Regardless of outcome, the protocol sets a high bar for methodological clarity in access-site trials, with standardized definitions and meaningful endpoints. Final results will inform procedural choice, training priorities, and potentially institutional pathways for emergent care.

Until results are available, practitioners should continue to individualize access decisions based on patient anatomy, operator expertise, and institutional capability. The trial underscores the continued value of detailed time-and-motion data in the cath lab, linking process with outcomes that matter to patients and systems. By engaging a broad, multicenter network, the design also enhances generalizability across diverse practice settings. This thoughtful methodology positions the field to translate findings promptly into practice once data mature.