Coronary angiography and angioplasty are commonly performed through the radial artery at the wrist as this approach is associated with fewer bleeding complications and faster recovery. In some patients, the radial artery becomes occluded after prior procedures, requiring selection of an alternative access site for future coronary interventions.

The ulnar artery is a potential alternative wrist access. However, limited data are available on the safety of using the ulnar artery in the same arm as an occluded radial artery and on the possible effects on hand strength, sensation, and daily hand function.

The goal of this observational study is to evaluate the safety of transulnar access and its effect on hand function in adults with ipsilateral radial artery occlusion undergoing coronary angiography or angioplasty.

The main questions addressed by the study are:

• How often do serious access-related vascular or nerve complications occur?
• Does hand strength, sensation, or functional use of the hand change during follow-up?
• Does the ulnar artery remain patent after the procedure? The choice of vascular access site is made by the treating physician based on clinical judgment. Participants who undergo transulnar access will undergo follow-up assessments, including ultrasound evaluation of arm arteries, standardized hand function testing, and short questionnaires assessing upper-limb function.

The findings of this study are expected to inform access-site selection, improve patient counseling, and support safer care for patients with radial artery occlusion undergoing coronary procedures.

Transradial access is the preferred approach for coronary angiography and angioplasty because it is associated with reduced bleeding complications and faster recovery compared with femoral access. Radial artery occlusion is a recognized complication of transradial procedures and may limit future use of this access site. In patients with radial artery occlusion, selection of an alternative vascular access is required, particularly when preservation of the contralateral radial artery is clinically important.

The ulnar artery represents an anatomically plausible alternative upper-limb access route, contributing substantially to hand perfusion through the palmar arterial network. However, concerns remain regarding the vascular and functional safety of transulnar access, especially when used ipsilateral to a pre-existing radial artery occlusion. Available evidence is limited and methodologically heterogeneous, with inconsistent assessment of vascular integrity and hand function.

ULNART is a prospective observational cohort designed to evaluate the safety and functional outcomes of transulnar arterial access in patients with ipsilateral radial artery occlusion undergoing coronary angiography or angioplasty. Vascular access selection is determined by the treating physician and is not assigned by the study protocol. The study observes outcomes following transulnar access without influencing procedural decision-making.

Participants undergo standardized baseline and follow-up assessments integrating vascular imaging, objective neuromuscular testing, and patient-reported outcome measures. Color duplex ultrasonography is used to assess upper-limb arterial anatomy and ulnar artery patency, while hand function is evaluated using quantitative strength testing, sensory assessment, and validated questionnaires addressing upper-limb function and cold sensitivity. Assessments are repeated shortly after the procedure and at predefined later time points to evaluate recovery and detect early or delayed access-related effects.

The primary objective is to estimate the incidence of serious access-related vascular and clinical neuromuscular complications. Secondary objectives include characterization of ulnar artery patency, changes in hand strength and sensory function over time, patient-reported functional outcomes, and identification of factors associated with adverse events. Data are collected prospectively using standardized protocols and analyzed according to a prespecified statistical analysis plan appropriate for an observational cohort.

The results of ULNART are expected to provide systematic evidence on the vascular safety and functional impact of transulnar access in patients with radial artery occlusion, supporting informed access-site selection and patient counseling when transradial access is unavailable or clinically undesirable.

Inclusion Criteria

Participants must meet all of the following criteria to be eligible:

• Adults aged 18 years or older
• Documented radial artery occlusion in the upper limb intended for vascular access, confirmed by ultrasound or angiography
• Scheduled to undergo elective coronary angiography and/or angioplasty
• Transulnar arterial access on the same side as the occluded radial artery is selected by the treating physician
• Contralateral radial artery access is not feasible or is clinically undesirable, including for reasons such as:
• documented occlusion or severe disease of the contralateral radial artery
• unfavorable anatomy or prior failed access
• strategic preservation of the contralateral radial artery for future surgical or dialysis needs
• Adequate ulnar artery flow and anatomy for access, as assessed by pre-procedural ultrasound
• Able and willing to provide written informed consent

Exclusion Criteria

Participants meeting any of the following criteria will be excluded:

• Inadequate or absent ulnar artery flow at the intended access site on ultrasound
• Known ulnar nerve injury or neuropathy affecting the access-side upper limb
• Severe pre-existing motor or sensory dysfunction of the access-side hand that would interfere with functional assessment
• Emergency coronary procedures that preclude baseline vascular or functional assessment
• Participation in another interventional clinical study involving vascular access or intervention in the same upper limb
• Local conditions at the intended access site, such as active infection, burn, or extensive scarring
• Pregnancy or breastfeeding
• Life expectancy less than 6 months

Participants are recruited from cardiac catheterization laboratories and cardiology services of two tertiary-care public hospitals in Greece, including high-volume referral centers performing invasive coronary procedures. The study population represents adults undergoing routine elective coronary angiography or angioplasty in these hospital settings, where vascular access decisions are made as part of standard clinical practice.

De-identified individual participant data that underlie the results reported in publications arising from this study will be made available, including demographic variables, procedural characteristics, vascular imaging findings, functional test results, and patient-reported outcome measures. A corresponding data dictionary and study protocol will be provided. Data will be shared after publication of the primary results, upon reasonable request, subject to approval by the study investigators and completion of a data-use agreement, in accordance with applicable ethical approvals and data protection regulations.