In a randomized, double-blind trial, 100 patients undergoing angiography were pre-treated with either topical nitroglycerin (NTG) or placebo. Outcomes assessed included radial artery spam (RAS) incidence, radial artery puncture success, number of attempts, procedural duration, patient discomfort, and complications. RAS was evaluated angiographically and clinically, with additional subgroup analyses for diabetic and smoking patients

During the period of April 2023 - June 2023, 100 consecutive patients that un-derwent invasive angiography using radial artery approach (deemed suitable access site by operating physician) were enrolled and randomized to either pretreatment with a topical cream 0.2% NTG, or application of a gel that contained no active substances. Randomization was done using a computer program designed to randomly produce either the digit 1 or 0, with 1 meaning the patient was assigned to nitroglycerine cohort and 0 to placebo cohort. The assigned nurse that handled the randomization also ad-ministered the patient's treatment. The NTG or placebo cream was applied 20-40 minutes before radial artery puncture by the assigned nurse. The study was designed as a randomized, double-blinded trial, with neither the patient nor the operator aware of the treatment allocation. Patients had indication of either elective or emergency coronary artery or peripheral artery angiography, and had no contraindication to ra-dial artery approach. Both right and left radial arteries were used, depending on oper-ator judgement, while distal radial approach was not utilized in any case. The operator assessed the radial artery pulse quality by manual palpation before puncture. Standard local subcutaneous anesthesia with 5 ml of 2% lidocaine solution was performed. A visual analog scale was used to judge patient discomfort related to the puncture and puncture site at several times during the procedure, with the worst pain level being documented (scale of 0 to 10, where 0 is no pain, and 10 is worst possible pain). The key objective was assessing spasm of the radial artery, which was judged both subjectively by the operator by judging the grade of resistance felt during manipulation of the catheters, and objectively by injection of contrast dye into the radial artery through the introducer sheath immediately after it had been placed inside the radial artery. Spasm was defined as narrowing of the radial artery lumen by more than 50%. Diffuse spasm was defined as spasm of a segment of radial artery greater than 2 cm, or more than two different sites of spasm. The diameter of the radial artery was also measured on the radial angiograms, and was indexed to the patient's body surface area. After sheath insertion and radial artery measurement, the operator could administer intraarterial NTG at his discretion throughout the procedure.

Other data that was included was number of attempts that lead to successful puncture and sheath placement, procedure duration (including angioplasty if needed), contrast dye used and hospital stay duration. Patients were screened for cardiovascu-lar risk factors such as smoking, diabetes mellitus, dyslipidemia, hypertension and obesity. Procedural anticoagulation was performed using 5000 units of unfractioned heparin for diagnostic procedures and 70 units/kilogram for angioplasties. At the end of the procedure, after sheath extraction, hemostasis was achieved using a compres-sive dressing that was left in place for ~12 hours. Bleeding complications at the site of puncture were noted (presence of local hematoma), and ultrasound screening at dis-charge was used to check postprocedural radial artery patency.

Radial sheaths used were 6 French, and the operator had the freedom to use any size of catheters he considered, most often choosing 6 French for both diagnostic angi-ography and percutaneous intervention. No preprocedural patient sedation was used, and cath lab temperature was similar for all cases.

Statistical analysis was performed using IBM SPSS Statistics version 20.0 software for Windows with a significant p<0.05. We used descriptive statistics, figures, and ta-bles to summarize our findings. Results for targeted variables were presented using descriptive statistics (mean, standard deviation, range, median, and associated inter-quartile range) for continuous data, and counts with associated percentages for cate-gorical data. Independent samples t-test was used to analyze differences in means for continuous variables, while differences between categorical variables were examined by Chi-squared test. Categorical data are presented as counts (percentages).

Inclusion Criteria:

• indication for invasive cardiology procedure (diagnostic or curative)
• deemed suitable for radial access by operating physician

Exclusion Criteria:

• refuses or unable to give consent
• demed unsuitable for radial artery access (no radial pulse, small patient size, anticipation of complex procedure that requires alternative access site)