Phase 1, single-center, open-label clinical study to assess the safety and efficacy of topical nitroglycerin on dilation of the radial artery. Subjects will receive nitroglycerin ointment prior to scheduled PCI and radial artery measurements will be performed to determine mean increase in radial artery diameter at several time points. There will be 20 subjects enrolled in this study.

This is a phase I study evaluating the safety, tolerability, and efficacy of topical nitroglycerin prior to percutaneous coronary intervention (PCI). Although the ultimate plan is to evaluate this intervention vs placebo, it is important to first determine whether topical nitroglycerin not only is safe for patients, but whether it effectively dilates the radial artery. Given that patients who receive topical nitroglycerin applied to the chest for other reasons (angina or acute coronary syndrome, hypertension, etc) have reported headaches and/or have experienced decreased blood pressure, it is important to determine whether these noted side effects are present when nitroglycerin ointment is applied to the arm. Prior to initiating any study procedures, we will perform a Barbeau test to determine normal blood flow through the radial artery and collateral circulation from the ulnar artery through the palmar arch. After the ointment is applied, we will also be measuring the dimensions of the radial artery for the degree of dilation in order to determine whether topical nitroglycerin is indeed a possible method for increasing the rate of PCI performed using the transradial approach (TRA).

Inclusion Criteria:

• Scheduled to undergo PCI using TRA in the cardiac catheterization laboratory

Exclusion Criteria:

1. Known nitrate allergy
2. Baseline hypotension with systolic blood pressure <90mmHg
3. Absence of radial artery blood flow in one or both arms
4. Presence or history of liver, rheumatologic, or chronic kidney disease
5. Current treatment with any vasodilator therapy (eg. Sildenafil)
6. Radial artery catheterization <30 days prior to enrollment
7. Active site infection
8. AV-fistula or prior radial artery harvest for bypass surgery
9. Abnormal Barbeau test

To be decided