Subcutaneous Nitroglycerin to Facilitate Trans-radial Access.

Femoral artery approach to perform coronary procedures is considered the standard technique for vascular access due to optimal catheter control, lower thromboembolic complications and immediate access due to the large diameter of the artery. Trans-radial approach has been shown to reduce major bleeding complications, vascular complications related to the site of puncture, including death from all causes, and to prevent post-procedure limb rest, greater comfort for patients, immediate ambulation, early discharge and reduction of costs. Previous studies have shown that intravenous, topical and intraarterial use of nitroglycerin produces vasodilation of the radial artery. Extravascular (subcutaneous) administration of nitroglycerin is extremely effective in restoring the radial pulse, and allows adequate cannulation.

Unlike femoral access, the trans-radial approach to coronary angiography requires a greater learning curve for the inexperienced interventionist, and demands a greater technical challenge than the femoral approach, which leads to a high incidence of failures and complications, mainly in the initial stages of their formation. Some explanations for procedural failure include inability for radial artery puncture, vessel tortuosity, and radial spasm. Radial spasm has been reported from 5 to 30% in experienced centers, with a decrease to 2.5% when associated with the administration of nitrate added to local anesthesia. Although radial spasm is infrequent and usually occurs once the artery is cannulated or during manipulation of the catheters, it can sometimes occur before cannulation due to multiple unsuccessful attempts to cannulate the artery, which can also produce pain in the patient.

The investigators will conduct an experimental, placebo-controlled, longitudinal, prospective, double-blind, parallel arm clinical trial. Patients will be randomized to receive 1:1 an intervention or placebo. Intervention group will receive a subcutaneous "cocktail" with 0.5 ml of 500 mcg of nitroglycerin + 1 ml of 2% simple lidocaine. Placebo group will receive a subcutaneous injection with 0.5 ml of 0.9% saline solution + 1 ml of 2% simple lidocaine.

The investigators hypothesize that the maneuver (subcutaneous infiltration of local anesthetic together with nitroglycerin) will facilitate radial access in terms of fewer punctures until the insertion of the arterial introducer, shorter access time, lower incidence of radial spasm, and lower crossover rate to femoral access, compared with placebo. In terms of safety, the investigators do not believe that the maneuver represents a risk to the patient in terms of incidence of hypotension or headache. In fact, the investigators believe that the maneuver will provide less pain at the site of puncture referred by the patient due to the less number of unsuccessful punctures.

For the calculation of the required sample, since the incidence of our primary end-point of a compound of crossover to femoral access and/or access site-related vascular complications has not been reported so far, the sample will be calculated with the rate of events obtained in our center at 6 months of recruiting patients. For this calculation, the proportional difference formula with an alpha value of 0,05 and a beta value of 0,20 will be used to have a statistical power of 80%. The investigators estimate that 1,500 patients will be required in a 11-month period.

Eligibility Criteria:
Inclusion Criteria:

* Men and women older than 18 years, scheduled consecutively to perform a coronary procedure in the department of hemodynamics of the National Institute of Cardiology "Ignacio Chavez".
* Patients may have any of the following indications for cardiac catheterization: Thoracic pain under study. Stable chronic coronary disease. Acute myocardial infarction with ST segment elevation, not perfused (without timely reperfusion therapy) with less than 4 weeks of evolution. Acute myocardial infarction with ST-segment elevation, successful thrombolytic therapy, which will undergo drug-invasive therapy. Acute myocardial infarction without ST segment elevation. Unstable angina. Any acute coronary syndrome, to intervene non-infarct-related artery. Disease of any heart valve. Myocarditis or pericarditis. Dilated cardiomyopathy. Patients in renal or cardiac transplantation protocol for any etiology. Congenital heart disease that requires knowing the coronary anatomy prior to surgical correction.
* The planned procedure can be any of the following: For diagnostic purposes (coronary angiography only, left catheterization, left and right catheterization). For therapeutic purposes: percutaneous coronary intervention (PCI), with or without stent placement.
* A priori access must be right or left radial artery.
* Radial arterial pulse may be present or absent by palpation.
* Modified Allen or Barbeau test should be positive (presence of collateral palmar flow).

Exclusion Criteria:

* Pregnant.
* Not have informed consent for the present clinical trial, or do not fully understand the meaning of informed consent.
* With acute myocardial infarction with ST segment elevation in the first 12 hours from the onset of symptoms.
* With any acute coronary syndrome complicated with acute pulmonary edema, cardiogenic shock and / or malignant ventricular arrhythmias.
* In which a cardiac catheterization is planned a priori to be performed via femoral, brachial or ulnar.
* Patients in whom first attempt of arterial puncture is performed by 2nd year interventional cardiology fellow or by physician in charge.
* Participating in another clinical trial.
* Be allergic or have contraindications to nitroglycerin or other nitrates.
* Any phosphodiesterase 5 inhibitor (sildenafil, tadalafil, avanafil, vardenafil) has been taken within 72 hours prior to the study.