Maximal sterile barrier precautions (MSBP) including head coverings and face masks are advocated by published guidelines for use in invasive procedures related to intravascular catheter placement and replacement [
1]. The rationale for MSBP is that it protects both the operator and the patient from infection transmission [
2]. Accordingly, the use of MSBP, including the use of a cap, mask, sterile gown, sterile gloves, and a sterile full body drape, for intravascular catheter insertion and/or guide wire exchange was recommended as category IB [
1,
3]. The original coronary catheterization laboratory (cath lab) procedure in the 1970s involved brachial artery cut-downs and was, therefore, considered an operation requiring complete sterile technique. In 2006, the Society for Cardiac Angiography and Interventions (SCAI) published infection control guidelines for the cath lab. These SCAI infection control guidelines indicated that for patient preparation, aseptic technique requires the use of cap, mask, sterile gown, sterile gloves, and large sterile sheet [
4]. The cardiac cath lab has evolved since, but remains a complex environment in which implantable devices, closure devices, and other equipment must be used in a secure sterile fashion. In defining recent cath lab protocol, infection control issues generated much expert discussion as the Joint Commission considered procedures in the cath lab as a sterile procedure, rather than a clean one. Eventually, the 2012 American College of Cardiology Foundation/Society for Cardiovascular Angiography and Interventions expert consensus document on cardiac catheterization laboratory standards update noted that it is reasonable to wear hats and masks in the cath lab, but they are not mandated except for certain high-risk procedures—those involving insertion of devices, such as prosthetic valves and electrophysiology devices, and to close septal defects and patent foramen ovale. In these cases it was recommended that each laboratory should have a written protocol for increased sterile technique for highly infectious cases that should include caps, masks, double gloving, and protective eyewear [
5]. In general, infectious complications in the cath lab are rare, ranging between 0.1 and 0.6% [
6]. However, previous reports did suggest that infection transmission may be relevant for interventions done in the cath lab and that implementation of “full dressing” protocols decreases vascular catheter-related infection [
7,
8]. In contrast, there is no evidence that rates increase without the use of hats and masks. This may explain the “daily practice” in which the many of interventional cardiologists in both the USA and Europe do not use head coverings and face masks. To clarify this debate and the struggle between regulatory instructions and daily practice, the purpose of the current study was to perform a systematic and thorough microbiological analysis in assessing the potential hazards of not using head coverings/face masks in percutaneous coronary interventions done routinely in the cath lab. To the best of our knowledge such a study in modern cath lab operating mode was not done in recent years.