BackgroundThere is very little information about the use of ad hoc percutaneous coronary intervention (PCI) in stable patients with multivessel (MV) disease or unprotected left main (LM) disease patients for whom a heart team approach is recommended. ObjectiveTo identify the extent of ad hoc PCI utilization for patients with multivessel disease or left main disease, and to explore the inter-hospital variation in ad hoc PCI utilization for those patients. MethodsNew York State’s cardiac registries were used to examine the use and variation in use of ad hoc PCI for MV/LM disease as a percentage of all MV/LM PCIs and revascularizations (PCIs plus coronary artery bypass graft procedures) during 2018 to 2019 in New York. ResultsAfter exclusions, 6,425 of the 8,196 stable PCI patients with MV/LM disease (78.4%) underwent ad hoc PCI, ranging from 58.7% for patients with unprotected LM disease to 85.4% for patients with 2-vessel proximal left anterior descending (PLAD) disease. Ad hoc PCIs comprised 35.1% of all revascularizations, ranging from 11.5% for patients with unprotected LM disease to 63.9% for patients with 2-vessel PLAD disease. The risk-adjusted utilization of ad hoc PCI as a percentage of all revascularizations varied widely among hospitals (eg, from 15% in the first quartile to 46% in the last quartile for 3-vessel disease). ConclusionsAd hoc PCIs occur frequently even among patients with MV/LM disease. This is particularly true among patients with 2-vessel PLAD disease. The frequency of ad hoc PCIs is lower but still high among patients with diabetes and low ejection fraction and higher in hospitals without surgery on-site (SOS). Given the magnitude of hospital- and physician-level variation in the use of ad hoc PCIs for such patients, consideration should be given to a systems approach to achieving heart team consultation and shared decision making that is consistent for SOS and non-SOS hospitals.