"Prevalence and Extent of Obstructive Coronary Artery Disease Among Patients Undergoing Elective Coronary Catheterization in New York State and Ontario"  
JAMA Jul 10  
http://jama.jamanetwork.com/article.aspx?articleid=1710454 
"Results   . . . The observed rate of obstructive CAD was significantly lower in New York at 30.4%  . . .  than in Ontario at 44.8% . . .  of patients undergoing cardiac catheterization in New York had a greater than 50% predicted probability of having obstructive CAD than those in Ontario at 41% . . . At 30 days, crude mortality for patients undergoing cardiac catheterization was slightly higher in New York  . . . 

Conclusions and Relevance  In Ontario compared with New York State, patients undergoing elective cardiac catheterization were significantly more likely to have obstructive CAD. This appears to be related to a higher percentage of patients in New York with low predicted probability of CAD undergoing cardiac catheterization."