Rates of Cardiac Catheterization in Ontario and New York State

A recent study found that only 1 in 3 patients in the United States who received electric cardiac catheterization had obstructive coronary artery disease (CAD), raising concerns about the necessity of cardiac procedures for patients with stable CAD. Other studies have demonstrated that physicians in New York State (New York) perform twice as many cardiac catheterizations per capita as those in Ontario for patients with stable CAD.

The role patient selection may play in these findings and their implications for detection of obstructive CAD are largely unknown, according to researchers, who recently conducted a study to evaluate the extent of obstructive CAD in New York and Ontario. A secondary objective was to evaluate whether there were different thresholds for selecting patients for cardiac catheterization by comparing the predicted probabilities of obstructive CAD in those jurisdictions. Study results were reported in JAMA [2013;310(2):163-169].

The primary outcomes and measures were observed rates and predicted probabilities of obstructive CAD. Predicted probabilities were estimated using logistic regression models.

Obstructive CAD was defined as stenosis of ≥50% of the left main coronary artery or stenosis of ≥70% of a major epicardial or branch vessel. The presence of 3-vessel CAD was defined by stenosis of ≥70% in the left anterior descending coronary artery, left circumflex coronary artery, and right coronary artery.

The original study cohort included 61,756 patients in New York and 160,563 patients in Ontario who underwent cardiac catheterization between October 1, 2008, and September 30, 2011. After applying inclusion and exclusion criteria, the final cohort included 18,114 patients in New York and 54,933 patients in Ontario (29.3% and 34.2%, respectively, of the original cohort).

After applying sequential exclusions to identify patients with elective procedures without prior heart disease, the rate of obstructive CAD was lower in New York (30.4%; 95% confidence interval [CI], 29.7%-31.0%) compared with Ontario (44.8%; 95% CI, 44.4%-45.3%; P<.001).

Patients in New York undergoing catheterization were significantly younger (mean, 61.2 years of age vs 63.7 years of age) and more likely to be female (45.3% vs 39.0%) than those in Ontario.

In New York, 2.5% (95% CI, 2.3%-2.8%) of catheterization patients had left main stenosis, 5.2% (95% CI, 4.9%-5.5%) had 3-vessel CAD, and 7.0% (95% CI, 6.6%-7.3%) had left main or 3-vessel CAD. In Ontario, patients undergoing catheterization were significantly more likely to have severe CAD; 5.0% (95% CI, 4.9%-5.2%) had left main stenosis, 9.8% (95% CI, 9.6%-10.1%) had 3-vessel coronary artery stenosis, and 13.0% (95% CI, 12.8%-13.3%) had left main or 3-vessel disease (P<.001 for all).

Factors predicting the presence of obstructive CAD were of similar importance in both jurisdictions. In New York, a higher percentage of patients with low predicted probability of obstructive CAD underwent catheterization compared with the similar cohort in Ontario. In New York, only 19.3% of patients undergoing catheterization had a >50% predicted probability of having obstructive CAD; the percentage in Ontario was 41% (P<.001).

Finally, at 30 days after the procedure, crude mortality for patients undergoing catheterization was higher in New York than in Ontario (0.65% vs 0.38%; P<.001).

In summary, the researchers said, “In Ontario compared with New York, patients undergoing elective 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.”