Association of glycemic control with mortality in patients with diabetes mellitus undergoing percutaneous coronary intervention

Background: Diabetes mellitus adversely affects outcomes in patients undergoing percutaneous coronary intervention. The association of baseline hemoglobin A1c (HbA1c) at the time of percutaneous coronary intervention with long-term mortality is unknown.

Methods and results: Consecutive patients with diabetes mellitus undergoing percutaneous coronary intervention between 1998 and 2008 were identified from our institutional database. Characteristics and outcomes of patients were compared based on HbA1c categories (≤7%, 7.1%-8.0%, 8.1%-9.0%, 9.1%-10.0%, and >10.0%). Among 3008 patients, 1321 had HbA1c ≤7%, 782 with HbA1c 7.1% to 8.0%, 401 with HbA1c 8.1% to 9.0%, 229 with HbA1c 9.1% to 10.0%, and 275 with HbA1c >10%. Compared with low HbA1c (≤7%), those with highest HbA1c (>10%) were younger (56.5 versus 67.5 years), had higher total cholesterol (188 versus 157 mg/dL), more insulin use (54% versus 26%), and presented more often with ST-segment-elevation myocardial infarction (10.9% versus 5.6%). Those with lower HbA1c (≤7%) more often had other comorbidities (more hypertension [90.4% versus 82.5%] and chronic renal failure [14.4% versus 7.6%]). On multivariable Cox proportional hazards modeling, survival analysis demonstrated a trend toward higher mortality with higher HbA1c. Compared with the reference group of patients with HbA1c ≤7%, patients with HbA1c >10% had a significantly higher mortality on follow-up (hazard ratio [95% confidence interval], 1.52 [1.17-1.99]; P=0.002). This difference was primarily seen among noninsulin users; however, insulin users had no significant differences in mortality among HbA1c categories.

Conclusions: Patients with diabetes mellitus who were not on insulin and had poor glycemic control (HbA1c >10%) had significantly higher long-term mortality after percutaneous coronary intervention as compared with those with well-controlled diabetes mellitus, evidenced by HbA1c ≤7%. Insulin users, however, had similar rates of mortality among different HbA1c categories.