Type 2 diabetes mellitus and myocardial ischemic preconditioning in symptomatic coronary artery disease patients

Background: The influence of diabetes mellitus on myocardial ischemic preconditioning is not clearly defined. Experimental studies are conflicting and human studies are scarce and inconclusive. Objectives: Identify whether diabetes mellitus intervenes on ischemic preconditioning in symptomatic coronary artery disease patients. Methods: Symptomatic multivessel coronary artery disease patients with preserved systolic ventricular function and a positive exercise test underwent two sequential exercise tests to demonstrate ischemic preconditioning. Ischemic parameters were compared among patients with and without type 2 diabetes mellitus. Ischemic preconditioning was considered present when the time to 1.0 mm ST deviation and rate pressure-product were greater in the second of 2 exercise tests. Sequential exercise tests were analyzed by 2 independent cardiologists. Results: Of the 2,140 consecutive coronary artery disease patients screened, 361 met inclusion criteria, and 174 patients (64.2 +/- 7.6 years) completed the study protocol. Of these, 86 had the diagnosis of type 2 diabetes. Among diabetic patients, 62 (72%) manifested an improvement in ischemic parameters consistent with ischemic preconditioning, whereas among nondiabetic patients, 60 (68%) manifested ischemic preconditioning (p = 0.62). The analysis of patients who demonstrated ischemic preconditioning showed similar improvement in the time to 1.0 mm ST deviation between diabetic and nondiabetic groups (79.4 +/- 47.6 vs 65.5 +/- 36.4 s, respectively, p = 0.12). Regarding rate pressure-product, the improvement was greater in diabetic compared to nondiabetic patients (3011 +/- 2430 vs 2081 +/- 2139 bpm x mmHg, respectively, p = 0.01). Conclusions: In this study, diabetes mellitus was not associated with impairment in ischemic preconditioning in symptomatic coronary artery disease patients. Furthermore, diabetic patients experienced an improvement in this significant mechanism of myocardial protection.