Lipid levels as predictors of silent myocardial ischemia in a type 2 diabetic population in Havana

INTRODUCTION Silent myocardial ischemia is frequent in type 2 diabetics, therefore, symptoms cannot be relied upon for diagnosis and followup in these patients. Various studies relate blood lipid levels to cardiovascular diseases, and several authors describe certain lipoproteins as independent predictors of ischemia. OBJECTIVE Identify blood lipid levels that predict silent myocardial ischemia in a type 2 diabetic population in Havana. METHODS From May 2005 through May 2009, assessment was done of 220 asymptomatic type 2 diabetics in ten polyclinics in Havana using laboratory tests and Single-Photon Emission-Computed Tomography, synchronized with electrocardiogram, known as gated SPECT (gSPECT). Coronary angiography was used for confirmation when gSPECT detected ischemia. Patients were classified into two groups: gSPECT positive and gSPECT negative. Descriptive statistics (mean and standard deviation) were calculated for all variables and mean comparison tests were conducted. Classification trees were developed relating lipid values to gSPECT results, identifying optimal cutoff points for their use as indicators of silent myocardial ischemia in the total study population and for each sex separately. RESULTS GSPECT found silent myocardial ischemia in 29.1% of those examined, and 68.4% of angiograms found multivessel disease. gSPECT-positive diabetics had higher levels of total cholesterol, LDL, and triglycerides (p < 0.05). HDL levels were lower in this group (p < 0.05). Classification trees showed optimal cutoff points, indicators for silent ischemia, for: HDL <44 mg/dL, LDL >119.9 mg/dL, and triglycerides >107.2 mg/d; 80.4% of diabetics with these HDL and triglyceride values had ischemia. HDL was the most important normalized variable when the entire population was analyzed. Analysis by sex showed a greater percentage of silent ischemia in men (33.3%) than in women (24.8%). The most important normalized variables were LDL of >100.8 mg/dL for men and HDL of <44 mg/dL for women. CONCLUSIONS A considerable percentage of the study population had silent myocardial ischemia. Type 2 diabetics with ischemia had higher levels of total cholesterol, LDL and triglycerides. HDL levels were significantly lower in these patients. The association of low HDL with high triglycerides was a strong indicator of myocardial ischemia in type 2 diabetics without clinical cardiovascular signs.