Aims: The association of triglyceride (TG) concentrations and cardiovascular risk in patients with cardiovascular disease remains to be fully understood. We performed a detailed lipid characterization and tested the association of fasting and postprandial lipoprotein composition and event-free survival in patients with coronary artery disease (CAD).
Methods: 195 patients with stable CAD on guideline-recommended cardiovascular medication were prospectively enrolled in the study, underwent a standardized oral triglyceride tolerance test (OTT) and were followed up for 4 years. Fasting and 5 hours (5h) postprandial plasma was subjected to serial ultracentrifugation and precipitation techniques to differentiate lipoprotein subclasses and to determine TG, cholesterol, phospholipids and apolipoproteins in chylomicrons, very low-density, low-density and high-density lipoproteins. TG/apoB ratios were calculated to indicate chylomicron particle size and TG content.
Results: The OTT induced a TG increase from 151±96 to 265±161 mg/dl after 5h (mean±SD). Cholesterol parameters and apolipoproteins A1, A2, B, C2, C3 and E remained unchanged. The postprandial TG increase was attributable to the increase of chylomicron-TG (0h: 80±83mg/dl, 5h: 181±140mg/dl; mean individual increase 313±261%). VLDL-TG increased from 12.5±12.7 to 17.9±14.6mg/dl and LDL- and HDL-TG remained unchanged. The chylomicron TG/apoB ratio increased from 3.3±2.8 to 8.4±9.2 after the OTT. Associations of lipoproteins and events were determined by Kaplan-Meier and Cox regression analyses. 97 patients experienced a primary endpoint (death, myocardial infarction, unplanned revascularization) during follow-up. Patients with events had a higher chylomicron TG/apoB ratio. After adjustment, both fasting and postprandial chylomicron TG/apoB ratios were associated with outcomes (per SD, log-values: fasting: HR 1.52 (CI 1.13–2.05), p=0.006; postprandial: HR 1.25 (CI 1.01–1.55), p=0.044), adjusted for age, gender, medication, risk factors, LDL and HDL). The TG/apoB index correlated with fasting TG concentrations (R=0.58). Only the fasting chylomicron TG/apoB index remained predictive for events after full adjustment including fasting TG (HR 1.47 (CI 1.03–2.09), p=0.034), but risk prediction by postprandial TG/apoB ratio was attenuated after adjustment for fasting TG.
Conclusions: The results of the detailed lipid characterization in CAD patients show no advantage of a postprandial compared to a fasting measurement. Importantly, elevated fasting chylomicron triglycerides identify CAD patients at higher risk for cardiovascular events.